package com.bookshop.behavioral.strategy;

import com.bookshop.domain.Book;
import com.bookshop.domain.Customer;
import java.math.BigDecimal;
import java.util.List;

/**
 * The context: computes totals without knowing which discount rule is in force.
 * Swapping the strategy changes pricing behaviour with zero changes here.
 */
public class PriceCalculator {

    private final DiscountStrategy discount;

    public PriceCalculator(DiscountStrategy discount) {
        this.discount = discount;
    }

    public BigDecimal totalFor(List<Book> books, Customer customer) {
        BigDecimal subtotal = books.stream().map(Book::price).reduce(BigDecimal.ZERO, BigDecimal::add);
        return subtotal.subtract(discount.discountFor(subtotal, customer));
    }
}