// TODO: Implement ShoppingCart using TDD.
//
// Domain rules (implement one at a time, test first!):
//   1. Add an item (name, price, quantity) to the cart
//   2. Get the subtotal (sum of price × quantity for all items)
//   3. Remove an item by name
//   4. Get total item count (sum of all quantities)
//   5. Apply a percentage discount to the subtotal (e.g. 10% off)
//   6. Items with zero or negative price are rejected
//
// CartItem is a Value Object — immutable, validated at construction.
// ShoppingCart is stateful — it accumulates items across calls.

class CartItem {
  final String name;
  final double price;
  final int quantity;

  CartItem({required this.name, required this.price, required this.quantity}) {
    // TODO: validate price > 0 and quantity > 0
  }
}

class ShoppingCart {
  // TODO: implement

  void addItem(CartItem item) {
    throw UnimplementedError();
  }

  void removeItem(String name) {
    throw UnimplementedError();
  }

  double subtotal() {
    throw UnimplementedError();
  }

  int itemCount() {
    throw UnimplementedError();
  }

  double totalAfterDiscount(double discountPercent) {
    throw UnimplementedError();
  }
}