"""A broken Redis must degrade the cache, not 500 the API.

A Redis that cannot persist (the default ``stop-writes-on-bgsave-error``)
or is simply unreachable used to raise inside the DRF throttle check on
every request; ``ResilientRedisCache`` treats that as a cache miss.
"""

from unittest import mock

from django.core.cache import cache
from django.core.cache.backends.redis import RedisCacheClient
from django.test import SimpleTestCase


def failing(method: str):
    return mock.patch.object(
        RedisCacheClient,
        method,
        side_effect=RuntimeError("redis is down"),
    )


class ResilientCacheTests(SimpleTestCase):
    def test_get_returns_the_default_when_redis_fails(self):
        with failing("get"):
            self.assertIsNone(cache.get("j621-cache-test"))
            self.assertEqual(cache.get("j621-cache-test", "fallback"), "fallback")

    def test_writes_report_failure_without_raising(self):
        with failing("set"):
            self.assertIsNone(cache.set("j621-cache-test", "value"))

    def test_bulk_and_delete_operations_degrade(self):
        with failing("get_many"), failing("delete"):
            self.assertEqual(cache.get_many(["a", "b"]), {})
            self.assertFalse(cache.delete("a"))