chongming-utils-cache/src/chongming_cache/backends/disk.py

"""diskcache 后端：基于 SQLite 的本地持久化缓存，多进程安全。"""

from pathlib import Path
from typing import Any, Iterator

from diskcache import Cache as DiskCache

from chongming_cache.backends.base import CacheBackend


class DiskBackend(CacheBackend):
    """包装 diskcache.Cache，提供统一接口。

    Args:
        path: 缓存目录（SQLite 数据文件所在目录），父目录不存在时自动创建。
    """

    def __init__(self, path: str | Path):
        self._cache = DiskCache(path)

    @property
    def client(self) -> DiskCache:
        """底层 diskcache.Cache 实例（逃生口）。"""
        return self._cache

    def __contains__(self, key) -> bool:
        return key in self._cache

    def __getitem__(self, key) -> Any:
        return self._cache[key]

    def __setitem__(self, key, value) -> None:
        self._cache[key] = value

    def __delitem__(self, key) -> None:
        del self._cache[key]

    def __len__(self) -> int:
        return len(self._cache)

    def __iter__(self) -> Iterator:
        return iter(self._cache)

    def get(self, key, default=None) -> Any:
        return self._cache.get(key, default)

    def set(self, key, value, expire: float | None = None) -> None:
        self._cache.set(key, value, expire=expire)

    def set_nx(self, key, value, expire: float | None = None) -> bool:
        # diskcache.add 仅在 key 不存在时写入，返回是否成功（SET NX 语义）且进程安全
        return bool(self._cache.add(key, value, expire=expire))

    def touch(self, key, expire: float | None = None) -> bool:
        return self._cache.touch(key, expire=expire)

    def delete(self, key) -> bool:
        return self._cache.delete(key)

    def clear(self) -> None:
        self._cache.clear()

    def close(self) -> None:
        self._cache.close()