from __future__ import annotations

import logging
import time
from collections import OrderedDict

logger = logging.getLogger(__name__)

DEFAULT_TTL_SECONDS = 120


class FileCacheEntry:
    __slots__ = ("file_key", "file_path", "file_name", "cached_at")

    def __init__(self, file_key: str, file_path: str = "", file_name: str = ""):
        self.file_key = file_key
        self.file_path = file_path
        self.file_name = file_name
        self.cached_at = time.monotonic()


class FileCache:
    def __init__(self, ttl_seconds: int = DEFAULT_TTL_SECONDS):
        self._ttl = ttl_seconds
        self._entries: OrderedDict[str, FileCacheEntry] = OrderedDict()

    def add(self, session_key: str, file_key: str, file_path: str = "", file_name: str = "") -> None:
        self._evict_expired()
        self._entries[session_key] = FileCacheEntry(file_key, file_path, file_name)

    def get(self, session_key: str) -> FileCacheEntry | None:
        self._evict_expired()
        entry = self._entries.get(session_key)
        if entry is not None:
            return entry
        return None

    def clear(self, session_key: str) -> None:
        self._entries.pop(session_key, None)

    def _evict_expired(self) -> None:
        now = time.monotonic()
        expired = [k for k, v in self._entries.items() if now - v.cached_at > self._ttl]
        for k in expired:
            self._entries.pop(k, None)


_cache_instance: FileCache | None = None


def get_file_cache() -> FileCache:
    global _cache_instance
    if _cache_instance is None:
        _cache_instance = FileCache()
    return _cache_instance