import datetime

from django.conf import settings
from django.db import backend, connection, transaction, DEFAULT_DB_ALIAS
from django.test import TestCase, TransactionTestCase

from models import Book, Award, AwardNote, Person, Child, Toy, PlayedWith, PlayedWithNote

# Can't run this test under SQLite, because you can't
# get two connections to an in-memory database.
if settings.DATABASES[DEFAULT_DB_ALIAS]['ENGINE'] != 'django.db.backends.sqlite3':
    class DeleteLockingTest(TransactionTestCase):
        def setUp(self):
            # Create a second connection to the default database
            conn_settings = settings.DATABASES[DEFAULT_DB_ALIAS]
            self.conn2 = backend.DatabaseWrapper({
                'HOST': conn_settings['HOST'],
                'NAME': conn_settings['NAME'],
                'OPTIONS': conn_settings['OPTIONS'],
                'PASSWORD': conn_settings['PASSWORD'],
                'PORT': conn_settings['PORT'],
                'USER': conn_settings['USER'],
                'TIME_ZONE': settings.TIME_ZONE,
            })

            # Put both DB connections into managed transaction mode
            transaction.enter_transaction_management()
            transaction.managed(True)
            self.conn2._enter_transaction_management(True)

        def tearDown(self):
            # Close down the second connection.
            transaction.leave_transaction_management()
            self.conn2.close()

        def test_concurrent_delete(self):
            "Deletes on concurrent transactions don't collide and lock the database. Regression for #9479"

            # Create some dummy data
            b1 = Book(id=1, pagecount=100)
            b2 = Book(id=2, pagecount=200)
            b3 = Book(id=3, pagecount=300)
            b1.save()
            b2.save()
            b3.save()

            transaction.commit()

            self.assertEquals(3, Book.objects.count())

            # Delete something using connection 2.
            cursor2 = self.conn2.cursor()
            cursor2.execute('DELETE from delete_regress_book WHERE id=1')
            self.conn2._commit();

            # Now perform a queryset delete that covers the object
            # deleted in connection 2. This causes an infinite loop
            # under MySQL InnoDB unless we keep track of already
            # deleted objects.
            Book.objects.filter(pagecount__lt=250).delete()
            transaction.commit()
            self.assertEquals(1, Book.objects.count())

class DeleteCascadeTests(TestCase):
    def test_generic_relation_cascade(self):
        """
        Test that Django cascades deletes through generic-related
        objects to their reverse relations.

        This might falsely succeed if the database cascades deletes
        itself immediately; the postgresql_psycopg2 backend does not
        give such a false success because ForeignKeys are created with
        DEFERRABLE INITIALLY DEFERRED, so its internal cascade is
        delayed until transaction commit.

        """
        person = Person.objects.create(name='Nelson Mandela')
        award = Award.objects.create(name='Nobel', content_object=person)
        note = AwardNote.objects.create(note='a peace prize',
                                        award=award)
        self.assertEquals(AwardNote.objects.count(), 1)
        person.delete()
        self.assertEquals(Award.objects.count(), 0)
        # first two asserts are just sanity checks, this is the kicker:
        self.assertEquals(AwardNote.objects.count(), 0)

    def test_fk_to_m2m_through(self):
        """
        Test that if a M2M relationship has an explicitly-specified
        through model, and some other model has an FK to that through
        model, deletion is cascaded from one of the participants in
        the M2M, to the through model, to its related model.

        Like the above test, this could in theory falsely succeed if
        the DB cascades deletes itself immediately.

        """
        juan = Child.objects.create(name='Juan')
        paints = Toy.objects.create(name='Paints')
        played = PlayedWith.objects.create(child=juan, toy=paints,
                                           date=datetime.date.today())
        note = PlayedWithNote.objects.create(played=played,
                                             note='the next Jackson Pollock')
        self.assertEquals(PlayedWithNote.objects.count(), 1)
        paints.delete()
        self.assertEquals(PlayedWith.objects.count(), 0)
        # first two asserts just sanity checks, this is the kicker:
        self.assertEquals(PlayedWithNote.objects.count(), 0)