import asyncio
import os
from unittest import mock

from asgiref.sync import async_to_sync

from django.core.cache import DEFAULT_CACHE_ALIAS, caches
from django.core.exceptions import ImproperlyConfigured, SynchronousOnlyOperation
from django.http import HttpResponse
from django.test import SimpleTestCase
from django.utils.asyncio import async_unsafe
from django.views.generic.base import View

from .models import SimpleModel


class CacheTest(SimpleTestCase):
    def test_caches_local(self):
        @async_to_sync
        async def async_cache():
            return caches[DEFAULT_CACHE_ALIAS]

        cache_1 = async_cache()
        cache_2 = async_cache()
        self.assertIs(cache_1, cache_2)


class DatabaseConnectionTest(SimpleTestCase):
    """A database connection cannot be used in an async context."""

    async def test_get_async_connection(self):
        with self.assertRaises(SynchronousOnlyOperation):
            list(SimpleModel.objects.all())


class AsyncUnsafeTest(SimpleTestCase):
    """
    async_unsafe decorator should work correctly and returns the correct
    message.
    """

    @async_unsafe
    def dangerous_method(self):
        return True

    async def test_async_unsafe(self):
        # async_unsafe decorator catches bad access and returns the right
        # message.
        msg = (
            "You cannot call this from an async context - use a thread or "
            "sync_to_async."
        )
        with self.assertRaisesMessage(SynchronousOnlyOperation, msg):
            self.dangerous_method()

    @mock.patch.dict(os.environ, {"DJANGO_ALLOW_ASYNC_UNSAFE": "true"})
    @async_to_sync  # mock.patch() is not async-aware.
    async def test_async_unsafe_suppressed(self):
        # Decorator doesn't trigger check when the environment variable to
        # suppress it is set.
        try:
            self.dangerous_method()
        except SynchronousOnlyOperation:
            self.fail("SynchronousOnlyOperation should not be raised.")


class SyncView(View):
    def get(self, request, *args, **kwargs):
        return HttpResponse("Hello (sync) world!")


class AsyncView(View):
    async def get(self, request, *args, **kwargs):
        return HttpResponse("Hello (async) world!")


class ViewTests(SimpleTestCase):
    def test_views_are_correctly_marked(self):
        tests = [
            (SyncView, False),
            (AsyncView, True),
        ]
        for view_cls, is_async in tests:
            with self.subTest(view_cls=view_cls, is_async=is_async):
                self.assertIs(view_cls.view_is_async, is_async)
                callback = view_cls.as_view()
                self.assertIs(asyncio.iscoroutinefunction(callback), is_async)

    def test_mixed_views_raise_error(self):
        class MixedView(View):
            def get(self, request, *args, **kwargs):
                return HttpResponse("Hello (mixed) world!")

            async def post(self, request, *args, **kwargs):
                return HttpResponse("Hello (mixed) world!")

        msg = (
            f"{MixedView.__qualname__} HTTP handlers must either be all sync or all "
            "async."
        )
        with self.assertRaisesMessage(ImproperlyConfigured, msg):
            MixedView.as_view()

    def test_options_handler_responds_correctly(self):
        tests = [
            (SyncView, False),
            (AsyncView, True),
        ]
        for view_cls, is_coroutine in tests:
            with self.subTest(view_cls=view_cls, is_coroutine=is_coroutine):
                instance = view_cls()
                response = instance.options(None)
                self.assertIs(
                    asyncio.iscoroutine(response),
                    is_coroutine,
                )
                if is_coroutine:
                    response = asyncio.run(response)

                self.assertIsInstance(response, HttpResponse)

    def test_base_view_class_is_sync(self):
        """
        View and by extension any subclasses that don't define handlers are
        sync.
        """
        self.assertIs(View.view_is_async, False)