from typing import Any, Protocol


class CacheClient(Protocol):
    async def get(self, key: str) -> Any: ...

    async def set(self, key: str, value: str, ex: int | None = None) -> Any: ...


class CacheReadResult:
    def __init__(self, value: Any, degraded: bool = False) -> None:
        self.value = value
        self.degraded = degraded


class MemoryCacheAdapter:
    """Cache is an optimization; failures must not block MySQL recall."""

    def __init__(self, client: CacheClient) -> None:
        self.client = client

    async def get(self, key: str) -> CacheReadResult:
        try:
            return CacheReadResult(await self.client.get(key))
        except Exception:
            return CacheReadResult(None, degraded=True)

    async def set(self, key: str, value: str, ttl_seconds: int = 300) -> bool:
        try:
            await self.client.set(key, value, ex=ttl_seconds)
            return True
        except Exception:
            return False

    async def delete(self, *keys: str) -> int:
        """删除若干缓存键；客户端不支持删除时返回 0，缓存只是可重建的优化层。

        记忆热缓存按客户维度失效，失效失败不得阻塞主流程，因此这里吞掉异常，
        由调用方通过返回值与 `degraded` 语义决定是否告警。
        """
        targets = [key for key in keys if key]
        if not targets:
            return 0
        delete = getattr(self.client, "delete", None)
        if delete is None:
            return 0
        try:
            removed = await delete(*targets)
        except Exception:
            return 0
        return int(removed) if isinstance(removed, int) else len(targets)