Replace indexOf with precomputed index map in renderItem

Avoids O(n) array scan per rendered row by precomputing a
reportActionID-to-index Map once per data change.

Co-authored-by: Aimane Chnaif <aimane-chnaif@users.noreply.github.com>

Author: MelvinBot

src/pages/inbox/report/ReportActionsList.tsx

@@ -695,6 +695,16 @@ function ReportActionsList({
         return isExpenseReport(report) || isIOUReport(report) || isInvoiceReport(report);
     }, [parentReportAction, report, sortedVisibleReportActions]);
 
+    // Precompute a reportActionID → index map so renderItem can resolve the real index in O(1)
+    // instead of scanning sortedVisibleReportActions with indexOf on every render.
+    const actionIndexMap = useMemo(() => {
+        const map = new Map<string, number>();
+        for (const [i, action] of sortedVisibleReportActions.entries()) {
+            map.set(action.reportActionID, i);
+        }
+        return map;
+    }, [sortedVisibleReportActions]);
+
     const renderItem = useCallback(
         ({item: reportAction, index}: ListRenderItemInfo<OnyxTypes.ReportAction>) => {
             const originalReportID = getOriginalReportID(report.reportID, reportAction, reportActionsFromOnyx);
@@ -703,8 +713,7 @@ function ReportActionsList({
             // Use the action's actual index in sortedVisibleReportActions rather than the FlashList-provided index,
             // because useFlashListScrollKey may slice the data for deep-link scroll positioning, making the
             // FlashList index offset from the full array and causing wrong displayAsGroup computation.
-            const actionIndex = sortedVisibleReportActions.indexOf(reportAction);
-            const safeIndex = actionIndex >= 0 ? actionIndex : index;
+            const safeIndex = actionIndexMap.get(reportAction.reportActionID) ?? index;
 
             return (
                 <>
@@ -760,6 +769,7 @@ function ReportActionsList({
             isOffline,
             transactionThreadReport,
             linkedReportActionID,
+            actionIndexMap,
             sortedVisibleReportActions,
             shouldHideThreadDividerLine,
             unreadMarkerReportActionID,