From bee1a0432936c228a15866e64b3696f40b99371b Mon Sep 17 00:00:00 2001
From: Vincent Chan <okcdz@diverse.space>
Date: Wed, 10 Aug 2022 17:24:39 +0800
Subject: [PATCH] feat: compute string indexes

---
 .../flowy_editor/lib/src/document/text_delta.dart | 15 +++++++++++++++
 .../packages/flowy_editor/test/delta_test.dart    |  5 +++++
 2 files changed, 20 insertions(+)

diff --git a/frontend/app_flowy/packages/flowy_editor/lib/src/document/text_delta.dart b/frontend/app_flowy/packages/flowy_editor/lib/src/document/text_delta.dart
index 6626ba7a86..03ae4ccc56 100644
--- a/frontend/app_flowy/packages/flowy_editor/lib/src/document/text_delta.dart
+++ b/frontend/app_flowy/packages/flowy_editor/lib/src/document/text_delta.dart
@@ -260,6 +260,7 @@ TextOperation? _textOperationFromJson(Map<String, dynamic> json) {
 class Delta extends Iterable<TextOperation> {
   final List<TextOperation> _operations;
   String? _rawString;
+  List<int>? _runeIndexes;
 
   factory Delta.fromJson(List<dynamic> list) {
     final operations = <TextOperation>[];
@@ -477,9 +478,23 @@ class Delta extends Iterable<TextOperation> {
   String toRawString() {
     _rawString ??=
         _operations.whereType<TextInsert>().map((op) => op.content).join();
+    _runeIndexes ??= stringIndexes(_rawString!);
     return _rawString!;
   }
 
   @override
   Iterator<TextOperation> get iterator => _operations.iterator;
 }
+
+List<int> stringIndexes(String content) {
+  final indexes = List<int>.filled(content.length, 0);
+  final iterator = content.runes.iterator;
+
+  while (iterator.moveNext()) {
+    for (var i = 0; i < iterator.currentSize; i++) {
+      indexes[iterator.rawIndex + i] = iterator.rawIndex;
+    }
+  }
+
+  return indexes;
+}
diff --git a/frontend/app_flowy/packages/flowy_editor/test/delta_test.dart b/frontend/app_flowy/packages/flowy_editor/test/delta_test.dart
index 7016da70e4..2b0d529414 100644
--- a/frontend/app_flowy/packages/flowy_editor/test/delta_test.dart
+++ b/frontend/app_flowy/packages/flowy_editor/test/delta_test.dart
@@ -279,4 +279,9 @@ void main() {
       expect(delta, expected);
     });
   });
+  test("stringIndexes", () {
+    final indexes = stringIndexes('😊');
+    expect(indexes[0], 0);
+    expect(indexes[1], 0);
+  });
 }