ref(hwi): Move hwi out of bdk

Fixes #872

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);
+//     }
+// }