# -*- coding: utf-8 -*-
# !/usr/bin/env python

import logging
import threading
from django.core.cache import CacheHandler, _create_cache, InvalidCacheBackendError

logger = logging.getLogger(__name__)

_getitem = CacheHandler.__getitem__


def patch_cache_handler():
    CacheHandler._poll_cache_lock = threading.Lock()

    def __getitem__(self, alias):
        from django.conf import settings
        if alias not in settings.CACHES:
            raise InvalidCacheBackendError(
                "Could not find config for '%s' in settings.CACHES" % alias
            )

        if settings.CACHES[alias].get('BACKEND_TYPE', '') == 'pool':
            try:
                return self._poll_caches[alias]
            except AttributeError:
                pass
            except KeyError:
                pass

            with self._poll_cache_lock:
                logger.debug('init cache poll<alias={}>'.format(alias))

                if getattr(self, '_poll_caches', None) is None:
                    self._poll_caches = {}

                cache = _create_cache(alias)
                self._poll_caches[alias] = cache

                return cache
        else:
            return _getitem(self, alias)

    CacheHandler.__getitem__ = __getitem__


patch_cache_handler()