h4-projekt-gruppe-0-sm/mobile/lib/controllers/cart.dart

import 'package:flutter/material.dart';
import 'package:mobile/models/product.dart';
import 'package:mobile/results.dart';

class ProductIdException implements Exception {}

class CartController extends ChangeNotifier {
  final List<CartItem> cart = [];

  List<CartItem> allCartItems() {
    return cart;
  }

  CartItem? withProductId(int productId) {
    for (var i = 0; i < cart.length; i++) {
      if (cart[i].product.id == productId) {
        return cart[i];
      }
    }
    return null;
  }

  void incrementAmount(int productId) {
    final cartItem = withProductId(productId);
    if (cartItem == null) {
      throw ProductIdException();
    }
    cartItem.amount++;
    notifyListeners();
  }

  void decrementAmount(int productId) {
    final cartItem = withProductId(productId);
    if (cartItem == null) {
      throw ProductIdException();
    }
    cartItem.amount -= 1;
    if (cartItem.amount <= 0) {
      cart.remove(cartItem);
    }
    notifyListeners();
  }

  bool willRemoveOnNextDecrement(int productId) {
    final cartItem = withProductId(productId);
    if (cartItem == null) {
      throw ProductIdException();
    }
    return cartItem.amount <= 1;
  }

  void removeCartItem(int productId) {
    final cartItem = withProductId(productId);
    if (cartItem == null) {
      throw ProductIdException();
    }
    cart.remove(cartItem);
    notifyListeners();
  }

  void addToCart(Product product) {
    final cartItem = withProductId(product.id);
    if (cartItem == null) {
      cart.add(CartItem(product: product, amount: 1));
    } else {
      cartItem.amount++;
    }
    notifyListeners();
  }

  int totalItemsInCart() {
    return cart.fold<int>(0, (prev, cartItem) => prev + cartItem.amount);
  }

  int totalPrice() {
    return cart.fold<int>(
        0,
        (prev, cartItem) =>
            prev + cartItem.amount * cartItem.product.priceInDkkCents);
  }

  void clearCart() {
    cart.clear();
    notifyListeners();
  }

  Result<Null, String> pay() {
    return const Err("Not implemented");
  }
}

class CartItem {
  final Product product;
  int amount;

  CartItem({required this.product, required this.amount});
}