test: invert

frontend/app_flowy/packages/flowy_editor/example/lib/plugin/image_node_widget.dart

@@ -1,6 +1,7 @@
 import 'package:flowy_editor/flowy_editor.dart';
 import 'package:flutter/material.dart';
 import 'package:provider/provider.dart';
+import 'package:flowy_editor/document/attributes.dart';
 
 class ImageNodeBuilder extends NodeWidgetBuilder {
   ImageNodeBuilder.create({

frontend/app_flowy/packages/flowy_editor/lib/document/attributes.dart

@@ -21,3 +21,22 @@ Attributes invertAttributes(Attributes? attr, Attributes? base) {
     return memo;
   });
 }
+
+Attributes? composeAttributes(Attributes? a, Attributes? b) {
+  a ??= {};
+  b ??= {};
+  final Attributes attributes = {};
+  attributes.addAll(b);
+
+  for (final entry in a.entries) {
+    if (!b.containsKey(entry.key)) {
+      attributes[entry.key] = entry.value;
+    }
+  }
+
+  if (attributes.isEmpty) {
+    return null;
+  }
+
+  return attributes;
+}

frontend/app_flowy/packages/flowy_editor/lib/document/text_delta.dart

@@ -336,7 +336,8 @@ class Delta {
         final length = min(thisIter.peekLength(), otherIter.peekLength());
         final thisOp = thisIter.next(length);
         final otherOp = otherIter.next(length);
-        final attributes = _composeMap(thisOp.attributes, otherOp.attributes);
+        final attributes =
+            composeAttributes(thisOp.attributes, otherOp.attributes);
         if (otherOp is TextRetain && otherOp.length > 0) {
           TextOperation? newOp;
           if (thisOp is TextRetain) {
@@ -423,22 +424,3 @@ class Delta {
     return inverted.chop();
   }
 }
-
-Attributes? _composeMap(Attributes? a, Attributes? b) {
-  a ??= {};
-  b ??= {};
-  final Attributes attributes = {};
-  attributes.addAll(b);
-
-  for (final entry in a.entries) {
-    if (!b.containsKey(entry.key)) {
-      attributes[entry.key] = entry.value;
-    }
-  }
-
-  if (attributes.isEmpty) {
-    return null;
-  }
-
-  return attributes;
-}

frontend/app_flowy/packages/flowy_editor/lib/editor_state.dart

@@ -1,5 +1,6 @@
 import 'package:flowy_editor/document/node.dart';
 import 'package:flowy_editor/operation/operation.dart';
+import 'package:flowy_editor/document/attributes.dart';
 import 'package:flutter/material.dart';
 
 import './document/state_tree.dart';

frontend/app_flowy/packages/flowy_editor/test/delta_test.dart

@@ -2,7 +2,7 @@ import 'package:flutter_test/flutter_test.dart';
 import 'package:flowy_editor/document/text_delta.dart';
 
 void main() {
-  TestWidgetsFlutterBinding.ensureInitialized();
+  group('compose', () {
     test('test delta', () {
       final delta = Delta(<TextOperation>[
         TextInsert('Gandalf', {
@@ -170,4 +170,31 @@ void main() {
           .insert('F');
       expect(a.compose(b), expected);
     });
+  });
+  group('invert', () {
+    test('insert', () {
+      final delta = Delta().retain(2).insert('A');
+      final base = Delta().insert('12346');
+      final expected = Delta().retain(2).delete(1);
+      final inverted = delta.invert(base);
+      expect(expected, inverted);
+      expect(base.compose(delta).compose(inverted), base);
+    });
+    test('delete', () {
+      final delta = Delta().retain(2).delete(3);
+      final base = Delta().insert('123456');
+      final expected = Delta().retain(2).insert('345');
+      final inverted = delta.invert(base);
+      expect(expected, inverted);
+      expect(base.compose(delta).compose(inverted), base);
+    });
+    // test('retain', () {
+    //   final delta = Delta().retain(2).retain(3, {'bold': true});
+    //   final base = Delta().insert('123456');
+    //   final expected = Delta().retain(2).retain(3, {'bold': null});
+    //   final inverted = delta.invert(base);
+    //   expect(expected, inverted);
+    //   expect(base.compose(delta).compose(inverted), base);
+    // });
+  });
 }