import json

from django.contrib.contenttypes.fields import GenericForeignKey

from django.db import models

from django.test import TestCase

from django.test.utils import isolate_apps

from .models import Answer, Post, Question

@isolate_apps("contenttypes_tests")

class GenericForeignKeyTests(TestCase):

    def test_str(self):

        class Model(models.Model):

            field = GenericForeignKey()

        self.assertEqual(str(Model.field), "contenttypes_tests.Model.field")

    def test_get_content_type_no_arguments(self):

        with self.assertRaisesMessage(

            Exception, "Impossible arguments to GFK.get_content_type!"

        ):

            Answer.question.get_content_type()

    def test_incorrect_get_prefetch_queryset_arguments(self):

        with self.assertRaisesMessage(

            ValueError, "Custom queryset can't be used for this lookup."

        ):

            Answer.question.get_prefetch_queryset(

                Answer.objects.all(), Answer.objects.all()

            )

    def test_get_object_cache_respects_deleted_objects(self):

        question = Question.objects.create(text="Who?")

        post = Post.objects.create(title="Answer", parent=question)

        question_pk = question.pk

        Question.objects.all().delete()

        post = Post.objects.get(pk=post.pk)

        with self.assertNumQueries(1):

            self.assertEqual(post.object_id, question_pk)

            self.assertIsNone(post.parent)

            self.assertIsNone(post.parent)

class GenericRelationTests(TestCase):

    def test_value_to_string(self):

        question = Question.objects.create(text="test")

        answer1 = Answer.objects.create(question=question)

        answer2 = Answer.objects.create(question=question)

        result = json.loads(Question.answer_set.field.value_to_string(question))

        self.assertCountEqual(result, [answer1.pk, answer2.pk])