import threading
from dataclasses import dataclass


class ParameterizedSingletonMeta(type):
    """
    参数化单例元类
    行为：
    - 相同 (类, args, kwargs) → 同一实例
    - 不同参数 → 不同实例
    """

    _instances: dict = {}
    _lock = threading.RLock()

    def __call__(cls, *args, **kwargs):
        # 1. kwargs 排序，保证顺序无关
        kwargs_key = tuple(sorted(kwargs.items()))

        # 2. 构造不可变的 key
        key = (cls, args, kwargs_key)

        # 3. 防御：确保所有参数都可 hash
        try:
            hash(key)
        except TypeError as e:
            raise ValueError(
                f"{cls.__name__} 的单例参数必须全部可 hash"
                ) from e

        with cls._lock:
            if key not in cls._instances:
                cls._instances[key] = super().__call__(*args, **kwargs)
            else:
                print(f"[HIT] 命中缓存实例: {key}")

        return cls._instances[key]

    @classmethod
    def get_all_instances(cls):
        """调试用：返回当前已创建的所有实例"""
        return list(cls._instances.values())


@dataclass
class Demo(metaclass=ParameterizedSingletonMeta):
    """
    示例：参数化单例对象
    """

    name: str

    def __post_init__(self):
        print(f"正在初始化 Demo(name={self.name})")

    def __str__(self):
        return f"<Demo name={self.name} id={id(self)}>"


if __name__ == "__main__":
    print("=== 测试 1：相同参数 ===")
    d1 = Demo(name="config_A")
    d2 = Demo(name="config_A")
    print(d1)
    print(d2)
    print("是否同一实例：", d1 is d2)
    print(ParameterizedSingletonMeta.get_all_instances())