package com.bookshop.behavioral.strategy;

import java.math.BigDecimal;
import java.math.RoundingMode;

/** The shop's standard discount strategies. */
public final class Discounts {

    private Discounts() {
    }

    public static DiscountStrategy none() {
        return (subtotal, customer) -> BigDecimal.ZERO;
    }

    /** 2% per full year of loyalty, capped at 10%. */
    public static DiscountStrategy loyalty() {
        return (subtotal, customer) -> {
            int percent = Math.min(customer.loyaltyYears() * 2, 10);
            return percentOf(subtotal, percent);
        };
    }

    /** 15% off orders of 50.00 or more. */
    public static DiscountStrategy bulkOrder() {
        return (subtotal, customer) -> subtotal.compareTo(new BigDecimal("50.00")) >= 0
                ? percentOf(subtotal, 15)
                : BigDecimal.ZERO;
    }

    /** A flat percentage off everything, e.g. a summer sale. */
    public static DiscountStrategy seasonalSale(int percent) {
        return (subtotal, customer) -> percentOf(subtotal, percent);
    }

    private static BigDecimal percentOf(BigDecimal amount, int percent) {
        return amount.multiply(BigDecimal.valueOf(percent))
                .divide(BigDecimal.valueOf(100), 2, RoundingMode.HALF_UP);
    }
}

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