"""
单例模式工具模块 - 统一管理全局服务实例
"""

from typing import TypeVar, Type, Dict, Callable, Optional

T = TypeVar('T')


class SingletonRegistry:
    """单例注册表 - 统一管理所有服务实例"""

    _instances: Dict[str, object] = {}
    _factories: Dict[str, Callable[[], object]] = {}

    @classmethod
    def register(cls, name: str, factory: Callable[[], T]) -> None:
        """注册服务工厂函数"""
        cls._factories[name] = factory

    @classmethod
    def get(cls, name: str, instance_type: Type[T]) -> T:
        """获取或创建服务实例"""
        if name not in cls._instances:
            if name not in cls._factories:
                raise KeyError(f"未注册的服务: {name}")
            cls._instances[name] = cls._factories[name]()
        return cls._instances[name]

    @classmethod
    def reset(cls, name: Optional[str] = None) -> None:
        """重置服务实例（用于测试）"""
        if name:
            cls._instances.pop(name, None)
        else:
            cls._instances.clear()


def singleton_factory(factory: Callable[[], T]) -> Callable[[], T]:
    """
    单例工厂装饰器

    用法:
        @singleton_factory
        def get_service():
            return Service()

        service = get_service()  # 始终返回同一实例
    """
    instance: Optional[T] = None

    def wrapper() -> T:
        nonlocal instance
        if instance is None:
            instance = factory()
        return instance

    return wrapper