package com.bookshop.behavioral.strategy;

import com.bookshop.domain.Customer;
import java.math.BigDecimal;

/**
 * The strategy: one interchangeable pricing rule. A functional interface, so
 * one-off strategies can be lambdas -- the modern face of this pattern.
 */
@FunctionalInterface
public interface DiscountStrategy {

    /** Returns the discount (not the final price) for this subtotal and customer. */
    BigDecimal discountFor(BigDecimal subtotal, Customer customer);
}