patterns/builder.dart

// предоставляет способ создания составного объекта

class PizzaBuilder {
  late String _crust;
  int _diameter;
  late Set<String> _toppings;

  PizzaBuilder(this._diameter);

  String get crust => _crust;
  set crust(String newCrust) => _crust = newCrust;

  int get diameter => _diameter;
  set diameter(int newDiameter) => _diameter = newDiameter;

  Set<String> get toppings => _toppings;
  set toppings(Set<String> newToppings) {
    _toppings = newToppings;
    _addCheese();
  }

  void _addCheese() => _toppings.add("сыр");

  Pizza build() {
    return Pizza(this);
  }
}

class Pizza {
  late String _crust;
  late int _diameter;
  late Set<String> _toppings;

  Pizza(PizzaBuilder builder) {
    _crust = builder.crust;
    _diameter = builder.diameter;
    _toppings = builder.toppings;
  }

  String get crust => _crust;
  int get diameter => _diameter;
  String get toppings => _stringifiedToppings();
  String _stringifiedToppings() {
    var stringToppings = _toppings.join(", ");
    var lastComma = stringToppings.lastIndexOf(",");
    var replacement = ",".allMatches(stringToppings).length > 1 ? ", и" : " и";

    return stringToppings.replaceRange(lastComma, lastComma + 1, replacement);
  }

  @override
  String toString() {
    return "Пицца с $_diameter\" диметром с $_crust корочкой. Ингридиенты: $toppings";
  }
}

void main() {
  var pizzaBuilder = PizzaBuilder(8);

  pizzaBuilder.crust = "хрустящей";
  pizzaBuilder.toppings = Set.from(["пеперони"]);

  var plainPizza = Pizza(pizzaBuilder);
  print("Заказана $plainPizza.");

  pizzaBuilder.crust = "сырной";
  pizzaBuilder.diameter = 10;
  pizzaBuilder.toppings = Set.from(["ананасы"]);

  var ananasPizza = pizzaBuilder.build();
  print("Заказана $ananasPizza!");
}