thesis_shop/lib/stores/cart_store.dart

import 'package:flutter/material.dart';
import 'package:thesis_shop/models/cart_item.dart';
import 'package:thesis_shop/models/product.dart';
import 'package:thesis_shop/stores/product_store.dart';

class CartStoreImplementation extends StatefulWidget {
  final Widget child;
  const CartStoreImplementation({Key? key, required this.child})
      : super(key: key);

  @override
  _CartStoreImplementationState createState() =>
      _CartStoreImplementationState();
}

class _CartStoreImplementationState extends State<CartStoreImplementation> {
  Map<ProductTitle, int> productAmounts = {};
  void increaseAmount(Product product) => setState(() {
        final currentAmount =
            productAmounts.putIfAbsent(product.title, () => 0);
        productAmounts[product.title] = currentAmount + 1;
      });
  void decreaseAmount(Product product) => setState(() {
        final currentAmount =
            productAmounts.putIfAbsent(product.title, () => 0);
        productAmounts[product.title] =
            currentAmount <= 0 ? 0 : currentAmount - 1;
      });
  @override
  Widget build(BuildContext context) {
    final products = ProductStore.of(context).productsOrNull ?? const [];
    final productsByTitle = {
      for (var product in products) product.title: product
    };
    final cartItems = productAmounts
        .map((key, value) => MapEntry(productsByTitle[key], value))
        .entries
        .where((entry) => entry.key != null && entry.value > 0)
        .map((entry) => CartItem(product: entry.key!, amount: entry.value))
        .toList();
    return CartStore(
      cartItems: cartItems,
      increaseAmount: increaseAmount,
      decreaseAmount: decreaseAmount,
      child: widget.child,
    );
  }
}

class CartStore extends InheritedWidget {
  const CartStore({
    Key? key,
    required this.cartItems,
    required this.increaseAmount,
    required this.decreaseAmount,
    required Widget child,
  }) : super(key: key, child: child);

  final List<CartItem> cartItems;

  final Function(Product) increaseAmount;
  final Function(Product) decreaseAmount;

  int amountOfProduct(Product product) {
    final amounts = {
      for (final item in cartItems) item.product: item.amount,
    };
    return amounts.putIfAbsent(product, () => 0);
  }

  static CartStore of(BuildContext context) {
    final CartStore? result =
        context.dependOnInheritedWidgetOfExactType<CartStore>();
    assert(result != null, 'No CartStore found in context');
    return result!;
  }

  @override
  bool updateShouldNotify(CartStore oldWidget) {
    return cartItems != oldWidget.cartItems;
  }
}