From 48554c3307dd6423298985a609a2b8cbd0782f89 Mon Sep 17 00:00:00 2001
From: ZhuchkaTriplesix <mrlololoshka94@gmail.com>
Date: Sun, 30 Aug 2026 17:35:55 +0300
Subject: [PATCH] perf(workspace): offload massive grid selection statistics
 calculation to background compute

- Introduce GridSelectionCalcEngine.computeAdaptive with computeThreshold of 5000
- Offload stats calculations on massive multi-cell selections to background isolate
- Update ResultsTab onSelectionValuesChanged to leverage adaptive compute
- Add unit tests for synchronous and isolate-based selection statistics calculation

Closes #652
---
 .../workspace/grid_selection_calc_engine.dart | 19 +++++++++++++++-
 lib/features/workspace/results_tab.dart       | 20 ++++++++++++++---
 .../workspace/data_grid_engines_test.dart     | 22 +++++++++++++++++++
 3 files changed, 57 insertions(+), 4 deletions(-)

diff --git a/lib/features/workspace/grid_selection_calc_engine.dart b/lib/features/workspace/grid_selection_calc_engine.dart
index c7a111f6..b56d1291 100644
--- a/lib/features/workspace/grid_selection_calc_engine.dart
+++ b/lib/features/workspace/grid_selection_calc_engine.dart
@@ -1,5 +1,6 @@
 import 'dart:math' as math;
-import 'package:flutter/foundation.dart';
+import 'package:flutter/foundation.dart' as foundation;
+import 'package:flutter/foundation.dart' show immutable;
 
 /// Aggregated statistical results for a selection of grid cell values.
 @immutable
@@ -93,6 +94,22 @@ class GridCalcStats {
 
 /// Calculation engine for computing stats (Count, Distinct, Sum, Avg, Median, Min, Max, StdDev) on grid selections.
 abstract final class GridSelectionCalcEngine {
+  /// Default threshold for offloading stats calculation to a background isolate.
+  static const int computeThreshold = 5000;
+
+  /// Computes statistics adaptively: synchronously for small lists (< [computeThreshold]),
+  /// and offloaded to a background isolate using [compute] for large selections.
+  static Future<GridCalcStats> computeAdaptive(
+    List<String> values, {
+    int threshold = computeThreshold,
+  }) async {
+    if (values.isEmpty) return GridCalcStats.empty;
+    if (values.length < threshold) {
+      return compute(values);
+    }
+    return foundation.compute(compute, values);
+  }
+
   /// Computes statistics for a list of string cell values.
   static GridCalcStats compute(List<String> values) {
     if (values.isEmpty) return GridCalcStats.empty;
diff --git a/lib/features/workspace/results_tab.dart b/lib/features/workspace/results_tab.dart
index 66fcc991..6335a3e6 100644
--- a/lib/features/workspace/results_tab.dart
+++ b/lib/features/workspace/results_tab.dart
@@ -371,9 +371,23 @@ class _ResultsTabState extends material.State<ResultsTab> {
                         stagingBuffer: widget.stagingBuffer,
                         onRowSelected: (row) => setState(() => _selectedRowIndex = row),
                         onSelectionValuesChanged: (values) {
-                          setState(() {
-                            _selectionStats = GridSelectionCalcEngine.compute(values);
-                          });
+                          if (values.isEmpty) {
+                            setState(() => _selectionStats = GridCalcStats.empty);
+                            return;
+                          }
+                          if (values.length < GridSelectionCalcEngine.computeThreshold) {
+                            setState(() {
+                              _selectionStats = GridSelectionCalcEngine.compute(values);
+                            });
+                          } else {
+                            unawaited(
+                              GridSelectionCalcEngine.computeAdaptive(values).then((stats) {
+                                if (mounted) {
+                                  setState(() => _selectionStats = stats);
+                                }
+                              }),
+                            );
+                          }
                         },
                         onCellFocused: (colName, cellVal, rowIdx) {
                           setState(() {
diff --git a/test/features/workspace/data_grid_engines_test.dart b/test/features/workspace/data_grid_engines_test.dart
index 3ff65e9a..be209d34 100644
--- a/test/features/workspace/data_grid_engines_test.dart
+++ b/test/features/workspace/data_grid_engines_test.dart
@@ -209,6 +209,28 @@ void main() {
       final expectedEvenMedian = (evenParsed[499] + evenParsed[500]) / 2.0;
       expect(evenStats.median, equals(expectedEvenMedian));
     });
+
+    test('computeAdaptive returns empty stats for empty list', () async {
+      final stats = await GridSelectionCalcEngine.computeAdaptive(const []);
+      expect(stats, equals(GridCalcStats.empty));
+    });
+
+    test('computeAdaptive computes synchronously below threshold', () async {
+      final values = ['10', '20', '30'];
+      final stats = await GridSelectionCalcEngine.computeAdaptive(values, threshold: 10);
+      expect(stats.totalCount, 3);
+      expect(stats.sum, 60.0);
+      expect(stats.average, 20.0);
+    });
+
+    test('computeAdaptive computes via background isolate above threshold', () async {
+      final values = List<String>.generate(100, (i) => '$i');
+      final stats = await GridSelectionCalcEngine.computeAdaptive(values, threshold: 50);
+      expect(stats.totalCount, 100);
+      expect(stats.min, 0.0);
+      expect(stats.max, 99.0);
+      expect(stats.sum, 4950.0);
+    });
   });
 
   group('GridGroupingsEngine', () {