fix(bdk): set a reasonable default lookahead when creating a wallet

Added wallet test "test_get_funded_wallet_balance_for_nonzero_index" to test new DEFAULT_LOOKAHEAD.

WIP: other tests still failing and need to be investigated.

crates/bdk/src/wallet/mod.rs

@@ -459,13 +459,13 @@ impl<D> Wallet<D> {
         let secp = Secp256k1::new();
         let (chain, chain_changeset) = LocalChain::from_genesis_hash(genesis_hash);
         let mut index = KeychainTxOutIndex::<KeychainKind>::default();
-        index.set_lookahead_for_all(DEFAULT_LOOKAHEAD);
 
         let (signers, change_signers) =
             create_signers(&mut index, &secp, descriptor, change_descriptor, network)
                 .map_err(NewError::Descriptor)?;
 
-        let indexed_graph = IndexedTxGraph::new(index);
+        let mut indexed_graph = IndexedTxGraph::new(index);
+        indexed_graph.index.set_lookahead_for_all(DEFAULT_LOOKAHEAD);
 
         let mut persist = Persist::new(db);
         persist.stage(ChangeSet {
@@ -2312,6 +2312,20 @@ impl<D> Wallet<D> {
         &self.indexed_graph.index
     }
 
+    // /// Set's inner [`KeychainTxOutIndex`] look ahead count for all keychains.
+    // ///
+    // /// See [`KeychainTxOutIndex::set_lookahead_for_all`] for more details.
+    // pub fn set_spk_lookahead_for_all(&mut self, lookahead: u32) {
+    //     self.indexed_graph.index.set_lookahead_for_all(lookahead);
+    // }
+    //
+    // /// Set's inner [`KeychainTxOutIndex`] look ahead count for the specified keychain.
+    // ///
+    // /// See [`KeychainTxOutIndex::set_lookahead`] for more details.
+    // pub fn set_lookahead(&mut self, keychain: &KeychainKind, lookahead: u32) {
+    //     self.indexed_graph.index.set_lookahead(keychain, lookahead);
+    // }
+
     /// Get a reference to the inner [`LocalChain`].
     pub fn local_chain(&self) -> &LocalChain {
         &self.chain

crates/bdk/tests/common.rs

@@ -108,10 +108,59 @@ pub fn get_funded_wallet(descriptor: &str) -> (Wallet, bitcoin::Txid) {
     get_funded_wallet_with_change(descriptor, None)
 }
 
+// Return a fake wallet that appears to have one UTXO sent at a specific address index.
+//
+// The funded wallet containing a tx with one 76_000 sats input.
+pub fn get_funded_wallet_at_index(descriptor: &str, address_index: AddressIndex) -> (Wallet, Txid) {
+    let mut wallet = Wallet::new_no_persist(descriptor, None, Network::Regtest).unwrap();
+    let utxo_address = wallet.get_address(address_index).address;
+
+    let tx0 = Transaction {
+        version: 1,
+        lock_time: bitcoin::absolute::LockTime::ZERO,
+        input: vec![TxIn {
+            previous_output: OutPoint {
+                txid: Txid::all_zeros(),
+                vout: 0,
+            },
+            script_sig: Default::default(),
+            sequence: Default::default(),
+            witness: Default::default(),
+        }],
+        output: vec![TxOut {
+            value: 76_000,
+            script_pubkey: utxo_address.script_pubkey(),
+        }],
+    };
+
+    wallet
+        .insert_checkpoint(BlockId {
+            height: 1_000,
+            hash: BlockHash::all_zeros(),
+        })
+        .unwrap();
+
+    wallet
+        .insert_tx(
+            tx0.clone(),
+            ConfirmationTime::Confirmed {
+                height: 1_000,
+                time: 100,
+            },
+        )
+        .unwrap();
+
+    (wallet, tx0.txid())
+}
+
 pub fn get_test_wpkh() -> &'static str {
     "wpkh(cVpPVruEDdmutPzisEsYvtST1usBR3ntr8pXSyt6D2YYqXRyPcFW)"
 }
 
+pub fn get_test_wpkh_xprv() -> &'static str {
+    "wpkh(tprv8ZgxMBicQKsPdDArR4xSAECuVxeX1jwwSXR4ApKbkYgZiziDc4LdBy2WvJeGDfUSE4UT4hHhbgEwbdq8ajjUHiKDegkwrNU6V55CxcxonVN/*)"
+}
+
 pub fn get_test_single_sig_csv() -> &'static str {
     // and(pk(Alice),older(6))
     "wsh(and_v(v:pk(cVpPVruEDdmutPzisEsYvtST1usBR3ntr8pXSyt6D2YYqXRyPcFW),older(6)))"

crates/bdk/tests/wallet.rs

@@ -188,6 +188,14 @@ fn test_get_funded_wallet_balance() {
     assert_eq!(wallet.get_balance().confirmed, 50_000);
 }
 
+#[test]
+fn test_get_funded_wallet_balance_for_nonzero_index() {
+    // The funded wallet contains a tx with a 76_000 sats outputs to spk at index 1 that is found
+    // with the default look ahead.
+    let (wallet, _) = get_funded_wallet_at_index(get_test_wpkh_xprv(), Peek(1));
+    assert_eq!(wallet.get_balance().confirmed, 76_000);
+}
+
 #[test]
 fn test_get_funded_wallet_sent_and_received() {
     let (wallet, txid) = get_funded_wallet(get_test_wpkh());