"""
实例：
汤宝宝成为了收银员，消费者可以使用现金或者支付宝支付。
"""

from abc import ABC, abstractmethod


class Strategy(ABC):
    @abstractmethod
    def pay(self, amount: float) -> str:
        pass


class CashPayment(Strategy):
    def pay(self, amount: float) -> str:
        return(f"使用现金支付了 {amount:.2f} 元。")


class AlipayPayment(Strategy):
    def pay(self, amount: float) -> str:
        return(f"使用支付宝支付了 {amount:.2f} 元。")


class Context:
    strategy: Strategy

    def set_strategy(self, strategy: Strategy) -> None:
        self._strategy = strategy

    def pay(self, amount: float) -> str:
        return self._strategy.pay(amount)

if __name__ == "__main__":
    print("=========== 策略模式 ===========")

    context = Context()
    context.set_strategy(CashPayment())
    print(context.pay(100.0))
    context.set_strategy(AlipayPayment())
    print(context.pay(200.0))

    print("\n========= 策略模式结束 =========")