from django.test import TestCase

from models import Reporter, Article

class ManyToOneNullTests(TestCase):

    def setUp(self):

        # Create a Reporter.

        self.r = Reporter(name='John Smith')

        self.r.save()

        # Create an Article.

        self.a = Article(headline="First", reporter=self.r)

        self.a.save()

        # Create an Article via the Reporter object.

        self.a2 = self.r.article_set.create(headline="Second")

        # Create an Article with no Reporter by passing "reporter=None".

        self.a3 = Article(headline="Third", reporter=None)

        self.a3.save()

        # Create another article and reporter

        self.r2 = Reporter(name='Paul Jones')

        self.r2.save()

        self.a4 = self.r2.article_set.create(headline='Fourth')

    def test_get_related(self):

        self.assertEqual(self.a.reporter.id, self.r.id)

        # Article objects have access to their related Reporter objects.

        r = self.a.reporter

        self.assertEqual(r.id, self.r.id)

    def test_created_via_related_set(self):

        self.assertEqual(self.a2.reporter.id, self.r.id)

    def test_related_set(self):

        # Reporter objects have access to their related Article objects.

        self.assertQuerysetEqual(self.r.article_set.all(),

                                 ['<Article: First>', '<Article: Second>'])

        self.assertQuerysetEqual(self.r.article_set.filter(headline__startswith='Fir'),

                                 ['<Article: First>'])

        self.assertEqual(self.r.article_set.count(), 2)

    def test_created_without_related(self):

        self.assertEqual(self.a3.reporter, None)

        # Need to reget a3 to refresh the cache

        a3 = Article.objects.get(pk=self.a3.pk)

        self.assertRaises(AttributeError, getattr, a3.reporter, 'id')

        # Accessing an article's 'reporter' attribute returns None

        # if the reporter is set to None.

        self.assertEqual(a3.reporter, None)

        # To retrieve the articles with no reporters set, use "reporter__isnull=True".

        self.assertQuerysetEqual(Article.objects.filter(reporter__isnull=True),

                                 ['<Article: Third>'])

        # We can achieve the same thing by filtering for the case where the

        # reporter is None.

        self.assertQuerysetEqual(Article.objects.filter(reporter=None),

                                 ['<Article: Third>'])

        # Set the reporter for the Third article

        self.assertQuerysetEqual(self.r.article_set.all(),

            ['<Article: First>', '<Article: Second>'])

        self.r.article_set.add(a3)

        self.assertQuerysetEqual(self.r.article_set.all(),

            ['<Article: First>', '<Article: Second>', '<Article: Third>'])

        # Remove an article from the set, and check that it was removed.

        self.r.article_set.remove(a3)

        self.assertQuerysetEqual(self.r.article_set.all(),

                                 ['<Article: First>', '<Article: Second>'])

        self.assertQuerysetEqual(Article.objects.filter(reporter__isnull=True),

                                 ['<Article: Third>'])

    def test_remove_from_wrong_set(self):

        self.assertQuerysetEqual(self.r2.article_set.all(), ['<Article: Fourth>'])

        # Try to remove a4 from a set it does not belong to

        self.assertRaises(Reporter.DoesNotExist, self.r.article_set.remove, self.a4)

        self.assertQuerysetEqual(self.r2.article_set.all(), ['<Article: Fourth>'])

    def test_assign_clear_related_set(self):

        # Use descriptor assignment to allocate ForeignKey. Null is legal, so

        # existing members of set that are not in the assignment set are set null

        self.r2.article_set = [self.a2, self.a3]

        self.assertQuerysetEqual(self.r2.article_set.all(),

                                 ['<Article: Second>', '<Article: Third>'])

        # Clear the rest of the set

        self.r.article_set.clear()

        self.assertQuerysetEqual(self.r.article_set.all(), [])

        self.assertQuerysetEqual(Article.objects.filter(reporter__isnull=True),

                                 ['<Article: First>', '<Article: Fourth>'])