AppFlowy/frontend/app_flowy/packages/flowy_editor/lib/operation/operation.dart

import 'package:flowy_editor/document/path.dart';
import 'package:flowy_editor/document/node.dart';

abstract class Operation {
  Operation invert();
}

class InsertOperation extends Operation {
  final Path path;
  final Node value;

  InsertOperation({
    required this.path,
    required this.value,
  });

  @override
  Operation invert() {
    return DeleteOperation(
      path: path,
      removedValue: value,
    );
  }
}

class UpdateOperation extends Operation {
  final Path path;
  final Attributes attributes;
  final Attributes oldAttributes;

  UpdateOperation({
    required this.path,
    required this.attributes,
    required this.oldAttributes,
  });

  @override
  Operation invert() {
    return UpdateOperation(
      path: path,
      attributes: oldAttributes,
      oldAttributes: attributes,
    );
  }
}

class DeleteOperation extends Operation {
  final Path path;
  final Node removedValue;

  DeleteOperation({
    required this.path,
    required this.removedValue,
  });

  @override
  Operation invert() {
    return InsertOperation(
      path: path,
      value: removedValue,
    );
  }
}