求大神帮忙看看这个结构设计是否有问题： [ 2.0 版本 ]

哪能一个产品就声明一个类？说一下我的方法:订单总金额由物品金额和服务金额两部分组成。你说的“满减”、“节假日优惠”等都可以算进服务。假设地砖的价格是 5元/块，明天就是双十一了，你想搞个促销——消费满 500 元减50元。你可以新建一个服务，该服务的计费逻辑是看物品金额是否大于等于 500,是则新建一条金额为 -50 的服务记录。

假设客人买了 100 块, 付款金额 = 5x100 (物品金额）-50 (服务金额）= 450. 说得有些笼统，我之前做过一个类似的项目，如果你有兴趣，可以详细讨论。

<?php
// 促销抽象类 (Component: 组件对象接口)
abstract class Promotion {
	public $price; // 统计优惠价格
	// 计算价格
	abstract public function calePrice();
}


// 原始订单 (ConcreteComponent: 具体的组件对象, 实现了组件接口, 被装饰器装饰的原始对象)
class Order extends Promotion {
	public $goodsInfo;
	public function __construct ($goodsInfo) {
		$this->goodsInfo = $goodsInfo;
	}
	
	public function calePrice() {
		// 计算商品价格
		foreach($this->goodsInfo as $key=>$val) {
			$this->price += $val['price'];
		}
		return $this->price;
	}
}

// 装饰器: 父类 (Decorator: 所有装饰器的父类, 需要定义一个与组件接口一致的接口)
class Decorator extends Promotion {
	public $promotion;
	public $goodsInfo;

	public function __construct(Promotion $promotion) {
		$this->promotion = $promotion;
		$this->goodsInfo = $promotion->goodsInfo;
	}
	public function calePrice(){
	}
}

// 装饰器: 代金券 (ConcreteDecorator: 具体的装饰器类)
class CashCoupon extends Decorator {
	public function calePrice() {
		foreach($this->goodsInfo as $key=>$val) {
			if($val['couponType'] == 1) {
				$this->price += $val['couponVal'];
			}
		}

		return $this->promotion->calePrice() - $this->price;
	}
}
// 装饰器: 打折券 (ConcreteDecorator: 具体的装饰器类)
class DiscountCoupon extends Decorator {
	public function calePrice(){
		foreach($this->goodsInfo as $key=>$val) {
			if($val['couponType'] == 2) {
				$this->price += $val['price'] * (1 - $val['couponVal']);
			}
		}

		return $this->promotion->calePrice() - $this->price;
	}
}
// 装饰器: 免单券 (ConcreteDecorator: 具体的装饰器类)
class FreeCoupon extends Decorator {
	public function calePrice(){
		foreach($this->goodsInfo as $key=>$val) {
			if($val['couponType'] == 3) {
				$this->price += $val['price'];
			}
		}

		return $this->promotion->calePrice() - $this->price;
	}
}
// 装饰器: 满减 (ConcreteDecorator: 具体的装饰器类)
class MoneyOff extends Decorator {
	// 满减规则, atLeastAmount: 满减金额, amountOff: 减免金额/优惠金额
	private $moneyOffRules = [
		['atLeastAmount'=> 1000, 'amountOff'=> 10, 'start'=>0, 'end'=>1000],
		['atLeastAmount'=> 2000, 'amountOff'=> 20, 'start'=>1000, 'end'=>2000],
		['atLeastAmount'=> 3000, 'amountOff'=> 30, 'start'=>2000, 'end'=>3000],
		['atLeastAmount'=> 4000, 'amountOff'=> 40, 'start'=>3000, 'end'=>4000],
	];
	public function calePrice() {
		$price = $this->promotion->calePrice();
		foreach($this->moneyOffRules as $key=>$val) {
			if($price >= $val['start'] and $price < $val['end']) {
				$this->price = $val['amountOff'];
			}
		}
		return $price - $this->price;
	}
}
// couponType: 优惠券类型( 1-代金券, 2-折扣券, 3-免单券)
// couponVal : 优惠金额或折扣

$goodsInfo = [
	['id'=>1, 'goodsName'=>'商品01', 'price'=>1000, 'couponType'=>1, 'couponVal'=>100],
	['id'=>2, 'goodsName'=>'商品02', 'price'=>1000, 'couponType'=>2, 'couponVal'=>0.5],
	['id'=>3, 'goodsName'=>'商品03', 'price'=>1000, 'couponType'=>3, 'couponVal'=>0],
	['id'=>4, 'goodsName'=>'商品04', 'price'=>1000, 'couponType'=>0, 'couponVal'=>0],
	['id'=>5, 'goodsName'=>'商品05', 'price'=>1000, 'couponType'=>2, 'couponVal'=>0.6],
];
$order = new Order($goodsInfo); // 5000
$order = new CashCoupon($order); // 使用优惠方式: 代金券 4900
$order = new DiscountCoupon($order); // 使用优惠方式: 打折券 4000
$order = new FreeCoupon($order); // 使用优惠方式: 免单券 3000
$order = new MoneyOff($order); // 使用优惠方式: 满减 2960

echo $order->calePrice(); // 3000