Merge bitcoindevkit/bdk#1307: Bump version to 1.0.0-alpha.5

d597f4c761 Bump version to 1.0.0-alpha.5 (Steve Myers)

Pull request description:

  ### Description

  Bump version to 1.0.0-alpha.5

  bdk_chain to 0.9.0
  bdk_bitcoind_rpc to 0.4.0
  bdk_electrum to 0.7.0
  bdk_esplora to 0.7.0
  bdk_file_store to 0.5.0

  ### Checklists

  #### All Submissions:

  * [x] I've signed all my commits
  * [x] I followed the [contribution guidelines](https://github.com/bitcoindevkit/bdk/blob/master/CONTRIBUTING.md)
  * [x] I ran `cargo fmt` and `cargo clippy` before committing

ACKs for top commit:
  danielabrozzoni:
    ACK d597f4c761

Tree-SHA512: 36ba783083441ddd8d209ede35ff46832fd2532f588ddbff0e4e23fb336aff398f8ca612e2bfd5fa214d0f4c14a4dea9147b34724734cc43b752789765e7a447

.github/workflows/code_coverage.yml

@@ -33,7 +33,7 @@ jobs:
       - name: Run simulator image
         run: docker run --name simulator --network=host hwi/ledger_emulator &
       - name: Install Python
-        uses: actions/setup-python@v5
+        uses: actions/setup-python@v4
         with:
           python-version: '3.9'
       - name: Install python dependencies

.github/workflows/cont_integration.yml

@@ -12,7 +12,7 @@ jobs:
         rust:
           - version: stable
             clippy: true
-          - version: 1.57.0 # MSRV
+          - version: 1.63.0 # MSRV
         features:
           - --no-default-features
           - --all-features
@@ -28,28 +28,12 @@ jobs:
       - name: Rust Cache
         uses: Swatinem/rust-cache@v2.2.1
       - name: Pin dependencies for MSRV
-        if: matrix.rust.version == '1.57.0'
+        if: matrix.rust.version == '1.63.0'
         run: |
-          cargo update -p log --precise "0.4.18"
-          cargo update -p tempfile --precise "3.6.0"
-          cargo update -p reqwest --precise "0.11.18"
-          cargo update -p hyper-rustls --precise 0.24.0
-          cargo update -p rustls:0.21.9 --precise "0.21.1"
-          cargo update -p rustls:0.20.9 --precise "0.20.8"
-          cargo update -p tokio --precise "1.29.1"
-          cargo update -p tokio-util --precise "0.7.8"
-          cargo update -p flate2 --precise "1.0.26"
-          cargo update -p h2 --precise "0.3.20"
-          cargo update -p rustls-webpki:0.100.3 --precise "0.100.1"
-          cargo update -p rustls-webpki:0.101.7 --precise "0.101.1"
-          cargo update -p zip --precise "0.6.2"
-          cargo update -p time --precise "0.3.13"
-          cargo update -p byteorder --precise "1.4.3"
-          cargo update -p webpki --precise "0.22.2"
-          cargo update -p os_str_bytes --precise 6.5.1
-          cargo update -p sct --precise 0.7.0
-          cargo update -p cc --precise "1.0.81"
+          cargo update -p zstd-sys --precise "2.0.8+zstd.1.5.5"
+          cargo update -p time --precise "0.3.20"
           cargo update -p jobserver --precise "0.1.26"
+          cargo update -p home --precise "0.5.5"
       - name: Build
         run: cargo build ${{ matrix.features }}
       - name: Test
@@ -134,9 +118,7 @@ jobs:
       - uses: actions/checkout@v1
       - uses: actions-rs/toolchain@v1
         with:
-            # we pin clippy instead of using "stable" so that our CI doesn't break
-            # at each new cargo release
-            toolchain: "1.67.0"
+            toolchain: stable
             components: clippy
             override: true
       - name: Rust Cache

Cargo.toml

@@ -7,6 +7,7 @@ members = [
     "crates/electrum",
     "crates/esplora",
     "crates/bitcoind_rpc",
+    "crates/hwi",
     "example-crates/example_cli",
     "example-crates/example_electrum",
     "example-crates/example_esplora",
@@ -14,6 +15,7 @@ members = [
     "example-crates/wallet_electrum",
     "example-crates/wallet_esplora_blocking",
     "example-crates/wallet_esplora_async",
+    "example-crates/wallet_rpc",
     "nursery/tmp_plan",
     "nursery/coin_select"
 ]

README.md

@@ -15,7 +15,7 @@
     <a href="https://github.com/bitcoindevkit/bdk/actions?query=workflow%3ACI"><img alt="CI Status" src="https://github.com/bitcoindevkit/bdk/workflows/CI/badge.svg"></a>
     <a href="https://coveralls.io/github/bitcoindevkit/bdk?branch=master"><img src="https://coveralls.io/repos/github/bitcoindevkit/bdk/badge.svg?branch=master"/></a>
     <a href="https://docs.rs/bdk"><img alt="API Docs" src="https://img.shields.io/badge/docs.rs-bdk-green"/></a>
-    <a href="https://blog.rust-lang.org/2021/12/02/Rust-1.57.0.html"><img alt="Rustc Version 1.57.0+" src="https://img.shields.io/badge/rustc-1.57.0%2B-lightgrey.svg"/></a>
+    <a href="https://blog.rust-lang.org/2022/08/11/Rust-1.63.0.html"><img alt="Rustc Version 1.63.0+" src="https://img.shields.io/badge/rustc-1.63.0%2B-lightgrey.svg"/></a>
     <a href="https://discord.gg/d7NkDKm"><img alt="Chat on Discord" src="https://img.shields.io/discord/753336465005608961?logo=discord"></a>
   </p>
 
@@ -48,6 +48,8 @@ The project is split up into several crates in the `/crates` directory:
 Fully working examples of how to use these components are in `/example-crates`:
 - [`example_cli`](./example-crates/example_cli): Library used by the `example_*` crates. Provides utilities for syncing, showing the balance, generating addresses and creating transactions without using the bdk `Wallet`.
 - [`example_electrum`](./example-crates/example_electrum): A command line Bitcoin wallet application built on top of `example_cli` and the `electrum` crate. It shows the power of the bdk tools (`chain` + `file_store` + `electrum`), without depending on the main `bdk` library.
+- [`example_esplora`](./example-crates/example_esplora): A command line Bitcoin wallet application built on top of `example_cli` and the `esplora` crate. It shows the power of the bdk tools (`chain` + `file_store` + `esplora`), without depending on the main `bdk` library.
+- [`example_bitcoind_rpc_polling`](./example-crates/example_bitcoind_rpc_polling): A command line Bitcoin wallet application built on top of `example_cli` and the `bitcoind_rpc` crate. It shows the power of the bdk tools (`chain` + `file_store` + `bitcoind_rpc`), without depending on the main `bdk` library.
 - [`wallet_esplora_blocking`](./example-crates/wallet_esplora_blocking): Uses the `Wallet` to sync and spend using the Esplora blocking interface.
 - [`wallet_esplora_async`](./example-crates/wallet_esplora_async): Uses the `Wallet` to sync and spend using the Esplora asynchronous interface.
 - [`wallet_electrum`](./example-crates/wallet_electrum): Uses the `Wallet` to sync and spend using Electrum.
@@ -60,51 +62,19 @@ Fully working examples of how to use these components are in `/example-crates`:
 [`bdk_chain`]: https://docs.rs/bdk-chain/
 
 ## Minimum Supported Rust Version (MSRV)
-This library should compile with any combination of features with Rust 1.57.0.
+This library should compile with any combination of features with Rust 1.63.0.
 
 To build with the MSRV you will need to pin dependencies as follows:
 
 ```shell
-# log 0.4.19 has MSRV 1.60.0+
-cargo update -p log --precise "0.4.18"
-# tempfile 3.7.0 has MSRV 1.63.0+
-cargo update -p tempfile --precise "3.6.0"
-# reqwest 0.11.19 has MSRV 1.63.0+
-cargo update -p reqwest --precise "0.11.18"
-# hyper-rustls 0.24.1 has MSRV 1.60.0+
-cargo update -p hyper-rustls --precise 0.24.0
-# rustls 0.21.7 has MSRV 1.60.0+
-cargo update -p rustls:0.21.9 --precise "0.21.1"
-# rustls 0.20.9 has MSRV 1.60.0+
-cargo update -p rustls:0.20.9 --precise "0.20.8"
-# tokio 1.33 has MSRV 1.63.0+
-cargo update -p tokio --precise "1.29.1"
-# tokio-util 0.7.9 doesn't build with MSRV 1.57.0
-cargo update -p tokio-util --precise "0.7.8"
-# flate2 1.0.27 has MSRV 1.63.0+
-cargo update -p flate2 --precise "1.0.26"
-# h2 0.3.21 has MSRV 1.63.0+
-cargo update -p h2 --precise "0.3.20"
-# rustls-webpki 0.100.3 has MSRV 1.60.0+
-cargo update -p rustls-webpki:0.100.3 --precise "0.100.1"
-# rustls-webpki 0.101.2 has MSRV 1.60.0+
-cargo update -p rustls-webpki:0.101.7 --precise "0.101.1"
-# zip 0.6.6 has MSRV 1.59.0+
+# zip 0.6.3 has MSRV 1.64.0
 cargo update -p zip --precise "0.6.2"
-# time 0.3.14 has MSRV 1.59.0+
-cargo update -p time --precise "0.3.13"
-# byteorder 1.5.0 has MSRV 1.60.0+
-cargo update -p byteorder --precise "1.4.3"
-# webpki 0.22.4 requires `ring:0.17.2` which has MSRV 1.61.0+
-cargo update -p webpki --precise "0.22.2"
-# os_str_bytes 6.6.0 has MSRV 1.61.0+
-cargo update -p os_str_bytes --precise 6.5.1
-# sct 0.7.1 has MSRV 1.61.0+
-cargo update -p sct --precise 0.7.0
-# cc 1.0.82 has MSRV 1.61.0+
-cargo update -p cc --precise "1.0.81"
-# jobserver 0.1.27 has MSRV 1.66.0+
+# time 0.3.21 has MSRV 1.65.0
+cargo update -p time --precise "0.3.20"
+# jobserver 0.1.27 has MSRV 1.66.0
 cargo update -p jobserver --precise "0.1.26"
+# home 0.5.9 has MSRV 1.70.0
+cargo update -p home --precise "0.5.5"
 ```
 
 ## License

clippy.toml

@@ -1 +1 @@
-msrv="1.57.0"
+msrv="1.63.0"

crates/bdk/Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 name = "bdk"
 homepage = "https://bitcoindevkit.org"
-version = "1.0.0-alpha.2"
+version = "1.0.0-alpha.5"
 repository = "https://github.com/bitcoindevkit/bdk"
 documentation = "https://docs.rs/bdk"
 description = "A modern, lightweight, descriptor-based wallet library"
@@ -10,7 +10,7 @@ readme = "README.md"
 license = "MIT OR Apache-2.0"
 authors = ["Bitcoin Dev Kit Developers"]
 edition = "2021"
-rust-version = "1.57"
+rust-version = "1.63"
 
 [dependencies]
 rand = "^0.8"
@@ -18,11 +18,10 @@ miniscript = { version = "10.0.0", features = ["serde"], default-features = fals
 bitcoin = { version = "0.30.0", features = ["serde", "base64", "rand-std"], default-features = false }
 serde = { version = "^1.0", features = ["derive"] }
 serde_json = { version = "^1.0" }
-bdk_chain = { path = "../chain", version = "0.6.0", features = ["miniscript", "serde"], default-features = false }
+bdk_chain = { path = "../chain", version = "0.9.0", features = ["miniscript", "serde"], default-features = false }
 
 # Optional dependencies
-hwi = { version = "0.7.0", optional = true, features = [ "miniscript"] }
-bip39 = { version = "1.0.1", optional = true }
+bip39 = { version = "2.0", optional = true }
 
 [target.'cfg(target_arch = "wasm32")'.dependencies]
 getrandom = "0.2"
@@ -34,8 +33,6 @@ std = ["bitcoin/std", "miniscript/std", "bdk_chain/std"]
 compiler = ["miniscript/compiler"]
 all-keys = ["keys-bip39"]
 keys-bip39 = ["bip39"]
-hardware-signer = ["hwi"]
-test-hardware-signer = ["hardware-signer"]
 
 # This feature is used to run `cargo check` in our CI targeting wasm. It's not recommended
 # for libraries to explicitly include the "getrandom/js" feature, so we only do it when

crates/bdk/README.md

@@ -13,7 +13,7 @@
     <a href="https://github.com/bitcoindevkit/bdk/actions?query=workflow%3ACI"><img alt="CI Status" src="https://github.com/bitcoindevkit/bdk/workflows/CI/badge.svg"></a>
     <a href="https://coveralls.io/github/bitcoindevkit/bdk?branch=master"><img src="https://coveralls.io/repos/github/bitcoindevkit/bdk/badge.svg?branch=master"/></a>
     <a href="https://docs.rs/bdk"><img alt="API Docs" src="https://img.shields.io/badge/docs.rs-bdk-green"/></a>
-    <a href="https://blog.rust-lang.org/2021/12/02/Rust-1.57.0.html"><img alt="Rustc Version 1.57.0+" src="https://img.shields.io/badge/rustc-1.57.0%2B-lightgrey.svg"/></a>
+    <a href="https://blog.rust-lang.org/2022/08/11/Rust-1.63.0.html"><img alt="Rustc Version 1.63.0+" src="https://img.shields.io/badge/rustc-1.63.0%2B-lightgrey.svg"/></a>
     <a href="https://discord.gg/d7NkDKm"><img alt="Chat on Discord" src="https://img.shields.io/discord/753336465005608961?logo=discord"></a>
   </p>
 

crates/bdk/examples/mnemonic_to_descriptors.rs

@@ -33,8 +33,8 @@ fn main() -> Result<(), anyhow::Error> {
     let mnemonic_with_passphrase = (mnemonic, None);
 
     // define external and internal derivation key path
-    let external_path = DerivationPath::from_str("m/86h/0h/0h/0").unwrap();
-    let internal_path = DerivationPath::from_str("m/86h/0h/0h/1").unwrap();
+    let external_path = DerivationPath::from_str("m/86h/1h/0h/0").unwrap();
+    let internal_path = DerivationPath::from_str("m/86h/1h/0h/1").unwrap();
 
     // generate external and internal descriptor from mnemonic
     let (external_descriptor, ext_keymap) =

crates/bdk/src/descriptor/checksum.rs

@@ -42,22 +42,16 @@ fn poly_mod(mut c: u64, val: u64) -> u64 {
     c
 }
 
-/// Computes the checksum bytes of a descriptor.
-/// `exclude_hash = true` ignores all data after the first '#' (inclusive).
-pub(crate) fn calc_checksum_bytes_internal(
-    mut desc: &str,
-    exclude_hash: bool,
-) -> Result<[u8; 8], DescriptorError> {
+/// Compute the checksum bytes of a descriptor, excludes any existing checksum in the descriptor string from the calculation
+pub fn calc_checksum_bytes(mut desc: &str) -> Result<[u8; 8], DescriptorError> {
     let mut c = 1;
     let mut cls = 0;
     let mut clscount = 0;
 
     let mut original_checksum = None;
-    if exclude_hash {
-        if let Some(split) = desc.split_once('#') {
-            desc = split.0;
-            original_checksum = Some(split.1);
-        }
+    if let Some(split) = desc.split_once('#') {
+        desc = split.0;
+        original_checksum = Some(split.1);
     }
 
     for ch in desc.as_bytes() {
@@ -95,39 +89,10 @@ pub(crate) fn calc_checksum_bytes_internal(
     Ok(checksum)
 }
 
-/// Compute the checksum bytes of a descriptor, excludes any existing checksum in the descriptor string from the calculation
-pub fn calc_checksum_bytes(desc: &str) -> Result<[u8; 8], DescriptorError> {
-    calc_checksum_bytes_internal(desc, true)
-}
-
 /// Compute the checksum of a descriptor, excludes any existing checksum in the descriptor string from the calculation
 pub fn calc_checksum(desc: &str) -> Result<String, DescriptorError> {
     // unsafe is okay here as the checksum only uses bytes in `CHECKSUM_CHARSET`
-    calc_checksum_bytes_internal(desc, true)
-        .map(|b| unsafe { String::from_utf8_unchecked(b.to_vec()) })
-}
-
-// TODO in release 0.25.0, remove get_checksum_bytes and get_checksum
-// TODO in release 0.25.0, consolidate calc_checksum_bytes_internal into calc_checksum_bytes
-
-/// Compute the checksum bytes of a descriptor
-#[deprecated(
-    since = "0.24.0",
-    note = "Use new `calc_checksum_bytes` function which excludes any existing checksum in the descriptor string before calculating the checksum hash bytes. See https://github.com/bitcoindevkit/bdk/pull/765."
-)]
-pub fn get_checksum_bytes(desc: &str) -> Result<[u8; 8], DescriptorError> {
-    calc_checksum_bytes_internal(desc, false)
-}
-
-/// Compute the checksum of a descriptor
-#[deprecated(
-    since = "0.24.0",
-    note = "Use new `calc_checksum` function which excludes any existing checksum in the descriptor string before calculating the checksum hash. See https://github.com/bitcoindevkit/bdk/pull/765."
-)]
-pub fn get_checksum(desc: &str) -> Result<String, DescriptorError> {
-    // unsafe is okay here as the checksum only uses bytes in `CHECKSUM_CHARSET`
-    calc_checksum_bytes_internal(desc, false)
-        .map(|b| unsafe { String::from_utf8_unchecked(b.to_vec()) })
+    calc_checksum_bytes(desc).map(|b| unsafe { String::from_utf8_unchecked(b.to_vec()) })
 }
 
 #[cfg(test)]

crates/bdk/src/descriptor/template.rs

@@ -575,7 +575,7 @@ mod test {
 
         if let ExtendedDescriptor::Pkh(pkh) = xdesc.0 {
             let path: Vec<ChildNumber> = pkh.into_inner().full_derivation_path().unwrap().into();
-            let purpose = path.get(0).unwrap();
+            let purpose = path.first().unwrap();
             assert_matches!(purpose, Hardened { index: 44 });
             let coin_type = path.get(1).unwrap();
             assert_matches!(coin_type, Hardened { index: 0 });
@@ -589,7 +589,7 @@ mod test {
 
         if let ExtendedDescriptor::Pkh(pkh) = tdesc.0 {
             let path: Vec<ChildNumber> = pkh.into_inner().full_derivation_path().unwrap().into();
-            let purpose = path.get(0).unwrap();
+            let purpose = path.first().unwrap();
             assert_matches!(purpose, Hardened { index: 44 });
             let coin_type = path.get(1).unwrap();
             assert_matches!(coin_type, Hardened { index: 1 });

crates/bdk/src/lib.rs

@@ -17,8 +17,6 @@ extern crate std;
 pub extern crate alloc;
 
 pub extern crate bitcoin;
-#[cfg(feature = "hardware-signer")]
-pub extern crate hwi;
 pub extern crate miniscript;
 extern crate serde;
 extern crate serde_json;

crates/bdk/src/wallet/coin_selection.rs

@@ -100,6 +100,7 @@
 //! # Ok::<(), anyhow::Error>(())
 //! ```
 
+use crate::chain::collections::HashSet;
 use crate::types::FeeRate;
 use crate::wallet::utils::IsDust;
 use crate::Utxo;
@@ -107,6 +108,7 @@ use crate::WeightedUtxo;
 
 use alloc::vec::Vec;
 use bitcoin::consensus::encode::serialize;
+use bitcoin::OutPoint;
 use bitcoin::{Script, Weight};
 
 use core::convert::TryInto;
@@ -711,6 +713,25 @@ impl BranchAndBoundCoinSelection {
     }
 }
 
+/// Remove duplicate UTXOs.
+///
+/// If a UTXO appears in both `required` and `optional`, the appearance in `required` is kept.
+pub(crate) fn filter_duplicates<I>(required: I, optional: I) -> (I, I)
+where
+    I: IntoIterator<Item = WeightedUtxo> + FromIterator<WeightedUtxo>,
+{
+    let mut visited = HashSet::<OutPoint>::new();
+    let required = required
+        .into_iter()
+        .filter(|utxo| visited.insert(utxo.utxo.outpoint()))
+        .collect::<I>();
+    let optional = optional
+        .into_iter()
+        .filter(|utxo| visited.insert(utxo.utxo.outpoint()))
+        .collect::<I>();
+    (required, optional)
+}
+
 #[cfg(test)]
 mod test {
     use assert_matches::assert_matches;
@@ -721,6 +742,7 @@ mod test {
 
     use super::*;
     use crate::types::*;
+    use crate::wallet::coin_selection::filter_duplicates;
     use crate::wallet::Vbytes;
 
     use rand::rngs::StdRng;
@@ -799,13 +821,14 @@ mod test {
 
     fn generate_random_utxos(rng: &mut StdRng, utxos_number: usize) -> Vec<WeightedUtxo> {
         let mut res = Vec::new();
-        for _ in 0..utxos_number {
+        for i in 0..utxos_number {
             res.push(WeightedUtxo {
                 satisfaction_weight: P2WPKH_SATISFACTION_SIZE,
                 utxo: Utxo::Local(LocalOutput {
-                    outpoint: OutPoint::from_str(
-                        "ebd9813ecebc57ff8f30797de7c205e3c7498ca950ea4341ee51a685ff2fa30a:0",
-                    )
+                    outpoint: OutPoint::from_str(&format!(
+                        "ebd9813ecebc57ff8f30797de7c205e3c7498ca950ea4341ee51a685ff2fa30a:{}",
+                        i
+                    ))
                     .unwrap(),
                     txout: TxOut {
                         value: rng.gen_range(0..200000000),
@@ -829,24 +852,26 @@ mod test {
     }
 
     fn generate_same_value_utxos(utxos_value: u64, utxos_number: usize) -> Vec<WeightedUtxo> {
-        let utxo = WeightedUtxo {
-            satisfaction_weight: P2WPKH_SATISFACTION_SIZE,
-            utxo: Utxo::Local(LocalOutput {
-                outpoint: OutPoint::from_str(
-                    "ebd9813ecebc57ff8f30797de7c205e3c7498ca950ea4341ee51a685ff2fa30a:0",
-                )
-                .unwrap(),
-                txout: TxOut {
-                    value: utxos_value,
-                    script_pubkey: ScriptBuf::new(),
-                },
-                keychain: KeychainKind::External,
-                is_spent: false,
-                derivation_index: 42,
-                confirmation_time: ConfirmationTime::Unconfirmed { last_seen: 0 },
-            }),
-        };
-        vec![utxo; utxos_number]
+        (0..utxos_number)
+            .map(|i| WeightedUtxo {
+                satisfaction_weight: P2WPKH_SATISFACTION_SIZE,
+                utxo: Utxo::Local(LocalOutput {
+                    outpoint: OutPoint::from_str(&format!(
+                        "ebd9813ecebc57ff8f30797de7c205e3c7498ca950ea4341ee51a685ff2fa30a:{}",
+                        i
+                    ))
+                    .unwrap(),
+                    txout: TxOut {
+                        value: utxos_value,
+                        script_pubkey: ScriptBuf::new(),
+                    },
+                    keychain: KeychainKind::External,
+                    is_spent: false,
+                    derivation_index: 42,
+                    confirmation_time: ConfirmationTime::Unconfirmed { last_seen: 0 },
+                }),
+            })
+            .collect()
     }
 
     fn sum_random_utxos(mut rng: &mut StdRng, utxos: &mut Vec<WeightedUtxo>) -> u64 {
@@ -1478,4 +1503,95 @@ mod test {
             })
         );
     }
+
+    #[test]
+    fn test_filter_duplicates() {
+        fn utxo(txid: &str, value: u64) -> WeightedUtxo {
+            WeightedUtxo {
+                satisfaction_weight: 0,
+                utxo: Utxo::Local(LocalOutput {
+                    outpoint: OutPoint::new(bitcoin::hashes::Hash::hash(txid.as_bytes()), 0),
+                    txout: TxOut {
+                        value,
+                        script_pubkey: ScriptBuf::new(),
+                    },
+                    keychain: KeychainKind::External,
+                    is_spent: false,
+                    derivation_index: 0,
+                    confirmation_time: ConfirmationTime::Confirmed {
+                        height: 12345,
+                        time: 12345,
+                    },
+                }),
+            }
+        }
+
+        fn to_utxo_vec(utxos: &[(&str, u64)]) -> Vec<WeightedUtxo> {
+            let mut v = utxos
+                .iter()
+                .map(|&(txid, value)| utxo(txid, value))
+                .collect::<Vec<_>>();
+            v.sort_by_key(|u| u.utxo.outpoint());
+            v
+        }
+
+        struct TestCase<'a> {
+            name: &'a str,
+            required: &'a [(&'a str, u64)],
+            optional: &'a [(&'a str, u64)],
+            exp_required: &'a [(&'a str, u64)],
+            exp_optional: &'a [(&'a str, u64)],
+        }
+
+        let test_cases = [
+            TestCase {
+                name: "no_duplicates",
+                required: &[("A", 1000), ("B", 2100)],
+                optional: &[("C", 1000)],
+                exp_required: &[("A", 1000), ("B", 2100)],
+                exp_optional: &[("C", 1000)],
+            },
+            TestCase {
+                name: "duplicate_required_utxos",
+                required: &[("A", 3000), ("B", 1200), ("C", 1234), ("A", 3000)],
+                optional: &[("D", 2100)],
+                exp_required: &[("A", 3000), ("B", 1200), ("C", 1234)],
+                exp_optional: &[("D", 2100)],
+            },
+            TestCase {
+                name: "duplicate_optional_utxos",
+                required: &[("A", 3000), ("B", 1200)],
+                optional: &[("C", 5000), ("D", 1300), ("C", 5000)],
+                exp_required: &[("A", 3000), ("B", 1200)],
+                exp_optional: &[("C", 5000), ("D", 1300)],
+            },
+            TestCase {
+                name: "duplicate_across_required_and_optional_utxos",
+                required: &[("A", 3000), ("B", 1200), ("C", 2100)],
+                optional: &[("A", 3000), ("D", 1200), ("E", 5000)],
+                exp_required: &[("A", 3000), ("B", 1200), ("C", 2100)],
+                exp_optional: &[("D", 1200), ("E", 5000)],
+            },
+        ];
+
+        for (i, t) in test_cases.into_iter().enumerate() {
+            println!("Case {}: {}", i, t.name);
+            let (required, optional) =
+                filter_duplicates(to_utxo_vec(t.required), to_utxo_vec(t.optional));
+            assert_eq!(
+                required,
+                to_utxo_vec(t.exp_required),
+                "[{}:{}] unexpected `required` result",
+                i,
+                t.name
+            );
+            assert_eq!(
+                optional,
+                to_utxo_vec(t.exp_optional),
+                "[{}:{}] unexpected `optional` result",
+                i,
+                t.name
+            );
+        }
+    }
 }

crates/bdk/src/wallet/mod.rs

@@ -11,7 +11,7 @@
 
 //! Wallet
 //!
-//! This module defines the [`Wallet`] structure.
+//! This module defines the [`Wallet`].
 use crate::collections::{BTreeMap, HashMap, HashSet};
 use alloc::{
     boxed::Box,
@@ -23,7 +23,9 @@ pub use bdk_chain::keychain::Balance;
 use bdk_chain::{
     indexed_tx_graph,
     keychain::{self, KeychainTxOutIndex},
-    local_chain::{self, CannotConnectError, CheckPoint, CheckPointIter, LocalChain},
+    local_chain::{
+        self, ApplyHeaderError, CannotConnectError, CheckPoint, CheckPointIter, LocalChain,
+    },
     tx_graph::{CanonicalTx, TxGraph},
     Append, BlockId, ChainPosition, ConfirmationTime, ConfirmationTimeHeightAnchor, FullTxOut,
     IndexedTxGraph, Persist, PersistBackend,
@@ -31,8 +33,8 @@ use bdk_chain::{
 use bitcoin::secp256k1::{All, Secp256k1};
 use bitcoin::sighash::{EcdsaSighashType, TapSighashType};
 use bitcoin::{
-    absolute, Address, Network, OutPoint, Script, ScriptBuf, Sequence, Transaction, TxOut, Txid,
-    Weight, Witness,
+    absolute, Address, Block, Network, OutPoint, Script, ScriptBuf, Sequence, Transaction, TxOut,
+    Txid, Weight, Witness,
 };
 use bitcoin::{consensus::encode::serialize, BlockHash};
 use bitcoin::{constants::genesis_block, psbt};
@@ -50,10 +52,6 @@ pub mod tx_builder;
 pub(crate) mod utils;
 
 pub mod error;
-#[cfg(feature = "hardware-signer")]
-#[cfg_attr(docsrs, doc(cfg(feature = "hardware-signer")))]
-pub mod hardwaresigner;
-
 pub use utils::IsDust;
 
 #[allow(deprecated)]
@@ -77,7 +75,7 @@ const COINBASE_MATURITY: u32 = 100;
 
 /// A Bitcoin wallet
 ///
-/// The `Wallet` struct acts as a way of coherently interfacing with output descriptors and related transactions.
+/// The `Wallet` acts as a way of coherently interfacing with output descriptors and related transactions.
 /// Its main components are:
 ///
 /// 1. output *descriptors* from which it can derive addresses.
@@ -237,6 +235,7 @@ impl Wallet {
         network: Network,
     ) -> Result<Self, DescriptorError> {
         Self::new(descriptor, change_descriptor, (), network).map_err(|e| match e {
+            NewError::NonEmptyDatabase => unreachable!("mock-database cannot have data"),
             NewError::Descriptor(e) => e,
             NewError::Write(_) => unreachable!("mock-write must always succeed"),
         })
@@ -251,6 +250,7 @@ impl Wallet {
     ) -> Result<Self, crate::descriptor::DescriptorError> {
         Self::new_with_genesis_hash(descriptor, change_descriptor, (), network, genesis_hash)
             .map_err(|e| match e {
+                NewError::NonEmptyDatabase => unreachable!("mock-database cannot have data"),
                 NewError::Descriptor(e) => e,
                 NewError::Write(_) => unreachable!("mock-write must always succeed"),
             })
@@ -264,6 +264,11 @@ where
     /// Infallibly return a derived address using the external descriptor, see [`AddressIndex`] for
     /// available address index selection strategies. If none of the keys in the descriptor are derivable
     /// (i.e. does not end with /*) then the same address will always be returned for any [`AddressIndex`].
+    ///
+    /// # Panics
+    ///
+    /// This panics when the caller requests for an address of derivation index greater than the
+    /// BIP32 max index.
     pub fn get_address(&mut self, address_index: AddressIndex) -> AddressInfo {
         self.try_get_address(address_index).unwrap()
     }
@@ -275,6 +280,11 @@ where
     /// see [`AddressIndex`] for available address index selection strategies. If none of the keys
     /// in the descriptor are derivable (i.e. does not end with /*) then the same address will always
     /// be returned for any [`AddressIndex`].
+    ///
+    /// # Panics
+    ///
+    /// This panics when the caller requests for an address of derivation index greater than the
+    /// BIP32 max index.
     pub fn get_internal_address(&mut self, address_index: AddressIndex) -> AddressInfo {
         self.try_get_internal_address(address_index).unwrap()
     }
@@ -288,6 +298,8 @@ where
 /// [`new_with_genesis_hash`]: Wallet::new_with_genesis_hash
 #[derive(Debug)]
 pub enum NewError<W> {
+    /// Database already has data.
+    NonEmptyDatabase,
     /// There was problem with the passed-in descriptor(s).
     Descriptor(crate::descriptor::DescriptorError),
     /// We were unable to write the wallet's data to the persistence backend.
@@ -300,6 +312,10 @@ where
 {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
+            NewError::NonEmptyDatabase => write!(
+                f,
+                "database already has data - use `load` or `new_or_load` methods instead"
+            ),
             NewError::Descriptor(e) => e.fmt(f),
             NewError::Write(e) => e.fmt(f),
         }
@@ -348,7 +364,7 @@ where
 #[cfg(feature = "std")]
 impl<L> std::error::Error for LoadError<L> where L: core::fmt::Display + core::fmt::Debug {}
 
-/// Error type for when we try load a [`Wallet`] from persistence and creating it if non-existant.
+/// Error type for when we try load a [`Wallet`] from persistence and creating it if non-existent.
 ///
 /// Methods [`new_or_load`] and [`new_or_load_with_genesis_hash`] may return this error.
 ///
@@ -424,6 +440,55 @@ pub enum InsertTxError {
     },
 }
 
+impl fmt::Display for InsertTxError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            InsertTxError::ConfirmationHeightCannotBeGreaterThanTip {
+                tip_height,
+                tx_height,
+            } => {
+                write!(f, "cannot insert tx with confirmation height ({}) higher than internal tip height ({})", tx_height, tip_height)
+            }
+        }
+    }
+}
+
+#[cfg(feature = "std")]
+impl std::error::Error for InsertTxError {}
+
+/// An error that may occur when applying a block to [`Wallet`].
+#[derive(Debug)]
+pub enum ApplyBlockError {
+    /// Occurs when the update chain cannot connect with original chain.
+    CannotConnect(CannotConnectError),
+    /// Occurs when the `connected_to` hash does not match the hash derived from `block`.
+    UnexpectedConnectedToHash {
+        /// Block hash of `connected_to`.
+        connected_to_hash: BlockHash,
+        /// Expected block hash of `connected_to`, as derived from `block`.
+        expected_hash: BlockHash,
+    },
+}
+
+impl fmt::Display for ApplyBlockError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            ApplyBlockError::CannotConnect(err) => err.fmt(f),
+            ApplyBlockError::UnexpectedConnectedToHash {
+                expected_hash: block_hash,
+                connected_to_hash: checkpoint_hash,
+            } => write!(
+                f,
+                "`connected_to` hash {} differs from the expected hash {} (which is derived from `block`)",
+                checkpoint_hash, block_hash
+            ),
+        }
+    }
+}
+
+#[cfg(feature = "std")]
+impl std::error::Error for ApplyBlockError {}
+
 impl<D> Wallet<D> {
     /// Initialize an empty [`Wallet`].
     pub fn new<E: IntoWalletDescriptor>(
@@ -446,13 +511,18 @@ impl<D> Wallet<D> {
     pub fn new_with_genesis_hash<E: IntoWalletDescriptor>(
         descriptor: E,
         change_descriptor: Option<E>,
-        db: D,
+        mut db: D,
         network: Network,
         genesis_hash: BlockHash,
     ) -> Result<Self, NewError<D::WriteError>>
     where
         D: PersistBackend<ChangeSet>,
     {
+        if let Ok(changeset) = db.load_from_persistence() {
+            if changeset.is_some() {
+                return Err(NewError::NonEmptyDatabase);
+            }
+        }
         let secp = Secp256k1::new();
         let (chain, chain_changeset) = LocalChain::from_genesis_hash(genesis_hash);
         let mut index = KeychainTxOutIndex::<KeychainKind>::default();
@@ -517,7 +587,9 @@ impl<D> Wallet<D> {
             create_signers(&mut index, &secp, descriptor, change_descriptor, network)
                 .map_err(LoadError::Descriptor)?;
 
-        let indexed_graph = IndexedTxGraph::new(index);
+        let mut indexed_graph = IndexedTxGraph::new(index);
+        indexed_graph.apply_changeset(changeset.indexed_tx_graph);
+
         let persist = Persist::new(db);
 
         Ok(Wallet {
@@ -613,6 +685,9 @@ impl<D> Wallet<D> {
                 genesis_hash,
             )
             .map_err(|e| match e {
+                NewError::NonEmptyDatabase => {
+                    unreachable!("database is already checked to have no data")
+                }
                 NewError::Descriptor(e) => NewOrLoadError::Descriptor(e),
                 NewError::Write(e) => NewOrLoadError::Write(e),
             }),
@@ -635,6 +710,11 @@ impl<D> Wallet<D> {
     ///
     /// A `PersistBackend<ChangeSet>::WriteError` will result if unable to persist the new address
     /// to the `PersistBackend`.
+    ///
+    /// # Panics
+    ///
+    /// This panics when the caller requests for an address of derivation index greater than the
+    /// BIP32 max index.
     pub fn try_get_address(
         &mut self,
         address_index: AddressIndex,
@@ -655,6 +735,11 @@ impl<D> Wallet<D> {
     /// see [`AddressIndex`] for available address index selection strategies. If none of the keys
     /// in the descriptor are derivable (i.e. does not end with /*) then the same address will always
     /// be returned for any [`AddressIndex`].
+    ///
+    /// # Panics
+    ///
+    /// This panics when the caller requests for an address of derivation index greater than the
+    /// BIP32 max index.
     pub fn try_get_internal_address(
         &mut self,
         address_index: AddressIndex,
@@ -677,6 +762,11 @@ impl<D> Wallet<D> {
     /// See [`AddressIndex`] for available address index selection strategies. If none of the keys
     /// in the descriptor are derivable (i.e. does not end with /*) then the same address will
     /// always be returned for any [`AddressIndex`].
+    ///
+    /// # Panics
+    ///
+    /// This panics when the caller requests for an address of derivation index greater than the
+    /// BIP32 max index.
     fn _get_address(
         &mut self,
         keychain: KeychainKind,
@@ -696,12 +786,14 @@ impl<D> Wallet<D> {
                 let ((index, spk), index_changeset) = txout_index.next_unused_spk(&keychain);
                 (index, spk.into(), Some(index_changeset))
             }
-            AddressIndex::Peek(index) => {
-                let (index, spk) = txout_index
-                    .spks_of_keychain(&keychain)
-                    .take(index as usize + 1)
-                    .last()
-                    .unwrap();
+            AddressIndex::Peek(mut peek_index) => {
+                let mut spk_iter = txout_index.unbounded_spk_iter(&keychain);
+                if !spk_iter.descriptor().has_wildcard() {
+                    peek_index = 0;
+                }
+                let (index, spk) = spk_iter
+                    .nth(peek_index as usize)
+                    .expect("derivation index is out of bounds");
                 (index, spk, None)
             }
         };
@@ -731,7 +823,7 @@ impl<D> Wallet<D> {
     ///
     /// Will only return `Some(_)` if the wallet has given out the spk.
     pub fn derivation_of_spk(&self, spk: &Script) -> Option<(KeychainKind, u32)> {
-        self.indexed_graph.index.index_of_spk(spk).copied()
+        self.indexed_graph.index.index_of_spk(spk)
     }
 
     /// Return the list of unspent outputs of this wallet
@@ -770,7 +862,7 @@ impl<D> Wallet<D> {
         self.chain.tip()
     }
 
-    /// Returns a iterators of all the script pubkeys for the `Internal` and External` variants in `KeychainKind`.
+    /// Get unbounded script pubkey iterators for both `Internal` and `External` keychains.
     ///
     /// This is intended to be used when doing a full scan of your addresses (e.g. after restoring
     /// from seed words). You pass the `BTreeMap` of iterators to a blockchain data source (e.g.
@@ -778,36 +870,36 @@ impl<D> Wallet<D> {
     ///
     /// Note carefully that iterators go over **all** script pubkeys on the keychains (not what
     /// script pubkeys the wallet is storing internally).
-    pub fn spks_of_all_keychains(
+    pub fn all_unbounded_spk_iters(
         &self,
     ) -> BTreeMap<KeychainKind, impl Iterator<Item = (u32, ScriptBuf)> + Clone> {
-        self.indexed_graph.index.spks_of_all_keychains()
+        self.indexed_graph.index.all_unbounded_spk_iters()
     }
 
-    /// Gets an iterator over all the script pubkeys in a single keychain.
+    /// Get an unbounded script pubkey iterator for the given `keychain`.
     ///
-    /// See [`spks_of_all_keychains`] for more documentation
+    /// See [`all_unbounded_spk_iters`] for more documentation
     ///
-    /// [`spks_of_all_keychains`]: Self::spks_of_all_keychains
-    pub fn spks_of_keychain(
+    /// [`all_unbounded_spk_iters`]: Self::all_unbounded_spk_iters
+    pub fn unbounded_spk_iter(
         &self,
         keychain: KeychainKind,
     ) -> impl Iterator<Item = (u32, ScriptBuf)> + Clone {
-        self.indexed_graph.index.spks_of_keychain(&keychain)
+        self.indexed_graph.index.unbounded_spk_iter(&keychain)
     }
 
     /// Returns the utxo owned by this wallet corresponding to `outpoint` if it exists in the
     /// wallet's database.
     pub fn get_utxo(&self, op: OutPoint) -> Option<LocalOutput> {
-        let (&spk_i, _) = self.indexed_graph.index.txout(op)?;
+        let (keychain, index, _) = self.indexed_graph.index.txout(op)?;
         self.indexed_graph
             .graph()
             .filter_chain_unspents(
                 &self.chain,
                 self.chain.tip().block_id(),
-                core::iter::once((spk_i, op)),
+                core::iter::once(((), op)),
             )
-            .map(|((k, i), full_txo)| new_local_utxo(k, i, full_txo))
+            .map(|(_, full_txo)| new_local_utxo(keychain, index, full_txo))
             .next()
     }
 
@@ -900,12 +992,11 @@ impl<D> Wallet<D> {
         })
     }
 
-    /// Computes total input value going from script pubkeys in the index (sent) and the total output
-    /// value going to script pubkeys in the index (received) in `tx`.
+    /// Compute the `tx`'s sent and received amounts (in satoshis).
     ///
-    /// For the `sent` to be computed correctly, the outputs being spent must have already been
-    /// scanned by the index. Calculating received just uses the [`Transaction`] outputs directly,
-    /// so it will be correct even if it has not been scanned.
+    /// This method returns a tuple `(sent, received)`. Sent is the sum of the txin amounts
+    /// that spend from previous txouts tracked by this wallet. Received is the summation
+    /// of this tx's outputs that send to script pubkeys tracked by this wallet.
     ///
     /// # Examples
     ///
@@ -1445,7 +1536,7 @@ impl<D> Wallet<D> {
                 let ((index, spk), index_changeset) =
                     self.indexed_graph.index.next_unused_spk(&change_keychain);
                 let spk = spk.into();
-                self.indexed_graph.index.mark_used(&change_keychain, index);
+                self.indexed_graph.index.mark_used(change_keychain, index);
                 self.persist
                     .stage(ChangeSet::from(indexed_tx_graph::ChangeSet::from(
                         index_changeset,
@@ -1455,6 +1546,9 @@ impl<D> Wallet<D> {
             }
         };
 
+        let (required_utxos, optional_utxos) =
+            coin_selection::filter_duplicates(required_utxos, optional_utxos);
+
         let coin_selection = coin_selection.coin_select(
             required_utxos,
             optional_utxos,
@@ -1626,7 +1720,7 @@ impl<D> Wallet<D> {
                     .into();
 
                 let weighted_utxo = match txout_index.index_of_spk(&txout.script_pubkey) {
-                    Some(&(keychain, derivation_index)) => {
+                    Some((keychain, derivation_index)) => {
                         #[allow(deprecated)]
                         let satisfaction_weight = self
                             .get_descriptor_for_keychain(keychain)
@@ -1670,7 +1764,7 @@ impl<D> Wallet<D> {
             for (index, txout) in tx.output.iter().enumerate() {
                 let change_type = self.map_keychain(KeychainKind::Internal);
                 match txout_index.index_of_spk(&txout.script_pubkey) {
-                    Some(&(keychain, _)) if keychain == change_type => change_index = Some(index),
+                    Some((keychain, _)) if keychain == change_type => change_index = Some(index),
                     _ => {}
                 }
             }
@@ -1925,10 +2019,10 @@ impl<D> Wallet<D> {
     pub fn cancel_tx(&mut self, tx: &Transaction) {
         let txout_index = &mut self.indexed_graph.index;
         for txout in &tx.output {
-            if let Some(&(keychain, index)) = txout_index.index_of_spk(&txout.script_pubkey) {
+            if let Some((keychain, index)) = txout_index.index_of_spk(&txout.script_pubkey) {
                 // NOTE: unmark_used will **not** make something unused if it has actually been used
                 // by a tx in the tracker. It only removes the superficial marking.
-                txout_index.unmark_used(&keychain, index);
+                txout_index.unmark_used(keychain, index);
             }
         }
     }
@@ -1944,7 +2038,7 @@ impl<D> Wallet<D> {
     }
 
     fn get_descriptor_for_txout(&self, txout: &TxOut) -> Option<DerivedDescriptor> {
-        let &(keychain, child) = self
+        let (keychain, child) = self
             .indexed_graph
             .index
             .index_of_spk(&txout.script_pubkey)?;
@@ -2158,7 +2252,7 @@ impl<D> Wallet<D> {
     {
         // Try to find the prev_script in our db to figure out if this is internal or external,
         // and the derivation index
-        let &(keychain, child) = self
+        let (keychain, child) = self
             .indexed_graph
             .index
             .index_of_spk(&utxo.txout.script_pubkey)
@@ -2212,7 +2306,7 @@ impl<D> Wallet<D> {
 
         // Try to figure out the keychain and derivation for every input and output
         for (is_input, index, out) in utxos.into_iter() {
-            if let Some(&(keychain, child)) =
+            if let Some((keychain, child)) =
                 self.indexed_graph.index.index_of_spk(&out.script_pubkey)
             {
                 let desc = self.get_descriptor_for_keychain(keychain);
@@ -2288,7 +2382,7 @@ impl<D> Wallet<D> {
         self.persist.commit().map(|c| c.is_some())
     }
 
-    /// Returns the changes that will be staged with the next call to [`commit`].
+    /// Returns the changes that will be committed with the next call to [`commit`].
     ///
     /// [`commit`]: Self::commit
     pub fn staged(&self) -> &ChangeSet
@@ -2312,6 +2406,86 @@ impl<D> Wallet<D> {
     pub fn local_chain(&self) -> &LocalChain {
         &self.chain
     }
+
+    /// Introduces a `block` of `height` to the wallet, and tries to connect it to the
+    /// `prev_blockhash` of the block's header.
+    ///
+    /// This is a convenience method that is equivalent to calling [`apply_block_connected_to`]
+    /// with `prev_blockhash` and `height-1` as the `connected_to` parameter.
+    ///
+    /// [`apply_block_connected_to`]: Self::apply_block_connected_to
+    pub fn apply_block(&mut self, block: &Block, height: u32) -> Result<(), CannotConnectError>
+    where
+        D: PersistBackend<ChangeSet>,
+    {
+        let connected_to = match height.checked_sub(1) {
+            Some(prev_height) => BlockId {
+                height: prev_height,
+                hash: block.header.prev_blockhash,
+            },
+            None => BlockId {
+                height,
+                hash: block.block_hash(),
+            },
+        };
+        self.apply_block_connected_to(block, height, connected_to)
+            .map_err(|err| match err {
+                ApplyHeaderError::InconsistentBlocks => {
+                    unreachable!("connected_to is derived from the block so must be consistent")
+                }
+                ApplyHeaderError::CannotConnect(err) => err,
+            })
+    }
+
+    /// Applies relevant transactions from `block` of `height` to the wallet, and connects the
+    /// block to the internal chain.
+    ///
+    /// The `connected_to` parameter informs the wallet how this block connects to the internal
+    /// [`LocalChain`]. Relevant transactions are filtered from the `block` and inserted into the
+    /// internal [`TxGraph`].
+    pub fn apply_block_connected_to(
+        &mut self,
+        block: &Block,
+        height: u32,
+        connected_to: BlockId,
+    ) -> Result<(), ApplyHeaderError>
+    where
+        D: PersistBackend<ChangeSet>,
+    {
+        let mut changeset = ChangeSet::default();
+        changeset.append(
+            self.chain
+                .apply_header_connected_to(&block.header, height, connected_to)?
+                .into(),
+        );
+        changeset.append(
+            self.indexed_graph
+                .apply_block_relevant(block, height)
+                .into(),
+        );
+        self.persist.stage(changeset);
+        Ok(())
+    }
+
+    /// Apply relevant unconfirmed transactions to the wallet.
+    ///
+    /// Transactions that are not relevant are filtered out.
+    ///
+    /// This method takes in an iterator of `(tx, last_seen)` where `last_seen` is the timestamp of
+    /// when the transaction was last seen in the mempool. This is used for conflict resolution
+    /// when there is conflicting unconfirmed transactions. The transaction with the later
+    /// `last_seen` is prioritied.
+    pub fn apply_unconfirmed_txs<'t>(
+        &mut self,
+        unconfirmed_txs: impl IntoIterator<Item = (&'t Transaction, u64)>,
+    ) where
+        D: PersistBackend<ChangeSet>,
+    {
+        let indexed_graph_changeset = self
+            .indexed_graph
+            .batch_insert_relevant_unconfirmed(unconfirmed_txs);
+        self.persist.stage(ChangeSet::from(indexed_graph_changeset));
+    }
 }
 
 impl<D> AsRef<bdk_chain::tx_graph::TxGraph<ConfirmationTimeHeightAnchor>> for Wallet<D> {

crates/bdk/src/wallet/signer.rs

@@ -80,6 +80,7 @@
 //! ```
 
 use crate::collections::BTreeMap;
+use alloc::string::String;
 use alloc::sync::Arc;
 use alloc::vec::Vec;
 use core::cmp::Ordering;
@@ -162,16 +163,10 @@ pub enum SignerError {
     SighashError(sighash::Error),
     /// Miniscript PSBT error
     MiniscriptPsbt(MiniscriptPsbtError),
-    /// Error while signing using hardware wallets
-    #[cfg(feature = "hardware-signer")]
-    HWIError(hwi::error::Error),
-}
-
-#[cfg(feature = "hardware-signer")]
-impl From<hwi::error::Error> for SignerError {
-    fn from(e: hwi::error::Error) -> Self {
-        SignerError::HWIError(e)
-    }
+    /// To be used only by external libraries implementing [`InputSigner`] or
+    /// [`TransactionSigner`], so that they can return their own custom errors, without having to
+    /// modify [`SignerError`] in BDK.
+    External(String),
 }
 
 impl From<sighash::Error> for SignerError {
@@ -196,8 +191,7 @@ impl fmt::Display for SignerError {
             Self::InvalidSighash => write!(f, "Invalid SIGHASH for the signing context in use"),
             Self::SighashError(err) => write!(f, "Error while computing the hash to sign: {}", err),
             Self::MiniscriptPsbt(err) => write!(f, "Miniscript PSBT error: {}", err),
-            #[cfg(feature = "hardware-signer")]
-            Self::HWIError(err) => write!(f, "Error while signing using hardware wallets: {}", err),
+            Self::External(err) => write!(f, "{}", err),
         }
     }
 }
@@ -221,7 +215,7 @@ pub enum SignerContext {
     },
 }
 
-/// Wrapper structure to pair a signer with its context
+/// Wrapper to pair a signer with its context
 #[derive(Debug, Clone)]
 pub struct SignerWrapper<S: Sized + fmt::Debug + Clone> {
     signer: S,
@@ -812,9 +806,10 @@ pub struct SignOptions {
 }
 
 /// Customize which taproot script-path leaves the signer should sign.
-#[derive(Debug, Clone, PartialEq, Eq)]
+#[derive(Default, Debug, Clone, PartialEq, Eq)]
 pub enum TapLeavesOptions {
     /// The signer will sign all the leaves it has a key for.
+    #[default]
     All,
     /// The signer won't sign leaves other than the ones specified. Note that it could still ignore
     /// some of the specified leaves, if it doesn't have the right key to sign them.
@@ -825,12 +820,6 @@ pub enum TapLeavesOptions {
     None,
 }
 
-impl Default for TapLeavesOptions {
-    fn default() -> Self {
-        TapLeavesOptions::All
-    }
-}
-
 #[allow(clippy::derivable_impls)]
 impl Default for SignOptions {
     fn default() -> Self {

crates/bdk/src/wallet/tx_builder.rs

@@ -811,9 +811,10 @@ impl<'a, D> TxBuilder<'a, D, DefaultCoinSelectionAlgorithm, BumpFee> {
 }
 
 /// Ordering of the transaction's inputs and outputs
-#[derive(Debug, Ord, PartialOrd, Eq, PartialEq, Hash, Clone, Copy)]
+#[derive(Default, Debug, Ord, PartialOrd, Eq, PartialEq, Hash, Clone, Copy)]
 pub enum TxOrdering {
     /// Randomized (default)
+    #[default]
     Shuffle,
     /// Unchanged
     Untouched,
@@ -821,12 +822,6 @@ pub enum TxOrdering {
     Bip69Lexicographic,
 }
 
-impl Default for TxOrdering {
-    fn default() -> Self {
-        TxOrdering::Shuffle
-    }
-}
-
 impl TxOrdering {
     /// Sort transaction inputs and outputs by [`TxOrdering`] variant
     pub fn sort_tx(&self, tx: &mut Transaction) {
@@ -880,9 +875,10 @@ impl RbfValue {
 }
 
 /// Policy regarding the use of change outputs when creating a transaction
-#[derive(Debug, Ord, PartialOrd, Eq, PartialEq, Hash, Clone, Copy)]
+#[derive(Default, Debug, Ord, PartialOrd, Eq, PartialEq, Hash, Clone, Copy)]
 pub enum ChangeSpendPolicy {
     /// Use both change and non-change outputs (default)
+    #[default]
     ChangeAllowed,
     /// Only use change outputs (see [`TxBuilder::only_spend_change`])
     OnlyChange,
@@ -890,12 +886,6 @@ pub enum ChangeSpendPolicy {
     ChangeForbidden,
 }
 
-impl Default for ChangeSpendPolicy {
-    fn default() -> Self {
-        ChangeSpendPolicy::ChangeAllowed
-    }
-}
-
 impl ChangeSpendPolicy {
     pub(crate) fn is_satisfied_by(&self, utxo: &LocalOutput) -> bool {
         match self {

crates/bdk/tests/wallet.rs

@@ -7,8 +7,8 @@ use bdk::signer::{SignOptions, SignerError};
 use bdk::wallet::coin_selection::{self, LargestFirstCoinSelection};
 use bdk::wallet::error::CreateTxError;
 use bdk::wallet::tx_builder::AddForeignUtxoError;
-use bdk::wallet::AddressIndex::*;
 use bdk::wallet::{AddressIndex, AddressInfo, Balance, Wallet};
+use bdk::wallet::{AddressIndex::*, NewError};
 use bdk::{FeeRate, KeychainKind};
 use bdk_chain::COINBASE_MATURITY;
 use bdk_chain::{BlockId, ConfirmationTime};
@@ -71,19 +71,33 @@ fn load_recovers_wallet() {
     let file_path = temp_dir.path().join("store.db");
 
     // create new wallet
-    let wallet_keychains = {
+    let wallet_spk_index = {
         let db = bdk_file_store::Store::create_new(DB_MAGIC, &file_path).expect("must create db");
-        let wallet =
-            Wallet::new(get_test_wpkh(), None, db, Network::Testnet).expect("must init wallet");
-        wallet.keychains().clone()
+        let mut wallet = Wallet::new(get_test_tr_single_sig_xprv(), None, db, Network::Testnet)
+            .expect("must init wallet");
+
+        wallet.try_get_address(New).unwrap();
+        wallet.spk_index().clone()
     };
 
     // recover wallet
     {
         let db = bdk_file_store::Store::open(DB_MAGIC, &file_path).expect("must recover db");
-        let wallet = Wallet::load(get_test_wpkh(), None, db).expect("must recover wallet");
+        let wallet =
+            Wallet::load(get_test_tr_single_sig_xprv(), None, db).expect("must recover wallet");
         assert_eq!(wallet.network(), Network::Testnet);
-        assert_eq!(wallet.spk_index().keychains(), &wallet_keychains);
+        assert_eq!(wallet.spk_index().keychains(), wallet_spk_index.keychains());
+        assert_eq!(
+            wallet.spk_index().last_revealed_indices(),
+            wallet_spk_index.last_revealed_indices()
+        );
+    }
+
+    // `new` can only be called on empty db
+    {
+        let db = bdk_file_store::Store::open(DB_MAGIC, &file_path).expect("must recover db");
+        let result = Wallet::new(get_test_tr_single_sig_xprv(), None, db, Network::Testnet);
+        assert!(matches!(result, Err(NewError::NonEmptyDatabase)));
     }
 }
 
@@ -92,7 +106,7 @@ fn new_or_load() {
     let temp_dir = tempfile::tempdir().expect("must create tempdir");
     let file_path = temp_dir.path().join("store.db");
 
-    // init wallet when non-existant
+    // init wallet when non-existent
     let wallet_keychains = {
         let db = bdk_file_store::Store::open_or_create_new(DB_MAGIC, &file_path)
             .expect("must create db");
@@ -3577,41 +3591,6 @@ fn test_fee_rate_sign_grinding_low_r() {
     assert_fee_rate!(psbt, fee.unwrap_or(0), fee_rate);
 }
 
-// #[cfg(feature = "test-hardware-signer")]
-// #[test]
-// fn test_hardware_signer() {
-//     use std::sync::Arc;
-//
-//     use bdk::signer::SignerOrdering;
-//     use bdk::wallet::hardwaresigner::HWISigner;
-//     use hwi::types::HWIChain;
-//     use hwi::HWIClient;
-//
-//     let mut devices = HWIClient::enumerate().unwrap();
-//     if devices.is_empty() {
-//         panic!("No devices found!");
-//     }
-//     let device = devices.remove(0).unwrap();
-//     let client = HWIClient::get_client(&device, true, HWIChain::Regtest).unwrap();
-//     let descriptors = client.get_descriptors::<String>(None).unwrap();
-//     let custom_signer = HWISigner::from_device(&device, HWIChain::Regtest).unwrap();
-//
-//     let (mut wallet, _) = get_funded_wallet(&descriptors.internal[0]);
-//     wallet.add_signer(
-//         KeychainKind::External,
-//         SignerOrdering(200),
-//         Arc::new(custom_signer),
-//     );
-//
-//     let addr = wallet.get_address(LastUnused);
-//     let mut builder = wallet.build_tx();
-//     builder.drain_to(addr.script_pubkey()).drain_wallet();
-//     let (mut psbt, _) = builder.finish().unwrap();
-//
-//     let finalized = wallet.sign(&mut psbt, Default::default()).unwrap();
-//     assert!(finalized);
-// }
-
 #[test]
 fn test_taproot_load_descriptor_duplicated_keys() {
     // Added after issue https://github.com/bitcoindevkit/bdk/issues/760

crates/bitcoind_rpc/Cargo.toml

@@ -1,8 +1,8 @@
 [package]
 name = "bdk_bitcoind_rpc"
-version = "0.1.0"
+version = "0.4.0"
 edition = "2021"
-rust-version = "1.57"
+rust-version = "1.63"
 homepage = "https://bitcoindevkit.org"
 repository = "https://github.com/bitcoindevkit/bdk"
 documentation = "https://docs.rs/bdk_bitcoind_rpc"
@@ -16,7 +16,7 @@ readme = "README.md"
 # For no-std, remember to enable the bitcoin/no-std feature
 bitcoin = { version = "0.30", default-features = false }
 bitcoincore-rpc = { version = "0.17" }
-bdk_chain = { path = "../chain", version = "0.6", default-features = false }
+bdk_chain = { path = "../chain", version = "0.9", default-features = false }
 
 [dev-dependencies]
 bitcoind = { version = "0.33", features = ["25_0"] }

crates/bitcoind_rpc/src/lib.rs

@@ -14,7 +14,7 @@ use bitcoin::{block::Header, Block, BlockHash, Transaction};
 pub use bitcoincore_rpc;
 use bitcoincore_rpc::bitcoincore_rpc_json;
 
-/// A structure that emits data sourced from [`bitcoincore_rpc::Client`].
+/// The [`Emitter`] is used to emit data sourced from [`bitcoincore_rpc::Client`].
 ///
 /// Refer to [module-level documentation] for more.
 ///
@@ -43,11 +43,13 @@ pub struct Emitter<'c, C> {
 }
 
 impl<'c, C: bitcoincore_rpc::RpcApi> Emitter<'c, C> {
-    /// Construct a new [`Emitter`] with the given RPC `client`, `last_cp` and `start_height`.
+    /// Construct a new [`Emitter`].
     ///
-    /// * `last_cp` is the check point used to find the latest block which is still part of the best
-    ///   chain.
-    /// * `start_height` is the block height to start emitting blocks from.
+    /// `last_cp` informs the emitter of the chain we are starting off with. This way, the emitter
+    /// can start emission from a block that connects to the original chain.
+    ///
+    /// `start_height` starts emission from a given height (if there are no conflicts with the
+    /// original chain).
     pub fn new(client: &'c C, last_cp: CheckPoint, start_height: u32) -> Self {
         Self {
             client,
@@ -127,13 +129,58 @@ impl<'c, C: bitcoincore_rpc::RpcApi> Emitter<'c, C> {
     }
 
     /// Emit the next block height and header (if any).
-    pub fn next_header(&mut self) -> Result<Option<(u32, Header)>, bitcoincore_rpc::Error> {
-        poll(self, |hash| self.client.get_block_header(hash))
+    pub fn next_header(&mut self) -> Result<Option<BlockEvent<Header>>, bitcoincore_rpc::Error> {
+        Ok(poll(self, |hash| self.client.get_block_header(hash))?
+            .map(|(checkpoint, block)| BlockEvent { block, checkpoint }))
     }
 
     /// Emit the next block height and block (if any).
-    pub fn next_block(&mut self) -> Result<Option<(u32, Block)>, bitcoincore_rpc::Error> {
-        poll(self, |hash| self.client.get_block(hash))
+    pub fn next_block(&mut self) -> Result<Option<BlockEvent<Block>>, bitcoincore_rpc::Error> {
+        Ok(poll(self, |hash| self.client.get_block(hash))?
+            .map(|(checkpoint, block)| BlockEvent { block, checkpoint }))
+    }
+}
+
+/// A newly emitted block from [`Emitter`].
+#[derive(Debug)]
+pub struct BlockEvent<B> {
+    /// Either a full [`Block`] or [`Header`] of the new block.
+    pub block: B,
+
+    /// The checkpoint of the new block.
+    ///
+    /// A [`CheckPoint`] is a node of a linked list of [`BlockId`]s. This checkpoint is linked to
+    /// all [`BlockId`]s originally passed in [`Emitter::new`] as well as emitted blocks since then.
+    /// These blocks are guaranteed to be of the same chain.
+    ///
+    /// This is important as BDK structures require block-to-apply to be connected with another
+    /// block in the original chain.
+    pub checkpoint: CheckPoint,
+}
+
+impl<B> BlockEvent<B> {
+    /// The block height of this new block.
+    pub fn block_height(&self) -> u32 {
+        self.checkpoint.height()
+    }
+
+    /// The block hash of this new block.
+    pub fn block_hash(&self) -> BlockHash {
+        self.checkpoint.hash()
+    }
+
+    /// The [`BlockId`] of a previous block that this block connects to.
+    ///
+    /// This either returns a [`BlockId`] of a previously emitted block or from the chain we started
+    /// with (passed in as `last_cp` in [`Emitter::new`]).
+    ///
+    /// This value is derived from [`BlockEvent::checkpoint`].
+    pub fn connected_to(&self) -> BlockId {
+        match self.checkpoint.prev() {
+            Some(prev_cp) => prev_cp.block_id(),
+            // there is no previous checkpoint, so just connect with itself
+            None => self.checkpoint.block_id(),
+        }
     }
 }
 
@@ -203,7 +250,7 @@ where
 fn poll<C, V, F>(
     emitter: &mut Emitter<C>,
     get_item: F,
-) -> Result<Option<(u32, V)>, bitcoincore_rpc::Error>
+) -> Result<Option<(CheckPoint, V)>, bitcoincore_rpc::Error>
 where
     C: bitcoincore_rpc::RpcApi,
     F: Fn(&BlockHash) -> Result<V, bitcoincore_rpc::Error>,
@@ -215,13 +262,14 @@ where
                 let hash = res.hash;
                 let item = get_item(&hash)?;
 
-                emitter.last_cp = emitter
+                let new_cp = emitter
                     .last_cp
                     .clone()
                     .push(BlockId { height, hash })
                     .expect("must push");
+                emitter.last_cp = new_cp.clone();
                 emitter.last_block = Some(res);
-                return Ok(Some((height, item)));
+                return Ok(Some((new_cp, item)));
             }
             PollResponse::NoMoreBlocks => {
                 emitter.last_block = None;

crates/bitcoind_rpc/tests/test_emitter.rs

@@ -157,28 +157,6 @@ impl TestEnv {
     }
 }
 
-fn block_to_chain_update(block: &bitcoin::Block, height: u32) -> local_chain::Update {
-    let this_id = BlockId {
-        height,
-        hash: block.block_hash(),
-    };
-    let tip = if block.header.prev_blockhash == BlockHash::all_zeros() {
-        CheckPoint::new(this_id)
-    } else {
-        CheckPoint::new(BlockId {
-            height: height - 1,
-            hash: block.header.prev_blockhash,
-        })
-        .extend(core::iter::once(this_id))
-        .expect("must construct checkpoint")
-    };
-
-    local_chain::Update {
-        tip,
-        introduce_older_blocks: false,
-    }
-}
-
 /// Ensure that blocks are emitted in order even after reorg.
 ///
 /// 1. Mine 101 blocks.
@@ -200,17 +178,21 @@ pub fn test_sync_local_chain() -> anyhow::Result<()> {
 
     // see if the emitter outputs the right blocks
     println!("first sync:");
-    while let Some((height, block)) = emitter.next_block()? {
+    while let Some(emission) = emitter.next_block()? {
+        let height = emission.block_height();
+        let hash = emission.block_hash();
         assert_eq!(
-            block.block_hash(),
+            emission.block_hash(),
             exp_hashes[height as usize],
             "emitted block hash is unexpected"
         );
 
-        let chain_update = block_to_chain_update(&block, height);
         assert_eq!(
-            local_chain.apply_update(chain_update)?,
-            BTreeMap::from([(height, Some(block.block_hash()))]),
+            local_chain.apply_update(local_chain::Update {
+                tip: emission.checkpoint,
+                introduce_older_blocks: false,
+            })?,
+            BTreeMap::from([(height, Some(hash))]),
             "chain update changeset is unexpected",
         );
     }
@@ -237,27 +219,30 @@ pub fn test_sync_local_chain() -> anyhow::Result<()> {
     // see if the emitter outputs the right blocks
     println!("after reorg:");
     let mut exp_height = exp_hashes.len() - reorged_blocks.len();
-    while let Some((height, block)) = emitter.next_block()? {
+    while let Some(emission) = emitter.next_block()? {
+        let height = emission.block_height();
+        let hash = emission.block_hash();
         assert_eq!(
             height, exp_height as u32,
             "emitted block has unexpected height"
         );
 
         assert_eq!(
-            block.block_hash(),
-            exp_hashes[height as usize],
+            hash, exp_hashes[height as usize],
             "emitted block is unexpected"
         );
 
-        let chain_update = block_to_chain_update(&block, height);
         assert_eq!(
-            local_chain.apply_update(chain_update)?,
+            local_chain.apply_update(local_chain::Update {
+                tip: emission.checkpoint,
+                introduce_older_blocks: false,
+            })?,
             if exp_height == exp_hashes.len() - reorged_blocks.len() {
-                core::iter::once((height, Some(block.block_hash())))
+                core::iter::once((height, Some(hash)))
                     .chain((height + 1..exp_hashes.len() as u32).map(|h| (h, None)))
                     .collect::<bdk_chain::local_chain::ChangeSet>()
             } else {
-                BTreeMap::from([(height, Some(block.block_hash()))])
+                BTreeMap::from([(height, Some(hash))])
             },
             "chain update changeset is unexpected",
         );
@@ -307,9 +292,13 @@ fn test_into_tx_graph() -> anyhow::Result<()> {
 
     let emitter = &mut Emitter::new(&env.client, chain.tip(), 0);
 
-    while let Some((height, block)) = emitter.next_block()? {
-        let _ = chain.apply_update(block_to_chain_update(&block, height))?;
-        let indexed_additions = indexed_tx_graph.apply_block_relevant(block, height);
+    while let Some(emission) = emitter.next_block()? {
+        let height = emission.block_height();
+        let _ = chain.apply_update(local_chain::Update {
+            tip: emission.checkpoint,
+            introduce_older_blocks: false,
+        })?;
+        let indexed_additions = indexed_tx_graph.apply_block_relevant(&emission.block, height);
         assert!(indexed_additions.is_empty());
     }
 
@@ -367,10 +356,13 @@ fn test_into_tx_graph() -> anyhow::Result<()> {
 
     // must receive mined block which will confirm the transactions.
     {
-        let (height, block) = emitter.next_block()?.expect("must get mined block");
-        let _ = chain
-            .apply_update(CheckPoint::from_header(&block.header, height).into_update(false))?;
-        let indexed_additions = indexed_tx_graph.apply_block_relevant(block, height);
+        let emission = emitter.next_block()?.expect("must get mined block");
+        let height = emission.block_height();
+        let _ = chain.apply_update(local_chain::Update {
+            tip: emission.checkpoint,
+            introduce_older_blocks: false,
+        })?;
+        let indexed_additions = indexed_tx_graph.apply_block_relevant(&emission.block, height);
         assert!(indexed_additions.graph.txs.is_empty());
         assert!(indexed_additions.graph.txouts.is_empty());
         assert_eq!(indexed_additions.graph.anchors, exp_anchors);
@@ -407,9 +399,12 @@ fn ensure_block_emitted_after_reorg_is_at_reorg_height() -> anyhow::Result<()> {
 
     for reorg_count in 1..=10 {
         let replaced_blocks = env.reorg_empty_blocks(reorg_count)?;
-        let (height, next_header) = emitter.next_header()?.expect("must emit block after reorg");
+        let next_emission = emitter.next_header()?.expect("must emit block after reorg");
         assert_eq!(
-            (height as usize, next_header.block_hash()),
+            (
+                next_emission.block_height() as usize,
+                next_emission.block_hash()
+            ),
             replaced_blocks[0],
             "block emitted after reorg should be at the reorg height"
         );
@@ -439,8 +434,9 @@ fn sync_from_emitter<C>(
 where
     C: bitcoincore_rpc::RpcApi,
 {
-    while let Some((height, block)) = emitter.next_block()? {
-        process_block(recv_chain, recv_graph, block, height)?;
+    while let Some(emission) = emitter.next_block()? {
+        let height = emission.block_height();
+        process_block(recv_chain, recv_graph, emission.block, height)?;
     }
     Ok(())
 }
@@ -660,7 +656,8 @@ fn mempool_re_emits_if_tx_introduction_height_not_reached() -> anyhow::Result<()
 
     // At this point, the emitter has seen all mempool transactions. It should only re-emit those
     // that have introduction heights less than the emitter's last-emitted block tip.
-    while let Some((height, _)) = emitter.next_header()? {
+    while let Some(emission) = emitter.next_header()? {
+        let height = emission.block_height();
         // We call `mempool()` twice.
         // The second call (at height `h`) should skip the tx introduced at height `h`.
         for try_index in 0..2 {
@@ -754,7 +751,8 @@ fn mempool_during_reorg() -> anyhow::Result<()> {
             .collect::<BTreeMap<_, _>>());
 
         // `next_header` emits the replacement block of the reorg
-        if let Some((height, _)) = emitter.next_header()? {
+        if let Some(emission) = emitter.next_header()? {
+            let height = emission.block_height();
             println!("\t- replacement height: {}", height);
 
             // the mempool emission (that follows the first block emission after reorg) should only
@@ -835,12 +833,12 @@ fn no_agreement_point() -> anyhow::Result<()> {
     env.mine_blocks(PREMINE_COUNT, None)?;
 
     // emit block 99a
-    let (_, block_header_99a) = emitter.next_header()?.expect("block 99a header");
+    let block_header_99a = emitter.next_header()?.expect("block 99a header").block;
     let block_hash_99a = block_header_99a.block_hash();
     let block_hash_98a = block_header_99a.prev_blockhash;
 
     // emit block 100a
-    let (_, block_header_100a) = emitter.next_header()?.expect("block 100a header");
+    let block_header_100a = emitter.next_header()?.expect("block 100a header").block;
     let block_hash_100a = block_header_100a.block_hash();
 
     // get hash for block 101a
@@ -855,7 +853,7 @@ fn no_agreement_point() -> anyhow::Result<()> {
     env.mine_blocks(3, None)?;
 
     // emit block header 99b
-    let (_, block_header_99b) = emitter.next_header()?.expect("block 99b header");
+    let block_header_99b = emitter.next_header()?.expect("block 99b header").block;
     let block_hash_99b = block_header_99b.block_hash();
     let block_hash_98b = block_header_99b.prev_blockhash;
 

crates/chain/Cargo.toml

@@ -1,8 +1,8 @@
 [package]
 name = "bdk_chain"
-version = "0.6.0"
+version = "0.9.0"
 edition = "2021"
-rust-version = "1.57"
+rust-version = "1.63"
 homepage = "https://bitcoindevkit.org"
 repository = "https://github.com/bitcoindevkit/bdk"
 documentation = "https://docs.rs/bdk_chain"

crates/chain/src/chain_data.rs

@@ -81,7 +81,7 @@ impl From<ChainPosition<ConfirmationTimeHeightAnchor>> for ConfirmationTime {
                 height: a.confirmation_height,
                 time: a.confirmation_time,
             },
-            ChainPosition::Unconfirmed(_) => Self::Unconfirmed { last_seen: 0 },
+            ChainPosition::Unconfirmed(last_seen) => Self::Unconfirmed { last_seen },
         }
     }
 }
@@ -147,6 +147,8 @@ impl From<(&u32, &BlockHash)> for BlockId {
 
 /// An [`Anchor`] implementation that also records the exact confirmation height of the transaction.
 ///
+/// Note that the confirmation block and the anchor block can be different here.
+///
 /// Refer to [`Anchor`] for more details.
 #[derive(Debug, Default, Clone, PartialEq, Eq, Copy, PartialOrd, Ord, core::hash::Hash)]
 #[cfg_attr(
@@ -186,6 +188,8 @@ impl AnchorFromBlockPosition for ConfirmationHeightAnchor {
 /// An [`Anchor`] implementation that also records the exact confirmation time and height of the
 /// transaction.
 ///
+/// Note that the confirmation block and the anchor block can be different here.
+///
 /// Refer to [`Anchor`] for more details.
 #[derive(Debug, Default, Clone, PartialEq, Eq, Copy, PartialOrd, Ord, core::hash::Hash)]
 #[cfg_attr(

crates/chain/src/chain_oracle.rs

@@ -3,7 +3,7 @@ use crate::BlockId;
 /// Represents a service that tracks the blockchain.
 ///
 /// The main method is [`is_block_in_chain`] which determines whether a given block of [`BlockId`]
-/// is an ancestor of another "static block".
+/// is an ancestor of the `chain_tip`.
 ///
 /// [`is_block_in_chain`]: Self::is_block_in_chain
 pub trait ChainOracle {

crates/chain/src/indexed_tx_graph.rs

@@ -1,7 +1,5 @@
-//! Contains the [`IndexedTxGraph`] structure and associated types.
-//!
-//! This is essentially a [`TxGraph`] combined with an indexer.
-
+//! Contains the [`IndexedTxGraph`] and associated types. Refer to the
+//! [`IndexedTxGraph`] documentation for more.
 use alloc::vec::Vec;
 use bitcoin::{Block, OutPoint, Transaction, TxOut, Txid};
 
@@ -11,9 +9,9 @@ use crate::{
     Anchor, AnchorFromBlockPosition, Append, BlockId,
 };
 
-/// A struct that combines [`TxGraph`] and an [`Indexer`] implementation.
+/// The [`IndexedTxGraph`] combines a [`TxGraph`] and an [`Indexer`] implementation.
 ///
-/// This structure ensures that [`TxGraph`] and [`Indexer`] are updated atomically.
+/// It ensures that [`TxGraph`] and [`Indexer`] are updated atomically.
 #[derive(Debug)]
 pub struct IndexedTxGraph<A, I> {
     /// Transaction index.
@@ -226,20 +224,26 @@ where
     /// Irrelevant transactions in `txs` will be ignored.
     pub fn apply_block_relevant(
         &mut self,
-        block: Block,
+        block: &Block,
         height: u32,
     ) -> ChangeSet<A, I::ChangeSet> {
         let block_id = BlockId {
             hash: block.block_hash(),
             height,
         };
-        let txs = block.txdata.iter().enumerate().map(|(tx_pos, tx)| {
-            (
-                tx,
-                core::iter::once(A::from_block_position(&block, block_id, tx_pos)),
-            )
-        });
-        self.batch_insert_relevant(txs)
+        let mut changeset = ChangeSet::<A, I::ChangeSet>::default();
+        for (tx_pos, tx) in block.txdata.iter().enumerate() {
+            changeset.indexer.append(self.index.index_tx(tx));
+            if self.index.is_tx_relevant(tx) {
+                let txid = tx.txid();
+                let anchor = A::from_block_position(block, block_id, tx_pos);
+                changeset.graph.append(self.graph.insert_tx(tx.clone()));
+                changeset
+                    .graph
+                    .append(self.graph.insert_anchor(txid, anchor));
+            }
+        }
+        changeset
     }
 
     /// Batch insert all transactions of the given `block` of `height`.
@@ -266,7 +270,7 @@ where
     }
 }
 
-/// A structure that represents changes to an [`IndexedTxGraph`].
+/// Represents changes to an [`IndexedTxGraph`].
 #[derive(Clone, Debug, PartialEq)]
 #[cfg_attr(
     feature = "serde",

crates/chain/src/keychain.rs

@@ -20,7 +20,7 @@ pub use txout_index::*;
 /// Represents updates to the derivation index of a [`KeychainTxOutIndex`].
 /// It maps each keychain `K` to its last revealed index.
 ///
-/// It can be applied to [`KeychainTxOutIndex`] with [`apply_changeset`]. [`ChangeSet] are
+/// It can be applied to [`KeychainTxOutIndex`] with [`apply_changeset`]. [`ChangeSet`]s are
 /// monotone in that they will never decrease the revealed derivation index.
 ///
 /// [`KeychainTxOutIndex`]: crate::keychain::KeychainTxOutIndex
@@ -58,8 +58,9 @@ impl<K: Ord> Append for ChangeSet<K> {
                 *index = other_index.max(*index);
             }
         });
-
-        self.0.append(&mut other.0);
+        // We use `extend` instead of `BTreeMap::append` due to performance issues with `append`.
+        // Refer to https://github.com/rust-lang/rust/issues/34666#issuecomment-675658420
+        self.0.extend(other.0);
     }
 
     /// Returns whether the changeset are empty.

crates/chain/src/keychain/txout_index.rs

@@ -5,23 +5,56 @@ use crate::{
     spk_iter::BIP32_MAX_INDEX,
     SpkIterator, SpkTxOutIndex,
 };
-use alloc::vec::Vec;
-use bitcoin::{OutPoint, Script, TxOut};
-use core::{fmt::Debug, ops::Deref};
+use bitcoin::{OutPoint, Script, Transaction, TxOut, Txid};
+use core::{
+    fmt::Debug,
+    ops::{Bound, RangeBounds},
+};
 
 use crate::Append;
 
-/// A convenient wrapper around [`SpkTxOutIndex`] that relates script pubkeys to miniscript public
-/// [`Descriptor`]s.
+const DEFAULT_LOOKAHEAD: u32 = 25;
+
+/// [`KeychainTxOutIndex`] controls how script pubkeys are revealed for multiple keychains, and
+/// indexes [`TxOut`]s with them.
 ///
-/// Descriptors are referenced by the provided keychain generic (`K`).
+/// A single keychain is a chain of script pubkeys derived from a single [`Descriptor`]. Keychains
+/// are identified using the `K` generic. Script pubkeys are identified by the keychain that they
+/// are derived from `K`, as well as the derivation index `u32`.
 ///
-/// Script pubkeys for a descriptor are revealed chronologically from index 0. I.e., If the last
-/// revealed index of a descriptor is 5; scripts of indices 0 to 4 are guaranteed to be already
-/// revealed. In addition to revealed scripts, we have a `lookahead` parameter for each keychain,
-/// which defines the number of script pubkeys to store ahead of the last revealed index.
+/// # Revealed script pubkeys
 ///
-/// Methods that could update the last revealed index will return [`super::ChangeSet`] to report
+/// Tracking how script pubkeys are revealed is useful for collecting chain data. For example, if
+/// the user has requested 5 script pubkeys (to receive money with), we only need to use those
+/// script pubkeys to scan for chain data.
+///
+/// Call [`reveal_to_target`] or [`reveal_next_spk`] to reveal more script pubkeys.
+/// Call [`revealed_keychain_spks`] or [`revealed_spks`] to iterate through revealed script pubkeys.
+///
+/// # Lookahead script pubkeys
+///
+/// When an user first recovers a wallet (i.e. from a recovery phrase and/or descriptor), we will
+/// NOT have knowledge of which script pubkeys are revealed. So when we index a transaction or
+/// txout (using [`index_tx`]/[`index_txout`]) we scan the txouts against script pubkeys derived
+/// above the last revealed index. These additionally-derived script pubkeys are called the
+/// lookahead.
+///
+/// The [`KeychainTxOutIndex`] is constructed with the `lookahead` and cannot be altered. The
+/// default `lookahead` count is 1000. Use [`new`] to set a custom `lookahead`.
+///
+/// # Unbounded script pubkey iterator
+///
+/// For script-pubkey-based chain sources (such as Electrum/Esplora), an initial scan is best done
+/// by iterating though derived script pubkeys one by one and requesting transaction histories for
+/// each script pubkey. We will stop after x-number of script pubkeys have empty histories. An
+/// unbounded script pubkey iterator is useful to pass to such a chain source.
+///
+/// Call [`unbounded_spk_iter`] to get an unbounded script pubkey iterator for a given keychain.
+/// Call [`all_unbounded_spk_iters`] to get unbounded script pubkey iterators for all keychains.
+///
+/// # Change sets
+///
+/// Methods that can update the last revealed index will return [`super::ChangeSet`] to report
 /// these changes. This can be persisted for future recovery.
 ///
 /// ## Synopsis
@@ -46,7 +79,7 @@ use crate::Append;
 /// # let secp = bdk_chain::bitcoin::secp256k1::Secp256k1::signing_only();
 /// # let (external_descriptor,_) = Descriptor::<DescriptorPublicKey>::parse_descriptor(&secp, "tr([73c5da0a/86'/0'/0']xprv9xgqHN7yz9MwCkxsBPN5qetuNdQSUttZNKw1dcYTV4mkaAFiBVGQziHs3NRSWMkCzvgjEe3n9xV8oYywvM8at9yRqyaZVz6TYYhX98VjsUk/0/*)").unwrap();
 /// # let (internal_descriptor,_) = Descriptor::<DescriptorPublicKey>::parse_descriptor(&secp, "tr([73c5da0a/86'/0'/0']xprv9xgqHN7yz9MwCkxsBPN5qetuNdQSUttZNKw1dcYTV4mkaAFiBVGQziHs3NRSWMkCzvgjEe3n9xV8oYywvM8at9yRqyaZVz6TYYhX98VjsUk/1/*)").unwrap();
-/// # let descriptor_for_user_42 = external_descriptor.clone();
+/// # let (descriptor_for_user_42, _) = Descriptor::<DescriptorPublicKey>::parse_descriptor(&secp, "tr([73c5da0a/86'/0'/0']xprv9xgqHN7yz9MwCkxsBPN5qetuNdQSUttZNKw1dcYTV4mkaAFiBVGQziHs3NRSWMkCzvgjEe3n9xV8oYywvM8at9yRqyaZVz6TYYhX98VjsUk/2/*)").unwrap();
 /// txout_index.add_keychain(MyKeychain::External, external_descriptor);
 /// txout_index.add_keychain(MyKeychain::Internal, internal_descriptor);
 /// txout_index.add_keychain(MyKeychain::MyAppUser { user_id: 42 }, descriptor_for_user_42);
@@ -57,6 +90,15 @@ use crate::Append;
 /// [`Ord`]: core::cmp::Ord
 /// [`SpkTxOutIndex`]: crate::spk_txout_index::SpkTxOutIndex
 /// [`Descriptor`]: crate::miniscript::Descriptor
+/// [`reveal_to_target`]: KeychainTxOutIndex::reveal_to_target
+/// [`reveal_next_spk`]: KeychainTxOutIndex::reveal_next_spk
+/// [`revealed_keychain_spks`]: KeychainTxOutIndex::revealed_keychain_spks
+/// [`revealed_spks`]: KeychainTxOutIndex::revealed_spks
+/// [`index_tx`]: KeychainTxOutIndex::index_tx
+/// [`index_txout`]: KeychainTxOutIndex::index_txout
+/// [`new`]: KeychainTxOutIndex::new
+/// [`unbounded_spk_iter`]: KeychainTxOutIndex::unbounded_spk_iter
+/// [`all_unbounded_spk_iters`]: KeychainTxOutIndex::all_unbounded_spk_iters
 #[derive(Clone, Debug)]
 pub struct KeychainTxOutIndex<K> {
     inner: SpkTxOutIndex<(K, u32)>,
@@ -65,25 +107,12 @@ pub struct KeychainTxOutIndex<K> {
     // last revealed indexes
     last_revealed: BTreeMap<K, u32>,
     // lookahead settings for each keychain
-    lookahead: BTreeMap<K, u32>,
+    lookahead: u32,
 }
 
 impl<K> Default for KeychainTxOutIndex<K> {
     fn default() -> Self {
-        Self {
-            inner: SpkTxOutIndex::default(),
-            keychains: BTreeMap::default(),
-            last_revealed: BTreeMap::default(),
-            lookahead: BTreeMap::default(),
-        }
-    }
-}
-
-impl<K> Deref for KeychainTxOutIndex<K> {
-    type Target = SpkTxOutIndex<(K, u32)>;
-
-    fn deref(&self) -> &Self::Target {
-        &self.inner
+        Self::new(DEFAULT_LOOKAHEAD)
     }
 }
 
@@ -114,12 +143,37 @@ impl<K: Clone + Ord + Debug> Indexer for KeychainTxOutIndex<K> {
     }
 
     fn is_tx_relevant(&self, tx: &bitcoin::Transaction) -> bool {
-        self.is_relevant(tx)
+        self.inner.is_relevant(tx)
     }
 }
 
+impl<K> KeychainTxOutIndex<K> {
+    /// Construct a [`KeychainTxOutIndex`] with the given `lookahead`.
+    ///
+    /// The `lookahead` is the number of script pubkeys to derive and cache from the internal
+    /// descriptors over and above the last revealed script index. Without a lookahead the index
+    /// will miss outputs you own when processing transactions whose output script pubkeys lie
+    /// beyond the last revealed index. In certain situations, such as when performing an initial
+    /// scan of the blockchain during wallet import, it may be uncertain or unknown what the index
+    /// of the last revealed script pubkey actually is.
+    ///
+    /// Refer to [struct-level docs](KeychainTxOutIndex) for more about `lookahead`.
+    pub fn new(lookahead: u32) -> Self {
+        Self {
+            inner: SpkTxOutIndex::default(),
+            keychains: BTreeMap::new(),
+            last_revealed: BTreeMap::new(),
+            lookahead,
+        }
+    }
+}
+
+/// Methods that are *re-exposed* from the internal [`SpkTxOutIndex`].
 impl<K: Clone + Ord + Debug> KeychainTxOutIndex<K> {
     /// Return a reference to the internal [`SpkTxOutIndex`].
+    ///
+    /// **WARNING:** The internal index will contain lookahead spks. Refer to
+    /// [struct-level docs](KeychainTxOutIndex) for more about `lookahead`.
     pub fn inner(&self) -> &SpkTxOutIndex<(K, u32)> {
         &self.inner
     }
@@ -129,7 +183,116 @@ impl<K: Clone + Ord + Debug> KeychainTxOutIndex<K> {
         self.inner.outpoints()
     }
 
-    /// Return a reference to the internal map of the keychain to descriptors.
+    /// Iterate over known txouts that spend to tracked script pubkeys.
+    pub fn txouts(
+        &self,
+    ) -> impl DoubleEndedIterator<Item = (K, u32, OutPoint, &TxOut)> + ExactSizeIterator {
+        self.inner
+            .txouts()
+            .map(|((k, i), op, txo)| (k.clone(), *i, op, txo))
+    }
+
+    /// Finds all txouts on a transaction that has previously been scanned and indexed.
+    pub fn txouts_in_tx(
+        &self,
+        txid: Txid,
+    ) -> impl DoubleEndedIterator<Item = (K, u32, OutPoint, &TxOut)> {
+        self.inner
+            .txouts_in_tx(txid)
+            .map(|((k, i), op, txo)| (k.clone(), *i, op, txo))
+    }
+
+    /// Return the [`TxOut`] of `outpoint` if it has been indexed.
+    ///
+    /// The associated keychain and keychain index of the txout's spk is also returned.
+    ///
+    /// This calls [`SpkTxOutIndex::txout`] internally.
+    pub fn txout(&self, outpoint: OutPoint) -> Option<(K, u32, &TxOut)> {
+        self.inner
+            .txout(outpoint)
+            .map(|((k, i), txo)| (k.clone(), *i, txo))
+    }
+
+    /// Return the script that exists under the given `keychain`'s `index`.
+    ///
+    /// This calls [`SpkTxOutIndex::spk_at_index`] internally.
+    pub fn spk_at_index(&self, keychain: K, index: u32) -> Option<&Script> {
+        self.inner.spk_at_index(&(keychain, index))
+    }
+
+    /// Returns the keychain and keychain index associated with the spk.
+    ///
+    /// This calls [`SpkTxOutIndex::index_of_spk`] internally.
+    pub fn index_of_spk(&self, script: &Script) -> Option<(K, u32)> {
+        self.inner.index_of_spk(script).cloned()
+    }
+
+    /// Returns whether the spk under the `keychain`'s `index` has been used.
+    ///
+    /// Here, "unused" means that after the script pubkey was stored in the index, the index has
+    /// never scanned a transaction output with it.
+    ///
+    /// This calls [`SpkTxOutIndex::is_used`] internally.
+    pub fn is_used(&self, keychain: K, index: u32) -> bool {
+        self.inner.is_used(&(keychain, index))
+    }
+
+    /// Marks the script pubkey at `index` as used even though the tracker hasn't seen an output
+    /// with it.
+    ///
+    /// This only has an effect when the `index` had been added to `self` already and was unused.
+    ///
+    /// Returns whether the `index` was initially present as `unused`.
+    ///
+    /// This is useful when you want to reserve a script pubkey for something but don't want to add
+    /// the transaction output using it to the index yet. Other callers will consider `index` on
+    /// `keychain` used until you call [`unmark_used`].
+    ///
+    /// This calls [`SpkTxOutIndex::mark_used`] internally.
+    ///
+    /// [`unmark_used`]: Self::unmark_used
+    pub fn mark_used(&mut self, keychain: K, index: u32) -> bool {
+        self.inner.mark_used(&(keychain, index))
+    }
+
+    /// Undoes the effect of [`mark_used`]. Returns whether the `index` is inserted back into
+    /// `unused`.
+    ///
+    /// Note that if `self` has scanned an output with this script pubkey, then this will have no
+    /// effect.
+    ///
+    /// This calls [`SpkTxOutIndex::unmark_used`] internally.
+    ///
+    /// [`mark_used`]: Self::mark_used
+    pub fn unmark_used(&mut self, keychain: K, index: u32) -> bool {
+        self.inner.unmark_used(&(keychain, index))
+    }
+
+    /// Computes total input value going from script pubkeys in the index (sent) and the total output
+    /// value going to script pubkeys in the index (received) in `tx`. For the `sent` to be computed
+    /// correctly, the output being spent must have already been scanned by the index. Calculating
+    /// received just uses the [`Transaction`] outputs directly, so it will be correct even if it has
+    /// not been scanned.
+    ///
+    /// This calls [`SpkTxOutIndex::sent_and_received`] internally.
+    pub fn sent_and_received(&self, tx: &Transaction) -> (u64, u64) {
+        self.inner.sent_and_received(tx)
+    }
+
+    /// Computes the net value that this transaction gives to the script pubkeys in the index and
+    /// *takes* from the transaction outputs in the index. Shorthand for calling
+    /// [`sent_and_received`] and subtracting sent from received.
+    ///
+    /// This calls [`SpkTxOutIndex::net_value`] internally.
+    ///
+    /// [`sent_and_received`]: Self::sent_and_received
+    pub fn net_value(&self, tx: &Transaction) -> i64 {
+        self.inner.net_value(tx)
+    }
+}
+
+impl<K: Clone + Ord + Debug> KeychainTxOutIndex<K> {
+    /// Return a reference to the internal map of keychain to descriptors.
     pub fn keychains(&self) -> &BTreeMap<K, Descriptor<DescriptorPublicKey>> {
         &self.keychains
     }
@@ -145,54 +308,22 @@ impl<K: Clone + Ord + Debug> KeychainTxOutIndex<K> {
     pub fn add_keychain(&mut self, keychain: K, descriptor: Descriptor<DescriptorPublicKey>) {
         let old_descriptor = &*self
             .keychains
-            .entry(keychain)
+            .entry(keychain.clone())
             .or_insert_with(|| descriptor.clone());
         assert_eq!(
             &descriptor, old_descriptor,
             "keychain already contains a different descriptor"
         );
+        self.replenish_lookahead(&keychain, self.lookahead);
     }
 
-    /// Return the lookahead setting for each keychain.
+    /// Get the lookahead setting.
     ///
-    /// Refer to [`set_lookahead`] for a deeper explanation of the `lookahead`.
+    /// Refer to [`new`] for more information on the `lookahead`.
     ///
-    /// [`set_lookahead`]: Self::set_lookahead
-    pub fn lookaheads(&self) -> &BTreeMap<K, u32> {
-        &self.lookahead
-    }
-
-    /// Convenience method to call [`set_lookahead`] for all keychains.
-    ///
-    /// [`set_lookahead`]: Self::set_lookahead
-    pub fn set_lookahead_for_all(&mut self, lookahead: u32) {
-        for keychain in &self.keychains.keys().cloned().collect::<Vec<_>>() {
-            self.set_lookahead(keychain, lookahead);
-        }
-    }
-
-    /// Set the lookahead count for `keychain`.
-    ///
-    /// The lookahead is the number of scripts to cache ahead of the last revealed script index. This
-    /// is useful to find outputs you own when processing block data that lie beyond the last revealed
-    /// index. In certain situations, such as when performing an initial scan of the blockchain during
-    /// wallet import, it may be uncertain or unknown what the last revealed index is.
-    ///
-    /// # Panics
-    ///
-    /// This will panic if the `keychain` does not exist.
-    pub fn set_lookahead(&mut self, keychain: &K, lookahead: u32) {
-        self.lookahead.insert(keychain.clone(), lookahead);
-        self.replenish_lookahead(keychain);
-    }
-
-    /// Convenience method to call [`lookahead_to_target`] for multiple keychains.
-    ///
-    /// [`lookahead_to_target`]: Self::lookahead_to_target
-    pub fn lookahead_to_target_multi(&mut self, target_indexes: BTreeMap<K, u32>) {
-        for (keychain, target_index) in target_indexes {
-            self.lookahead_to_target(&keychain, target_index)
-        }
+    /// [`new`]: Self::new
+    pub fn lookahead(&self) -> u32 {
+        self.lookahead
     }
 
     /// Store lookahead scripts until `target_index`.
@@ -201,22 +332,14 @@ impl<K: Clone + Ord + Debug> KeychainTxOutIndex<K> {
     pub fn lookahead_to_target(&mut self, keychain: &K, target_index: u32) {
         let next_index = self.next_store_index(keychain);
         if let Some(temp_lookahead) = target_index.checked_sub(next_index).filter(|&v| v > 0) {
-            let old_lookahead = self.lookahead.insert(keychain.clone(), temp_lookahead);
-            self.replenish_lookahead(keychain);
-
-            // revert
-            match old_lookahead {
-                Some(lookahead) => self.lookahead.insert(keychain.clone(), lookahead),
-                None => self.lookahead.remove(keychain),
-            };
+            self.replenish_lookahead(keychain, temp_lookahead);
         }
     }
 
-    fn replenish_lookahead(&mut self, keychain: &K) {
+    fn replenish_lookahead(&mut self, keychain: &K, lookahead: u32) {
         let descriptor = self.keychains.get(keychain).expect("keychain must exist");
         let next_store_index = self.next_store_index(keychain);
         let next_reveal_index = self.last_revealed.get(keychain).map_or(0, |v| *v + 1);
-        let lookahead = self.lookahead.get(keychain).map_or(0, |v| *v);
 
         for (new_index, new_spk) in
             SpkIterator::new_with_range(descriptor, next_store_index..next_reveal_index + lookahead)
@@ -231,64 +354,74 @@ impl<K: Clone + Ord + Debug> KeychainTxOutIndex<K> {
     fn next_store_index(&self, keychain: &K) -> u32 {
         self.inner()
             .all_spks()
+            // This range is filtering out the spks with a keychain different than
+            // `keychain`. We don't use filter here as range is more optimized.
             .range((keychain.clone(), u32::MIN)..(keychain.clone(), u32::MAX))
             .last()
-            .map_or(0, |((_, v), _)| *v + 1)
+            .map_or(0, |((_, index), _)| *index + 1)
     }
 
-    /// Generates script pubkey iterators for every `keychain`. The iterators iterate over all
-    /// derivable script pubkeys.
-    pub fn spks_of_all_keychains(
+    /// Get an unbounded spk iterator over a given `keychain`.
+    ///
+    /// # Panics
+    ///
+    /// This will panic if the given `keychain`'s descriptor does not exist.
+    pub fn unbounded_spk_iter(&self, keychain: &K) -> SpkIterator<Descriptor<DescriptorPublicKey>> {
+        SpkIterator::new(
+            self.keychains
+                .get(keychain)
+                .expect("keychain does not exist")
+                .clone(),
+        )
+    }
+
+    /// Get unbounded spk iterators for all keychains.
+    pub fn all_unbounded_spk_iters(
         &self,
     ) -> BTreeMap<K, SpkIterator<Descriptor<DescriptorPublicKey>>> {
         self.keychains
             .iter()
-            .map(|(keychain, descriptor)| {
-                (
-                    keychain.clone(),
-                    SpkIterator::new_with_range(descriptor.clone(), 0..),
-                )
-            })
+            .map(|(k, descriptor)| (k.clone(), SpkIterator::new(descriptor.clone())))
             .collect()
     }
 
-    /// Generates a script pubkey iterator for the given `keychain`'s descriptor (if it exists). The
-    /// iterator iterates over all derivable scripts of the keychain's descriptor.
-    ///
-    /// # Panics
-    ///
-    /// This will panic if the `keychain` does not exist.
-    pub fn spks_of_keychain(&self, keychain: &K) -> SpkIterator<Descriptor<DescriptorPublicKey>> {
-        let descriptor = self
-            .keychains
-            .get(keychain)
-            .expect("keychain must exist")
-            .clone();
-        SpkIterator::new_with_range(descriptor, 0..)
+    /// Iterate over revealed spks of all keychains.
+    pub fn revealed_spks(&self) -> impl DoubleEndedIterator<Item = (K, u32, &Script)> + Clone {
+        self.keychains.keys().flat_map(|keychain| {
+            self.revealed_keychain_spks(keychain)
+                .map(|(i, spk)| (keychain.clone(), i, spk))
+        })
     }
 
-    /// Convenience method to get [`revealed_spks_of_keychain`] of all keychains.
-    ///
-    /// [`revealed_spks_of_keychain`]: Self::revealed_spks_of_keychain
-    pub fn revealed_spks_of_all_keychains(
-        &self,
-    ) -> BTreeMap<K, impl Iterator<Item = (u32, &Script)> + Clone> {
-        self.keychains
-            .keys()
-            .map(|keychain| (keychain.clone(), self.revealed_spks_of_keychain(keychain)))
-            .collect()
-    }
-
-    /// Iterates over the script pubkeys revealed by this index under `keychain`.
-    pub fn revealed_spks_of_keychain(
+    /// Iterate over revealed spks of the given `keychain`.
+    pub fn revealed_keychain_spks(
         &self,
         keychain: &K,
     ) -> impl DoubleEndedIterator<Item = (u32, &Script)> + Clone {
-        let next_index = self.last_revealed.get(keychain).map_or(0, |v| *v + 1);
+        let next_i = self.last_revealed.get(keychain).map_or(0, |&i| i + 1);
         self.inner
             .all_spks()
-            .range((keychain.clone(), u32::MIN)..(keychain.clone(), next_index))
-            .map(|((_, derivation_index), spk)| (*derivation_index, spk.as_script()))
+            .range((keychain.clone(), u32::MIN)..(keychain.clone(), next_i))
+            .map(|((_, i), spk)| (*i, spk.as_script()))
+    }
+
+    /// Iterate over revealed, but unused, spks of all keychains.
+    pub fn unused_spks(&self) -> impl DoubleEndedIterator<Item = (K, u32, &Script)> + Clone {
+        self.keychains.keys().flat_map(|keychain| {
+            self.unused_keychain_spks(keychain)
+                .map(|(i, spk)| (keychain.clone(), i, spk))
+        })
+    }
+
+    /// Iterate over revealed, but unused, spks of the given `keychain`.
+    pub fn unused_keychain_spks(
+        &self,
+        keychain: &K,
+    ) -> impl DoubleEndedIterator<Item = (u32, &Script)> + Clone {
+        let next_i = self.last_revealed.get(keychain).map_or(0, |&i| i + 1);
+        self.inner
+            .unused_spks((keychain.clone(), u32::MIN)..(keychain.clone(), next_i))
+            .map(|((_, i), spk)| (*i, spk))
     }
 
     /// Get the next derivation index for `keychain`. The next index is the index after the last revealed
@@ -387,55 +520,45 @@ impl<K: Clone + Ord + Debug> KeychainTxOutIndex<K> {
         let has_wildcard = descriptor.has_wildcard();
 
         let target_index = if has_wildcard { target_index } else { 0 };
-        let next_reveal_index = self.last_revealed.get(keychain).map_or(0, |v| *v + 1);
-        let lookahead = self.lookahead.get(keychain).map_or(0, |v| *v);
+        let next_reveal_index = self
+            .last_revealed
+            .get(keychain)
+            .map_or(0, |index| *index + 1);
 
-        debug_assert_eq!(
-            next_reveal_index + lookahead,
-            self.next_store_index(keychain)
-        );
+        debug_assert!(next_reveal_index + self.lookahead >= self.next_store_index(keychain));
 
-        // if we need to reveal new indices, the latest revealed index goes here
-        let mut reveal_to_index = None;
-
-        // if the target is not yet revealed, but is already stored (due to lookahead), we need to
-        // set the `reveal_to_index` as target here (as the `for` loop below only updates
-        // `reveal_to_index` for indexes that are NOT stored)
-        if next_reveal_index <= target_index && target_index < next_reveal_index + lookahead {
-            reveal_to_index = Some(target_index);
-        }
-
-        // we range over indexes that are not stored
-        let range = next_reveal_index + lookahead..=target_index + lookahead;
-        for (new_index, new_spk) in SpkIterator::new_with_range(descriptor, range) {
-            let _inserted = self
-                .inner
-                .insert_spk((keychain.clone(), new_index), new_spk);
-            debug_assert!(_inserted, "must not have existing spk",);
-
-            // everything after `target_index` is stored for lookahead only
-            if new_index <= target_index {
-                reveal_to_index = Some(new_index);
-            }
-        }
-
-        match reveal_to_index {
-            Some(index) => {
-                let _old_index = self.last_revealed.insert(keychain.clone(), index);
-                debug_assert!(_old_index < Some(index));
-                (
-                    SpkIterator::new_with_range(descriptor.clone(), next_reveal_index..index + 1),
-                    super::ChangeSet(core::iter::once((keychain.clone(), index)).collect()),
-                )
-            }
-            None => (
+        // If the target_index is already revealed, we are done
+        if next_reveal_index > target_index {
+            return (
                 SpkIterator::new_with_range(
                     descriptor.clone(),
                     next_reveal_index..next_reveal_index,
                 ),
                 super::ChangeSet::default(),
-            ),
+            );
         }
+
+        // We range over the indexes that are not stored and insert their spks in the index.
+        // Indexes from next_reveal_index to next_reveal_index + lookahead are already stored (due
+        // to lookahead), so we only range from next_reveal_index + lookahead to target + lookahead
+        let range = next_reveal_index + self.lookahead..=target_index + self.lookahead;
+        for (new_index, new_spk) in SpkIterator::new_with_range(descriptor, range) {
+            let _inserted = self
+                .inner
+                .insert_spk((keychain.clone(), new_index), new_spk);
+            debug_assert!(_inserted, "must not have existing spk");
+            debug_assert!(
+                has_wildcard || new_index == 0,
+                "non-wildcard descriptors must not iterate past index 0"
+            );
+        }
+
+        let _old_index = self.last_revealed.insert(keychain.clone(), target_index);
+        debug_assert!(_old_index < Some(target_index));
+        (
+            SpkIterator::new_with_range(descriptor.clone(), next_reveal_index..target_index + 1),
+            super::ChangeSet(core::iter::once((keychain.clone(), target_index)).collect()),
+        )
     }
 
     /// Attempts to reveal the next script pubkey for `keychain`.
@@ -475,13 +598,13 @@ impl<K: Clone + Ord + Debug> KeychainTxOutIndex<K> {
     ///
     /// Panics if `keychain` has never been added to the index
     pub fn next_unused_spk(&mut self, keychain: &K) -> ((u32, &Script), super::ChangeSet<K>) {
-        let need_new = self.unused_spks_of_keychain(keychain).next().is_none();
+        let need_new = self.unused_keychain_spks(keychain).next().is_none();
         // this rather strange branch is needed because of some lifetime issues
         if need_new {
             self.reveal_next_spk(keychain)
         } else {
             (
-                self.unused_spks_of_keychain(keychain)
+                self.unused_keychain_spks(keychain)
                     .next()
                     .expect("we already know next exists"),
                 super::ChangeSet::default(),
@@ -489,58 +612,44 @@ impl<K: Clone + Ord + Debug> KeychainTxOutIndex<K> {
         }
     }
 
-    /// Marks the script pubkey at `index` as used even though the tracker hasn't seen an output with it.
-    /// This only has an effect when the `index` had been added to `self` already and was unused.
-    ///
-    /// Returns whether the `index` was initially present as `unused`.
-    ///
-    /// This is useful when you want to reserve a script pubkey for something but don't want to add
-    /// the transaction output using it to the index yet. Other callers will consider `index` on
-    /// `keychain` used until you call [`unmark_used`].
-    ///
-    /// [`unmark_used`]: Self::unmark_used
-    pub fn mark_used(&mut self, keychain: &K, index: u32) -> bool {
-        self.inner.mark_used(&(keychain.clone(), index))
-    }
-
-    /// Undoes the effect of [`mark_used`]. Returns whether the `index` is inserted back into
-    /// `unused`.
-    ///
-    /// Note that if `self` has scanned an output with this script pubkey, then this will have no
-    /// effect.
-    ///
-    /// [`mark_used`]: Self::mark_used
-    pub fn unmark_used(&mut self, keychain: &K, index: u32) -> bool {
-        self.inner.unmark_used(&(keychain.clone(), index))
-    }
-
-    /// Iterates over all unused script pubkeys for a `keychain` stored in the index.
-    pub fn unused_spks_of_keychain(
-        &self,
-        keychain: &K,
-    ) -> impl DoubleEndedIterator<Item = (u32, &Script)> {
-        let next_index = self.last_revealed.get(keychain).map_or(0, |&v| v + 1);
-        let range = (keychain.clone(), u32::MIN)..(keychain.clone(), next_index);
-        self.inner
-            .unused_spks(range)
-            .map(|((_, i), script)| (*i, script))
-    }
-
-    /// Iterates over all the [`OutPoint`] that have a `TxOut` with a script pubkey derived from
+    /// Iterate over all [`OutPoint`]s that point to `TxOut`s with script pubkeys derived from
     /// `keychain`.
-    pub fn txouts_of_keychain(
+    ///
+    /// Use [`keychain_outpoints_in_range`](KeychainTxOutIndex::keychain_outpoints_in_range) to
+    /// iterate over a specific derivation range.
+    pub fn keychain_outpoints(
         &self,
         keychain: &K,
     ) -> impl DoubleEndedIterator<Item = (u32, OutPoint)> + '_ {
+        self.keychain_outpoints_in_range(keychain, ..)
+    }
+
+    /// Iterate over [`OutPoint`]s that point to `TxOut`s with script pubkeys derived from
+    /// `keychain` in a given derivation `range`.
+    pub fn keychain_outpoints_in_range(
+        &self,
+        keychain: &K,
+        range: impl RangeBounds<u32>,
+    ) -> impl DoubleEndedIterator<Item = (u32, OutPoint)> + '_ {
+        let start = match range.start_bound() {
+            Bound::Included(i) => Bound::Included((keychain.clone(), *i)),
+            Bound::Excluded(i) => Bound::Excluded((keychain.clone(), *i)),
+            Bound::Unbounded => Bound::Unbounded,
+        };
+        let end = match range.end_bound() {
+            Bound::Included(i) => Bound::Included((keychain.clone(), *i)),
+            Bound::Excluded(i) => Bound::Excluded((keychain.clone(), *i)),
+            Bound::Unbounded => Bound::Unbounded,
+        };
         self.inner
-            .outputs_in_range((keychain.clone(), u32::MIN)..(keychain.clone(), u32::MAX))
+            .outputs_in_range((start, end))
             .map(|((_, i), op)| (*i, op))
     }
 
     /// Returns the highest derivation index of the `keychain` where [`KeychainTxOutIndex`] has
     /// found a [`TxOut`] with it's script pubkey.
     pub fn last_used_index(&self, keychain: &K) -> Option<u32> {
-        self.txouts_of_keychain(keychain).last().map(|(i, _)| i)
+        self.keychain_outpoints(keychain).last().map(|(i, _)| i)
     }
 
     /// Returns the highest derivation index of each keychain that [`KeychainTxOutIndex`] has found

crates/chain/src/lib.rs

@@ -1,4 +1,4 @@
-//! This crate is a collection of core structures for [Bitcoin Dev Kit] (alpha release).
+//! This crate is a collection of core structures for [Bitcoin Dev Kit].
 //!
 //! The goal of this crate is to give wallets the mechanisms needed to:
 //!
@@ -12,9 +12,8 @@
 //!    you do it synchronously or asynchronously. If you know a fact about the blockchain, you can just
 //!    tell `bdk_chain`'s APIs about it, and that information will be integrated, if it can be done
 //!    consistently.
-//! 2. Error-free APIs.
-//! 3. Data persistence agnostic -- `bdk_chain` does not care where you cache on-chain data, what you
-//!    cache or how you fetch it.
+//! 2. Data persistence agnostic -- `bdk_chain` does not care where you cache on-chain data, what you
+//!    cache or how you retrieve it from persistent storage.
 //!
 //! [Bitcoin Dev Kit]: https://bitcoindevkit.org/
 

crates/chain/src/local_chain.rs

@@ -5,9 +5,10 @@ use core::convert::Infallible;
 use crate::collections::BTreeMap;
 use crate::{BlockId, ChainOracle};
 use alloc::sync::Arc;
+use bitcoin::block::Header;
 use bitcoin::BlockHash;
 
-/// A structure that represents changes to [`LocalChain`].
+/// The [`ChangeSet`] represents changes to [`LocalChain`].
 ///
 /// The key represents the block height, and the value either represents added a new [`CheckPoint`]
 /// (if [`Some`]), or removing a [`CheckPoint`] (if [`None`]).
@@ -39,6 +40,28 @@ impl CheckPoint {
         Self(Arc::new(CPInner { block, prev: None }))
     }
 
+    /// Construct a checkpoint from a list of [`BlockId`]s in ascending height order.
+    ///
+    /// # Errors
+    ///
+    /// This method will error if any of the follow occurs:
+    ///
+    /// - The `blocks` iterator is empty, in which case, the error will be `None`.
+    /// - The `blocks` iterator is not in ascending height order.
+    /// - The `blocks` iterator contains multiple [`BlockId`]s of the same height.
+    ///
+    /// The error type is the last successful checkpoint constructed (if any).
+    pub fn from_block_ids(
+        block_ids: impl IntoIterator<Item = BlockId>,
+    ) -> Result<Self, Option<Self>> {
+        let mut blocks = block_ids.into_iter();
+        let mut acc = CheckPoint::new(blocks.next().ok_or(None)?);
+        for id in blocks {
+            acc = acc.push(id).map_err(Some)?;
+        }
+        Ok(acc)
+    }
+
     /// Construct a checkpoint from the given `header` and block `height`.
     ///
     /// If `header` is of the genesis block, the checkpoint won't have a [`prev`] node. Otherwise,
@@ -127,7 +150,7 @@ impl CheckPoint {
     }
 }
 
-/// A structure that iterates over checkpoints backwards.
+/// Iterates over checkpoints backwards.
 pub struct CheckPointIter {
     current: Option<Arc<CPInner>>,
 }
@@ -153,7 +176,7 @@ impl IntoIterator for CheckPoint {
     }
 }
 
-/// A struct to update [`LocalChain`].
+/// Used to update [`LocalChain`].
 ///
 /// This is used as input for [`LocalChain::apply_update`]. It contains the update's chain `tip` and
 /// a flag `introduce_older_blocks` which signals whether this update intends to introduce missing
@@ -347,6 +370,95 @@ impl LocalChain {
         Ok(changeset)
     }
 
+    /// Update the chain with a given [`Header`] at `height` which you claim is connected to a existing block in the chain.
+    ///
+    /// This is useful when you have a block header that you want to record as part of the chain but
+    /// don't necessarily know that the `prev_blockhash` is in the chain.
+    ///
+    /// This will usually insert two new [`BlockId`]s into the chain: the header's block and the
+    /// header's `prev_blockhash` block. `connected_to` must already be in the chain but is allowed
+    /// to be `prev_blockhash` (in which case only one new block id will be inserted).
+    /// To be successful, `connected_to` must be chosen carefully so that `LocalChain`'s [update
+    /// rules][`apply_update`] are satisfied.
+    ///
+    /// # Errors
+    ///
+    /// [`ApplyHeaderError::InconsistentBlocks`] occurs if the `connected_to` block and the
+    /// [`Header`] is inconsistent. For example, if the `connected_to` block is the same height as
+    /// `header` or `prev_blockhash`, but has a different block hash. Or if the `connected_to`
+    /// height is greater than the header's `height`.
+    ///
+    /// [`ApplyHeaderError::CannotConnect`] occurs if the internal call to [`apply_update`] fails.
+    ///
+    /// [`apply_update`]: Self::apply_update
+    pub fn apply_header_connected_to(
+        &mut self,
+        header: &Header,
+        height: u32,
+        connected_to: BlockId,
+    ) -> Result<ChangeSet, ApplyHeaderError> {
+        let this = BlockId {
+            height,
+            hash: header.block_hash(),
+        };
+        let prev = height.checked_sub(1).map(|prev_height| BlockId {
+            height: prev_height,
+            hash: header.prev_blockhash,
+        });
+        let conn = match connected_to {
+            // `connected_to` can be ignored if same as `this` or `prev` (duplicate)
+            conn if conn == this || Some(conn) == prev => None,
+            // this occurs if:
+            // - `connected_to` height is the same as `prev`, but different hash
+            // - `connected_to` height is the same as `this`, but different hash
+            // - `connected_to` height is greater than `this` (this is not allowed)
+            conn if conn.height >= height.saturating_sub(1) => {
+                return Err(ApplyHeaderError::InconsistentBlocks)
+            }
+            conn => Some(conn),
+        };
+
+        let update = Update {
+            tip: CheckPoint::from_block_ids([conn, prev, Some(this)].into_iter().flatten())
+                .expect("block ids must be in order"),
+            introduce_older_blocks: false,
+        };
+
+        self.apply_update(update)
+            .map_err(ApplyHeaderError::CannotConnect)
+    }
+
+    /// Update the chain with a given [`Header`] connecting it with the previous block.
+    ///
+    /// This is a convenience method to call [`apply_header_connected_to`] with the `connected_to`
+    /// parameter being `height-1:prev_blockhash`. If there is no previous block (i.e. genesis), we
+    /// use the current block as `connected_to`.
+    ///
+    /// [`apply_header_connected_to`]: LocalChain::apply_header_connected_to
+    pub fn apply_header(
+        &mut self,
+        header: &Header,
+        height: u32,
+    ) -> Result<ChangeSet, CannotConnectError> {
+        let connected_to = match height.checked_sub(1) {
+            Some(prev_height) => BlockId {
+                height: prev_height,
+                hash: header.prev_blockhash,
+            },
+            None => BlockId {
+                height,
+                hash: header.block_hash(),
+            },
+        };
+        self.apply_header_connected_to(header, height, connected_to)
+            .map_err(|err| match err {
+                ApplyHeaderError::InconsistentBlocks => {
+                    unreachable!("connected_to is derived from the block so is always consistent")
+                }
+                ApplyHeaderError::CannotConnect(err) => err,
+            })
+    }
+
     /// Apply the given `changeset`.
     pub fn apply_changeset(&mut self, changeset: &ChangeSet) -> Result<(), MissingGenesisError> {
         if let Some(start_height) = changeset.keys().next().cloned() {
@@ -420,6 +532,28 @@ impl LocalChain {
         Ok(changeset)
     }
 
+    /// Removes blocks from (and inclusive of) the given `block_id`.
+    ///
+    /// This will remove blocks with a height equal or greater than `block_id`, but only if
+    /// `block_id` exists in the chain.
+    ///
+    /// # Errors
+    ///
+    /// This will fail with [`MissingGenesisError`] if the caller attempts to disconnect from the
+    /// genesis block.
+    pub fn disconnect_from(&mut self, block_id: BlockId) -> Result<ChangeSet, MissingGenesisError> {
+        if self.index.get(&block_id.height) != Some(&block_id.hash) {
+            return Ok(ChangeSet::default());
+        }
+
+        let changeset = self
+            .index
+            .range(block_id.height..)
+            .map(|(&height, _)| (height, None))
+            .collect::<ChangeSet>();
+        self.apply_changeset(&changeset).map(|_| changeset)
+    }
+
     /// Reindex the heights in the chain from (and including) `from` height
     fn reindex(&mut self, from: u32) {
         let _ = self.index.split_off(&from);
@@ -535,6 +669,30 @@ impl core::fmt::Display for CannotConnectError {
 #[cfg(feature = "std")]
 impl std::error::Error for CannotConnectError {}
 
+/// The error type for [`LocalChain::apply_header_connected_to`].
+#[derive(Debug, Clone, PartialEq)]
+pub enum ApplyHeaderError {
+    /// Occurs when `connected_to` block conflicts with either the current block or previous block.
+    InconsistentBlocks,
+    /// Occurs when the update cannot connect with the original chain.
+    CannotConnect(CannotConnectError),
+}
+
+impl core::fmt::Display for ApplyHeaderError {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        match self {
+            ApplyHeaderError::InconsistentBlocks => write!(
+                f,
+                "the `connected_to` block conflicts with either the current or previous block"
+            ),
+            ApplyHeaderError::CannotConnect(err) => core::fmt::Display::fmt(err, f),
+        }
+    }
+}
+
+#[cfg(feature = "std")]
+impl std::error::Error for ApplyHeaderError {}
+
 fn merge_chains(
     original_tip: CheckPoint,
     update_tip: CheckPoint,

crates/chain/src/persist.rs

@@ -55,6 +55,18 @@ where
             // if written successfully, take and return `self.stage`
             .map(|_| Some(core::mem::take(&mut self.stage)))
     }
+
+    /// Stages a new changeset and commits it (along with any other previously staged changes) to
+    /// the persistence backend
+    ///
+    /// Convience method for calling [`stage`] and then [`commit`].
+    ///
+    /// [`stage`]: Self::stage
+    /// [`commit`]: Self::commit
+    pub fn stage_and_commit(&mut self, changeset: C) -> Result<Option<C>, B::WriteError> {
+        self.stage(changeset);
+        self.commit()
+    }
 }
 
 /// A persistence backend for [`Persist`].

crates/chain/src/spk_iter.rs

@@ -43,18 +43,24 @@ impl<D> SpkIterator<D>
 where
     D: Borrow<Descriptor<DescriptorPublicKey>>,
 {
-    /// Creates a new script pubkey iterator starting at 0 from a descriptor.
+    /// Create a new script pubkey iterator from `descriptor`.
+    ///
+    /// This iterates from derivation index 0 and stops at index 0x7FFFFFFF (as specified in
+    /// BIP-32). Non-wildcard descriptors will only return one script pubkey at derivation index 0.
+    ///
+    /// Use [`new_with_range`](SpkIterator::new_with_range) to create an iterator with a specified
+    /// derivation index range.
     pub fn new(descriptor: D) -> Self {
         SpkIterator::new_with_range(descriptor, 0..=BIP32_MAX_INDEX)
     }
 
-    // Creates a new script pubkey iterator from a descriptor with a given range.
-    // If the descriptor doesn't have a wildcard, we shorten whichever range you pass in
-    // to have length <= 1. This means that if you pass in 0..0 or 0..1 the range will
-    // remain the same, but if you pass in 0..10, we'll shorten it to 0..1
-    // Also note that if the descriptor doesn't have a wildcard, passing in a range starting
-    // from n > 0, will return an empty iterator.
-    pub(crate) fn new_with_range<R>(descriptor: D, range: R) -> Self
+    /// Create a new script pubkey iterator from `descriptor` and a given `range`.
+    ///
+    /// Non-wildcard descriptors will only emit a single script pubkey (at derivation index 0).
+    /// Wildcard descriptors have an end-bound of 0x7FFFFFFF (inclusive).
+    ///
+    /// Refer to [`new`](SpkIterator::new) for more.
+    pub fn new_with_range<R>(descriptor: D, range: R) -> Self
     where
         R: RangeBounds<u32>,
     {
@@ -73,13 +79,6 @@ where
         // Because `end` is exclusive, we want the maximum value to be BIP32_MAX_INDEX + 1.
         end = end.min(BIP32_MAX_INDEX + 1);
 
-        if !descriptor.borrow().has_wildcard() {
-            // The length of the range should be at most 1
-            if end != start {
-                end = start + 1;
-            }
-        }
-
         Self {
             next_index: start,
             end,
@@ -87,6 +86,11 @@ where
             secp: Secp256k1::verification_only(),
         }
     }
+
+    /// Get a reference to the internal descriptor.
+    pub fn descriptor(&self) -> &D {
+        &self.descriptor
+    }
 }
 
 impl<D> Iterator for SpkIterator<D>
@@ -148,7 +152,7 @@ mod test {
         Descriptor<DescriptorPublicKey>,
         Descriptor<DescriptorPublicKey>,
     ) {
-        let mut txout_index = KeychainTxOutIndex::<TestKeychain>::default();
+        let mut txout_index = KeychainTxOutIndex::<TestKeychain>::new(0);
 
         let secp = Secp256k1::signing_only();
         let (external_descriptor,_) = Descriptor::<DescriptorPublicKey>::parse_descriptor(&secp, "tr([73c5da0a/86'/0'/0']xprv9xgqHN7yz9MwCkxsBPN5qetuNdQSUttZNKw1dcYTV4mkaAFiBVGQziHs3NRSWMkCzvgjEe3n9xV8oYywvM8at9yRqyaZVz6TYYhX98VjsUk/0/*)").unwrap();
@@ -245,6 +249,14 @@ mod test {
             SpkIterator::new_with_range(&no_wildcard_descriptor, 1..=2).next(),
             None
         );
+        assert_eq!(
+            SpkIterator::new_with_range(&no_wildcard_descriptor, 10..11).next(),
+            None
+        );
+        assert_eq!(
+            SpkIterator::new_with_range(&no_wildcard_descriptor, 10..=10).next(),
+            None
+        );
     }
 
     // The following dummy traits were created to test if SpkIterator is working properly.

crates/chain/src/spk_txout_index.rs

@@ -168,9 +168,7 @@ impl<I: Clone + Ord> SpkTxOutIndex<I> {
     ///
     /// Returns `None` if the `TxOut` hasn't been scanned or if nothing matching was found there.
     pub fn txout(&self, outpoint: OutPoint) -> Option<(&I, &TxOut)> {
-        self.txouts
-            .get(&outpoint)
-            .map(|(spk_i, txout)| (spk_i, txout))
+        self.txouts.get(&outpoint).map(|v| (&v.0, &v.1))
     }
 
     /// Returns the script that has been inserted at the `index`.
@@ -217,7 +215,7 @@ impl<I: Clone + Ord> SpkTxOutIndex<I> {
     /// let unused_change_spks =
     ///     txout_index.unused_spks((change_index, u32::MIN)..(change_index, u32::MAX));
     /// ```
-    pub fn unused_spks<R>(&self, range: R) -> impl DoubleEndedIterator<Item = (&I, &Script)>
+    pub fn unused_spks<R>(&self, range: R) -> impl DoubleEndedIterator<Item = (&I, &Script)> + Clone
     where
         R: RangeBounds<I>,
     {

crates/chain/src/tx_data_traits.rs

@@ -5,21 +5,25 @@ use alloc::vec::Vec;
 
 /// Trait that "anchors" blockchain data to a specific block of height and hash.
 ///
-/// [`Anchor`] implementations must be [`Ord`] by the anchor block's [`BlockId`] first.
-///
-/// I.e. If transaction A is anchored in block B, then if block B is in the best chain, we can
+/// If transaction A is anchored in block B, and block B is in the best chain, we can
 /// assume that transaction A is also confirmed in the best chain. This does not necessarily mean
 /// that transaction A is confirmed in block B. It could also mean transaction A is confirmed in a
 /// parent block of B.
 ///
+/// Every [`Anchor`] implementation must contain a [`BlockId`] parameter, and must implement
+/// [`Ord`]. When implementing [`Ord`], the anchors' [`BlockId`]s should take precedence
+/// over other elements inside the [`Anchor`]s for comparison purposes, i.e., you should first
+/// compare the anchors' [`BlockId`]s and then care about the rest.
+///
+/// The example shows different types of anchors:
 /// ```
 /// # use bdk_chain::local_chain::LocalChain;
 /// # use bdk_chain::tx_graph::TxGraph;
 /// # use bdk_chain::BlockId;
 /// # use bdk_chain::ConfirmationHeightAnchor;
+/// # use bdk_chain::ConfirmationTimeHeightAnchor;
 /// # use bdk_chain::example_utils::*;
 /// # use bitcoin::hashes::Hash;
-///
 /// // Initialize the local chain with two blocks.
 /// let chain = LocalChain::from_blocks(
 ///     [
@@ -47,6 +51,7 @@ use alloc::vec::Vec;
 /// );
 ///
 /// // Insert `tx` into a `TxGraph` that uses `ConfirmationHeightAnchor` as the anchor type.
+/// // This anchor records the anchor block and the confirmation height of the transaction.
 /// // When a transaction is anchored with `ConfirmationHeightAnchor`, the anchor block and
 /// // confirmation block can be different. However, the confirmation block cannot be higher than
 /// // the anchor block and both blocks must be in the same chain for the anchor to be valid.
@@ -62,6 +67,25 @@ use alloc::vec::Vec;
 ///         confirmation_height: 1,
 ///     },
 /// );
+///
+/// // Insert `tx` into a `TxGraph` that uses `ConfirmationTimeHeightAnchor` as the anchor type.
+/// // This anchor records the anchor block, the confirmation height and time of the transaction.
+/// // When a transaction is anchored with `ConfirmationTimeHeightAnchor`, the anchor block and
+/// // confirmation block can be different. However, the confirmation block cannot be higher than
+/// // the anchor block and both blocks must be in the same chain for the anchor to be valid.
+/// let mut graph_c = TxGraph::<ConfirmationTimeHeightAnchor>::default();
+/// let _ = graph_c.insert_tx(tx.clone());
+/// graph_c.insert_anchor(
+///     tx.txid(),
+///     ConfirmationTimeHeightAnchor {
+///         anchor_block: BlockId {
+///             height: 2,
+///             hash: Hash::hash("third".as_bytes()),
+///         },
+///         confirmation_height: 1,
+///         confirmation_time: 123,
+///     },
+/// );
 /// ```
 pub trait Anchor: core::fmt::Debug + Clone + Eq + PartialOrd + Ord + core::hash::Hash {
     /// Returns the [`BlockId`] that the associated blockchain data is "anchored" in.
@@ -99,8 +123,10 @@ pub trait Append {
 }
 
 impl<K: Ord, V> Append for BTreeMap<K, V> {
-    fn append(&mut self, mut other: Self) {
-        BTreeMap::append(self, &mut other)
+    fn append(&mut self, other: Self) {
+        // We use `extend` instead of `BTreeMap::append` due to performance issues with `append`.
+        // Refer to https://github.com/rust-lang/rust/issues/34666#issuecomment-675658420
+        BTreeMap::extend(self, other)
     }
 
     fn is_empty(&self) -> bool {
@@ -109,8 +135,10 @@ impl<K: Ord, V> Append for BTreeMap<K, V> {
 }
 
 impl<T: Ord> Append for BTreeSet<T> {
-    fn append(&mut self, mut other: Self) {
-        BTreeSet::append(self, &mut other)
+    fn append(&mut self, other: Self) {
+        // We use `extend` instead of `BTreeMap::append` due to performance issues with `append`.
+        // Refer to https://github.com/rust-lang/rust/issues/34666#issuecomment-675658420
+        BTreeSet::extend(self, other)
     }
 
     fn is_empty(&self) -> bool {

crates/chain/src/tx_graph.rs

@@ -1,12 +1,32 @@
 //! Module for structures that store and traverse transactions.
 //!
-//! [`TxGraph`] is a monotone structure that inserts transactions and indexes the spends. The
-//! [`ChangeSet`] structure reports changes of [`TxGraph`] but can also be applied to a
-//! [`TxGraph`] as well. Lastly, [`TxDescendants`] is an [`Iterator`] that traverses descendants of
-//! a given transaction.
+//! [`TxGraph`] contains transactions and indexes them so you can easily traverse the graph of those transactions.
+//! `TxGraph` is *monotone* in that you can always insert a transaction -- it doesn't care whether that
+//! transaction is in the current best chain or whether it conflicts with any of the
+//! existing transactions or what order you insert the transactions. This means that you can always
+//! combine two [`TxGraph`]s together, without resulting in inconsistencies.
+//! Furthermore, there is currently no way to delete a transaction.
+//!
+//! Transactions can be either whole or partial (i.e., transactions for which we only
+//! know some outputs, which we usually call "floating outputs"; these are usually inserted
+//! using the [`insert_txout`] method.).
+//!
+//! The graph contains transactions in the form of [`TxNode`]s. Each node contains the
+//! txid, the transaction (whole or partial), the blocks it's anchored in (see the [`Anchor`]
+//! documentation for more details), and the timestamp of the last time we saw
+//! the transaction as unconfirmed.
 //!
 //! Conflicting transactions are allowed to coexist within a [`TxGraph`]. This is useful for
-//! identifying and traversing conflicts and descendants of a given transaction.
+//! identifying and traversing conflicts and descendants of a given transaction. Some [`TxGraph`]
+//! methods only consider "canonical" (i.e., in the best chain or in mempool) transactions,
+//! we decide which transactions are canonical based on anchors `last_seen_unconfirmed`;
+//! see the [`try_get_chain_position`] documentation for more details.
+//!
+//! The [`ChangeSet`] reports changes made to a [`TxGraph`]; it can be used to either save to
+//! persistent storage, or to be applied to another [`TxGraph`].
+//!
+//! Lastly, you can use [`TxAncestors`]/[`TxDescendants`] to traverse ancestors and descendants of
+//! a given transaction, respectively.
 //!
 //! # Applying changes
 //!
@@ -49,6 +69,8 @@
 //! let changeset = graph.apply_update(update);
 //! assert!(changeset.is_empty());
 //! ```
+//! [`try_get_chain_position`]: TxGraph::try_get_chain_position
+//! [`insert_txout`]: TxGraph::insert_txout
 
 use crate::{
     collections::*, keychain::Balance, local_chain::LocalChain, Anchor, Append, BlockId,
@@ -91,7 +113,7 @@ impl<A> Default for TxGraph<A> {
     }
 }
 
-/// An outward-facing view of a (transaction) node in the [`TxGraph`].
+/// A transaction node in the [`TxGraph`].
 #[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
 pub struct TxNode<'a, T, A> {
     /// Txid of the transaction.
@@ -128,7 +150,7 @@ impl Default for TxNodeInternal {
     }
 }
 
-/// An outwards-facing view of a transaction that is part of the *best chain*'s history.
+/// A transaction that is included in the chain, or is still in mempool.
 #[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
 pub struct CanonicalTx<'a, T, A> {
     /// How the transaction is observed as (confirmed or unconfirmed).
@@ -315,7 +337,7 @@ impl<A> TxGraph<A> {
 
     /// The transactions spending from this output.
     ///
-    /// `TxGraph` allows conflicting transactions within the graph. Obviously the transactions in
+    /// [`TxGraph`] allows conflicting transactions within the graph. Obviously the transactions in
     /// the returned set will never be in the same active-chain.
     pub fn outspends(&self, outpoint: OutPoint) -> &HashSet<Txid> {
         self.spends.get(&outpoint).unwrap_or(&self.empty_outspends)
@@ -475,7 +497,7 @@ impl<A: Clone + Ord> TxGraph<A> {
     /// Batch insert unconfirmed transactions.
     ///
     /// Items of `txs` are tuples containing the transaction and a *last seen* timestamp. The
-    /// *last seen* communicates when the transaction is last seen in the mempool which is used for
+    /// *last seen* communicates when the transaction is last seen in mempool which is used for
     /// conflict-resolution (refer to [`TxGraph::insert_seen_at`] for details).
     pub fn batch_insert_unconfirmed(
         &mut self,
@@ -559,10 +581,7 @@ impl<A: Clone + Ord> TxGraph<A> {
         }
 
         for (outpoint, txout) in changeset.txouts {
-            let tx_entry = self
-                .txs
-                .entry(outpoint.txid)
-                .or_insert_with(Default::default);
+            let tx_entry = self.txs.entry(outpoint.txid).or_default();
 
             match tx_entry {
                 (TxNodeInternal::Whole(_), _, _) => { /* do nothing since we already have full tx */
@@ -575,13 +594,13 @@ impl<A: Clone + Ord> TxGraph<A> {
 
         for (anchor, txid) in changeset.anchors {
             if self.anchors.insert((anchor.clone(), txid)) {
-                let (_, anchors, _) = self.txs.entry(txid).or_insert_with(Default::default);
+                let (_, anchors, _) = self.txs.entry(txid).or_default();
                 anchors.insert(anchor);
             }
         }
 
         for (txid, new_last_seen) in changeset.last_seen {
-            let (_, _, last_seen) = self.txs.entry(txid).or_insert_with(Default::default);
+            let (_, _, last_seen) = self.txs.entry(txid).or_default();
             if new_last_seen > *last_seen {
                 *last_seen = new_last_seen;
             }
@@ -708,8 +727,20 @@ impl<A: Anchor> TxGraph<A> {
 
     /// Get the position of the transaction in `chain` with tip `chain_tip`.
     ///
-    /// If the given transaction of `txid` does not exist in the chain of `chain_tip`, `None` is
-    /// returned.
+    /// Chain data is fetched from `chain`, a [`ChainOracle`] implementation.
+    ///
+    /// This method returns `Ok(None)` if the transaction is not found in the chain, and no longer
+    /// belongs in the mempool. The following factors are used to approximate whether an
+    /// unconfirmed transaction exists in the mempool (not evicted):
+    ///
+    /// 1. Unconfirmed transactions that conflict with confirmed transactions are evicted.
+    /// 2. Unconfirmed transactions that spend from transactions that are evicted, are also
+    ///    evicted.
+    /// 3. Given two conflicting unconfirmed transactions, the transaction with the lower
+    ///    `last_seen_unconfirmed` parameter is evicted. A transaction's `last_seen_unconfirmed`
+    ///    parameter is the max of all it's descendants' `last_seen_unconfirmed` parameters. If the
+    ///    final `last_seen_unconfirmed`s are the same, the transaction with the lower `txid` (by
+    ///    lexicographical order) is evicted.
     ///
     /// # Error
     ///
@@ -735,7 +766,7 @@ impl<A: Anchor> TxGraph<A> {
             }
         }
 
-        // The tx is not anchored to a block which is in the best chain, which means that it
+        // The tx is not anchored to a block in the best chain, which means that it
         // might be in mempool, or it might have been dropped already.
         // Let's check conflicts to find out!
         let tx = match tx_node {
@@ -945,7 +976,8 @@ impl<A: Anchor> TxGraph<A> {
     /// (`OI`) for convenience. If `OI` is not necessary, the caller can use `()`, or
     /// [`Iterator::enumerate`] over a list of [`OutPoint`]s.
     ///
-    /// Floating outputs are ignored.
+    /// Floating outputs (i.e., outputs for which we don't have the full transaction in the graph)
+    /// are ignored.
     ///
     /// # Error
     ///
@@ -1136,9 +1168,9 @@ impl<A: Anchor> TxGraph<A> {
     }
 }
 
-/// A structure that represents changes to a [`TxGraph`].
+/// The [`ChangeSet`] represents changes to a [`TxGraph`].
 ///
-/// Since [`TxGraph`] is monotone "changeset" can only contain transactions to be added and
+/// Since [`TxGraph`] is monotone, the "changeset" can only contain transactions to be added and
 /// not removed.
 ///
 /// Refer to [module-level documentation] for more.
@@ -1239,10 +1271,12 @@ impl<A> ChangeSet<A> {
 }
 
 impl<A: Ord> Append for ChangeSet<A> {
-    fn append(&mut self, mut other: Self) {
-        self.txs.append(&mut other.txs);
-        self.txouts.append(&mut other.txouts);
-        self.anchors.append(&mut other.anchors);
+    fn append(&mut self, other: Self) {
+        // We use `extend` instead of `BTreeMap::append` due to performance issues with `append`.
+        // Refer to https://github.com/rust-lang/rust/issues/34666#issuecomment-675658420
+        self.txs.extend(other.txs);
+        self.txouts.extend(other.txouts);
+        self.anchors.extend(other.anchors);
 
         // last_seen timestamps should only increase
         self.last_seen.extend(
@@ -1272,7 +1306,7 @@ impl<A> AsRef<TxGraph<A>> for TxGraph<A> {
 ///
 /// The iterator excludes partial transactions.
 ///
-/// This `struct` is created by the [`walk_ancestors`] method of [`TxGraph`].
+/// Returned by the [`walk_ancestors`] method of [`TxGraph`].
 ///
 /// [`walk_ancestors`]: TxGraph::walk_ancestors
 pub struct TxAncestors<'g, A, F> {
@@ -1390,7 +1424,7 @@ where
 
 /// An iterator that traverses transaction descendants.
 ///
-/// This `struct` is created by the [`walk_descendants`] method of [`TxGraph`].
+/// Returned by the [`walk_descendants`] method of [`TxGraph`].
 ///
 /// [`walk_descendants`]: TxGraph::walk_descendants
 pub struct TxDescendants<'g, A, F> {

crates/chain/tests/common/mod.rs

@@ -1,4 +1,5 @@
 mod tx_template;
+#[allow(unused_imports)]
 pub use tx_template::*;
 
 #[allow(unused_macros)]

crates/chain/tests/test_indexed_tx_graph.rs

@@ -27,9 +27,10 @@ fn insert_relevant_txs() {
     let spk_0 = descriptor.at_derivation_index(0).unwrap().script_pubkey();
     let spk_1 = descriptor.at_derivation_index(9).unwrap().script_pubkey();
 
-    let mut graph = IndexedTxGraph::<ConfirmationHeightAnchor, KeychainTxOutIndex<()>>::default();
+    let mut graph = IndexedTxGraph::<ConfirmationHeightAnchor, KeychainTxOutIndex<()>>::new(
+        KeychainTxOutIndex::new(10),
+    );
     graph.index.add_keychain((), descriptor);
-    graph.index.set_lookahead(&(), 10);
 
     let tx_a = Transaction {
         output: vec![
@@ -118,12 +119,12 @@ fn test_list_owned_txouts() {
     let (desc_1, _) = Descriptor::parse_descriptor(&Secp256k1::signing_only(), "tr(tprv8ZgxMBicQKsPd3krDUsBAmtnRsK3rb8u5yi1zhQgMhF1tR8MW7xfE4rnrbbsrbPR52e7rKapu6ztw1jXveJSCGHEriUGZV7mCe88duLp5pj/86'/1'/0'/0/*)").unwrap();
     let (desc_2, _) = Descriptor::parse_descriptor(&Secp256k1::signing_only(), "tr(tprv8ZgxMBicQKsPd3krDUsBAmtnRsK3rb8u5yi1zhQgMhF1tR8MW7xfE4rnrbbsrbPR52e7rKapu6ztw1jXveJSCGHEriUGZV7mCe88duLp5pj/86'/1'/0'/1/*)").unwrap();
 
-    let mut graph =
-        IndexedTxGraph::<ConfirmationHeightAnchor, KeychainTxOutIndex<String>>::default();
+    let mut graph = IndexedTxGraph::<ConfirmationHeightAnchor, KeychainTxOutIndex<String>>::new(
+        KeychainTxOutIndex::new(10),
+    );
 
     graph.index.add_keychain("keychain_1".into(), desc_1);
     graph.index.add_keychain("keychain_2".into(), desc_2);
-    graph.index.set_lookahead_for_all(10);
 
     // Get trusted and untrusted addresses
 

crates/chain/tests/test_keychain_txout_index.rs

@@ -18,12 +18,14 @@ enum TestKeychain {
     Internal,
 }
 
-fn init_txout_index() -> (
+fn init_txout_index(
+    lookahead: u32,
+) -> (
     bdk_chain::keychain::KeychainTxOutIndex<TestKeychain>,
     Descriptor<DescriptorPublicKey>,
     Descriptor<DescriptorPublicKey>,
 ) {
-    let mut txout_index = bdk_chain::keychain::KeychainTxOutIndex::<TestKeychain>::default();
+    let mut txout_index = bdk_chain::keychain::KeychainTxOutIndex::<TestKeychain>::new(lookahead);
 
     let secp = bdk_chain::bitcoin::secp256k1::Secp256k1::signing_only();
     let (external_descriptor,_) = Descriptor::<DescriptorPublicKey>::parse_descriptor(&secp, "tr([73c5da0a/86'/0'/0']xprv9xgqHN7yz9MwCkxsBPN5qetuNdQSUttZNKw1dcYTV4mkaAFiBVGQziHs3NRSWMkCzvgjEe3n9xV8oYywvM8at9yRqyaZVz6TYYhX98VjsUk/0/*)").unwrap();
@@ -46,7 +48,7 @@ fn spk_at_index(descriptor: &Descriptor<DescriptorPublicKey>, index: u32) -> Scr
 fn test_set_all_derivation_indices() {
     use bdk_chain::indexed_tx_graph::Indexer;
 
-    let (mut txout_index, _, _) = init_txout_index();
+    let (mut txout_index, _, _) = init_txout_index(0);
     let derive_to: BTreeMap<_, _> =
         [(TestKeychain::External, 12), (TestKeychain::Internal, 24)].into();
     assert_eq!(
@@ -64,19 +66,10 @@ fn test_set_all_derivation_indices() {
 
 #[test]
 fn test_lookahead() {
-    let (mut txout_index, external_desc, internal_desc) = init_txout_index();
-
-    // ensure it does not break anything if lookahead is set multiple times
-    (0..=10).for_each(|lookahead| txout_index.set_lookahead(&TestKeychain::External, lookahead));
-    (0..=20)
-        .filter(|v| v % 2 == 0)
-        .for_each(|lookahead| txout_index.set_lookahead(&TestKeychain::Internal, lookahead));
-
-    assert_eq!(txout_index.inner().all_spks().len(), 30);
+    let (mut txout_index, external_desc, internal_desc) = init_txout_index(10);
 
     // given:
     // - external lookahead set to 10
-    // - internal lookahead set to 20
     // when:
     // - set external derivation index to value higher than last, but within the lookahead value
     // expect:
@@ -97,37 +90,37 @@ fn test_lookahead() {
         assert_eq!(
             txout_index.inner().all_spks().len(),
             10 /* external lookahead */ +
-            20 /* internal lookahead */ +
+            10 /* internal lookahead */ +
             index as usize + 1 /* `derived` count */
         );
         assert_eq!(
             txout_index
-                .revealed_spks_of_keychain(&TestKeychain::External)
+                .revealed_keychain_spks(&TestKeychain::External)
                 .count(),
             index as usize + 1,
         );
         assert_eq!(
             txout_index
-                .revealed_spks_of_keychain(&TestKeychain::Internal)
+                .revealed_keychain_spks(&TestKeychain::Internal)
                 .count(),
             0,
         );
         assert_eq!(
             txout_index
-                .unused_spks_of_keychain(&TestKeychain::External)
+                .unused_keychain_spks(&TestKeychain::External)
                 .count(),
             index as usize + 1,
         );
         assert_eq!(
             txout_index
-                .unused_spks_of_keychain(&TestKeychain::Internal)
+                .unused_keychain_spks(&TestKeychain::Internal)
                 .count(),
             0,
         );
     }
 
     // given:
-    // - internal lookahead is 20
+    // - internal lookahead is 10
     // - internal derivation index is `None`
     // when:
     // - derivation index is set ahead of current derivation index + lookahead
@@ -148,13 +141,13 @@ fn test_lookahead() {
     assert_eq!(
         txout_index.inner().all_spks().len(),
         10 /* external lookahead */ +
-        20 /* internal lookahead */ +
+        10 /* internal lookahead */ +
         20 /* external stored index count */ +
         25 /* internal stored index count */
     );
     assert_eq!(
         txout_index
-            .revealed_spks_of_keychain(&TestKeychain::Internal)
+            .revealed_keychain_spks(&TestKeychain::Internal)
             .count(),
         25,
     );
@@ -206,13 +199,13 @@ fn test_lookahead() {
         );
         assert_eq!(
             txout_index
-                .revealed_spks_of_keychain(&TestKeychain::External)
+                .revealed_keychain_spks(&TestKeychain::External)
                 .count(),
             last_external_index as usize + 1,
         );
         assert_eq!(
             txout_index
-                .revealed_spks_of_keychain(&TestKeychain::Internal)
+                .revealed_keychain_spks(&TestKeychain::Internal)
                 .count(),
             last_internal_index as usize + 1,
         );
@@ -226,8 +219,7 @@ fn test_lookahead() {
 // - last used index should change as expected
 #[test]
 fn test_scan_with_lookahead() {
-    let (mut txout_index, external_desc, _) = init_txout_index();
-    txout_index.set_lookahead_for_all(10);
+    let (mut txout_index, external_desc, _) = init_txout_index(10);
 
     let spks: BTreeMap<u32, ScriptBuf> = [0, 10, 20, 30]
         .into_iter()
@@ -281,7 +273,7 @@ fn test_scan_with_lookahead() {
 #[test]
 #[rustfmt::skip]
 fn test_wildcard_derivations() {
-    let (mut txout_index, external_desc, _) = init_txout_index();
+    let (mut txout_index, external_desc, _) = init_txout_index(0);
     let external_spk_0 = external_desc.at_derivation_index(0).unwrap().script_pubkey();
     let external_spk_16 = external_desc.at_derivation_index(16).unwrap().script_pubkey();
     let external_spk_26 = external_desc.at_derivation_index(26).unwrap().script_pubkey();
@@ -313,7 +305,7 @@ fn test_wildcard_derivations() {
 
     (0..=15)
         .chain([17, 20, 23])
-        .for_each(|index| assert!(txout_index.mark_used(&TestKeychain::External, index)));
+        .for_each(|index| assert!(txout_index.mark_used(TestKeychain::External, index)));
 
     assert_eq!(txout_index.next_index(&TestKeychain::External), (26, true));
 
@@ -329,7 +321,7 @@ fn test_wildcard_derivations() {
     // - Use all the derived till 26.
     // - next_unused() = ((27, <spk>), keychain::ChangeSet)
     (0..=26).for_each(|index| {
-        txout_index.mark_used(&TestKeychain::External, index);
+        txout_index.mark_used(TestKeychain::External, index);
     });
 
     let (spk, changeset) = txout_index.next_unused_spk(&TestKeychain::External);
@@ -339,7 +331,7 @@ fn test_wildcard_derivations() {
 
 #[test]
 fn test_non_wildcard_derivations() {
-    let mut txout_index = KeychainTxOutIndex::<TestKeychain>::default();
+    let mut txout_index = KeychainTxOutIndex::<TestKeychain>::new(0);
 
     let secp = bitcoin::secp256k1::Secp256k1::signing_only();
     let (no_wildcard_descriptor, _) = Descriptor::<DescriptorPublicKey>::parse_descriptor(&secp, "wpkh([73c5da0a/86'/0'/0']xprv9xgqHN7yz9MwCkxsBPN5qetuNdQSUttZNKw1dcYTV4mkaAFiBVGQziHs3NRSWMkCzvgjEe3n9xV8oYywvM8at9yRqyaZVz6TYYhX98VjsUk/1/0)").unwrap();
@@ -372,7 +364,7 @@ fn test_non_wildcard_derivations() {
     // - derive new and next unused should return the old script
     // - store_up_to should not panic and return empty changeset
     assert_eq!(txout_index.next_index(&TestKeychain::External), (0, false));
-    txout_index.mark_used(&TestKeychain::External, 0);
+    txout_index.mark_used(TestKeychain::External, 0);
 
     let (spk, changeset) = txout_index.reveal_next_spk(&TestKeychain::External);
     assert_eq!(spk, (0, external_spk.as_script()));
@@ -389,7 +381,7 @@ fn test_non_wildcard_derivations() {
     // we check that spks_of_keychain returns a SpkIterator with just one element
     assert_eq!(
         txout_index
-            .spks_of_keychain(&TestKeychain::External)
+            .revealed_keychain_spks(&TestKeychain::External)
             .count(),
         1,
     );

crates/chain/tests/test_local_chain.rs

@@ -1,7 +1,11 @@
-use bdk_chain::local_chain::{
-    AlterCheckPointError, CannotConnectError, ChangeSet, LocalChain, Update,
+use bdk_chain::{
+    local_chain::{
+        AlterCheckPointError, ApplyHeaderError, CannotConnectError, ChangeSet, CheckPoint,
+        LocalChain, MissingGenesisError, Update,
+    },
+    BlockId,
 };
-use bitcoin::BlockHash;
+use bitcoin::{block::Header, hashes::Hash, BlockHash};
 
 #[macro_use]
 mod common;
@@ -288,6 +292,27 @@ fn update_local_chain() {
                 ],
             },
         },
+        // Allow update that is shorter than original chain
+        //        | 0 | 1 | 2 | 3 | 4 | 5
+        // chain  | A       C   D   E   F
+        // update | A       C   D'
+        TestLocalChain {
+            name: "allow update that is shorter than original chain",
+            chain: local_chain![(0, h!("_")), (2, h!("C")), (3, h!("D")), (4, h!("E")), (5, h!("F"))],
+            update: chain_update![(0, h!("_")), (2, h!("C")), (3, h!("D'"))],
+            exp: ExpectedResult::Ok {
+                changeset: &[
+                    (3, Some(h!("D'"))),
+                    (4, None),
+                    (5, None),
+                ],
+                init_changeset: &[
+                    (0, Some(h!("_"))),
+                    (2, Some(h!("C"))),
+                    (3, Some(h!("D'"))),
+                ],
+            },
+        },
     ]
     .into_iter()
     .for_each(TestLocalChain::run);
@@ -350,3 +375,307 @@ fn local_chain_insert_block() {
         assert_eq!(chain, t.expected_final, "[{}] unexpected final chain", i,);
     }
 }
+
+#[test]
+fn local_chain_disconnect_from() {
+    struct TestCase {
+        name: &'static str,
+        original: LocalChain,
+        disconnect_from: (u32, BlockHash),
+        exp_result: Result<ChangeSet, MissingGenesisError>,
+        exp_final: LocalChain,
+    }
+
+    let test_cases = [
+        TestCase {
+            name: "try_replace_genesis_should_fail",
+            original: local_chain![(0, h!("_"))],
+            disconnect_from: (0, h!("_")),
+            exp_result: Err(MissingGenesisError),
+            exp_final: local_chain![(0, h!("_"))],
+        },
+        TestCase {
+            name: "try_replace_genesis_should_fail_2",
+            original: local_chain![(0, h!("_")), (2, h!("B")), (3, h!("C"))],
+            disconnect_from: (0, h!("_")),
+            exp_result: Err(MissingGenesisError),
+            exp_final: local_chain![(0, h!("_")), (2, h!("B")), (3, h!("C"))],
+        },
+        TestCase {
+            name: "from_does_not_exist",
+            original: local_chain![(0, h!("_")), (3, h!("C"))],
+            disconnect_from: (2, h!("B")),
+            exp_result: Ok(ChangeSet::default()),
+            exp_final: local_chain![(0, h!("_")), (3, h!("C"))],
+        },
+        TestCase {
+            name: "from_has_different_blockhash",
+            original: local_chain![(0, h!("_")), (2, h!("B"))],
+            disconnect_from: (2, h!("not_B")),
+            exp_result: Ok(ChangeSet::default()),
+            exp_final: local_chain![(0, h!("_")), (2, h!("B"))],
+        },
+        TestCase {
+            name: "disconnect_one",
+            original: local_chain![(0, h!("_")), (2, h!("B"))],
+            disconnect_from: (2, h!("B")),
+            exp_result: Ok(ChangeSet::from_iter([(2, None)])),
+            exp_final: local_chain![(0, h!("_"))],
+        },
+        TestCase {
+            name: "disconnect_three",
+            original: local_chain![(0, h!("_")), (2, h!("B")), (3, h!("C")), (4, h!("D"))],
+            disconnect_from: (2, h!("B")),
+            exp_result: Ok(ChangeSet::from_iter([(2, None), (3, None), (4, None)])),
+            exp_final: local_chain![(0, h!("_"))],
+        },
+    ];
+
+    for (i, t) in test_cases.into_iter().enumerate() {
+        println!("Case {}: {}", i, t.name);
+
+        let mut chain = t.original;
+        let result = chain.disconnect_from(t.disconnect_from.into());
+        assert_eq!(
+            result, t.exp_result,
+            "[{}:{}] unexpected changeset result",
+            i, t.name
+        );
+        assert_eq!(
+            chain, t.exp_final,
+            "[{}:{}] unexpected final chain",
+            i, t.name
+        );
+    }
+}
+
+#[test]
+fn checkpoint_from_block_ids() {
+    struct TestCase<'a> {
+        name: &'a str,
+        blocks: &'a [(u32, BlockHash)],
+        exp_result: Result<(), Option<(u32, BlockHash)>>,
+    }
+
+    let test_cases = [
+        TestCase {
+            name: "in_order",
+            blocks: &[(0, h!("A")), (1, h!("B")), (3, h!("D"))],
+            exp_result: Ok(()),
+        },
+        TestCase {
+            name: "with_duplicates",
+            blocks: &[(1, h!("B")), (2, h!("C")), (2, h!("C'"))],
+            exp_result: Err(Some((2, h!("C")))),
+        },
+        TestCase {
+            name: "not_in_order",
+            blocks: &[(1, h!("B")), (3, h!("D")), (2, h!("C"))],
+            exp_result: Err(Some((3, h!("D")))),
+        },
+        TestCase {
+            name: "empty",
+            blocks: &[],
+            exp_result: Err(None),
+        },
+        TestCase {
+            name: "single",
+            blocks: &[(21, h!("million"))],
+            exp_result: Ok(()),
+        },
+    ];
+
+    for (i, t) in test_cases.into_iter().enumerate() {
+        println!("running test case {}: '{}'", i, t.name);
+        let result = CheckPoint::from_block_ids(
+            t.blocks
+                .iter()
+                .map(|&(height, hash)| BlockId { height, hash }),
+        );
+        match t.exp_result {
+            Ok(_) => {
+                assert!(result.is_ok(), "[{}:{}] should be Ok", i, t.name);
+                let result_vec = {
+                    let mut v = result
+                        .unwrap()
+                        .into_iter()
+                        .map(|cp| (cp.height(), cp.hash()))
+                        .collect::<Vec<_>>();
+                    v.reverse();
+                    v
+                };
+                assert_eq!(
+                    &result_vec, t.blocks,
+                    "[{}:{}] not equal to original block ids",
+                    i, t.name
+                );
+            }
+            Err(exp_last) => {
+                assert!(result.is_err(), "[{}:{}] should be Err", i, t.name);
+                let err = result.unwrap_err();
+                assert_eq!(
+                    err.as_ref()
+                        .map(|last_cp| (last_cp.height(), last_cp.hash())),
+                    exp_last,
+                    "[{}:{}] error's last cp height should be {:?}, got {:?}",
+                    i,
+                    t.name,
+                    exp_last,
+                    err
+                );
+            }
+        }
+    }
+}
+
+#[test]
+fn local_chain_apply_header_connected_to() {
+    fn header_from_prev_blockhash(prev_blockhash: BlockHash) -> Header {
+        Header {
+            version: bitcoin::block::Version::default(),
+            prev_blockhash,
+            merkle_root: bitcoin::hash_types::TxMerkleNode::all_zeros(),
+            time: 0,
+            bits: bitcoin::CompactTarget::default(),
+            nonce: 0,
+        }
+    }
+
+    struct TestCase {
+        name: &'static str,
+        chain: LocalChain,
+        header: Header,
+        height: u32,
+        connected_to: BlockId,
+        exp_result: Result<Vec<(u32, Option<BlockHash>)>, ApplyHeaderError>,
+    }
+
+    let test_cases = [
+        {
+            let header = header_from_prev_blockhash(h!("A"));
+            let hash = header.block_hash();
+            let height = 2;
+            let connected_to = BlockId { height, hash };
+            TestCase {
+                name: "connected_to_self_header_applied_to_self",
+                chain: local_chain![(0, h!("_")), (height, hash)],
+                header,
+                height,
+                connected_to,
+                exp_result: Ok(vec![]),
+            }
+        },
+        {
+            let prev_hash = h!("A");
+            let prev_height = 1;
+            let header = header_from_prev_blockhash(prev_hash);
+            let hash = header.block_hash();
+            let height = prev_height + 1;
+            let connected_to = BlockId {
+                height: prev_height,
+                hash: prev_hash,
+            };
+            TestCase {
+                name: "connected_to_prev_header_applied_to_self",
+                chain: local_chain![(0, h!("_")), (prev_height, prev_hash)],
+                header,
+                height,
+                connected_to,
+                exp_result: Ok(vec![(height, Some(hash))]),
+            }
+        },
+        {
+            let header = header_from_prev_blockhash(BlockHash::all_zeros());
+            let hash = header.block_hash();
+            let height = 0;
+            let connected_to = BlockId { height, hash };
+            TestCase {
+                name: "genesis_applied_to_self",
+                chain: local_chain![(0, hash)],
+                header,
+                height,
+                connected_to,
+                exp_result: Ok(vec![]),
+            }
+        },
+        {
+            let header = header_from_prev_blockhash(h!("Z"));
+            let height = 10;
+            let hash = header.block_hash();
+            let prev_height = height - 1;
+            let prev_hash = header.prev_blockhash;
+            TestCase {
+                name: "connect_at_connected_to",
+                chain: local_chain![(0, h!("_")), (2, h!("B")), (3, h!("C"))],
+                header,
+                height: 10,
+                connected_to: BlockId {
+                    height: 3,
+                    hash: h!("C"),
+                },
+                exp_result: Ok(vec![(prev_height, Some(prev_hash)), (height, Some(hash))]),
+            }
+        },
+        {
+            let prev_hash = h!("A");
+            let prev_height = 1;
+            let header = header_from_prev_blockhash(prev_hash);
+            let connected_to = BlockId {
+                height: prev_height,
+                hash: h!("not_prev_hash"),
+            };
+            TestCase {
+                name: "inconsistent_prev_hash",
+                chain: local_chain![(0, h!("_")), (prev_height, h!("not_prev_hash"))],
+                header,
+                height: prev_height + 1,
+                connected_to,
+                exp_result: Err(ApplyHeaderError::InconsistentBlocks),
+            }
+        },
+        {
+            let prev_hash = h!("A");
+            let prev_height = 1;
+            let header = header_from_prev_blockhash(prev_hash);
+            let height = prev_height + 1;
+            let connected_to = BlockId {
+                height,
+                hash: h!("not_current_hash"),
+            };
+            TestCase {
+                name: "inconsistent_current_block",
+                chain: local_chain![(0, h!("_")), (height, h!("not_current_hash"))],
+                header,
+                height,
+                connected_to,
+                exp_result: Err(ApplyHeaderError::InconsistentBlocks),
+            }
+        },
+        {
+            let header = header_from_prev_blockhash(h!("B"));
+            let height = 3;
+            let connected_to = BlockId {
+                height: 4,
+                hash: h!("D"),
+            };
+            TestCase {
+                name: "connected_to_is_greater",
+                chain: local_chain![(0, h!("_")), (2, h!("B"))],
+                header,
+                height,
+                connected_to,
+                exp_result: Err(ApplyHeaderError::InconsistentBlocks),
+            }
+        },
+    ];
+
+    for (i, t) in test_cases.into_iter().enumerate() {
+        println!("running test case {}: '{}'", i, t.name);
+        let mut chain = t.chain;
+        let result = chain.apply_header_connected_to(&t.header, t.height, t.connected_to);
+        let exp_result = t
+            .exp_result
+            .map(|cs| cs.iter().cloned().collect::<ChangeSet>());
+        assert_eq!(result, exp_result, "[{}:{}] unexpected result", i, t.name);
+    }
+}

crates/chain/tests/test_tx_graph_conflicts.rs

@@ -110,6 +110,7 @@ fn test_tx_conflict_handling() {
                     ..Default::default()
                 },
             ],
+            // the txgraph is going to pick tx_conflict_2 because of higher lexicographical txid
             exp_chain_txs: HashSet::from(["tx1", "tx_conflict_2"]),
             exp_chain_txouts: HashSet::from([("tx1", 0), ("tx_conflict_2", 0)]),
             exp_unspents: HashSet::from([("tx_conflict_2", 0)]),

crates/electrum/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "bdk_electrum"
-version = "0.4.0"
+version = "0.7.0"
 edition = "2021"
 homepage = "https://bitcoindevkit.org"
 repository = "https://github.com/bitcoindevkit/bdk"
@@ -12,6 +12,6 @@ readme = "README.md"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
-bdk_chain = { path = "../chain", version = "0.6.0", default-features = false }
+bdk_chain = { path = "../chain", version = "0.9.0", default-features = false }
 electrum-client = { version = "0.18" }
 #rustls = { version = "=0.21.1", optional = true, features = ["dangerous_configuration"] }

crates/electrum/README.md

@@ -1,3 +1,7 @@
 # BDK Electrum
 
-BDK Electrum client library for updating the keychain tracker.
+BDK Electrum extends [`electrum-client`] to update [`bdk_chain`] structures
+from an Electrum server.
+
+[`electrum-client`]: https://docs.rs/electrum-client/
+[`bdk_chain`]: https://docs.rs/bdk-chain/

crates/electrum/src/electrum_ext.rs

@@ -56,12 +56,14 @@ impl RelevantTxids {
         Ok(graph)
     }
 
-    /// Finalizes [`RelevantTxids`] with `new_txs` and anchors of type
-    /// [`ConfirmationTimeHeightAnchor`].
+    /// Finalizes the update by fetching `missing` txids from the `client`, where the
+    /// resulting [`TxGraph`] has anchors of type [`ConfirmationTimeHeightAnchor`].
+    ///
+    /// Refer to [`RelevantTxids`] for more details.
     ///
     /// **Note:** The confirmation time might not be precisely correct if there has been a reorg.
-    /// Electrum's API intends that we use the merkle proof API, we should change `bdk_electrum` to
-    /// use it.
+    // Electrum's API intends that we use the merkle proof API, we should change `bdk_electrum` to
+    // use it.
     pub fn into_confirmation_time_tx_graph(
         self,
         client: &Client,
@@ -134,76 +136,63 @@ pub struct ElectrumUpdate {
 
 /// Trait to extend [`Client`] functionality.
 pub trait ElectrumExt {
-    /// Scan the blockchain (via electrum) for the data specified and returns updates for
-    /// [`bdk_chain`] data structures.
+    /// Full scan the keychain scripts specified with the blockchain (via an Electrum client) and
+    /// returns updates for [`bdk_chain`] data structures.
     ///
     /// - `prev_tip`: the most recent blockchain tip present locally
     /// - `keychain_spks`: keychains that we want to scan transactions for
-    /// - `txids`: transactions for which we want updated [`Anchor`]s
-    /// - `outpoints`: transactions associated with these outpoints (residing, spending) that we
-    ///     want to included in the update
     ///
-    /// The scan for each keychain stops after a gap of `stop_gap` script pubkeys with no associated
+    /// The full scan for each keychain stops after a gap of `stop_gap` script pubkeys with no associated
     /// transactions. `batch_size` specifies the max number of script pubkeys to request for in a
     /// single batch request.
-    fn scan<K: Ord + Clone>(
+    fn full_scan<K: Ord + Clone>(
         &self,
         prev_tip: CheckPoint,
         keychain_spks: BTreeMap<K, impl IntoIterator<Item = (u32, ScriptBuf)>>,
-        txids: impl IntoIterator<Item = Txid>,
-        outpoints: impl IntoIterator<Item = OutPoint>,
         stop_gap: usize,
         batch_size: usize,
     ) -> Result<(ElectrumUpdate, BTreeMap<K, u32>), Error>;
 
-    /// Convenience method to call [`scan`] without requiring a keychain.
+    /// Sync a set of scripts with the blockchain (via an Electrum client) for the data specified
+    /// and returns updates for [`bdk_chain`] data structures.
     ///
-    /// [`scan`]: ElectrumExt::scan
-    fn scan_without_keychain(
+    /// - `prev_tip`: the most recent blockchain tip present locally
+    /// - `misc_spks`: an iterator of scripts we want to sync transactions for
+    /// - `txids`: transactions for which we want updated [`Anchor`]s
+    /// - `outpoints`: transactions associated with these outpoints (residing, spending) that we
+    ///     want to include in the update
+    ///
+    /// `batch_size` specifies the max number of script pubkeys to request for in a single batch
+    /// request.
+    ///
+    /// If the scripts to sync are unknown, such as when restoring or importing a keychain that
+    /// may include scripts that have been used, use [`full_scan`] with the keychain.
+    ///
+    /// [`full_scan`]: ElectrumExt::full_scan
+    fn sync(
         &self,
         prev_tip: CheckPoint,
         misc_spks: impl IntoIterator<Item = ScriptBuf>,
         txids: impl IntoIterator<Item = Txid>,
         outpoints: impl IntoIterator<Item = OutPoint>,
         batch_size: usize,
-    ) -> Result<ElectrumUpdate, Error> {
-        let spk_iter = misc_spks
-            .into_iter()
-            .enumerate()
-            .map(|(i, spk)| (i as u32, spk));
-
-        let (electrum_update, _) = self.scan(
-            prev_tip,
-            [((), spk_iter)].into(),
-            txids,
-            outpoints,
-            usize::MAX,
-            batch_size,
-        )?;
-
-        Ok(electrum_update)
-    }
+    ) -> Result<ElectrumUpdate, Error>;
 }
 
-impl ElectrumExt for Client {
-    fn scan<K: Ord + Clone>(
+impl<A: ElectrumApi> ElectrumExt for A {
+    fn full_scan<K: Ord + Clone>(
         &self,
         prev_tip: CheckPoint,
         keychain_spks: BTreeMap<K, impl IntoIterator<Item = (u32, ScriptBuf)>>,
-        txids: impl IntoIterator<Item = Txid>,
-        outpoints: impl IntoIterator<Item = OutPoint>,
         stop_gap: usize,
         batch_size: usize,
     ) -> Result<(ElectrumUpdate, BTreeMap<K, u32>), Error> {
         let mut request_spks = keychain_spks
             .into_iter()
-            .map(|(k, s)| (k, s.into_iter()))
+            .map(|(k, s)| (k.clone(), s.into_iter()))
             .collect::<BTreeMap<K, _>>();
         let mut scanned_spks = BTreeMap::<(K, u32), (ScriptBuf, bool)>::new();
 
-        let txids = txids.into_iter().collect::<Vec<_>>();
-        let outpoints = outpoints.into_iter().collect::<Vec<_>>();
-
         let (electrum_update, keychain_update) = loop {
             let (tip, _) = construct_update_tip(self, prev_tip.clone())?;
             let mut relevant_txids = RelevantTxids::default();
@@ -242,15 +231,6 @@ impl ElectrumExt for Client {
                 }
             }
 
-            populate_with_txids(self, &cps, &mut relevant_txids, &mut txids.iter().cloned())?;
-
-            let _txs = populate_with_outpoints(
-                self,
-                &cps,
-                &mut relevant_txids,
-                &mut outpoints.iter().cloned(),
-            )?;
-
             // check for reorgs during scan process
             let server_blockhash = self.block_header(tip.height() as usize)?.block_hash();
             if tip.hash() != server_blockhash {
@@ -284,11 +264,46 @@ impl ElectrumExt for Client {
 
         Ok((electrum_update, keychain_update))
     }
+
+    fn sync(
+        &self,
+        prev_tip: CheckPoint,
+        misc_spks: impl IntoIterator<Item = ScriptBuf>,
+        txids: impl IntoIterator<Item = Txid>,
+        outpoints: impl IntoIterator<Item = OutPoint>,
+        batch_size: usize,
+    ) -> Result<ElectrumUpdate, Error> {
+        let spk_iter = misc_spks
+            .into_iter()
+            .enumerate()
+            .map(|(i, spk)| (i as u32, spk));
+
+        let (mut electrum_update, _) = self.full_scan(
+            prev_tip.clone(),
+            [((), spk_iter)].into(),
+            usize::MAX,
+            batch_size,
+        )?;
+
+        let (tip, _) = construct_update_tip(self, prev_tip)?;
+        let cps = tip
+            .iter()
+            .take(10)
+            .map(|cp| (cp.height(), cp))
+            .collect::<BTreeMap<u32, CheckPoint>>();
+
+        populate_with_txids(self, &cps, &mut electrum_update.relevant_txids, txids)?;
+
+        let _txs =
+            populate_with_outpoints(self, &cps, &mut electrum_update.relevant_txids, outpoints)?;
+
+        Ok(electrum_update)
+    }
 }
 
 /// Return a [`CheckPoint`] of the latest tip, that connects with `prev_tip`.
 fn construct_update_tip(
-    client: &Client,
+    client: &impl ElectrumApi,
     prev_tip: CheckPoint,
 ) -> Result<(CheckPoint, Option<u32>), Error> {
     let HeaderNotification { height, .. } = client.block_headers_subscribe()?;
@@ -402,10 +417,10 @@ fn determine_tx_anchor(
 }
 
 fn populate_with_outpoints(
-    client: &Client,
+    client: &impl ElectrumApi,
     cps: &BTreeMap<u32, CheckPoint>,
     relevant_txids: &mut RelevantTxids,
-    outpoints: &mut impl Iterator<Item = OutPoint>,
+    outpoints: impl IntoIterator<Item = OutPoint>,
 ) -> Result<HashMap<Txid, Transaction>, Error> {
     let mut full_txs = HashMap::new();
     for outpoint in outpoints {
@@ -463,10 +478,10 @@ fn populate_with_outpoints(
 }
 
 fn populate_with_txids(
-    client: &Client,
+    client: &impl ElectrumApi,
     cps: &BTreeMap<u32, CheckPoint>,
     relevant_txids: &mut RelevantTxids,
-    txids: &mut impl Iterator<Item = Txid>,
+    txids: impl IntoIterator<Item = Txid>,
 ) -> Result<(), Error> {
     for txid in txids {
         let tx = match client.transaction_get(&txid) {
@@ -477,7 +492,7 @@ fn populate_with_txids(
 
         let spk = tx
             .output
-            .get(0)
+            .first()
             .map(|txo| &txo.script_pubkey)
             .expect("tx must have an output");
 
@@ -499,7 +514,7 @@ fn populate_with_txids(
 }
 
 fn populate_with_spks<I: Ord + Clone>(
-    client: &Client,
+    client: &impl ElectrumApi,
     cps: &BTreeMap<u32, CheckPoint>,
     relevant_txids: &mut RelevantTxids,
     spks: &mut impl Iterator<Item = (I, ScriptBuf)>,

crates/electrum/src/lib.rs

@@ -1,26 +1,26 @@
-//! This crate is used for updating structures of the [`bdk_chain`] crate with data from electrum.
+//! This crate is used for updating structures of [`bdk_chain`] with data from an Electrum server.
 //!
-//! The star of the show is the [`ElectrumExt::scan`] method, which scans for relevant blockchain
-//! data (via electrum) and outputs updates for [`bdk_chain`] structures as a tuple of form:
+//! The two primary methods are [`ElectrumExt::sync`] and [`ElectrumExt::full_scan`]. In most cases
+//! [`ElectrumExt::sync`] is used to sync the transaction histories of scripts that the application
+//! cares about, for example the scripts for all the receive addresses of a Wallet's keychain that it
+//! has shown a user. [`ElectrumExt::full_scan`] is meant to be used when importing or restoring a
+//! keychain where the range of possibly used scripts is not known. In this case it is necessary to
+//! scan all keychain scripts until a number (the "stop gap") of unused scripts is discovered. For a
+//! sync or full scan the user receives relevant blockchain data and output updates for
+//! [`bdk_chain`] including [`RelevantTxids`].
 //!
-//! ([`bdk_chain::local_chain::Update`], [`RelevantTxids`], `keychain_update`)
+//! The [`RelevantTxids`] only includes `txid`s and not full transactions. The caller is responsible
+//! for obtaining full transactions before applying new data to their [`bdk_chain`]. This can be
+//! done with these steps:
 //!
-//! An [`RelevantTxids`] only includes `txid`s and no full transactions. The caller is
-//! responsible for obtaining full transactions before applying. This can be done with
-//! these steps:
+//! 1. Determine which full transactions are missing. Use [`RelevantTxids::missing_full_txs`].
 //!
-//! 1. Determine which full transactions are missing. The method [`missing_full_txs`] of
-//! [`RelevantTxids`] can be used.
+//! 2. Obtaining the full transactions. To do this via electrum use [`ElectrumApi::batch_transaction_get`].
 //!
-//! 2. Obtaining the full transactions. To do this via electrum, the method
-//! [`batch_transaction_get`] can be used.
+//! Refer to [`example_electrum`] for a complete example.
 //!
-//! Refer to [`bdk_electrum_example`] for a complete example.
-//!
-//! [`ElectrumClient::scan`]: electrum_client::ElectrumClient::scan
-//! [`missing_full_txs`]: RelevantTxids::missing_full_txs
-//! [`batch_transaction_get`]: electrum_client::ElectrumApi::batch_transaction_get
-//! [`bdk_electrum_example`]: https://github.com/LLFourn/bdk_core_staging/tree/master/bdk_electrum_example
+//! [`ElectrumApi::batch_transaction_get`]: electrum_client::ElectrumApi::batch_transaction_get
+//! [`example_electrum`]: https://github.com/bitcoindevkit/bdk/tree/master/example-crates/example_electrum
 
 #![warn(missing_docs)]
 

crates/esplora/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "bdk_esplora"
-version = "0.4.0"
+version = "0.7.0"
 edition = "2021"
 homepage = "https://bitcoindevkit.org"
 repository = "https://github.com/bitcoindevkit/bdk"
@@ -12,7 +12,7 @@ readme = "README.md"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
-bdk_chain = { path = "../chain", version = "0.6.0", default-features = false }
+bdk_chain = { path = "../chain", version = "0.9.0", default-features = false }
 esplora-client = { version = "0.6.0", default-features = false }
 async-trait = { version = "0.1.66", optional = true }
 futures = { version = "0.3.26", optional = true }

crates/esplora/README.md

@@ -30,7 +30,7 @@ use bdk_esplora::EsploraExt;
 // use bdk_esplora::EsploraAsyncExt;
 ```
 
-For full examples, refer to [`example-crates/wallet_esplora`](https://github.com/bitcoindevkit/bdk/tree/master/example-crates/wallet_esplora) (blocking) and [`example-crates/wallet_esplora_async`](https://github.com/bitcoindevkit/bdk/tree/master/example-crates/wallet_esplora_async).
+For full examples, refer to [`example-crates/wallet_esplora_blocking`](https://github.com/bitcoindevkit/bdk/tree/master/example-crates/wallet_esplora_blocking) and [`example-crates/wallet_esplora_async`](https://github.com/bitcoindevkit/bdk/tree/master/example-crates/wallet_esplora_async).
 
 [`esplora-client`]: https://docs.rs/esplora-client/
 [`bdk_chain`]: https://docs.rs/bdk-chain/

crates/esplora/src/async_ext.rs

@@ -2,14 +2,14 @@ use async_trait::async_trait;
 use bdk_chain::collections::btree_map;
 use bdk_chain::{
     bitcoin::{BlockHash, OutPoint, ScriptBuf, Txid},
-    collections::{BTreeMap, BTreeSet},
+    collections::BTreeMap,
     local_chain::{self, CheckPoint},
     BlockId, ConfirmationTimeHeightAnchor, TxGraph,
 };
 use esplora_client::{Error, TxStatus};
 use futures::{stream::FuturesOrdered, TryStreamExt};
 
-use crate::{anchor_from_status, ASSUME_FINAL_DEPTH};
+use crate::anchor_from_status;
 
 /// Trait to extend the functionality of [`esplora_client::AsyncClient`].
 ///
@@ -19,13 +19,19 @@ use crate::{anchor_from_status, ASSUME_FINAL_DEPTH};
 #[cfg_attr(target_arch = "wasm32", async_trait(?Send))]
 #[cfg_attr(not(target_arch = "wasm32"), async_trait)]
 pub trait EsploraAsyncExt {
-    /// Prepare an [`LocalChain`] update with blocks fetched from Esplora.
+    /// Prepare a [`LocalChain`] update with blocks fetched from Esplora.
     ///
     /// * `local_tip` is the previous tip of [`LocalChain::tip`].
     /// * `request_heights` is the block heights that we are interested in fetching from Esplora.
     ///
     /// The result of this method can be applied to [`LocalChain::apply_update`].
     ///
+    /// ## Consistency
+    ///
+    /// The chain update returned is guaranteed to be consistent as long as there is not a *large* re-org
+    /// during the call. The size of re-org we can tollerate is server dependent but will be at
+    /// least 10.
+    ///
     /// [`LocalChain`]: bdk_chain::local_chain::LocalChain
     /// [`LocalChain::tip`]: bdk_chain::local_chain::LocalChain::tip
     /// [`LocalChain::apply_update`]: bdk_chain::local_chain::LocalChain::apply_update
@@ -36,58 +42,45 @@ pub trait EsploraAsyncExt {
         request_heights: impl IntoIterator<IntoIter = impl Iterator<Item = u32> + Send> + Send,
     ) -> Result<local_chain::Update, Error>;
 
-    /// Scan Esplora for the data specified and return a [`TxGraph`] and a map of last active
-    /// indices.
+    /// Full scan the keychain scripts specified with the blockchain (via an Esplora client) and
+    /// returns a [`TxGraph`] and a map of last active indices.
     ///
     /// * `keychain_spks`: keychains that we want to scan transactions for
-    /// * `txids`: transactions for which we want updated [`ConfirmationTimeHeightAnchor`]s
-    /// * `outpoints`: transactions associated with these outpoints (residing, spending) that we
-    ///     want to include in the update
     ///
-    /// The scan for each keychain stops after a gap of `stop_gap` script pubkeys with no associated
+    /// The full scan for each keychain stops after a gap of `stop_gap` script pubkeys with no associated
     /// transactions. `parallel_requests` specifies the max number of HTTP requests to make in
     /// parallel.
     #[allow(clippy::result_large_err)]
-    async fn scan_txs_with_keychains<K: Ord + Clone + Send>(
+    async fn full_scan<K: Ord + Clone + Send>(
         &self,
         keychain_spks: BTreeMap<
             K,
             impl IntoIterator<IntoIter = impl Iterator<Item = (u32, ScriptBuf)> + Send> + Send,
         >,
-        txids: impl IntoIterator<IntoIter = impl Iterator<Item = Txid> + Send> + Send,
-        outpoints: impl IntoIterator<IntoIter = impl Iterator<Item = OutPoint> + Send> + Send,
         stop_gap: usize,
         parallel_requests: usize,
     ) -> Result<(TxGraph<ConfirmationTimeHeightAnchor>, BTreeMap<K, u32>), Error>;
 
-    /// Convenience method to call [`scan_txs_with_keychains`] without requiring a keychain.
+    /// Sync a set of scripts with the blockchain (via an Esplora client) for the data
+    /// specified and return a [`TxGraph`].
     ///
-    /// [`scan_txs_with_keychains`]: EsploraAsyncExt::scan_txs_with_keychains
+    /// * `misc_spks`: scripts that we want to sync transactions for
+    /// * `txids`: transactions for which we want updated [`ConfirmationTimeHeightAnchor`]s
+    /// * `outpoints`: transactions associated with these outpoints (residing, spending) that we
+    ///     want to include in the update
+    ///
+    /// If the scripts to sync are unknown, such as when restoring or importing a keychain that
+    /// may include scripts that have been used, use [`full_scan`] with the keychain.
+    ///
+    /// [`full_scan`]: EsploraAsyncExt::full_scan
     #[allow(clippy::result_large_err)]
-    async fn scan_txs(
+    async fn sync(
         &self,
         misc_spks: impl IntoIterator<IntoIter = impl Iterator<Item = ScriptBuf> + Send> + Send,
         txids: impl IntoIterator<IntoIter = impl Iterator<Item = Txid> + Send> + Send,
         outpoints: impl IntoIterator<IntoIter = impl Iterator<Item = OutPoint> + Send> + Send,
         parallel_requests: usize,
-    ) -> Result<TxGraph<ConfirmationTimeHeightAnchor>, Error> {
-        self.scan_txs_with_keychains(
-            [(
-                (),
-                misc_spks
-                    .into_iter()
-                    .enumerate()
-                    .map(|(i, spk)| (i as u32, spk)),
-            )]
-            .into(),
-            txids,
-            outpoints,
-            usize::MAX,
-            parallel_requests,
-        )
-        .await
-        .map(|(g, _)| g)
-    }
+    ) -> Result<TxGraph<ConfirmationTimeHeightAnchor>, Error>;
 }
 
 #[cfg_attr(target_arch = "wasm32", async_trait(?Send))]
@@ -98,21 +91,22 @@ impl EsploraAsyncExt for esplora_client::AsyncClient {
         local_tip: CheckPoint,
         request_heights: impl IntoIterator<IntoIter = impl Iterator<Item = u32> + Send> + Send,
     ) -> Result<local_chain::Update, Error> {
-        let request_heights = request_heights.into_iter().collect::<BTreeSet<_>>();
-        let new_tip_height = self.get_height().await?;
+        // Fetch latest N (server dependent) blocks from Esplora. The server guarantees these are
+        // consistent.
+        let mut fetched_blocks = self
+            .get_blocks(None)
+            .await?
+            .into_iter()
+            .map(|b| (b.time.height, b.id))
+            .collect::<BTreeMap<u32, BlockHash>>();
+        let new_tip_height = fetched_blocks
+            .keys()
+            .last()
+            .copied()
+            .expect("must have atleast one block");
 
-        // atomically fetch blocks from esplora
-        let mut fetched_blocks = {
-            let heights = (0..=new_tip_height).rev();
-            let hashes = self
-                .get_blocks(Some(new_tip_height))
-                .await?
-                .into_iter()
-                .map(|b| b.id);
-            heights.zip(hashes).collect::<BTreeMap<u32, BlockHash>>()
-        };
-
-        // fetch heights that the caller is interested in
+        // Fetch blocks of heights that the caller is interested in, skipping blocks that are
+        // already fetched when constructing `fetched_blocks`.
         for height in request_heights {
             // do not fetch blocks higher than remote tip
             if height > new_tip_height {
@@ -120,93 +114,47 @@ impl EsploraAsyncExt for esplora_client::AsyncClient {
             }
             // only fetch what is missing
             if let btree_map::Entry::Vacant(entry) = fetched_blocks.entry(height) {
-                let hash = self.get_block_hash(height).await?;
-                entry.insert(hash);
+                // ❗The return value of `get_block_hash` is not strictly guaranteed to be consistent
+                // with the chain at the time of `get_blocks` above (there could have been a deep
+                // re-org). Since `get_blocks` returns 10 (or so) blocks we are assuming that it's
+                // not possible to have a re-org deeper than that.
+                entry.insert(self.get_block_hash(height).await?);
             }
         }
 
-        // find the earliest point of agreement between local chain and fetched chain
-        let earliest_agreement_cp = {
-            let mut earliest_agreement_cp = Option::<CheckPoint>::None;
-
-            let local_tip_height = local_tip.height();
-            for local_cp in local_tip.iter() {
-                let local_block = local_cp.block_id();
-
-                // the updated hash (block hash at this height after the update), can either be:
-                // 1. a block that already existed in `fetched_blocks`
-                // 2. a block that exists locally and at least has a depth of ASSUME_FINAL_DEPTH
-                // 3. otherwise we can freshly fetch the block from remote, which is safe as it
-                //    is guaranteed that this would be at or below ASSUME_FINAL_DEPTH from the
-                //    remote tip
-                let updated_hash = match fetched_blocks.entry(local_block.height) {
-                    btree_map::Entry::Occupied(entry) => *entry.get(),
-                    btree_map::Entry::Vacant(entry) => *entry.insert(
-                        if local_tip_height - local_block.height >= ASSUME_FINAL_DEPTH {
-                            local_block.hash
-                        } else {
-                            self.get_block_hash(local_block.height).await?
-                        },
-                    ),
-                };
-
-                // since we may introduce blocks below the point of agreement, we cannot break
-                // here unconditionally - we only break if we guarantee there are no new heights
-                // below our current local checkpoint
-                if local_block.hash == updated_hash {
-                    earliest_agreement_cp = Some(local_cp);
-
-                    let first_new_height = *fetched_blocks
-                        .keys()
-                        .next()
-                        .expect("must have at least one new block");
-                    if first_new_height >= local_block.height {
-                        break;
-                    }
-                }
+        // Ensure `fetched_blocks` can create an update that connects with the original chain by
+        // finding a "Point of Agreement".
+        for (height, local_hash) in local_tip.iter().map(|cp| (cp.height(), cp.hash())) {
+            if height > new_tip_height {
+                continue;
             }
 
-            earliest_agreement_cp
-        };
-
-        let tip = {
-            // first checkpoint to use for the update chain
-            let first_cp = match earliest_agreement_cp {
-                Some(cp) => cp,
-                None => {
-                    let (&height, &hash) = fetched_blocks
-                        .iter()
-                        .next()
-                        .expect("must have at least one new block");
-                    CheckPoint::new(BlockId { height, hash })
+            let fetched_hash = match fetched_blocks.entry(height) {
+                btree_map::Entry::Occupied(entry) => *entry.get(),
+                btree_map::Entry::Vacant(entry) => {
+                    *entry.insert(self.get_block_hash(height).await?)
                 }
             };
-            // transform fetched chain into the update chain
-            fetched_blocks
-                // we exclude anything at or below the first cp of the update chain otherwise
-                // building the chain will fail
-                .split_off(&(first_cp.height() + 1))
-                .into_iter()
-                .map(|(height, hash)| BlockId { height, hash })
-                .fold(first_cp, |prev_cp, block| {
-                    prev_cp.push(block).expect("must extend checkpoint")
-                })
-        };
+
+            // We have found point of agreement so the update will connect!
+            if fetched_hash == local_hash {
+                break;
+            }
+        }
 
         Ok(local_chain::Update {
-            tip,
+            tip: CheckPoint::from_block_ids(fetched_blocks.into_iter().map(BlockId::from))
+                .expect("must be in height order"),
             introduce_older_blocks: true,
         })
     }
 
-    async fn scan_txs_with_keychains<K: Ord + Clone + Send>(
+    async fn full_scan<K: Ord + Clone + Send>(
         &self,
         keychain_spks: BTreeMap<
             K,
             impl IntoIterator<IntoIter = impl Iterator<Item = (u32, ScriptBuf)> + Send> + Send,
         >,
-        txids: impl IntoIterator<IntoIter = impl Iterator<Item = Txid> + Send> + Send,
-        outpoints: impl IntoIterator<IntoIter = impl Iterator<Item = OutPoint> + Send> + Send,
         stop_gap: usize,
         parallel_requests: usize,
     ) -> Result<(TxGraph<ConfirmationTimeHeightAnchor>, BTreeMap<K, u32>), Error> {
@@ -275,6 +223,32 @@ impl EsploraAsyncExt for esplora_client::AsyncClient {
             }
         }
 
+        Ok((graph, last_active_indexes))
+    }
+
+    async fn sync(
+        &self,
+        misc_spks: impl IntoIterator<IntoIter = impl Iterator<Item = ScriptBuf> + Send> + Send,
+        txids: impl IntoIterator<IntoIter = impl Iterator<Item = Txid> + Send> + Send,
+        outpoints: impl IntoIterator<IntoIter = impl Iterator<Item = OutPoint> + Send> + Send,
+        parallel_requests: usize,
+    ) -> Result<TxGraph<ConfirmationTimeHeightAnchor>, Error> {
+        let mut graph = self
+            .full_scan(
+                [(
+                    (),
+                    misc_spks
+                        .into_iter()
+                        .enumerate()
+                        .map(|(i, spk)| (i as u32, spk)),
+                )]
+                .into(),
+                usize::MAX,
+                parallel_requests,
+            )
+            .await
+            .map(|(g, _)| g)?;
+
         let mut txids = txids.into_iter();
         loop {
             let handles = txids
@@ -323,7 +297,6 @@ impl EsploraAsyncExt for esplora_client::AsyncClient {
                 }
             }
         }
-
-        Ok((graph, last_active_indexes))
+        Ok(graph)
     }
 }

crates/esplora/src/blocking_ext.rs

@@ -1,7 +1,7 @@
 use std::thread::JoinHandle;
 
 use bdk_chain::collections::btree_map;
-use bdk_chain::collections::{BTreeMap, BTreeSet};
+use bdk_chain::collections::BTreeMap;
 use bdk_chain::{
     bitcoin::{BlockHash, OutPoint, ScriptBuf, Txid},
     local_chain::{self, CheckPoint},
@@ -9,7 +9,7 @@ use bdk_chain::{
 };
 use esplora_client::{Error, TxStatus};
 
-use crate::{anchor_from_status, ASSUME_FINAL_DEPTH};
+use crate::anchor_from_status;
 
 /// Trait to extend the functionality of [`esplora_client::BlockingClient`].
 ///
@@ -17,13 +17,19 @@ use crate::{anchor_from_status, ASSUME_FINAL_DEPTH};
 ///
 /// [crate-level documentation]: crate
 pub trait EsploraExt {
-    /// Prepare an [`LocalChain`] update with blocks fetched from Esplora.
+    /// Prepare a [`LocalChain`] update with blocks fetched from Esplora.
     ///
-    /// * `prev_tip` is the previous tip of [`LocalChain::tip`].
-    /// * `get_heights` is the block heights that we are interested in fetching from Esplora.
+    /// * `local_tip` is the previous tip of [`LocalChain::tip`].
+    /// * `request_heights` is the block heights that we are interested in fetching from Esplora.
     ///
     /// The result of this method can be applied to [`LocalChain::apply_update`].
     ///
+    /// ## Consistency
+    ///
+    /// The chain update returned is guaranteed to be consistent as long as there is not a *large* re-org
+    /// during the call. The size of re-org we can tollerate is server dependent but will be at
+    /// least 10.
+    ///
     /// [`LocalChain`]: bdk_chain::local_chain::LocalChain
     /// [`LocalChain::tip`]: bdk_chain::local_chain::LocalChain::tip
     /// [`LocalChain::apply_update`]: bdk_chain::local_chain::LocalChain::apply_update
@@ -34,54 +40,42 @@ pub trait EsploraExt {
         request_heights: impl IntoIterator<Item = u32>,
     ) -> Result<local_chain::Update, Error>;
 
-    /// Scan Esplora for the data specified and return a [`TxGraph`] and a map of last active
-    /// indices.
+    /// Full scan the keychain scripts specified with the blockchain (via an Esplora client) and
+    /// returns a [`TxGraph`] and a map of last active indices.
     ///
     /// * `keychain_spks`: keychains that we want to scan transactions for
-    /// * `txids`: transactions for which we want updated [`ConfirmationTimeHeightAnchor`]s
-    /// * `outpoints`: transactions associated with these outpoints (residing, spending) that we
-    ///     want to include in the update
     ///
-    /// The scan for each keychain stops after a gap of `stop_gap` script pubkeys with no associated
+    /// The full scan for each keychain stops after a gap of `stop_gap` script pubkeys with no associated
     /// transactions. `parallel_requests` specifies the max number of HTTP requests to make in
     /// parallel.
     #[allow(clippy::result_large_err)]
-    fn scan_txs_with_keychains<K: Ord + Clone>(
+    fn full_scan<K: Ord + Clone>(
         &self,
         keychain_spks: BTreeMap<K, impl IntoIterator<Item = (u32, ScriptBuf)>>,
-        txids: impl IntoIterator<Item = Txid>,
-        outpoints: impl IntoIterator<Item = OutPoint>,
         stop_gap: usize,
         parallel_requests: usize,
     ) -> Result<(TxGraph<ConfirmationTimeHeightAnchor>, BTreeMap<K, u32>), Error>;
 
-    /// Convenience method to call [`scan_txs_with_keychains`] without requiring a keychain.
+    /// Sync a set of scripts with the blockchain (via an Esplora client) for the data
+    /// specified and return a [`TxGraph`].
     ///
-    /// [`scan_txs_with_keychains`]: EsploraExt::scan_txs_with_keychains
+    /// * `misc_spks`: scripts that we want to sync transactions for
+    /// * `txids`: transactions for which we want updated [`ConfirmationTimeHeightAnchor`]s
+    /// * `outpoints`: transactions associated with these outpoints (residing, spending) that we
+    ///     want to include in the update
+    ///
+    /// If the scripts to sync are unknown, such as when restoring or importing a keychain that
+    /// may include scripts that have been used, use [`full_scan`] with the keychain.
+    ///
+    /// [`full_scan`]: EsploraExt::full_scan
     #[allow(clippy::result_large_err)]
-    fn scan_txs(
+    fn sync(
         &self,
         misc_spks: impl IntoIterator<Item = ScriptBuf>,
         txids: impl IntoIterator<Item = Txid>,
         outpoints: impl IntoIterator<Item = OutPoint>,
         parallel_requests: usize,
-    ) -> Result<TxGraph<ConfirmationTimeHeightAnchor>, Error> {
-        self.scan_txs_with_keychains(
-            [(
-                (),
-                misc_spks
-                    .into_iter()
-                    .enumerate()
-                    .map(|(i, spk)| (i as u32, spk)),
-            )]
-            .into(),
-            txids,
-            outpoints,
-            usize::MAX,
-            parallel_requests,
-        )
-        .map(|(g, _)| g)
-    }
+    ) -> Result<TxGraph<ConfirmationTimeHeightAnchor>, Error>;
 }
 
 impl EsploraExt for esplora_client::BlockingClient {
@@ -90,20 +84,21 @@ impl EsploraExt for esplora_client::BlockingClient {
         local_tip: CheckPoint,
         request_heights: impl IntoIterator<Item = u32>,
     ) -> Result<local_chain::Update, Error> {
-        let request_heights = request_heights.into_iter().collect::<BTreeSet<_>>();
-        let new_tip_height = self.get_height()?;
+        // Fetch latest N (server dependent) blocks from Esplora. The server guarantees these are
+        // consistent.
+        let mut fetched_blocks = self
+            .get_blocks(None)?
+            .into_iter()
+            .map(|b| (b.time.height, b.id))
+            .collect::<BTreeMap<u32, BlockHash>>();
+        let new_tip_height = fetched_blocks
+            .keys()
+            .last()
+            .copied()
+            .expect("must atleast have one block");
 
-        // atomically fetch blocks from esplora
-        let mut fetched_blocks = {
-            let heights = (0..=new_tip_height).rev();
-            let hashes = self
-                .get_blocks(Some(new_tip_height))?
-                .into_iter()
-                .map(|b| b.id);
-            heights.zip(hashes).collect::<BTreeMap<u32, BlockHash>>()
-        };
-
-        // fetch heights that the caller is interested in
+        // Fetch blocks of heights that the caller is interested in, skipping blocks that are
+        // already fetched when constructing `fetched_blocks`.
         for height in request_heights {
             // do not fetch blocks higher than remote tip
             if height > new_tip_height {
@@ -111,90 +106,42 @@ impl EsploraExt for esplora_client::BlockingClient {
             }
             // only fetch what is missing
             if let btree_map::Entry::Vacant(entry) = fetched_blocks.entry(height) {
-                let hash = self.get_block_hash(height)?;
-                entry.insert(hash);
+                // ❗The return value of `get_block_hash` is not strictly guaranteed to be consistent
+                // with the chain at the time of `get_blocks` above (there could have been a deep
+                // re-org). Since `get_blocks` returns 10 (or so) blocks we are assuming that it's
+                // not possible to have a re-org deeper than that.
+                entry.insert(self.get_block_hash(height)?);
             }
         }
 
-        // find the earliest point of agreement between local chain and fetched chain
-        let earliest_agreement_cp = {
-            let mut earliest_agreement_cp = Option::<CheckPoint>::None;
-
-            let local_tip_height = local_tip.height();
-            for local_cp in local_tip.iter() {
-                let local_block = local_cp.block_id();
-
-                // the updated hash (block hash at this height after the update), can either be:
-                // 1. a block that already existed in `fetched_blocks`
-                // 2. a block that exists locally and at least has a depth of ASSUME_FINAL_DEPTH
-                // 3. otherwise we can freshly fetch the block from remote, which is safe as it
-                //    is guaranteed that this would be at or below ASSUME_FINAL_DEPTH from the
-                //    remote tip
-                let updated_hash = match fetched_blocks.entry(local_block.height) {
-                    btree_map::Entry::Occupied(entry) => *entry.get(),
-                    btree_map::Entry::Vacant(entry) => *entry.insert(
-                        if local_tip_height - local_block.height >= ASSUME_FINAL_DEPTH {
-                            local_block.hash
-                        } else {
-                            self.get_block_hash(local_block.height)?
-                        },
-                    ),
-                };
-
-                // since we may introduce blocks below the point of agreement, we cannot break
-                // here unconditionally - we only break if we guarantee there are no new heights
-                // below our current local checkpoint
-                if local_block.hash == updated_hash {
-                    earliest_agreement_cp = Some(local_cp);
-
-                    let first_new_height = *fetched_blocks
-                        .keys()
-                        .next()
-                        .expect("must have at least one new block");
-                    if first_new_height >= local_block.height {
-                        break;
-                    }
-                }
+        // Ensure `fetched_blocks` can create an update that connects with the original chain by
+        // finding a "Point of Agreement".
+        for (height, local_hash) in local_tip.iter().map(|cp| (cp.height(), cp.hash())) {
+            if height > new_tip_height {
+                continue;
             }
 
-            earliest_agreement_cp
-        };
-
-        let tip = {
-            // first checkpoint to use for the update chain
-            let first_cp = match earliest_agreement_cp {
-                Some(cp) => cp,
-                None => {
-                    let (&height, &hash) = fetched_blocks
-                        .iter()
-                        .next()
-                        .expect("must have at least one new block");
-                    CheckPoint::new(BlockId { height, hash })
-                }
+            let fetched_hash = match fetched_blocks.entry(height) {
+                btree_map::Entry::Occupied(entry) => *entry.get(),
+                btree_map::Entry::Vacant(entry) => *entry.insert(self.get_block_hash(height)?),
             };
-            // transform fetched chain into the update chain
-            fetched_blocks
-                // we exclude anything at or below the first cp of the update chain otherwise
-                // building the chain will fail
-                .split_off(&(first_cp.height() + 1))
-                .into_iter()
-                .map(|(height, hash)| BlockId { height, hash })
-                .fold(first_cp, |prev_cp, block| {
-                    prev_cp.push(block).expect("must extend checkpoint")
-                })
-        };
+
+            // We have found point of agreement so the update will connect!
+            if fetched_hash == local_hash {
+                break;
+            }
+        }
 
         Ok(local_chain::Update {
-            tip,
+            tip: CheckPoint::from_block_ids(fetched_blocks.into_iter().map(BlockId::from))
+                .expect("must be in height order"),
             introduce_older_blocks: true,
         })
     }
 
-    fn scan_txs_with_keychains<K: Ord + Clone>(
+    fn full_scan<K: Ord + Clone>(
         &self,
         keychain_spks: BTreeMap<K, impl IntoIterator<Item = (u32, ScriptBuf)>>,
-        txids: impl IntoIterator<Item = Txid>,
-        outpoints: impl IntoIterator<Item = OutPoint>,
         stop_gap: usize,
         parallel_requests: usize,
     ) -> Result<(TxGraph<ConfirmationTimeHeightAnchor>, BTreeMap<K, u32>), Error> {
@@ -266,6 +213,31 @@ impl EsploraExt for esplora_client::BlockingClient {
             }
         }
 
+        Ok((graph, last_active_indexes))
+    }
+
+    fn sync(
+        &self,
+        misc_spks: impl IntoIterator<Item = ScriptBuf>,
+        txids: impl IntoIterator<Item = Txid>,
+        outpoints: impl IntoIterator<Item = OutPoint>,
+        parallel_requests: usize,
+    ) -> Result<TxGraph<ConfirmationTimeHeightAnchor>, Error> {
+        let mut graph = self
+            .full_scan(
+                [(
+                    (),
+                    misc_spks
+                        .into_iter()
+                        .enumerate()
+                        .map(|(i, spk)| (i as u32, spk)),
+                )]
+                .into(),
+                usize::MAX,
+                parallel_requests,
+            )
+            .map(|(g, _)| g)?;
+
         let mut txids = txids.into_iter();
         loop {
             let handles = txids
@@ -292,7 +264,7 @@ impl EsploraExt for esplora_client::BlockingClient {
             }
         }
 
-        for op in outpoints.into_iter() {
+        for op in outpoints {
             if graph.get_tx(op.txid).is_none() {
                 if let Some(tx) = self.get_tx(&op.txid)? {
                     let _ = graph.insert_tx(tx);
@@ -317,7 +289,6 @@ impl EsploraExt for esplora_client::BlockingClient {
                 }
             }
         }
-
-        Ok((graph, last_active_indexes))
+        Ok(graph)
     }
 }

crates/esplora/src/lib.rs

@@ -1,4 +1,21 @@
 #![doc = include_str!("../README.md")]
+
+//! This crate is used for updating structures of [`bdk_chain`] with data from an Esplora server.
+//!
+//! The two primary methods are [`EsploraExt::sync`] and [`EsploraExt::full_scan`]. In most cases
+//! [`EsploraExt::sync`] is used to sync the transaction histories of scripts that the application
+//! cares about, for example the scripts for all the receive addresses of a Wallet's keychain that it
+//! has shown a user. [`EsploraExt::full_scan`] is meant to be used when importing or restoring a
+//! keychain where the range of possibly used scripts is not known. In this case it is necessary to
+//! scan all keychain scripts until a number (the "stop gap") of unused scripts is discovered. For a
+//! sync or full scan the user receives relevant blockchain data and output updates for [`bdk_chain`]
+//! via a new [`TxGraph`] to be appended to any existing [`TxGraph`] data.
+//!
+//! Refer to [`example_esplora`] for a complete example.
+//!
+//! [`TxGraph`]: bdk_chain::tx_graph::TxGraph
+//! [`example_esplora`]: https://github.com/bitcoindevkit/bdk/tree/master/example-crates/example_esplora
+
 use bdk_chain::{BlockId, ConfirmationTimeHeightAnchor};
 use esplora_client::TxStatus;
 
@@ -14,8 +31,6 @@ mod async_ext;
 #[cfg(feature = "async")]
 pub use async_ext::*;
 
-const ASSUME_FINAL_DEPTH: u32 = 15;
-
 fn anchor_from_status(status: &TxStatus) -> Option<ConfirmationTimeHeightAnchor> {
     if let TxStatus {
         block_height: Some(height),

crates/esplora/tests/async_ext.rs

@@ -101,7 +101,7 @@ pub async fn test_update_tx_graph_without_keychain() -> anyhow::Result<()> {
 
     let graph_update = env
         .client
-        .scan_txs(
+        .sync(
             misc_spks.into_iter(),
             vec![].into_iter(),
             vec![].into_iter(),
@@ -166,28 +166,10 @@ pub async fn test_async_update_tx_graph_gap_limit() -> anyhow::Result<()> {
 
     // A scan with a gap limit of 2 won't find the transaction, but a scan with a gap limit of 3
     // will.
-    let (graph_update, active_indices) = env
-        .client
-        .scan_txs_with_keychains(
-            keychains.clone(),
-            vec![].into_iter(),
-            vec![].into_iter(),
-            2,
-            1,
-        )
-        .await?;
+    let (graph_update, active_indices) = env.client.full_scan(keychains.clone(), 2, 1).await?;
     assert!(graph_update.full_txs().next().is_none());
     assert!(active_indices.is_empty());
-    let (graph_update, active_indices) = env
-        .client
-        .scan_txs_with_keychains(
-            keychains.clone(),
-            vec![].into_iter(),
-            vec![].into_iter(),
-            3,
-            1,
-        )
-        .await?;
+    let (graph_update, active_indices) = env.client.full_scan(keychains.clone(), 3, 1).await?;
     assert_eq!(graph_update.full_txs().next().unwrap().txid, txid_4th_addr);
     assert_eq!(active_indices[&0], 3);
 
@@ -209,24 +191,12 @@ pub async fn test_async_update_tx_graph_gap_limit() -> anyhow::Result<()> {
 
     // A scan with gap limit 4 won't find the second transaction, but a scan with gap limit 5 will.
     // The last active indice won't be updated in the first case but will in the second one.
-    let (graph_update, active_indices) = env
-        .client
-        .scan_txs_with_keychains(
-            keychains.clone(),
-            vec![].into_iter(),
-            vec![].into_iter(),
-            4,
-            1,
-        )
-        .await?;
+    let (graph_update, active_indices) = env.client.full_scan(keychains.clone(), 4, 1).await?;
     let txs: HashSet<_> = graph_update.full_txs().map(|tx| tx.txid).collect();
     assert_eq!(txs.len(), 1);
     assert!(txs.contains(&txid_4th_addr));
     assert_eq!(active_indices[&0], 3);
-    let (graph_update, active_indices) = env
-        .client
-        .scan_txs_with_keychains(keychains, vec![].into_iter(), vec![].into_iter(), 5, 1)
-        .await?;
+    let (graph_update, active_indices) = env.client.full_scan(keychains, 5, 1).await?;
     let txs: HashSet<_> = graph_update.full_txs().map(|tx| tx.txid).collect();
     assert_eq!(txs.len(), 2);
     assert!(txs.contains(&txid_4th_addr) && txs.contains(&txid_last_addr));

crates/esplora/tests/blocking_ext.rs

@@ -1,15 +1,31 @@
+use bdk_chain::local_chain::LocalChain;
+use bdk_chain::BlockId;
 use bdk_esplora::EsploraExt;
 use electrsd::bitcoind::bitcoincore_rpc::RpcApi;
 use electrsd::bitcoind::{self, anyhow, BitcoinD};
 use electrsd::{Conf, ElectrsD};
 use esplora_client::{self, BlockingClient, Builder};
-use std::collections::{BTreeMap, HashSet};
+use std::collections::{BTreeMap, BTreeSet, HashSet};
 use std::str::FromStr;
 use std::thread::sleep;
 use std::time::Duration;
 
 use bdk_chain::bitcoin::{Address, Amount, BlockHash, Txid};
 
+macro_rules! h {
+    ($index:literal) => {{
+        bdk_chain::bitcoin::hashes::Hash::hash($index.as_bytes())
+    }};
+}
+
+macro_rules! local_chain {
+    [ $(($height:expr, $block_hash:expr)), * ] => {{
+        #[allow(unused_mut)]
+        bdk_chain::local_chain::LocalChain::from_blocks([$(($height, $block_hash).into()),*].into_iter().collect())
+            .expect("chain must have genesis block")
+    }};
+}
+
 struct TestEnv {
     bitcoind: BitcoinD,
     #[allow(dead_code)]
@@ -39,6 +55,20 @@ impl TestEnv {
         })
     }
 
+    fn reset_electrsd(mut self) -> anyhow::Result<Self> {
+        let mut electrs_conf = Conf::default();
+        electrs_conf.http_enabled = true;
+        let electrs_exe =
+            electrsd::downloaded_exe_path().expect("electrs version feature must be enabled");
+        let electrsd = ElectrsD::with_conf(electrs_exe, &self.bitcoind, &electrs_conf)?;
+
+        let base_url = format!("http://{}", &electrsd.esplora_url.clone().unwrap());
+        let client = Builder::new(base_url.as_str()).build_blocking()?;
+        self.electrsd = electrsd;
+        self.client = client;
+        Ok(self)
+    }
+
     fn mine_blocks(
         &self,
         count: usize,
@@ -99,7 +129,7 @@ pub fn test_update_tx_graph_without_keychain() -> anyhow::Result<()> {
         sleep(Duration::from_millis(10))
     }
 
-    let graph_update = env.client.scan_txs(
+    let graph_update = env.client.sync(
         misc_spks.into_iter(),
         vec![].into_iter(),
         vec![].into_iter(),
@@ -164,22 +194,10 @@ pub fn test_update_tx_graph_gap_limit() -> anyhow::Result<()> {
 
     // A scan with a gap limit of 2 won't find the transaction, but a scan with a gap limit of 3
     // will.
-    let (graph_update, active_indices) = env.client.scan_txs_with_keychains(
-        keychains.clone(),
-        vec![].into_iter(),
-        vec![].into_iter(),
-        2,
-        1,
-    )?;
+    let (graph_update, active_indices) = env.client.full_scan(keychains.clone(), 2, 1)?;
     assert!(graph_update.full_txs().next().is_none());
     assert!(active_indices.is_empty());
-    let (graph_update, active_indices) = env.client.scan_txs_with_keychains(
-        keychains.clone(),
-        vec![].into_iter(),
-        vec![].into_iter(),
-        3,
-        1,
-    )?;
+    let (graph_update, active_indices) = env.client.full_scan(keychains.clone(), 3, 1)?;
     assert_eq!(graph_update.full_txs().next().unwrap().txid, txid_4th_addr);
     assert_eq!(active_indices[&0], 3);
 
@@ -201,24 +219,12 @@ pub fn test_update_tx_graph_gap_limit() -> anyhow::Result<()> {
 
     // A scan with gap limit 4 won't find the second transaction, but a scan with gap limit 5 will.
     // The last active indice won't be updated in the first case but will in the second one.
-    let (graph_update, active_indices) = env.client.scan_txs_with_keychains(
-        keychains.clone(),
-        vec![].into_iter(),
-        vec![].into_iter(),
-        4,
-        1,
-    )?;
+    let (graph_update, active_indices) = env.client.full_scan(keychains.clone(), 4, 1)?;
     let txs: HashSet<_> = graph_update.full_txs().map(|tx| tx.txid).collect();
     assert_eq!(txs.len(), 1);
     assert!(txs.contains(&txid_4th_addr));
     assert_eq!(active_indices[&0], 3);
-    let (graph_update, active_indices) = env.client.scan_txs_with_keychains(
-        keychains,
-        vec![].into_iter(),
-        vec![].into_iter(),
-        5,
-        1,
-    )?;
+    let (graph_update, active_indices) = env.client.full_scan(keychains, 5, 1)?;
     let txs: HashSet<_> = graph_update.full_txs().map(|tx| tx.txid).collect();
     assert_eq!(txs.len(), 2);
     assert!(txs.contains(&txid_4th_addr) && txs.contains(&txid_last_addr));
@@ -226,3 +232,180 @@ pub fn test_update_tx_graph_gap_limit() -> anyhow::Result<()> {
 
     Ok(())
 }
+
+#[test]
+fn update_local_chain() -> anyhow::Result<()> {
+    const TIP_HEIGHT: u32 = 50;
+
+    let env = TestEnv::new()?;
+    let blocks = {
+        let bitcoind_client = &env.bitcoind.client;
+        assert_eq!(bitcoind_client.get_block_count()?, 1);
+        [
+            (0, bitcoind_client.get_block_hash(0)?),
+            (1, bitcoind_client.get_block_hash(1)?),
+        ]
+        .into_iter()
+        .chain((2..).zip(env.mine_blocks((TIP_HEIGHT - 1) as usize, None)?))
+        .collect::<BTreeMap<_, _>>()
+    };
+    // so new blocks can be seen by Electrs
+    let env = env.reset_electrsd()?;
+
+    struct TestCase {
+        name: &'static str,
+        chain: LocalChain,
+        request_heights: &'static [u32],
+        exp_update_heights: &'static [u32],
+    }
+
+    let test_cases = [
+        TestCase {
+            name: "request_later_blocks",
+            chain: local_chain![(0, blocks[&0]), (21, blocks[&21])],
+            request_heights: &[22, 25, 28],
+            exp_update_heights: &[21, 22, 25, 28],
+        },
+        TestCase {
+            name: "request_prev_blocks",
+            chain: local_chain![(0, blocks[&0]), (1, blocks[&1]), (5, blocks[&5])],
+            request_heights: &[4],
+            exp_update_heights: &[4, 5],
+        },
+        TestCase {
+            name: "request_prev_blocks_2",
+            chain: local_chain![(0, blocks[&0]), (1, blocks[&1]), (10, blocks[&10])],
+            request_heights: &[4, 6],
+            exp_update_heights: &[4, 6, 10],
+        },
+        TestCase {
+            name: "request_later_and_prev_blocks",
+            chain: local_chain![(0, blocks[&0]), (7, blocks[&7]), (11, blocks[&11])],
+            request_heights: &[8, 9, 15],
+            exp_update_heights: &[8, 9, 11, 15],
+        },
+        TestCase {
+            name: "request_tip_only",
+            chain: local_chain![(0, blocks[&0]), (5, blocks[&5]), (49, blocks[&49])],
+            request_heights: &[TIP_HEIGHT],
+            exp_update_heights: &[49],
+        },
+        TestCase {
+            name: "request_nothing",
+            chain: local_chain![(0, blocks[&0]), (13, blocks[&13]), (23, blocks[&23])],
+            request_heights: &[],
+            exp_update_heights: &[23],
+        },
+        TestCase {
+            name: "request_nothing_during_reorg",
+            chain: local_chain![(0, blocks[&0]), (13, blocks[&13]), (23, h!("23"))],
+            request_heights: &[],
+            exp_update_heights: &[13, 23],
+        },
+        TestCase {
+            name: "request_nothing_during_reorg_2",
+            chain: local_chain![
+                (0, blocks[&0]),
+                (21, blocks[&21]),
+                (22, h!("22")),
+                (23, h!("23"))
+            ],
+            request_heights: &[],
+            exp_update_heights: &[21, 22, 23],
+        },
+        TestCase {
+            name: "request_prev_blocks_during_reorg",
+            chain: local_chain![
+                (0, blocks[&0]),
+                (21, blocks[&21]),
+                (22, h!("22")),
+                (23, h!("23"))
+            ],
+            request_heights: &[17, 20],
+            exp_update_heights: &[17, 20, 21, 22, 23],
+        },
+        TestCase {
+            name: "request_later_blocks_during_reorg",
+            chain: local_chain![
+                (0, blocks[&0]),
+                (9, blocks[&9]),
+                (22, h!("22")),
+                (23, h!("23"))
+            ],
+            request_heights: &[25, 27],
+            exp_update_heights: &[9, 22, 23, 25, 27],
+        },
+        TestCase {
+            name: "request_later_blocks_during_reorg_2",
+            chain: local_chain![(0, blocks[&0]), (9, h!("9"))],
+            request_heights: &[10],
+            exp_update_heights: &[0, 9, 10],
+        },
+        TestCase {
+            name: "request_later_and_prev_blocks_during_reorg",
+            chain: local_chain![(0, blocks[&0]), (1, blocks[&1]), (9, h!("9"))],
+            request_heights: &[8, 11],
+            exp_update_heights: &[1, 8, 9, 11],
+        },
+    ];
+
+    for (i, t) in test_cases.into_iter().enumerate() {
+        println!("Case {}: {}", i, t.name);
+        let mut chain = t.chain;
+
+        let update = env
+            .client
+            .update_local_chain(chain.tip(), t.request_heights.iter().copied())
+            .map_err(|err| {
+                anyhow::format_err!("[{}:{}] `update_local_chain` failed: {}", i, t.name, err)
+            })?;
+
+        let update_blocks = update
+            .tip
+            .iter()
+            .map(|cp| cp.block_id())
+            .collect::<BTreeSet<_>>();
+
+        let exp_update_blocks = t
+            .exp_update_heights
+            .iter()
+            .map(|&height| {
+                let hash = blocks[&height];
+                BlockId { height, hash }
+            })
+            .chain(
+                // Electrs Esplora `get_block` call fetches 10 blocks which is included in the
+                // update
+                blocks
+                    .range(TIP_HEIGHT - 9..)
+                    .map(|(&height, &hash)| BlockId { height, hash }),
+            )
+            .collect::<BTreeSet<_>>();
+
+        assert_eq!(
+            update_blocks, exp_update_blocks,
+            "[{}:{}] unexpected update",
+            i, t.name
+        );
+
+        let _ = chain
+            .apply_update(update)
+            .unwrap_or_else(|err| panic!("[{}:{}] update failed to apply: {}", i, t.name, err));
+
+        // all requested heights must exist in the final chain
+        for height in t.request_heights {
+            let exp_blockhash = blocks.get(height).expect("block must exist in bitcoind");
+            assert_eq!(
+                chain.blocks().get(height),
+                Some(exp_blockhash),
+                "[{}:{}] block {}:{} must exist in final chain",
+                i,
+                t.name,
+                height,
+                exp_blockhash
+            );
+        }
+    }
+
+    Ok(())
+}

crates/file_store/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "bdk_file_store"
-version = "0.2.0"
+version = "0.5.0"
 edition = "2021"
 license = "MIT OR Apache-2.0"
 repository = "https://github.com/bitcoindevkit/bdk"
@@ -11,7 +11,7 @@ authors = ["Bitcoin Dev Kit Developers"]
 readme = "README.md"
 
 [dependencies]
-bdk_chain = { path = "../chain", version = "0.6.0", features = [ "serde", "miniscript" ] }
+bdk_chain = { path = "../chain", version = "0.9.0", features = [ "serde", "miniscript" ] }
 bincode = { version = "1" }
 serde = { version = "1", features = ["derive"] }
 

crates/file_store/src/entry_iter.rs

@@ -1,7 +1,7 @@
 use bincode::Options;
 use std::{
     fs::File,
-    io::{self, Seek},
+    io::{self, BufReader, Seek},
     marker::PhantomData,
 };
 
@@ -14,8 +14,9 @@ use crate::bincode_options;
 ///
 /// [`next`]: Self::next
 pub struct EntryIter<'t, T> {
-    db_file: Option<&'t mut File>,
-
+    /// Buffered reader around the file
+    db_file: BufReader<&'t mut File>,
+    finished: bool,
     /// The file position for the first read of `db_file`.
     start_pos: Option<u64>,
     types: PhantomData<T>,
@@ -24,8 +25,9 @@ pub struct EntryIter<'t, T> {
 impl<'t, T> EntryIter<'t, T> {
     pub fn new(start_pos: u64, db_file: &'t mut File) -> Self {
         Self {
-            db_file: Some(db_file),
+            db_file: BufReader::new(db_file),
             start_pos: Some(start_pos),
+            finished: false,
             types: PhantomData,
         }
     }
@@ -38,44 +40,44 @@ where
     type Item = Result<T, IterError>;
 
     fn next(&mut self) -> Option<Self::Item> {
-        // closure which reads a single entry starting from `self.pos`
-        let read_one = |f: &mut File, start_pos: Option<u64>| -> Result<Option<T>, IterError> {
-            let pos = match start_pos {
-                Some(pos) => f.seek(io::SeekFrom::Start(pos))?,
-                None => f.stream_position()?,
-            };
+        if self.finished {
+            return None;
+        }
+        (|| {
+            if let Some(start) = self.start_pos.take() {
+                self.db_file.seek(io::SeekFrom::Start(start))?;
+            }
 
-            match bincode_options().deserialize_from(&*f) {
-                Ok(changeset) => {
-                    f.stream_position()?;
-                    Ok(Some(changeset))
-                }
+            let pos_before_read = self.db_file.stream_position()?;
+            match bincode_options().deserialize_from(&mut self.db_file) {
+                Ok(changeset) => Ok(Some(changeset)),
                 Err(e) => {
+                    self.finished = true;
+                    let pos_after_read = self.db_file.stream_position()?;
+                    // allow unexpected EOF if 0 bytes were read
                     if let bincode::ErrorKind::Io(inner) = &*e {
-                        if inner.kind() == io::ErrorKind::UnexpectedEof {
-                            let eof = f.seek(io::SeekFrom::End(0))?;
-                            if pos == eof {
-                                return Ok(None);
-                            }
+                        if inner.kind() == io::ErrorKind::UnexpectedEof
+                            && pos_after_read == pos_before_read
+                        {
+                            return Ok(None);
                         }
                     }
-                    f.seek(io::SeekFrom::Start(pos))?;
+                    self.db_file.seek(io::SeekFrom::Start(pos_before_read))?;
                     Err(IterError::Bincode(*e))
                 }
             }
-        };
-
-        let result = read_one(self.db_file.as_mut()?, self.start_pos.take());
-        if result.is_err() {
-            self.db_file = None;
-        }
-        result.transpose()
+        })()
+        .transpose()
     }
 }
 
-impl From<io::Error> for IterError {
-    fn from(value: io::Error) -> Self {
-        IterError::Io(value)
+impl<'t, T> Drop for EntryIter<'t, T> {
+    fn drop(&mut self) {
+        // This syncs the underlying file's offset with the buffer's position. This way, we
+        // maintain the correct position to start the next read/write.
+        if let Ok(pos) = self.db_file.stream_position() {
+            let _ = self.db_file.get_mut().seek(io::SeekFrom::Start(pos));
+        }
     }
 }
 
@@ -97,4 +99,10 @@ impl core::fmt::Display for IterError {
     }
 }
 
+impl From<io::Error> for IterError {
+    fn from(value: io::Error) -> Self {
+        IterError::Io(value)
+    }
+}
+
 impl std::error::Error for IterError {}

crates/file_store/src/lib.rs

@@ -13,14 +13,14 @@ pub(crate) fn bincode_options() -> impl bincode::Options {
 
 /// Error that occurs due to problems encountered with the file.
 #[derive(Debug)]
-pub enum FileError<'a> {
+pub enum FileError {
     /// IO error, this may mean that the file is too short.
     Io(io::Error),
     /// Magic bytes do not match what is expected.
-    InvalidMagicBytes { got: Vec<u8>, expected: &'a [u8] },
+    InvalidMagicBytes { got: Vec<u8>, expected: Vec<u8> },
 }
 
-impl<'a> core::fmt::Display for FileError<'a> {
+impl core::fmt::Display for FileError {
     fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
         match self {
             Self::Io(e) => write!(f, "io error trying to read file: {}", e),
@@ -33,10 +33,10 @@ impl<'a> core::fmt::Display for FileError<'a> {
     }
 }
 
-impl<'a> From<io::Error> for FileError<'a> {
+impl From<io::Error> for FileError {
     fn from(value: io::Error) -> Self {
         Self::Io(value)
     }
 }
 
-impl<'a> std::error::Error for FileError<'a> {}
+impl std::error::Error for FileError {}

crates/file_store/src/store.rs

@@ -15,13 +15,13 @@ use crate::{bincode_options, EntryIter, FileError, IterError};
 ///
 /// The changesets are the results of altering a tracker implementation (`T`).
 #[derive(Debug)]
-pub struct Store<'a, C> {
-    magic: &'a [u8],
+pub struct Store<C> {
+    magic_len: usize,
     db_file: File,
     marker: PhantomData<C>,
 }
 
-impl<'a, C> PersistBackend<C> for Store<'a, C>
+impl<C> PersistBackend<C> for Store<C>
 where
     C: Append + serde::Serialize + serde::de::DeserializeOwned,
 {
@@ -38,7 +38,7 @@ where
     }
 }
 
-impl<'a, C> Store<'a, C>
+impl<C> Store<C>
 where
     C: Append + serde::Serialize + serde::de::DeserializeOwned,
 {
@@ -48,7 +48,7 @@ where
     /// the `Store` in the future with [`open`].
     ///
     /// [`open`]: Store::open
-    pub fn create_new<P>(magic: &'a [u8], file_path: P) -> Result<Self, FileError>
+    pub fn create_new<P>(magic: &[u8], file_path: P) -> Result<Self, FileError>
     where
         P: AsRef<Path>,
     {
@@ -67,7 +67,7 @@ where
             .open(file_path)?;
         f.write_all(magic)?;
         Ok(Self {
-            magic,
+            magic_len: magic.len(),
             db_file: f,
             marker: Default::default(),
         })
@@ -83,7 +83,7 @@ where
     /// [`FileError::InvalidMagicBytes`] error variant will be returned.
     ///
     /// [`create_new`]: Store::create_new
-    pub fn open<P>(magic: &'a [u8], file_path: P) -> Result<Self, FileError>
+    pub fn open<P>(magic: &[u8], file_path: P) -> Result<Self, FileError>
     where
         P: AsRef<Path>,
     {
@@ -94,24 +94,24 @@ where
         if magic_buf != magic {
             return Err(FileError::InvalidMagicBytes {
                 got: magic_buf,
-                expected: magic,
+                expected: magic.to_vec(),
             });
         }
 
         Ok(Self {
-            magic,
+            magic_len: magic.len(),
             db_file: f,
             marker: Default::default(),
         })
     }
 
-    /// Attempt to open existing [`Store`] file; create it if the file is non-existant.
+    /// Attempt to open existing [`Store`] file; create it if the file is non-existent.
     ///
     /// Internally, this calls either [`open`] or [`create_new`].
     ///
     /// [`open`]: Store::open
     /// [`create_new`]: Store::create_new
-    pub fn open_or_create_new<P>(magic: &'a [u8], file_path: P) -> Result<Self, FileError>
+    pub fn open_or_create_new<P>(magic: &[u8], file_path: P) -> Result<Self, FileError>
     where
         P: AsRef<Path>,
     {
@@ -132,14 +132,14 @@ where
     /// always iterate over all entries until `None` is returned if you want your next write to go
     /// at the end; otherwise, you will write over existing entries.
     pub fn iter_changesets(&mut self) -> EntryIter<C> {
-        EntryIter::new(self.magic.len() as u64, &mut self.db_file)
+        EntryIter::new(self.magic_len as u64, &mut self.db_file)
     }
 
     /// Loads all the changesets that have been stored as one giant changeset.
     ///
-    /// This function returns a tuple of the aggregate changeset and a result that indicates
-    /// whether an error occurred while reading or deserializing one of the entries. If so the
-    /// changeset will consist of all of those it was able to read.
+    /// This function returns the aggregate changeset, or `None` if nothing was persisted.
+    /// If reading or deserializing any of the entries fails, an error is returned that
+    /// consists of all those it was able to read.
     ///
     /// You should usually check the error. In many applications, it may make sense to do a full
     /// wallet scan with a stop-gap after getting an error, since it is likely that one of the
@@ -219,6 +219,7 @@ mod test {
 
     use bincode::DefaultOptions;
     use std::{
+        collections::BTreeSet,
         io::{Read, Write},
         vec::Vec,
     };
@@ -228,7 +229,7 @@ mod test {
     const TEST_MAGIC_BYTES: [u8; TEST_MAGIC_BYTES_LEN] =
         [98, 100, 107, 102, 115, 49, 49, 49, 49, 49, 49, 49];
 
-    type TestChangeSet = Vec<String>;
+    type TestChangeSet = BTreeSet<String>;
 
     #[derive(Debug)]
     struct TestTracker;
@@ -253,7 +254,7 @@ mod test {
     fn open_or_create_new() {
         let temp_dir = tempfile::tempdir().unwrap();
         let file_path = temp_dir.path().join("db_file");
-        let changeset = vec!["hello".to_string(), "world".to_string()];
+        let changeset = BTreeSet::from(["hello".to_string(), "world".to_string()]);
 
         {
             let mut db = Store::<TestChangeSet>::open_or_create_new(&TEST_MAGIC_BYTES, &file_path)
@@ -304,7 +305,7 @@ mod test {
         let mut data = [255_u8; 2000];
         data[..TEST_MAGIC_BYTES_LEN].copy_from_slice(&TEST_MAGIC_BYTES);
 
-        let changeset = vec!["one".into(), "two".into(), "three!".into()];
+        let changeset = TestChangeSet::from(["one".into(), "two".into(), "three!".into()]);
 
         let mut file = NamedTempFile::new().unwrap();
         file.write_all(&data).expect("should write");
@@ -340,4 +341,119 @@ mod test {
 
         assert_eq!(got_bytes, expected_bytes);
     }
+
+    #[test]
+    fn last_write_is_short() {
+        let temp_dir = tempfile::tempdir().unwrap();
+
+        let changesets = [
+            TestChangeSet::from(["1".into()]),
+            TestChangeSet::from(["2".into(), "3".into()]),
+            TestChangeSet::from(["4".into(), "5".into(), "6".into()]),
+        ];
+        let last_changeset = TestChangeSet::from(["7".into(), "8".into(), "9".into()]);
+        let last_changeset_bytes = bincode_options().serialize(&last_changeset).unwrap();
+
+        for short_write_len in 1..last_changeset_bytes.len() - 1 {
+            let file_path = temp_dir.path().join(format!("{}.dat", short_write_len));
+            println!("Test file: {:?}", file_path);
+
+            // simulate creating a file, writing data where the last write is incomplete
+            {
+                let mut db =
+                    Store::<TestChangeSet>::create_new(&TEST_MAGIC_BYTES, &file_path).unwrap();
+                for changeset in &changesets {
+                    db.append_changeset(changeset).unwrap();
+                }
+                // this is the incomplete write
+                db.db_file
+                    .write_all(&last_changeset_bytes[..short_write_len])
+                    .unwrap();
+            }
+
+            // load file again and aggregate changesets
+            // write the last changeset again (this time it succeeds)
+            {
+                let mut db = Store::<TestChangeSet>::open(&TEST_MAGIC_BYTES, &file_path).unwrap();
+                let err = db
+                    .aggregate_changesets()
+                    .expect_err("should return error as last read is short");
+                assert_eq!(
+                    err.changeset,
+                    changesets.iter().cloned().reduce(|mut acc, cs| {
+                        Append::append(&mut acc, cs);
+                        acc
+                    }),
+                    "should recover all changesets that are written in full",
+                );
+                db.db_file.write_all(&last_changeset_bytes).unwrap();
+            }
+
+            // load file again - this time we should successfully aggregate all changesets
+            {
+                let mut db = Store::<TestChangeSet>::open(&TEST_MAGIC_BYTES, &file_path).unwrap();
+                let aggregated_changesets = db
+                    .aggregate_changesets()
+                    .expect("aggregating all changesets should succeed");
+                assert_eq!(
+                    aggregated_changesets,
+                    changesets
+                        .iter()
+                        .cloned()
+                        .chain(core::iter::once(last_changeset.clone()))
+                        .reduce(|mut acc, cs| {
+                            Append::append(&mut acc, cs);
+                            acc
+                        }),
+                    "should recover all changesets",
+                );
+            }
+        }
+    }
+
+    #[test]
+    fn write_after_short_read() {
+        let temp_dir = tempfile::tempdir().unwrap();
+
+        let changesets = (0..20)
+            .map(|n| TestChangeSet::from([format!("{}", n)]))
+            .collect::<Vec<_>>();
+        let last_changeset = TestChangeSet::from(["last".into()]);
+
+        for read_count in 0..changesets.len() {
+            let file_path = temp_dir.path().join(format!("{}.dat", read_count));
+            println!("Test file: {:?}", file_path);
+
+            // First, we create the file with all the changesets!
+            let mut db = Store::<TestChangeSet>::create_new(&TEST_MAGIC_BYTES, &file_path).unwrap();
+            for changeset in &changesets {
+                db.append_changeset(changeset).unwrap();
+            }
+            drop(db);
+
+            // We re-open the file and read `read_count` number of changesets.
+            let mut db = Store::<TestChangeSet>::open(&TEST_MAGIC_BYTES, &file_path).unwrap();
+            let mut exp_aggregation = db
+                .iter_changesets()
+                .take(read_count)
+                .map(|r| r.expect("must read valid changeset"))
+                .fold(TestChangeSet::default(), |mut acc, v| {
+                    Append::append(&mut acc, v);
+                    acc
+                });
+            // We write after a short read.
+            db.write_changes(&last_changeset)
+                .expect("last write must succeed");
+            Append::append(&mut exp_aggregation, last_changeset.clone());
+            drop(db);
+
+            // We open the file again and check whether aggregate changeset is expected.
+            let aggregation = Store::<TestChangeSet>::open(&TEST_MAGIC_BYTES, &file_path)
+                .unwrap()
+                .aggregate_changesets()
+                .expect("must aggregate changesets")
+                .unwrap_or_default();
+            assert_eq!(aggregation, exp_aggregation);
+        }
+    }
 }

crates/hwi/Cargo.toml

@@ -0,0 +1,13 @@
+[package]
+name = "bdk_hwi"
+version = "0.1.0"
+edition = "2021"
+homepage = "https://bitcoindevkit.org"
+repository = "https://github.com/bitcoindevkit/bdk"
+description = "Utilities to use bdk with hardware wallets"
+license = "MIT OR Apache-2.0"
+readme = "README.md"
+
+[dependencies]
+bdk = { path = "../bdk" }
+hwi = { version = "0.7.0", features = [ "miniscript"] }

crates/hwi/src/lib.rs

@@ -0,0 +1,42 @@
+//! HWI Signer
+//!
+//! This crate contains HWISigner, an implementation of a [`TransactionSigner`] to be
+//! used with hardware wallets.
+//! ```no_run
+//! # use bdk::bitcoin::Network;
+//! # use bdk::signer::SignerOrdering;
+//! # use bdk_hwi::HWISigner;
+//! # use bdk::wallet::AddressIndex::New;
+//! # use bdk::{FeeRate, KeychainKind, SignOptions, Wallet};
+//! # use hwi::HWIClient;
+//! # use std::sync::Arc;
+//! #
+//! # fn main() -> Result<(), Box<dyn std::error::Error>> {
+//! let mut devices = HWIClient::enumerate()?;
+//! if devices.is_empty() {
+//!     panic!("No devices found!");
+//! }
+//! let first_device = devices.remove(0)?;
+//! let custom_signer = HWISigner::from_device(&first_device, Network::Testnet.into())?;
+//!
+//! # let mut wallet = Wallet::new_no_persist(
+//! #     "",
+//! #     None,
+//! #     Network::Testnet,
+//! # )?;
+//! #
+//! // Adding the hardware signer to the BDK wallet
+//! wallet.add_signer(
+//!     KeychainKind::External,
+//!     SignerOrdering(200),
+//!     Arc::new(custom_signer),
+//! );
+//!
+//! # Ok(())
+//! # }
+//! ```
+//!
+//! [`TransactionSigner`]: bdk::wallet::signer::TransactionSigner
+
+mod signer;
+pub use signer::*;

crates/hwi/src/signer.rs

@@ -0,0 +1,94 @@
+use bdk::bitcoin::bip32::Fingerprint;
+use bdk::bitcoin::psbt::PartiallySignedTransaction;
+use bdk::bitcoin::secp256k1::{All, Secp256k1};
+
+use hwi::error::Error;
+use hwi::types::{HWIChain, HWIDevice};
+use hwi::HWIClient;
+
+use bdk::signer::{SignerCommon, SignerError, SignerId, TransactionSigner};
+
+#[derive(Debug)]
+/// Custom signer for Hardware Wallets
+///
+/// This ignores `sign_options` and leaves the decisions up to the hardware wallet.
+pub struct HWISigner {
+    fingerprint: Fingerprint,
+    client: HWIClient,
+}
+
+impl HWISigner {
+    /// Create a instance from the specified device and chain
+    pub fn from_device(device: &HWIDevice, chain: HWIChain) -> Result<HWISigner, Error> {
+        let client = HWIClient::get_client(device, false, chain)?;
+        Ok(HWISigner {
+            fingerprint: device.fingerprint,
+            client,
+        })
+    }
+}
+
+impl SignerCommon for HWISigner {
+    fn id(&self, _secp: &Secp256k1<All>) -> SignerId {
+        SignerId::Fingerprint(self.fingerprint)
+    }
+}
+
+impl TransactionSigner for HWISigner {
+    fn sign_transaction(
+        &self,
+        psbt: &mut PartiallySignedTransaction,
+        _sign_options: &bdk::SignOptions,
+        _secp: &Secp256k1<All>,
+    ) -> Result<(), SignerError> {
+        psbt.combine(
+            self.client
+                .sign_tx(psbt)
+                .map_err(|e| {
+                    SignerError::External(format!("While signing with hardware wallet: {}", e))
+                })?
+                .psbt,
+        )
+        .expect("Failed to combine HW signed psbt with passed PSBT");
+        Ok(())
+    }
+}
+
+// TODO: re-enable this once we have the `get_funded_wallet` test util
+// #[cfg(test)]
+// mod tests {
+//     #[test]
+//     fn test_hardware_signer() {
+//         use std::sync::Arc;
+//
+//         use bdk::tests::get_funded_wallet;
+//         use bdk::signer::SignerOrdering;
+//         use bdk::bitcoin::Network;
+//         use crate::HWISigner;
+//         use hwi::HWIClient;
+//
+//         let mut devices = HWIClient::enumerate().unwrap();
+//         if devices.is_empty() {
+//             panic!("No devices found!");
+//         }
+//         let device = devices.remove(0).unwrap();
+//         let client = HWIClient::get_client(&device, true, Network::Regtest.into()).unwrap();
+//         let descriptors = client.get_descriptors::<String>(None).unwrap();
+//         let custom_signer = HWISigner::from_device(&device, Network::Regtest.into()).unwrap();
+//
+//         let (mut wallet, _) = get_funded_wallet(&descriptors.internal[0]);
+//         wallet.add_signer(
+//             bdk::KeychainKind::External,
+//             SignerOrdering(200),
+//             Arc::new(custom_signer),
+//         );
+//
+//         let addr = wallet.get_address(bdk::wallet::AddressIndex::LastUnused);
+//         let mut builder = wallet.build_tx();
+//         builder.drain_to(addr.script_pubkey()).drain_wallet();
+//         let (mut psbt, _) = builder.finish().unwrap();
+//
+//         let finalized = wallet.sign(&mut psbt, Default::default()).unwrap();
+//         assert!(finalized);
+//     }
+// }

example-crates/example_bitcoind_rpc_polling/README.md

@@ -0,0 +1,68 @@
+# Example RPC CLI
+
+### Simple Regtest Test
+
+1. Start local regtest bitcoind.
+   ```
+    mkdir -p /tmp/regtest/bitcoind
+    bitcoind -regtest -server -fallbackfee=0.0002 -rpcuser=<your-rpc-username> -rpcpassword=<your-rpc-password> -datadir=/tmp/regtest/bitcoind -daemon
+   ```
+2. Create a test bitcoind wallet and set bitcoind env.
+   ```
+   bitcoin-cli -datadir=/tmp/regtest/bitcoind -regtest -rpcuser=<your-rpc-username> -rpcpassword=<your-rpc-password> -named createwallet wallet_name="test"
+   export RPC_URL=127.0.0.1:18443
+   export RPC_USER=<your-rpc-username>
+   export RPC_PASS=<your-rpc-password>
+   ```
+3. Get test bitcoind wallet info.
+   ```
+   bitcoin-cli -rpcwallet="test" -rpcuser=<your-rpc-username> -rpcpassword=<your-rpc-password> -datadir=/tmp/regtest/bitcoind -regtest getwalletinfo
+   ```
+4. Get new test bitcoind wallet address.
+   ```
+   BITCOIND_ADDRESS=$(bitcoin-cli -rpcwallet="test" -datadir=/tmp/regtest/bitcoind -regtest -rpcuser=<your-rpc-username> -rpcpassword=<your-rpc-password> getnewaddress)
+   echo $BITCOIND_ADDRESS
+   ```
+5. Generate 101 blocks with reward to test bitcoind wallet address.
+   ```
+   bitcoin-cli -datadir=/tmp/regtest/bitcoind -regtest -rpcuser=<your-rpc-username> -rpcpassword=<your-rpc-password> generatetoaddress 101 $BITCOIND_ADDRESS
+   ```
+6. Verify test bitcoind wallet balance.
+   ```
+   bitcoin-cli -rpcwallet="test" -datadir=/tmp/regtest/bitcoind -regtest -rpcuser=<your-rpc-username> -rpcpassword=<your-rpc-password> getbalances
+   ```
+7. Set descriptor env and get address from RPC CLI wallet.
+   ```
+   export DESCRIPTOR="wpkh(tprv8ZgxMBicQKsPfK9BTf82oQkHhawtZv19CorqQKPFeaHDMA4dXYX6eWsJGNJ7VTQXWmoHdrfjCYuDijcRmNFwSKcVhswzqs4fugE8turndGc/1/*)"
+   cargo run -- --network regtest address next
+   ```
+8. Send 5 test bitcoin to RPC CLI wallet.
+   ```
+   bitcoin-cli -rpcwallet="test" -datadir=/tmp/regtest/bitcoind -regtest -rpcuser=<your-rpc-username> -rpcpassword=<your-rpc-password> sendtoaddress <address> 5
+   ```
+9. Sync blockchain with RPC CLI wallet.
+   ```
+   cargo run -- --network regtest sync
+   <CNTRL-C to stop syncing>
+   ```
+10. Get RPC CLI wallet unconfirmed balances.
+   ```
+   cargo run -- --network regtest balance
+   ```
+11. Generate 1 block with reward to test bitcoind wallet address.
+   ```
+   bitcoin-cli -datadir=/tmp/regtest/bitcoind -rpcuser=<your-rpc-username> -rpcpassword=<your-rpc-password> -regtest generatetoaddress 10 $BITCOIND_ADDRESS
+   ```
+12. Sync the blockchain with RPC CLI wallet.
+   ```
+   cargo run -- --network regtest sync
+   <CNTRL-C to stop syncing>
+   ```
+13. Get RPC CLI wallet confirmed balances.
+   ```
+   cargo run -- --network regtest balance
+   ```
+14. Get RPC CLI wallet transactions.
+   ```
+   cargo run -- --network regtest txout list
+   ```

example-crates/example_bitcoind_rpc_polling/src/main.rs

@@ -12,9 +12,9 @@ use bdk_bitcoind_rpc::{
     Emitter,
 };
 use bdk_chain::{
-    bitcoin::{Block, Transaction},
+    bitcoin::{constants::genesis_block, Block, Transaction},
     indexed_tx_graph, keychain,
-    local_chain::{self, CheckPoint, LocalChain},
+    local_chain::{self, LocalChain},
     ConfirmationTimeHeightAnchor, IndexedTxGraph,
 };
 use example_cli::{
@@ -42,7 +42,7 @@ type ChangeSet = (
 
 #[derive(Debug)]
 enum Emission {
-    Block { height: u32, block: Block },
+    Block(bdk_bitcoind_rpc::BlockEvent<Block>),
     Mempool(Vec<(Transaction, u64)>),
     Tip(u32),
 }
@@ -64,9 +64,6 @@ struct RpcArgs {
     /// Starting block height to fallback to if no point of agreement if found
     #[clap(env = "FALLBACK_HEIGHT", long, default_value = "0")]
     fallback_height: u32,
-    /// The unused-scripts lookahead will be kept at this size
-    #[clap(long, default_value = "10")]
-    lookahead: u32,
 }
 
 impl From<RpcArgs> for Auth {
@@ -120,10 +117,11 @@ fn main() -> anyhow::Result<()> {
         "[{:>10}s] loaded initial changeset from db",
         start.elapsed().as_secs_f32()
     );
+    let (init_chain_changeset, init_graph_changeset) = init_changeset;
 
     let graph = Mutex::new({
         let mut graph = IndexedTxGraph::new(index);
-        graph.apply_changeset(init_changeset.1);
+        graph.apply_changeset(init_graph_changeset);
         graph
     });
     println!(
@@ -131,7 +129,16 @@ fn main() -> anyhow::Result<()> {
         start.elapsed().as_secs_f32()
     );
 
-    let chain = Mutex::new(LocalChain::from_changeset(init_changeset.0)?);
+    let chain = Mutex::new(if init_chain_changeset.is_empty() {
+        let genesis_hash = genesis_block(args.network).block_hash();
+        let (chain, chain_changeset) = LocalChain::from_genesis_hash(genesis_hash);
+        let mut db = db.lock().unwrap();
+        db.stage((chain_changeset, Default::default()));
+        db.commit()?;
+        chain
+    } else {
+        LocalChain::from_changeset(init_chain_changeset)?
+    });
     println!(
         "[{:>10}s] loaded local chain from changeset",
         start.elapsed().as_secs_f32()
@@ -140,7 +147,7 @@ fn main() -> anyhow::Result<()> {
     let rpc_cmd = match args.command {
         example_cli::Commands::ChainSpecific(rpc_cmd) => rpc_cmd,
         general_cmd => {
-            let res = example_cli::handle_commands(
+            return example_cli::handle_commands(
                 &graph,
                 &db,
                 &chain,
@@ -153,21 +160,15 @@ fn main() -> anyhow::Result<()> {
                 },
                 general_cmd,
             );
-            db.lock().unwrap().commit()?;
-            return res;
         }
     };
 
     match rpc_cmd {
         RpcCommands::Sync { rpc_args } => {
             let RpcArgs {
-                fallback_height,
-                lookahead,
-                ..
+                fallback_height, ..
             } = rpc_args;
 
-            graph.lock().unwrap().index.set_lookahead_for_all(lookahead);
-
             let chain_tip = chain.lock().unwrap().tip();
             let rpc_client = rpc_args.new_client()?;
             let mut emitter = Emitter::new(&rpc_client, chain_tip, fallback_height);
@@ -175,17 +176,20 @@ fn main() -> anyhow::Result<()> {
             let mut last_db_commit = Instant::now();
             let mut last_print = Instant::now();
 
-            while let Some((height, block)) = emitter.next_block()? {
+            while let Some(emission) = emitter.next_block()? {
+                let height = emission.block_height();
+
                 let mut chain = chain.lock().unwrap();
                 let mut graph = graph.lock().unwrap();
                 let mut db = db.lock().unwrap();
 
-                let chain_update =
-                    CheckPoint::from_header(&block.header, height).into_update(false);
                 let chain_changeset = chain
-                    .apply_update(chain_update)
+                    .apply_update(local_chain::Update {
+                        tip: emission.checkpoint,
+                        introduce_older_blocks: false,
+                    })
                     .expect("must always apply as we receive blocks in order from emitter");
-                let graph_changeset = graph.apply_block_relevant(block, height);
+                let graph_changeset = graph.apply_block_relevant(&emission.block, height);
                 db.stage((chain_changeset, graph_changeset));
 
                 // commit staged db changes in intervals
@@ -233,13 +237,10 @@ fn main() -> anyhow::Result<()> {
         }
         RpcCommands::Live { rpc_args } => {
             let RpcArgs {
-                fallback_height,
-                lookahead,
-                ..
+                fallback_height, ..
             } = rpc_args;
             let sigterm_flag = start_ctrlc_handler();
 
-            graph.lock().unwrap().index.set_lookahead_for_all(lookahead);
             let last_cp = chain.lock().unwrap().tip();
 
             println!(
@@ -256,7 +257,8 @@ fn main() -> anyhow::Result<()> {
 
                 loop {
                     match emitter.next_block()? {
-                        Some((height, block)) => {
+                        Some(block_emission) => {
+                            let height = block_emission.block_height();
                             if sigterm_flag.load(Ordering::Acquire) {
                                 break;
                             }
@@ -264,7 +266,7 @@ fn main() -> anyhow::Result<()> {
                                 block_count = rpc_client.get_block_count()? as u32;
                                 tx.send(Emission::Tip(block_count))?;
                             }
-                            tx.send(Emission::Block { height, block })?;
+                            tx.send(Emission::Block(block_emission))?;
                         }
                         None => {
                             if await_flag(&sigterm_flag, MEMPOOL_EMIT_DELAY) {
@@ -293,13 +295,17 @@ fn main() -> anyhow::Result<()> {
                 let mut chain = chain.lock().unwrap();
 
                 let changeset = match emission {
-                    Emission::Block { height, block } => {
-                        let chain_update =
-                            CheckPoint::from_header(&block.header, height).into_update(false);
+                    Emission::Block(block_emission) => {
+                        let height = block_emission.block_height();
+                        let chain_update = local_chain::Update {
+                            tip: block_emission.checkpoint,
+                            introduce_older_blocks: false,
+                        };
                         let chain_changeset = chain
                             .apply_update(chain_update)
                             .expect("must always apply as we receive blocks in order from emitter");
-                        let graph_changeset = graph.apply_block_relevant(block, height);
+                        let graph_changeset =
+                            graph.apply_block_relevant(&block_emission.block, height);
                         (chain_changeset, graph_changeset)
                     }
                     Emission::Mempool(mempool_txs) => {

example-crates/example_cli/src/lib.rs

@@ -29,7 +29,7 @@ pub type KeychainChangeSet<A> = (
     local_chain::ChangeSet,
     indexed_tx_graph::ChangeSet<A, keychain::ChangeSet<Keychain>>,
 );
-pub type Database<'m, C> = Persist<Store<'m, C>, C>;
+pub type Database<C> = Persist<Store<C>, C>;
 
 #[derive(Parser)]
 #[clap(author, version, about, long_about = None)]
@@ -73,7 +73,9 @@ pub enum Commands<CS: clap::Subcommand, S: clap::Args> {
     },
     /// Send coins to an address.
     Send {
+        /// Amount to send in satoshis
         value: u64,
+        /// Destination address
         address: Address<address::NetworkUnchecked>,
         #[clap(short, default_value = "bnb")]
         coin_select: CoinSelectionAlgo,
@@ -144,14 +146,17 @@ pub enum AddressCmd {
     New,
     /// List all addresses
     List {
+        /// List change addresses
         #[clap(long)]
         change: bool,
     },
+    /// Get last revealed address index for each keychain.
     Index,
 }
 
 #[derive(Subcommand, Debug, Clone)]
 pub enum TxOutCmd {
+    /// List transaction outputs.
     List {
         /// Return only spent outputs.
         #[clap(short, long)]
@@ -457,11 +462,10 @@ where
 
                     let ((spk_i, spk), index_changeset) = spk_chooser(index, &Keychain::External);
                     let db = &mut *db.lock().unwrap();
-                    db.stage(C::from((
+                    db.stage_and_commit(C::from((
                         local_chain::ChangeSet::default(),
                         indexed_tx_graph::ChangeSet::from(index_changeset),
-                    )));
-                    db.commit()?;
+                    )))?;
                     let addr =
                         Address::from_script(spk, network).context("failed to derive address")?;
                     println!("[address @ {}] {}", spk_i, addr);
@@ -478,14 +482,14 @@ where
                         true => Keychain::Internal,
                         false => Keychain::External,
                     };
-                    for (spk_i, spk) in index.revealed_spks_of_keychain(&target_keychain) {
+                    for (spk_i, spk) in index.revealed_keychain_spks(&target_keychain) {
                         let address = Address::from_script(spk, network)
                             .expect("should always be able to derive address");
                         println!(
                             "{:?} {} used:{}",
                             spk_i,
                             address,
-                            index.is_used(&(target_keychain, spk_i))
+                            index.is_used(target_keychain, spk_i)
                         );
                     }
                     Ok(())
@@ -601,17 +605,16 @@ where
                     // If we're unable to persist this, then we don't want to broadcast.
                     {
                         let db = &mut *db.lock().unwrap();
-                        db.stage(C::from((
+                        db.stage_and_commit(C::from((
                             local_chain::ChangeSet::default(),
                             indexed_tx_graph::ChangeSet::from(index_changeset),
-                        )));
-                        db.commit()?;
+                        )))?;
                     }
 
                     // We don't want other callers/threads to use this address while we're using it
                     // but we also don't want to scan the tx we just created because it's not
                     // technically in the blockchain yet.
-                    graph.index.mark_used(&change_keychain, index);
+                    graph.index.mark_used(change_keychain, index);
                     (tx, Some((change_keychain, index)))
                 } else {
                     (tx, None)
@@ -627,16 +630,16 @@ where
                     // We know the tx is at least unconfirmed now. Note if persisting here fails,
                     // it's not a big deal since we can always find it again form
                     // blockchain.
-                    db.lock().unwrap().stage(C::from((
+                    db.lock().unwrap().stage_and_commit(C::from((
                         local_chain::ChangeSet::default(),
                         keychain_changeset,
-                    )));
+                    )))?;
                     Ok(())
                 }
                 Err(e) => {
                     if let Some((keychain, index)) = change_index {
                         // We failed to broadcast, so allow our change address to be used in the future
-                        graph.lock().unwrap().index.unmark_used(&keychain, index);
+                        graph.lock().unwrap().index.unmark_used(keychain, index);
                     }
                     Err(e)
                 }
@@ -646,14 +649,14 @@ where
 }
 
 #[allow(clippy::type_complexity)]
-pub fn init<'m, CS: clap::Subcommand, S: clap::Args, C>(
-    db_magic: &'m [u8],
+pub fn init<CS: clap::Subcommand, S: clap::Args, C>(
+    db_magic: &[u8],
     db_default_path: &str,
 ) -> anyhow::Result<(
     Args<CS, S>,
     KeyMap,
     KeychainTxOutIndex<Keychain>,
-    Mutex<Database<'m, C>>,
+    Mutex<Database<C>>,
     C,
 )>
 where
@@ -681,7 +684,7 @@ where
         index.add_keychain(Keychain::Internal, internal_descriptor);
     }
 
-    let mut db_backend = match Store::<'m, C>::open_or_create_new(db_magic, &args.db_path) {
+    let mut db_backend = match Store::<C>::open_or_create_new(db_magic, &args.db_path) {
         Ok(db_backend) => db_backend,
         // we cannot return `err` directly as it has lifetime `'m`
         Err(err) => return Err(anyhow::anyhow!("failed to init db backend: {:?}", err)),

example-crates/example_electrum/src/main.rs

@@ -5,7 +5,7 @@ use std::{
 };
 
 use bdk_chain::{
-    bitcoin::{Address, Network, OutPoint, ScriptBuf, Txid},
+    bitcoin::{constants::genesis_block, Address, Network, OutPoint, Txid},
     indexed_tx_graph::{self, IndexedTxGraph},
     keychain,
     local_chain::{self, LocalChain},
@@ -112,12 +112,17 @@ fn main() -> anyhow::Result<()> {
         graph
     });
 
-    let chain = Mutex::new(LocalChain::from_changeset(disk_local_chain)?);
+    let chain = Mutex::new({
+        let genesis_hash = genesis_block(args.network).block_hash();
+        let (mut chain, _) = LocalChain::from_genesis_hash(genesis_hash);
+        chain.apply_changeset(&disk_local_chain)?;
+        chain
+    });
 
     let electrum_cmd = match &args.command {
         example_cli::Commands::ChainSpecific(electrum_cmd) => electrum_cmd,
         general_cmd => {
-            let res = example_cli::handle_commands(
+            return example_cli::handle_commands(
                 &graph,
                 &db,
                 &chain,
@@ -130,9 +135,6 @@ fn main() -> anyhow::Result<()> {
                 },
                 general_cmd.clone(),
             );
-
-            db.lock().unwrap().commit()?;
-            return res;
         }
     };
 
@@ -150,7 +152,7 @@ fn main() -> anyhow::Result<()> {
 
                 let keychain_spks = graph
                     .index
-                    .spks_of_all_keychains()
+                    .all_unbounded_spk_iters()
                     .into_iter()
                     .map(|(keychain, iter)| {
                         let mut first = true;
@@ -172,14 +174,7 @@ fn main() -> anyhow::Result<()> {
             };
 
             client
-                .scan(
-                    tip,
-                    keychain_spks,
-                    core::iter::empty(),
-                    core::iter::empty(),
-                    stop_gap,
-                    scan_options.batch_size,
-                )
+                .full_scan(tip, keychain_spks, stop_gap, scan_options.batch_size)
                 .context("scanning the blockchain")?
         }
         ElectrumCommands::Sync {
@@ -208,29 +203,28 @@ fn main() -> anyhow::Result<()> {
             if all_spks {
                 let all_spks = graph
                     .index
-                    .all_spks()
-                    .iter()
-                    .map(|(k, v)| (*k, v.clone()))
+                    .revealed_spks()
+                    .map(|(k, i, spk)| (k, i, spk.to_owned()))
                     .collect::<Vec<_>>();
-                spks = Box::new(spks.chain(all_spks.into_iter().map(|(index, script)| {
-                    eprintln!("scanning {:?}", index);
-                    script
+                spks = Box::new(spks.chain(all_spks.into_iter().map(|(k, i, spk)| {
+                    eprintln!("scanning {}:{}", k, i);
+                    spk
                 })));
             }
             if unused_spks {
                 let unused_spks = graph
                     .index
-                    .unused_spks(..)
-                    .map(|(k, v)| (*k, ScriptBuf::from(v)))
+                    .unused_spks()
+                    .map(|(k, i, spk)| (k, i, spk.to_owned()))
                     .collect::<Vec<_>>();
-                spks = Box::new(spks.chain(unused_spks.into_iter().map(|(index, script)| {
+                spks = Box::new(spks.chain(unused_spks.into_iter().map(|(k, i, spk)| {
                     eprintln!(
-                        "Checking if address {} {:?} has been used",
-                        Address::from_script(&script, args.network).unwrap(),
-                        index
+                        "Checking if address {} {}:{} has been used",
+                        Address::from_script(&spk, args.network).unwrap(),
+                        k,
+                        i,
                     );
-
-                    script
+                    spk
                 })));
             }
 
@@ -279,7 +273,7 @@ fn main() -> anyhow::Result<()> {
             drop((graph, chain));
 
             let electrum_update = client
-                .scan_without_keychain(tip, spks, txids, outpoints, scan_options.batch_size)
+                .sync(tip, spks, txids, outpoints, scan_options.batch_size)
                 .context("scanning the blockchain")?;
             (electrum_update, BTreeMap::new())
         }

example-crates/example_esplora/src/main.rs

@@ -125,7 +125,7 @@ fn main() -> anyhow::Result<()> {
         example_cli::Commands::ChainSpecific(esplora_cmd) => esplora_cmd,
         // These are general commands handled by example_cli. Execute the cmd and return.
         general_cmd => {
-            let res = example_cli::handle_commands(
+            return example_cli::handle_commands(
                 &graph,
                 &db,
                 &chain,
@@ -140,9 +140,6 @@ fn main() -> anyhow::Result<()> {
                 },
                 general_cmd.clone(),
             );
-
-            db.lock().unwrap().commit()?;
-            return res;
         }
     };
 
@@ -165,7 +162,7 @@ fn main() -> anyhow::Result<()> {
                 .lock()
                 .expect("mutex must not be poisoned")
                 .index
-                .spks_of_all_keychains()
+                .all_unbounded_spk_iters()
                 .into_iter()
                 // This `map` is purely for logging.
                 .map(|(keychain, iter)| {
@@ -188,13 +185,7 @@ fn main() -> anyhow::Result<()> {
             // represents the last active spk derivation indices of keychains
             // (`keychain_indices_update`).
             let (graph_update, last_active_indices) = client
-                .scan_txs_with_keychains(
-                    keychain_spks,
-                    core::iter::empty(),
-                    core::iter::empty(),
-                    *stop_gap,
-                    scan_options.parallel_requests,
-                )
+                .full_scan(keychain_spks, *stop_gap, scan_options.parallel_requests)
                 .context("scanning for transactions")?;
 
             let mut graph = graph.lock().expect("mutex must not be poisoned");
@@ -241,32 +232,32 @@ fn main() -> anyhow::Result<()> {
                 if *all_spks {
                     let all_spks = graph
                         .index
-                        .all_spks()
-                        .iter()
-                        .map(|(k, v)| (*k, v.clone()))
+                        .revealed_spks()
+                        .map(|(k, i, spk)| (k, i, spk.to_owned()))
                         .collect::<Vec<_>>();
-                    spks = Box::new(spks.chain(all_spks.into_iter().map(|(index, script)| {
-                        eprintln!("scanning {:?}", index);
+                    spks = Box::new(spks.chain(all_spks.into_iter().map(|(k, i, spk)| {
+                        eprintln!("scanning {}:{}", k, i);
                         // Flush early to ensure we print at every iteration.
                         let _ = io::stderr().flush();
-                        script
+                        spk
                     })));
                 }
                 if unused_spks {
                     let unused_spks = graph
                         .index
-                        .unused_spks(..)
-                        .map(|(k, v)| (*k, v.to_owned()))
+                        .unused_spks()
+                        .map(|(k, i, spk)| (k, i, spk.to_owned()))
                         .collect::<Vec<_>>();
-                    spks = Box::new(spks.chain(unused_spks.into_iter().map(|(index, script)| {
+                    spks = Box::new(spks.chain(unused_spks.into_iter().map(|(k, i, spk)| {
                         eprintln!(
-                            "Checking if address {} {:?} has been used",
-                            Address::from_script(&script, args.network).unwrap(),
-                            index
+                            "Checking if address {} {}:{} has been used",
+                            Address::from_script(&spk, args.network).unwrap(),
+                            k,
+                            i,
                         );
                         // Flush early to ensure we print at every iteration.
                         let _ = io::stderr().flush();
-                        script
+                        spk
                     })));
                 }
                 if utxos {
@@ -312,7 +303,7 @@ fn main() -> anyhow::Result<()> {
             }
 
             let graph_update =
-                client.scan_txs(spks, txids, outpoints, scan_options.parallel_requests)?;
+                client.sync(spks, txids, outpoints, scan_options.parallel_requests)?;
 
             graph.lock().unwrap().apply_update(graph_update)
         }

example-crates/wallet_electrum/src/main.rs

@@ -40,7 +40,7 @@ fn main() -> Result<(), anyhow::Error> {
 
     let prev_tip = wallet.latest_checkpoint();
     let keychain_spks = wallet
-        .spks_of_all_keychains()
+        .all_unbounded_spk_iters()
         .into_iter()
         .map(|(k, k_spks)| {
             let mut once = Some(());
@@ -61,7 +61,7 @@ fn main() -> Result<(), anyhow::Error> {
             relevant_txids,
         },
         keychain_update,
-    ) = client.scan(prev_tip, keychain_spks, None, None, STOP_GAP, BATCH_SIZE)?;
+    ) = client.full_scan(prev_tip, keychain_spks, STOP_GAP, BATCH_SIZE)?;
 
     println!();
 

example-crates/wallet_esplora_async/src/main.rs

@@ -39,7 +39,7 @@ async fn main() -> Result<(), anyhow::Error> {
 
     let prev_tip = wallet.latest_checkpoint();
     let keychain_spks = wallet
-        .spks_of_all_keychains()
+        .all_unbounded_spk_iters()
         .into_iter()
         .map(|(k, k_spks)| {
             let mut once = Some(());
@@ -54,7 +54,7 @@ async fn main() -> Result<(), anyhow::Error> {
         })
         .collect();
     let (update_graph, last_active_indices) = client
-        .scan_txs_with_keychains(keychain_spks, None, None, STOP_GAP, PARALLEL_REQUESTS)
+        .full_scan(keychain_spks, STOP_GAP, PARALLEL_REQUESTS)
         .await?;
     let missing_heights = update_graph.missing_heights(wallet.local_chain());
     let chain_update = client.update_local_chain(prev_tip, missing_heights).await?;

example-crates/wallet_esplora_blocking/src/main.rs

@@ -38,7 +38,7 @@ fn main() -> Result<(), anyhow::Error> {
 
     let prev_tip = wallet.latest_checkpoint();
     let keychain_spks = wallet
-        .spks_of_all_keychains()
+        .all_unbounded_spk_iters()
         .into_iter()
         .map(|(k, k_spks)| {
             let mut once = Some(());
@@ -54,7 +54,7 @@ fn main() -> Result<(), anyhow::Error> {
         .collect();
 
     let (update_graph, last_active_indices) =
-        client.scan_txs_with_keychains(keychain_spks, None, None, STOP_GAP, PARALLEL_REQUESTS)?;
+        client.full_scan(keychain_spks, STOP_GAP, PARALLEL_REQUESTS)?;
     let missing_heights = update_graph.missing_heights(wallet.local_chain());
     let chain_update = client.update_local_chain(prev_tip, missing_heights)?;
     let update = Update {

example-crates/wallet_rpc/Cargo.toml

@@ -0,0 +1,15 @@
+[package]
+name = "wallet_rpc"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+bdk = { path = "../../crates/bdk" }
+bdk_file_store = { path = "../../crates/file_store" }
+bdk_bitcoind_rpc = { path = "../../crates/bitcoind_rpc" }
+
+anyhow = "1"
+clap = { version = "3.2.25", features = ["derive", "env"] }
+ctrlc = "2.0.1"

example-crates/wallet_rpc/README.md

@@ -0,0 +1,45 @@
+# Wallet RPC Example 
+
+```
+$ cargo run --bin wallet_rpc -- --help
+
+wallet_rpc 0.1.0
+Bitcoind RPC example usign `bdk::Wallet`
+
+USAGE:
+    wallet_rpc [OPTIONS] <DESCRIPTOR> [CHANGE_DESCRIPTOR]
+
+ARGS:
+    <DESCRIPTOR>           Wallet descriptor [env: DESCRIPTOR=]
+    <CHANGE_DESCRIPTOR>    Wallet change descriptor [env: CHANGE_DESCRIPTOR=]
+
+OPTIONS:
+        --db-path <DB_PATH>
+            Where to store wallet data [env: BDK_DB_PATH=] [default: .bdk_wallet_rpc_example.db]
+
+    -h, --help
+            Print help information
+
+        --network <NETWORK>
+            Bitcoin network to connect to [env: BITCOIN_NETWORK=] [default: testnet]
+
+        --rpc-cookie <RPC_COOKIE>
+            RPC auth cookie file [env: RPC_COOKIE=]
+
+        --rpc-pass <RPC_PASS>
+            RPC auth password [env: RPC_PASS=]
+
+        --rpc-user <RPC_USER>
+            RPC auth username [env: RPC_USER=]
+
+        --start-height <START_HEIGHT>
+            Earliest block height to start sync from [env: START_HEIGHT=] [default: 481824]
+
+        --url <URL>
+            RPC URL [env: RPC_URL=] [default: 127.0.0.1:8332]
+
+    -V, --version
+            Print version information
+
+```
+

example-crates/wallet_rpc/src/main.rs

@@ -0,0 +1,182 @@
+use bdk::{
+    bitcoin::{Block, Network, Transaction},
+    wallet::Wallet,
+};
+use bdk_bitcoind_rpc::{
+    bitcoincore_rpc::{Auth, Client, RpcApi},
+    Emitter,
+};
+use bdk_file_store::Store;
+use clap::{self, Parser};
+use std::{path::PathBuf, sync::mpsc::sync_channel, thread::spawn, time::Instant};
+
+const DB_MAGIC: &str = "bdk-rpc-wallet-example";
+
+/// Bitcoind RPC example usign `bdk::Wallet`.
+///
+/// This syncs the chain block-by-block and prints the current balance, transaction count and UTXO
+/// count.
+#[derive(Parser, Debug)]
+#[clap(author, version, about, long_about = None)]
+#[clap(propagate_version = true)]
+pub struct Args {
+    /// Wallet descriptor
+    #[clap(env = "DESCRIPTOR")]
+    pub descriptor: String,
+    /// Wallet change descriptor
+    #[clap(env = "CHANGE_DESCRIPTOR")]
+    pub change_descriptor: Option<String>,
+    /// Earliest block height to start sync from
+    #[clap(env = "START_HEIGHT", long, default_value = "481824")]
+    pub start_height: u32,
+    /// Bitcoin network to connect to
+    #[clap(env = "BITCOIN_NETWORK", long, default_value = "testnet")]
+    pub network: Network,
+    /// Where to store wallet data
+    #[clap(
+        env = "BDK_DB_PATH",
+        long,
+        default_value = ".bdk_wallet_rpc_example.db"
+    )]
+    pub db_path: PathBuf,
+
+    /// RPC URL
+    #[clap(env = "RPC_URL", long, default_value = "127.0.0.1:8332")]
+    pub url: String,
+    /// RPC auth cookie file
+    #[clap(env = "RPC_COOKIE", long)]
+    pub rpc_cookie: Option<PathBuf>,
+    /// RPC auth username
+    #[clap(env = "RPC_USER", long)]
+    pub rpc_user: Option<String>,
+    /// RPC auth password
+    #[clap(env = "RPC_PASS", long)]
+    pub rpc_pass: Option<String>,
+}
+
+impl Args {
+    fn client(&self) -> anyhow::Result<Client> {
+        Ok(Client::new(
+            &self.url,
+            match (&self.rpc_cookie, &self.rpc_user, &self.rpc_pass) {
+                (None, None, None) => Auth::None,
+                (Some(path), _, _) => Auth::CookieFile(path.clone()),
+                (_, Some(user), Some(pass)) => Auth::UserPass(user.clone(), pass.clone()),
+                (_, Some(_), None) => panic!("rpc auth: missing rpc_pass"),
+                (_, None, Some(_)) => panic!("rpc auth: missing rpc_user"),
+            },
+        )?)
+    }
+}
+
+#[derive(Debug)]
+enum Emission {
+    SigTerm,
+    Block(bdk_bitcoind_rpc::BlockEvent<Block>),
+    Mempool(Vec<(Transaction, u64)>),
+}
+
+fn main() -> anyhow::Result<()> {
+    let args = Args::parse();
+
+    let rpc_client = args.client()?;
+    println!(
+        "Connected to Bitcoin Core RPC at {:?}",
+        rpc_client.get_blockchain_info().unwrap()
+    );
+
+    let start_load_wallet = Instant::now();
+    let mut wallet = Wallet::new_or_load(
+        &args.descriptor,
+        args.change_descriptor.as_ref(),
+        Store::<bdk::wallet::ChangeSet>::open_or_create_new(DB_MAGIC.as_bytes(), args.db_path)?,
+        args.network,
+    )?;
+    println!(
+        "Loaded wallet in {}s",
+        start_load_wallet.elapsed().as_secs_f32()
+    );
+
+    let balance = wallet.get_balance();
+    println!("Wallet balance before syncing: {} sats", balance.total());
+
+    let wallet_tip = wallet.latest_checkpoint();
+    println!(
+        "Wallet tip: {} at height {}",
+        wallet_tip.hash(),
+        wallet_tip.height()
+    );
+
+    let (sender, receiver) = sync_channel::<Emission>(21);
+
+    let signal_sender = sender.clone();
+    ctrlc::set_handler(move || {
+        signal_sender
+            .send(Emission::SigTerm)
+            .expect("failed to send sigterm")
+    });
+
+    let emitter_tip = wallet_tip.clone();
+    spawn(move || -> Result<(), anyhow::Error> {
+        let mut emitter = Emitter::new(&rpc_client, emitter_tip, args.start_height);
+        while let Some(emission) = emitter.next_block()? {
+            sender.send(Emission::Block(emission))?;
+        }
+        sender.send(Emission::Mempool(emitter.mempool()?))?;
+        Ok(())
+    });
+
+    let mut blocks_received = 0_usize;
+    for emission in receiver {
+        match emission {
+            Emission::SigTerm => {
+                println!("Sigterm received, exiting...");
+                break;
+            }
+            Emission::Block(block_emission) => {
+                blocks_received += 1;
+                let height = block_emission.block_height();
+                let hash = block_emission.block_hash();
+                let connected_to = block_emission.connected_to();
+                let start_apply_block = Instant::now();
+                wallet.apply_block_connected_to(&block_emission.block, height, connected_to)?;
+                wallet.commit()?;
+                let elapsed = start_apply_block.elapsed().as_secs_f32();
+                println!(
+                    "Applied block {} at height {} in {}s",
+                    hash, height, elapsed
+                );
+            }
+            Emission::Mempool(mempool_emission) => {
+                let start_apply_mempool = Instant::now();
+                wallet.apply_unconfirmed_txs(mempool_emission.iter().map(|(tx, time)| (tx, *time)));
+                wallet.commit()?;
+                println!(
+                    "Applied unconfirmed transactions in {}s",
+                    start_apply_mempool.elapsed().as_secs_f32()
+                );
+                break;
+            }
+        }
+    }
+    let wallet_tip_end = wallet.latest_checkpoint();
+    let balance = wallet.get_balance();
+    println!(
+        "Synced {} blocks in {}s",
+        blocks_received,
+        start_load_wallet.elapsed().as_secs_f32(),
+    );
+    println!(
+        "Wallet tip is '{}:{}'",
+        wallet_tip_end.height(),
+        wallet_tip_end.hash()
+    );
+    println!("Wallet balance is {} sats", balance.total());
+    println!(
+        "Wallet has {} transactions and {} utxos",
+        wallet.transactions().count(),
+        wallet.list_unspent().count()
+    );
+
+    Ok(())
+}