/**
 * @name 装饰器模式
 * @brief: 动态添加职责
 * @note 场景：流处理（加密/压缩装饰）、GUI 组件增强
 */

class Coffee {
public:
    virtual double cost() = 0;
};
class SimpleCoffee : public Coffee {
public:
    double cost() override { return 6.9; }
};

class CoffeeDecorator : public Coffee {
protected:
    Coffee* coffee;
public:
    CoffeeDecorator(Coffee* c) : coffee(c) {}
};

class MilkDecorator : public CoffeeDecorator {
public:
    MilkDecorator(Coffee* c) : CoffeeDecorator(c) {}
    double cost() override {
        return coffee->cost() + 0.5; // 增加牛奶费用
    }
};

// 使用
int main()
{
    Coffee* coffee = new SimpleCoffee();
    coffee = new MilkDecorator(coffee); // 动态装饰
    coffee->cost(); // 基础 + 牛奶
}