"""后端注册表测试：覆盖 register / get / 内置 backend 注册。"""

from common.storage.base import AsyncStorageBackend
from common.storage.exceptions import StorageConfigError
from common.storage.registry import (
    get_backend_class,
    register_backend,
    registered_backends,
)


def test_local_and_s3_are_registered_at_import_time():
    """import common.storage 应该触发 local / s3 的注册。"""
    backend_classes = registered_backends()
    assert "local" in backend_classes
    assert "s3" in backend_classes
    for cls in backend_classes.values():
        assert issubclass(cls, AsyncStorageBackend)


def test_get_backend_class_returns_async_subclass():
    cls = get_backend_class("local")
    assert issubclass(cls, AsyncStorageBackend)


def test_get_backend_class_unknown_raises():
    import pytest

    with pytest.raises(StorageConfigError) as exc_info:
        get_backend_class("does-not-exist")
    assert "未知的存储后端" in str(exc_info.value)
    assert "does-not-exist" in str(exc_info.value)


def test_register_backend_idempotent_for_same_class():
    """同一个类对象重复注册是 no-op，不抛错（``is`` 比对，避免重复 import 时误冲突）。"""
    from common.storage.registry import _REGISTRY

    class _SameAgain(AsyncStorageBackend):
        pass

    _REGISTRY["same-again-test"] = _SameAgain

    # 第二次装饰同一个类对象：当前实现里装饰器返回 cls 并把 _REGISTRY[name] 重新写一遍。
    # 直接重新调用 register_backend("same-again-test")(_SameAgain) 不抛错即可。
    fn = register_backend("same-again-test")
    result = fn(_SameAgain)
    assert result is _SameAgain
    assert _REGISTRY["same-again-test"] is _SameAgain

    _REGISTRY.pop("same-again-test", None)


def test_register_backend_conflict_raises():
    import pytest

    @register_backend("conflict-test")
    class A(AsyncStorageBackend):
        pass

    with pytest.raises(StorageConfigError) as exc_info:

        @register_backend("conflict-test")
        class B(AsyncStorageBackend):
            pass

    assert "已被注册" in str(exc_info.value)

    # cleanup：避免污染全局 registry 影响其他测试
    from common.storage.registry import _REGISTRY
    _REGISTRY.pop("conflict-test", None)