From 6244a8e4e8fb77d246f3c3d9e7056f6f342f751e Mon Sep 17 00:00:00 2001
From: Angel Castillo <angel.castillo@iohk.io>
Date: Fri, 15 Nov 2024 12:39:46 +0800
Subject: [PATCH] fixup! feat(wallet): the wallet now only fetches UTXOs on tx
 history change

---
 .../src/services/TransactionsTracker.ts       | 96 ++++++++++---------
 1 file changed, 49 insertions(+), 47 deletions(-)

diff --git a/packages/wallet/src/services/TransactionsTracker.ts b/packages/wallet/src/services/TransactionsTracker.ts
index a4efd89e2a0..26f7fbd8c47 100644
--- a/packages/wallet/src/services/TransactionsTracker.ts
+++ b/packages/wallet/src/services/TransactionsTracker.ts
@@ -123,6 +123,30 @@ const getLastTransactionsAtBlock = (
   return txsFromSameBlock;
 };
 
+export const revertLastBlock = (
+  localTransactions: Cardano.HydratedTx[],
+  blockNo: Cardano.BlockNo,
+  rollback$: Subject<Cardano.HydratedTx>,
+  logger: Logger
+) => {
+  const result = [...localTransactions];
+
+  while (result.length > 0) {
+    const lastKnownTx = result[result.length - 1];
+
+    if (lastKnownTx.blockHeader.blockNo === blockNo) {
+      logger.debug(`Transaction ${lastKnownTx.id} was rolled back`);
+
+      rollback$.next(lastKnownTx);
+      result.pop();
+    } else {
+      break;
+    }
+  }
+
+  return result;
+};
+
 const findIntersectionAndUpdateTxStore = ({
   chainHistoryProvider,
   logger,
@@ -148,12 +172,9 @@ const findIntersectionAndUpdateTxStore = ({
     combinator: exhaustMap,
     equals: transactionsEquals,
     onFatalError,
-    // eslint-disable-next-line complexity
     provider: async () => {
       // eslint-disable-next-line no-constant-condition
       while (true) {
-        let rollbackOccured = false;
-
         const lastStoredTransaction: Cardano.HydratedTx | undefined = localTransactions[localTransactions.length - 1];
 
         lastStoredTransaction &&
@@ -172,65 +193,46 @@ const findIntersectionAndUpdateTxStore = ({
           lowerBound !== undefined && `since block ${lowerBound}`
         );
 
+        // Fetching transactions from scratch, nothing else to do here.
         if (lowerBound === undefined) {
-          localTransactions = newTransactions;
-          return localTransactions;
+          return newTransactions;
         }
 
+        // If no transactions found from that block range, it means the last known block has been rolled back.
         if (newTransactions.length === 0) {
-          // If no transactions found from that block range, it means the last known block has been rolled back.
-          while (localTransactions.length > 0) {
-            const lastKnownTx = localTransactions[localTransactions.length - 1];
-
-            if (lastKnownTx.blockHeader.blockNo === lowerBound) {
-              rollbackOccured = true;
-              logger.debug(`Transaction ${lastKnownTx.id} was rolled back`);
-              rollback$.next(lastKnownTx);
-              localTransactions.pop();
-            } else {
-              break;
-            }
-          }
-
+          localTransactions = revertLastBlock(localTransactions, lowerBound, rollback$, logger);
           continue;
         }
 
         const localTxsFromSameBlock = getLastTransactionsAtBlock(localTransactions, lowerBound);
+        const firstSegmentOfNewTransactions = newTransactions.slice(0, localTxsFromSameBlock.length);
 
-        // Roll back transactions from this block not found in the result
-        for (const localTx of localTxsFromSameBlock) {
-          const txFound = newTransactions.find((tx) => tx.id === localTx.id);
-
-          if (!txFound) {
-            rollbackOccured = true;
-            logger.debug(`Transaction ${localTx.id} was rolled back`);
-            rollback$.next(localTx);
+        // The first segment of new transaction should match exactly (same txs and same order) our last know TXs. Otherwise
+        // roll them back and re-apply in new order.
+        const sameLength = localTxsFromSameBlock.length === firstSegmentOfNewTransactions.length;
+        const sameOrder =
+          sameLength && localTxsFromSameBlock.every((tx, index) => tx.id === firstSegmentOfNewTransactions[index].id);
 
-            const index = localTransactions.findLastIndex((tx) => tx.id === localTx.id);
+        if (!sameLength || !sameOrder) {
+          localTransactions = revertLastBlock(localTransactions, lowerBound, rollback$, logger);
+          localTransactions = [...localTransactions, ...newTransactions];
+          store.setAll(localTransactions);
 
-            if (index !== -1) {
-              localTransactions.splice(index, 1);
-            }
-          }
+          continue;
         }
 
-        if (!rollbackOccured) {
-          const lastLocalTxs = localTransactions.slice(-newTransactions.length);
-
-          const areTransactionsSame =
-            lastLocalTxs.length === newTransactions.length &&
-            lastLocalTxs.every((tx, index) => tx.id === newTransactions[index].id);
+        // No rollbacks, if they overlap 100% do nothing, otherwise add the difference.
+        const areTransactionsSame =
+          newTransactions.length === localTxsFromSameBlock.length &&
+          localTxsFromSameBlock.every((tx, index) => tx.id === newTransactions[index].id);
 
-          if (!areTransactionsSame) {
-            // Remove overlapping transactions
-            localTransactions = localTransactions.slice(0, -localTxsFromSameBlock.length);
-            localTransactions = [...localTransactions, ...newTransactions];
-
-            store.setAll(localTransactions);
-          }
-
-          return localTransactions;
+        if (!areTransactionsSame) {
+          // Skip overlapping transactions to avoid duplicates
+          localTransactions = [...localTransactions, ...newTransactions.slice(localTxsFromSameBlock.length)];
+          store.setAll(localTransactions);
         }
+
+        return localTransactions;
       }
     },
     retryBackoffConfig,