app/utils/cache.py

"""Simple in-memory TTL cache for thumbnail results."""
import time
import asyncio
from typing import Any, Optional
from collections import OrderedDict

class TTLCache:
    def __init__(self, max_size: int = 500, ttl_seconds: int = 300):
        self.max_size = max_size
        self.ttl = ttl_seconds
        self._store: OrderedDict[str, tuple[Any, float]] = OrderedDict()
        self._lock = asyncio.Lock()

    async def get(self, key: str) -> Optional[Any]:
        async with self._lock:
            if key not in self._store:
                return None
            value, ts = self._store[key]
            if time.time() - ts > self.ttl:
                del self._store[key]
                return None
            # move to end (LRU)
            self._store.move_to_end(key)
            return value

    async def set(self, key: str, value: Any) -> None:
        async with self._lock:
            if key in self._store:
                self._store.move_to_end(key)
            self._store[key] = (value, time.time())
            if len(self._store) > self.max_size:
                self._store.popitem(last=False)

    async def invalidate(self, key: str) -> None:
        async with self._lock:
            self._store.pop(key, None)

    def size(self) -> int:
        return len(self._store)


# Global cache instance
thumbnail_cache = TTLCache(max_size=500, ttl_seconds=300)