import threading
from datetime import timedelta

from requests_cache import CachedSession

# Cache for "semi-static" data retrieved from a URL. This is a layet of caching in addition to the normal caching of
# spots, alerts and other data in the DataStore class. Its purpose is to avoid hitting remote endpoints frequently when
# e.g. restarting Spothole many times during testing.
_session = CachedSession("cache/semi_static_urls", expire_after=timedelta(days=1),
                         allowable_codes=(200, 400, 401, 403, 404))
_lock = threading.Lock()


class _ThreadSafeSession:
    """Wraps CachedSession with a lock to prevent concurrent SQLite access across threads. This allows a single object
    to be used freely across the application."""

    def get(self, *args, **kwargs):
        with _lock:
            return _session.get(*args, **kwargs)

# Global object
URL_DATA_CACHE = _ThreadSafeSession()