import threading
from datetime import timedelta

from requests_cache import CachedSession

# Cache for "semi-static" data such as the locations of parks, CSVs of reference lists, etc.
# This has an expiry time of 30 days, so will re-request from the source after that amount
# of time has passed. This is used throughout Spothole to cache data that does not change
# rapidly. The ThreadSafeSession construct here protects it against some multithreading
# contention weirdness we sometimes used to see on startup where the cache was hammered
# pretty hard. The expanded list of allowable_codes ensures we also cache and return 400-type
# responses, e.g "this SOTA summit ref doesn't actually exist", to avoid hammering remote
# servers for data they've told us they can't provide.
_session = CachedSession("cache/semi_static_url_data_cache", expire_after=timedelta(days=30),
                         allowable_codes=(200, 400, 401, 403, 404))
_lock = threading.Lock()


class _ThreadSafeSession:
    """Wraps CachedSession with a lock to prevent concurrent SQLite access across threads."""

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


SEMI_STATIC_URL_DATA_CACHE = _ThreadSafeSession()