public interface RuleTemplate {
    // 計算優(yōu)惠券
    ShoppingCart calculate(ShoppingCart settlement);
}

public ShoppingCart calculate(ShoppingCart order) {
    // 獲取訂單總價
    Long orderTotalAmount = getTotalPrice(order.getProducts());
    // 獲取以shopId為維度的總價統(tǒng)計
    Map<Long, Long> sumAmount = getTotalPriceGroupByShop(order.getProducts());
    CouponTemplateInfo template = order.getCouponInfos().get(0).getTemplate();
    // 最低消費限制
    Long threshold = template.getRule().getDiscount().getThreshold();
    // 優(yōu)惠金額或者打折比例
    Long quota = template.getRule().getDiscount().getQuota();
    // 如果優(yōu)惠券未指定shopId，則shopTotalAmount=orderTotalAmount
    // 如果指定了shopId，則shopTotalAmount=對應門店下商品總價
    Long shopId = template.getShopId();
    Long shopTotalAmount = (shopId == null) ? orderTotalAmount : sumAmount.get(shopId);
    // 如果不符合優(yōu)惠券使用標準, 則直接按原價走，不使用優(yōu)惠券
    if (shopTotalAmount == null || shopTotalAmount < threshold) {
        log.debug("Totals of amount not meet");
        order.setCost(orderTotalAmount);
        order.setCouponInfos(Collections.emptyList());
        return order;
    }
    // 子類中實現calculateNewPrice計算新的價格
    Long newCost = calculateNewPrice(orderTotalAmount, shopTotalAmount, quota);
    if (newCost < minCost()) {
        newCost = minCost();
    }
    order.setCost(newCost);
    log.debug("original price={}, new price={}", orderTotalAmount, newCost);
    return order;
}

@Slf4j
@Component
public class MoneyOffTemplate extends AbstractRuleTemplate implements RuleTemplate {
    @Override
    protected Long calculateNewPrice(Long totalAmount, Long shopAmount, Long quota) {
        // benefitAmount是扣減的價格
        // 如果當前門店的商品總價<quota，那么最多只能扣減shopAmount的錢數
        Long benefitAmount = shopAmount < quota ? shopAmount : quota;
        return totalAmount - benefitAmount;
    }    
}

@Component
@Slf4j
public class CouponTemplateFactory {
    @Autowired
    private MoneyOffTemplate moneyOffTemplate;
    @Autowired
    private DiscountTemplate discountTemplate;
    @Autowired
    private RandomReductionTemplate randomReductionTemplate;
    @Autowired
    private LonelyNightTemplate lonelyNightTemplate;
    @Autowired
    private DummyTemplate dummyTemplate;
    @Autowired
    private AntiPauTemplate antiPauTemplate;
    public RuleTemplate getTemplate(ShoppingCart order) {
        // 不使用優(yōu)惠券
        if (CollectionUtils.isEmpty(order.getCouponInfos())) {
            // dummy模板直接返回原價，不進行優(yōu)惠計算
            return dummyTemplate;
        }
        // 獲取優(yōu)惠券的類別
        // 目前每個訂單只支持單張優(yōu)惠券
        CouponTemplateInfo template = order.getCouponInfos().get(0).getTemplate();
        CouponType category = CouponType.convert(template.getType());
        switch (category) {
            // 訂單滿減券
            case MONEY_OFF:
                return moneyOffTemplate;
            // 隨機立減券
            case RANDOM_DISCOUNT:
                return randomReductionTemplate;
            // 午夜下單優(yōu)惠翻倍
            case LONELY_NIGHT_MONEY_OFF:
                return lonelyNightTemplate;
            // 打折券
            case DISCOUNT:
                return discountTemplate;
            case ANTI_PUA:
                return antiPauTemplate;
            // 未知類型的券模板
            default:
                return dummyTemplate;
        }
    }
}

    @Autowired
    private CouponTemplateFactory couponProcessorFactory;
    // 優(yōu)惠券結算
    // 這里通過Factory類決定使用哪個底層Rule，底層規(guī)則對上層透明
    @Override
    public ShoppingCart calculateOrderPrice(@RequestBody ShoppingCart cart) {
        log.info("calculate order price: {}", JSON.toJSONString(cart));
        RuleTemplate ruleTemplate = couponProcessorFactory.getTemplate(cart);
        return ruleTemplate.calculate(cart);
    }