feat(chain)!: wrap TxGraph txs with Arc

Wrapping transactions as `Arc<Transaction>` allows us to share
transactions cheaply between the chain-source and receiving structures.
Therefore the chain-source can keep already-fetched transactions (save
bandwidth) and have a shared pointer to the transactions (save memory).

This is better than the current way we do things, which is to refer back
to the receiving structures mid-sync.

Documentation for `TxGraph` is also updated.

crates/chain/tests/test_indexed_tx_graph.rs

@@ -1,7 +1,7 @@
 #[macro_use]
 mod common;
 
-use std::collections::BTreeSet;
+use std::{collections::BTreeSet, sync::Arc};
 
 use bdk_chain::{
     indexed_tx_graph::{self, IndexedTxGraph},
@@ -66,7 +66,7 @@ fn insert_relevant_txs() {
 
     let changeset = indexed_tx_graph::ChangeSet {
         graph: tx_graph::ChangeSet {
-            txs: txs.clone().into(),
+            txs: txs.iter().cloned().map(Arc::new).collect(),
             ..Default::default()
         },
         indexer: keychain::ChangeSet([((), 9_u32)].into()),
@@ -80,7 +80,6 @@ fn insert_relevant_txs() {
     assert_eq!(graph.initial_changeset(), changeset,);
 }
 
-#[test]
 /// Ensure consistency IndexedTxGraph list_* and balance methods. These methods lists
 /// relevant txouts and utxos from the information fetched from a ChainOracle (here a LocalChain).
 ///
@@ -108,7 +107,7 @@ fn insert_relevant_txs() {
 ///
 /// Finally Add more blocks to local chain until tx1 coinbase maturity hits.
 /// Assert maturity at coinbase maturity inflection height. Block height 98 and 99.
-
+#[test]
 fn test_list_owned_txouts() {
     // Create Local chains
     let local_chain = LocalChain::from_blocks((0..150).map(|i| (i as u32, h!("random"))).collect())

crates/chain/tests/test_tx_graph.rs

@@ -13,6 +13,7 @@ use bitcoin::{
 use common::*;
 use core::iter;
 use rand::RngCore;
+use std::sync::Arc;
 use std::vec;
 
 #[test]
@@ -119,7 +120,7 @@ fn insert_txouts() {
         assert_eq!(
             graph.insert_tx(update_txs.clone()),
             ChangeSet {
-                txs: [update_txs.clone()].into(),
+                txs: [Arc::new(update_txs.clone())].into(),
                 ..Default::default()
             }
         );
@@ -143,7 +144,7 @@ fn insert_txouts() {
     assert_eq!(
         changeset,
         ChangeSet {
-            txs: [update_txs.clone()].into(),
+            txs: [Arc::new(update_txs.clone())].into(),
             txouts: update_ops.clone().into(),
             anchors: [(conf_anchor, update_txs.txid()), (unconf_anchor, h!("tx2"))].into(),
             last_seen: [(h!("tx2"), 1000000)].into()
@@ -194,7 +195,7 @@ fn insert_txouts() {
     assert_eq!(
         graph.initial_changeset(),
         ChangeSet {
-            txs: [update_txs.clone()].into(),
+            txs: [Arc::new(update_txs.clone())].into(),
             txouts: update_ops.into_iter().chain(original_ops).collect(),
             anchors: [(conf_anchor, update_txs.txid()), (unconf_anchor, h!("tx2"))].into(),
             last_seen: [(h!("tx2"), 1000000)].into()
@@ -276,7 +277,10 @@ fn insert_tx_can_retrieve_full_tx_from_graph() {
 
     let mut graph = TxGraph::<()>::default();
     let _ = graph.insert_tx(tx.clone());
-    assert_eq!(graph.get_tx(tx.txid()), Some(&tx));
+    assert_eq!(
+        graph.get_tx(tx.txid()).map(|tx| tx.as_ref().clone()),
+        Some(tx)
+    );
 }
 
 #[test]
@@ -643,7 +647,7 @@ fn test_walk_ancestors() {
         ..common::new_tx(0)
     };
 
-    let mut graph = TxGraph::<BlockId>::new(vec![
+    let mut graph = TxGraph::<BlockId>::new([
         tx_a0.clone(),
         tx_b0.clone(),
         tx_b1.clone(),
@@ -664,17 +668,17 @@ fn test_walk_ancestors() {
 
     let ancestors = [
         graph
-            .walk_ancestors(&tx_c0, |depth, tx| Some((depth, tx)))
+            .walk_ancestors(tx_c0.clone(), |depth, tx| Some((depth, tx)))
             .collect::<Vec<_>>(),
         graph
-            .walk_ancestors(&tx_d0, |depth, tx| Some((depth, tx)))
+            .walk_ancestors(tx_d0.clone(), |depth, tx| Some((depth, tx)))
             .collect::<Vec<_>>(),
         graph
-            .walk_ancestors(&tx_e0, |depth, tx| Some((depth, tx)))
+            .walk_ancestors(tx_e0.clone(), |depth, tx| Some((depth, tx)))
             .collect::<Vec<_>>(),
         // Only traverse unconfirmed ancestors of tx_e0 this time
         graph
-            .walk_ancestors(&tx_e0, |depth, tx| {
+            .walk_ancestors(tx_e0.clone(), |depth, tx| {
                 let tx_node = graph.get_tx_node(tx.txid())?;
                 for block in tx_node.anchors {
                     match local_chain.is_block_in_chain(block.anchor_block(), tip.block_id()) {
@@ -701,8 +705,14 @@ fn test_walk_ancestors() {
         vec![(1, &tx_d1), (2, &tx_c2), (2, &tx_c3), (3, &tx_b2)],
     ];
 
-    for (txids, expected_txids) in ancestors.iter().zip(expected_ancestors.iter()) {
-        assert_eq!(txids, expected_txids);
+    for (txids, expected_txids) in ancestors.into_iter().zip(expected_ancestors) {
+        assert_eq!(
+            txids,
+            expected_txids
+                .into_iter()
+                .map(|(i, tx)| (i, Arc::new(tx.clone())))
+                .collect::<Vec<_>>()
+        );
     }
 }