import pytest

from app.foundation.singleton import Singleton, SingletonClass, WeakSingleton


def test_singleton_class_can_read_existing_instance_without_creating(monkeypatch):
    """按类单例可以只读取已存在实例"""

    class Example(metaclass=SingletonClass):
        pass

    monkeypatch.setattr(SingletonClass, "_instances", {})

    assert Example.get_existing_instance() is None
    instance = Example()
    assert Example.get_existing_instance() is instance


def test_parameterized_singleton_can_read_matching_instance_without_creating(monkeypatch):
    """参数化单例按相同参数读取已存在实例"""

    class Example(metaclass=Singleton):
        def __init__(self, name):
            self.name = name

    monkeypatch.setattr(Singleton, "_instances", {})

    assert Example.get_existing_instance("first") is None
    instance = Example("first")
    assert Example.get_existing_instance("first") is instance
    assert Example.get_existing_instance("second") is None


def test_parameterized_singleton_releases_only_matching_owner(monkeypatch):
    """迟到的旧 owner 不得释放同类当前已发布的新 owner。"""

    class Example(metaclass=Singleton):
        """用于验证按参数单例 owner 身份。"""

    monkeypatch.setattr(Singleton, "_instances", {})
    current = Example()

    assert Example.release_existing_instance(object()) is False
    assert Example.get_existing_instance() is current
    assert Example.release_existing_instance(current) is True
    assert Example.get_existing_instance() is None


def test_class_singleton_releases_only_matching_owner(monkeypatch):
    """按类单例仅允许当前 owner 释放自身身份。"""

    class Example(metaclass=SingletonClass):
        """用于验证按类单例 owner 身份。"""

    monkeypatch.setattr(SingletonClass, "_instances", {})
    current = Example()

    assert Example.release_existing_instance(object()) is False
    assert Example.get_existing_instance() is current
    assert Example.release_existing_instance(current) is True
    assert Example.get_existing_instance() is None


def test_weak_singleton_reads_and_releases_only_current_owner(monkeypatch):
    """弱单例应支持不触发构造的读取，并只释放当前 owner。"""

    class Example(metaclass=WeakSingleton):
        """用于验证弱单例 owner 身份。"""

    monkeypatch.setattr(WeakSingleton, "_instances", {})

    assert Example.get_existing_instance() is None
    current = Example()
    assert Example.get_existing_instance() is current
    assert Example.release_existing_instance(object()) is False
    assert Example.release_existing_instance(current) is True
    assert Example.get_existing_instance() is None


def test_parameterized_singleton_can_retain_failed_lifecycle_owner(monkeypatch):
    """构造中途失败时，可选 owner 单例必须仍能由启动失败清理读取。"""

    class Example(metaclass=Singleton):
        """模拟在构造期已创建后台 owner 后抛错的参数化单例。"""

        _retain_failed_singleton = True

        def __init__(self) -> None:
            """发布可观察 owner 后模拟后续启动失败。"""
            self.owner_started = True
            raise RuntimeError("startup failed")

    monkeypatch.setattr(Singleton, "_instances", {})

    with pytest.raises(RuntimeError, match="startup failed"):
        Example()

    retained = Example.get_existing_instance()
    assert retained is not None
    assert retained.owner_started is True


def test_class_singleton_can_retain_failed_lifecycle_owner(monkeypatch):
    """按类 owner 单例也必须在 __init__ 抛错后保留可清理身份。"""

    class Example(metaclass=SingletonClass):
        """模拟目录监控构造中途失败的按类单例。"""

        _retain_failed_singleton = True

        def __init__(self) -> None:
            """发布可观察 owner 后模拟后续启动失败。"""
            self.owner_started = True
            raise RuntimeError("startup failed")

    monkeypatch.setattr(SingletonClass, "_instances", {})

    with pytest.raises(RuntimeError, match="startup failed"):
        Example()

    retained = Example.get_existing_instance()
    assert retained is not None
    assert retained.owner_started is True