mirrored_repositories/flutter-shopping-cart-app/lib
import 'package:flutter/foundation.dart';
import 'package:provider/provider.dart';

class CartItem {
  final String id;
  final String title;
  final int quantity;
  final double price;

  CartItem(
      {@required this.id,
      @required this.title,
      @required this.quantity,
      @required this.price});
}

class Cart with ChangeNotifier {
  Map<String, CartItem> _items = {};

  Map<String, CartItem> get items {
    return {..._items};
  }

  int get itemCount {
    return _items.length;
  }

  double get totalAmount {
    var total = 0.0;
    _items.forEach((key, cartItem) => total += cartItem.price*cartItem.quantity);
    return total;
  }

  void addItem(String productId, double price, String title) {
    if (_items.containsKey(productId)) {
      _items.update(productId, (existingCartItem) => CartItem(
        id: existingCartItem.id,
        title: existingCartItem.title,
        price: existingCartItem.price,
        quantity: existingCartItem.quantity + 1,
      ));
    } else {
      _items.putIfAbsent(
          productId,
          () => CartItem(
              id: DateTime.now().toString(),
              title: title,
              price: price,
              quantity: 1,
          )
      );
    }
    notifyListeners();
  }

  void removeItem(String productId) {
    _items.remove(productId);
    notifyListeners();
  }

  void removeSingleItem(String productId) {
    if(!_items.containsKey(productId)) {
      return;
    }
    if(_items[productId].quantity > 1) {
      _items.update(productId, (existingCartItem) => CartItem(
        id: existingCartItem.id,
        title: existingCartItem.title,
        price: existingCartItem.price,
        quantity: existingCartItem.quantity - 1,
      ));
    } else {
      _items.remove(productId);
    }
    notifyListeners();
  }

  void clearCart() {
    _items = {};
    notifyListeners();
  }

}
