feat: convert = and > to ⇒ (#523)

lib/src/editor/editor_component/service/shortcuts/character_shortcut_events/character_shortcut_events.dart

@@ -1,13 +1,12 @@
-export 'insert_newline.dart';
-export 'slash_command.dart';
-export 'markdown_syntax_character_shortcut_events.dart';
-
-export 'format_single_character/format_single_character.dart';
-export 'format_single_character/format_italic.dart';
-export 'format_single_character/format_code.dart';
-export 'format_single_character/format_strikethrough.dart';
-
-export 'format_double_characters/format_double_characters.dart';
 export 'format_double_characters/format_bold.dart';
-export 'format_double_characters/format_strikethrough.dart';
+export 'format_double_characters/format_double_characters.dart';
 export 'format_double_characters/format_double_hyphen.dart';
+export 'format_double_characters/format_equal_greater_character.dart';
+export 'format_double_characters/format_strikethrough.dart';
+export 'format_single_character/format_code.dart';
+export 'format_single_character/format_italic.dart';
+export 'format_single_character/format_single_character.dart';
+export 'format_single_character/format_strikethrough.dart';
+export 'insert_newline.dart';
+export 'markdown_syntax_character_shortcut_events.dart';
+export 'slash_command.dart';

lib/src/editor/editor_component/service/shortcuts/character_shortcut_events/format_double_characters/format_equal_greater_character.dart

@@ -0,0 +1,75 @@
+import 'package:appflowy_editor/appflowy_editor.dart';
+
+const _greater = '>';
+const _equals = '=';
+const _arrow = '⇒';
+
+/// format '=' + '>' into an ⇒
+///
+/// - support
+///   - desktop
+///   - mobile
+///   - web
+///
+final CharacterShortcutEvent formatGreaterEqual = CharacterShortcutEvent(
+  key: 'format = + > into ⇒',
+  character: _greater,
+  handler: (editorState) async => handleEqualGreaterReplacement(
+    editorState: editorState,
+    character: _greater,
+    replacement: _arrow,
+  ),
+);
+
+// TODO(Xazin): Combine two character replacement methods into
+//  a helper function
+Future<bool> handleEqualGreaterReplacement({
+  required EditorState editorState,
+  required String character,
+  required String replacement,
+}) async {
+  assert(character.length == 1);
+
+  Selection? selection = editorState.selection;
+  if (selection == null) {
+    return false;
+  }
+
+  if (!selection.isCollapsed) {
+    await editorState.deleteSelection(selection);
+  }
+
+  selection = editorState.selection;
+  if (selection == null) {
+    return false;
+  }
+
+  final node = editorState.getNodeAtPath(selection.end.path);
+  final delta = node?.delta;
+  if (node == null || delta == null || delta.isEmpty) {
+    return false;
+  }
+
+  if (selection.end.offset > 0) {
+    final plain = delta.toPlainText();
+
+    final previousCharacter = plain[selection.end.offset - 1];
+    if (previousCharacter != _equals) {
+      return false;
+    }
+
+    final replace = editorState.transaction
+      ..replaceText(
+        node,
+        selection.end.offset - 1,
+        1,
+        _arrow,
+      );
+
+    await editorState.apply(replace);
+
+    return true;
+  }
+
+  return false;
+}

lib/src/editor/editor_component/service/shortcuts/character_shortcut_events/markdown_syntax_character_shortcut_events.dart

@@ -32,4 +32,6 @@ final List<CharacterShortcutEvent> markdownSyntaxShortcutEvents = [
 
   // format -- into em dash
   formatDoubleHyphenEmDash,
+  // format = + > into ⇒
+  formatGreaterEqual,
 ];

test/new/service/shortcuts/character_shortcut_events/double_characters_shortcut_events/format_equal_greater_test.dart

@@ -0,0 +1,64 @@
+import 'package:appflowy_editor/appflowy_editor.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+import '../../../../infra/testable_editor.dart';
+
+const _greater = '>';
+const _equals = '=';
+const _arrow = '⇒';
+
+void main() async {
+  group('format_equal_greater.dart', () {
+    testWidgets('= + > to ⇒ in empty paragraph', (tester) async {
+      final editor = tester.editor..addEmptyParagraph();
+      await editor.startTesting();
+
+      await editor.updateSelection(Selection.collapsed(Position(path: [0])));
+
+      await editor.ime.typeText(_equals);
+      await editor.ime.typeText(_greater);
+
+      final delta = editor.nodeAtPath([0])!.delta!;
+      expect(delta.length, 1);
+      expect(delta.toPlainText(), _arrow);
+
+      await editor.dispose();
+    });
+
+    testWidgets('= + > to ⇒ in non-empty paragraph, undo, redo',
+        (tester) async {
+      const text = 'Hello World';
+      final editor = tester.editor..addParagraph(initialText: text);
+      await editor.startTesting();
+
+      await editor.updateSelection(
+        Selection.collapsed(
+          Position(
+            path: [0],
+            offset: text.length,
+          ),
+        ),
+      );
+
+      await editor.ime.typeText(_equals);
+      await editor.ime.typeText(_greater);
+
+      Delta delta = editor.nodeAtPath([0])!.delta!;
+      expect(delta.toPlainText(), text + _arrow);
+
+      undoCommand.execute(editor.editorState);
+      await tester.pumpAndSettle();
+
+      delta = editor.nodeAtPath([0])!.delta!;
+      expect(delta.toPlainText(), text + _equals);
+
+      undoCommand.execute(editor.editorState);
+      await tester.pumpAndSettle();
+
+      delta = editor.nodeAtPath([0])!.delta!;
+      expect(delta.toPlainText(), text);
+
+      await editor.dispose();
+    });
+  });
+}