gobang/lib/memorandum/checkerboard.dart

import 'package:gobang/flyweight/position.dart';
import 'package:gobang/memorandum/care_taker.dart';
import 'package:gobang/memorandum/memo.dart';

class Checkerboard {
  Checkerboard._();

  static final Checkerboard instance = Checkerboard._();

  static Checkerboard getInstance() => instance;

  List<Position> _state = [];

  List<Position> get state => _state;

  final CareTaker _careTaker = CareTaker();

  void add(Position position) {
    _state.add(position);
    _careTaker.add(_save());
  }

  void _from(Memo memo) {
    _state = List.of(memo.state);
  }

  Memo _save() => Memo(_state);

  void clean() {
    _state = [];
    _careTaker.clear();
  }

  void undo() {
    final memo = _careTaker.getLast();
    _from(memo);
  }
}