import 'dart:core';

void main() async {
  final table = Table(items: [
    CartProduct(productId: '1'),
    CartProduct(productId: '2'),
  ]);

  void saveTableOrder() {
    print('Saving table order...  $table');
  }

  void addToTable(List<CartProduct> carts) {
    if (table.items.isNotEmpty) {
      final newItems = <CartProduct>[];

      for (var cart in carts) {
        var found = false;
        for (var tableItem in table.items) {
          if (cart.productId == tableItem.productId) {
            tableItem.increment();
            found = true;
            break;
          }
        }
        if (!found) {
          newItems.add(cart);
        }
      }

      table.items.addAll(newItems);
      newItems.clear();
      saveTableOrder();
    } else {
      table.items.addAll(carts);
      saveTableOrder();
    }
  }

  addToTable([
    CartProduct(productId: '2'),
    CartProduct(productId: '3'),
  ]);
  addToTable([
    CartProduct(productId: '2'),
    CartProduct(productId: '3'),
  ]);
}

class CartProduct {
  final String productId;

  int quantity = 1;
  CartProduct({
    required this.productId,
  });

  void increment() {
    quantity++;
  }

  String toString() => 'id: $productId, quantity: $quantity';
}

class Table {
  List<CartProduct> items;
  Table({
    required this.items,
  });

  String toString() => items.toString();
}

// Saving table order...  [id: 1, quantity: 1, id: 2, quantity: 2, id: 3, quantity: 1]
// Saving table order...  [id: 1, quantity: 1, id: 2, quantity: 3, id: 3, quantity: 2]