Sort txs according to position within block

src/chain_access.rs

@@ -72,15 +72,7 @@ impl LipaChainAccess {
             debug!("{} confirmed transactions", confirmed_txs.len());
             debug!("Confirmed transaction list: {:?}", confirmed_txs);
 
-            // Sort all confirmed transactions by block height and feed them to the interface
-            // in order.
-            confirmed_txs.sort_unstable_by(|(_, block_height1, _, _), (_, block_height2, _, _)| {
-                block_height1.cmp(block_height2)
-            });
-
-            // todo also sort within block
-            // From the Confirm trait documentation:
-            // Dependent transactions within the same block must be given in topological order, possibly in separate calls
+            sort_txs(&mut confirmed_txs);
 
             for (tx, block_height, block_header, pos) in confirmed_txs {
                 for c in &confirmables {
@@ -368,6 +360,16 @@ impl LipaChainAccess {
     }
 }
 
+// Sorting by blocks and by transaction position within the each block
+// From the Confirm trait documentation:
+// - Transactions confirmed in a block must be given before transactions confirmed in a later
+//   block.
+// - Dependent transactions within the same block must be given in topological order, possibly in
+//   separate calls.
+fn sort_txs(txs: &mut [(Transaction, u32, BlockHeader, usize)]) {
+    txs.sort_unstable_by_key(|tx| (tx.1, tx.3));
+}
+
 impl Filter for LipaChainAccess {
     fn register_tx(&self, txid: &Txid, script_pubkey: &Script) {
         self.queued_txs
@@ -388,10 +390,11 @@ impl Filter for LipaChainAccess {
 
 #[cfg(test)]
 mod tests {
+    use crate::chain_access::sort_txs;
     use crate::LipaChainAccess;
     use bitcoin::consensus::deserialize;
     use bitcoin::hashes::hex::FromHex;
-    use bitcoin::Transaction;
+    use bitcoin::{BlockHeader, Transaction};
     use esplora_client::Builder;
     use lightning::chain::transaction::OutPoint;
     use lightning::chain::{Filter, WatchedOutput};
@@ -417,6 +420,17 @@ mod tests {
         tx.unwrap()
     }
 
+    fn build_default_block_header() -> BlockHeader {
+        BlockHeader {
+            version: 0,
+            prev_blockhash: Default::default(),
+            merkle_root: Default::default(),
+            time: 0,
+            bits: 0,
+            nonce: 0,
+        }
+    }
+
     #[test]
     fn filter_is_initialised_empty() {
         let filter = build_filter();
@@ -480,4 +494,49 @@ mod tests {
         assert_eq!(filter_output.outpoint, output.outpoint);
         assert_eq!(filter_output.block_hash, output.block_hash);
     }
+
+    #[test]
+    fn txs_are_sorted_by_block_and_position_within_block() {
+        let mut txs = vec![
+            (
+                build_sample_tx(),
+                10, // block height
+                build_default_block_header(),
+                10, // position within block
+            ),
+            (
+                build_sample_tx(),
+                5, // block height
+                build_default_block_header(),
+                5, // position within block
+            ),
+            (
+                build_sample_tx(),
+                10, // block height
+                build_default_block_header(),
+                5, // position within block
+            ),
+            (
+                build_sample_tx(),
+                5, // block height
+                build_default_block_header(),
+                10, // position within block
+            ),
+        ];
+
+        let unsorted: Vec<(u32, usize)> = txs
+            .iter()
+            .map(|(_, block_height, _, pos_within_block)| (*block_height, *pos_within_block))
+            .collect();
+
+        sort_txs(&mut txs);
+
+        let sorted: Vec<(u32, usize)> = txs
+            .iter()
+            .map(|(_, block_height, _, pos_within_block)| (*block_height, *pos_within_block))
+            .collect();
+
+        assert_eq!(unsorted, vec![(10, 10), (5, 5), (10, 5), (5, 10)]);
+        assert_eq!(sorted, vec![(5, 5), (5, 10), (10, 5), (10, 10)]);
+    }
 }