import static org.junit.Assert.assertEquals;

import java.util.Random;

import org.junit.Test;

public class CheckoutTests {

	@Test
	public void basicPrices() {
		Money priceOfA = randomPrice();
		MultibuyDiscount discount = new MultibuyDiscount("A", Money.fromPence(20), 2);
		Checkout checkout = new Checkout(discount);
		Money priceOfB = randomPrice();
		checkout.scan("A", priceOfA).scan("B", priceOfB);
		assertEquals(priceOfA.add(priceOfB), checkout.currentBalance());
	}

	@Test
	public void discountForTwoAs() {
		Money priceOfA = randomPrice();
		Money priceOfB = randomPrice();
		MultibuyDiscount discount = new MultibuyDiscount("A", Money.fromPence(20), 2);
		Checkout checkout = new Checkout(discount);
		checkout.scan("A", priceOfA).scan("B", priceOfB)
				.scan("A", priceOfA);
		Money expectedTotal = priceOfA.add(priceOfA).add(priceOfB)
				.subtract(Money.fromPence(20));
		assertEquals(expectedTotal, checkout.currentBalance());
	}

	@Test
	public void independentCheckouts() {
		Money priceOfA = randomPrice();
		MultibuyDiscount discount = new MultibuyDiscount("A", Money.fromPence(20), 2);
		Checkout checkout1 = new Checkout(discount);
		Checkout checkout2 = new Checkout(discount);
		checkout1.scan("A", priceOfA);
		checkout2.scan("A", priceOfA);
		assertEquals(priceOfA, checkout1.currentBalance());
		assertEquals(priceOfA, checkout2.currentBalance());
	}

	private Money randomPrice() {
		int pence = new Random().nextInt(1000);
		return Money.fromPence(pence);
	}
}