import pickle
from functools import wraps

from django.db import IntegrityError, connections, transaction
from django.test import TestCase, skipUnlessDBFeature
from django.test.testcases import DatabaseOperationForbidden, SimpleTestCase, TestData

from .models import Car, Person, PossessedCar


class TestSimpleTestCase(SimpleTestCase):
    def test_is_picklable_with_non_picklable_properties(self):
        """ParallelTestSuite requires that all TestCases are picklable."""
        self.non_picklable = lambda: 0
        self.assertEqual(self, pickle.loads(pickle.dumps(self)))


class TestTestCase(TestCase):
    @skipUnlessDBFeature("can_defer_constraint_checks")
    @skipUnlessDBFeature("supports_foreign_keys")
    def test_fixture_teardown_checks_constraints(self):
        rollback_atomics = self._rollback_atomics
        self._rollback_atomics = lambda connection: None  # noop
        try:
            car = PossessedCar.objects.create(car_id=1, belongs_to_id=1)
            with self.assertRaises(IntegrityError), transaction.atomic():
                self._fixture_teardown()
            car.delete()
        finally:
            self._rollback_atomics = rollback_atomics

    def test_disallowed_database_connection(self):
        message = (
            "Database connections to 'other' are not allowed in this test. "
            "Add 'other' to test_utils.test_testcase.TestTestCase.databases to "
            "ensure proper test isolation and silence this failure."
        )
        with self.assertRaisesMessage(DatabaseOperationForbidden, message):
            connections["other"].connect()
        with self.assertRaisesMessage(DatabaseOperationForbidden, message):
            connections["other"].temporary_connection()

    def test_disallowed_database_queries(self):
        message = (
            "Database queries to 'other' are not allowed in this test. "
            "Add 'other' to test_utils.test_testcase.TestTestCase.databases to "
            "ensure proper test isolation and silence this failure."
        )
        with self.assertRaisesMessage(DatabaseOperationForbidden, message):
            Car.objects.using("other").get()

    @skipUnlessDBFeature("supports_transactions")
    def test_reset_sequences(self):
        old_reset_sequences = self.reset_sequences
        self.reset_sequences = True
        msg = "reset_sequences cannot be used on TestCase instances"
        try:
            with self.assertRaisesMessage(TypeError, msg):
                self._fixture_setup()
        finally:
            self.reset_sequences = old_reset_sequences


def assert_no_queries(test):
    @wraps(test)
    def inner(self):
        with self.assertNumQueries(0):
            test(self)

    return inner


# On databases with no transaction support (for instance, MySQL with the MyISAM
# engine), setUpTestData() is called before each test, so there is no need to
# clone class level test data.
@skipUnlessDBFeature("supports_transactions")
class TestDataTests(TestCase):
    # setUpTestData re-assignment are also wrapped in TestData.
    jim_douglas = None

    @classmethod
    def setUpTestData(cls):
        cls.jim_douglas = Person.objects.create(name="Jim Douglas")
        cls.car = Car.objects.create(name="1963 Volkswagen Beetle")
        cls.herbie = cls.jim_douglas.possessed_cars.create(
            car=cls.car,
            belongs_to=cls.jim_douglas,
        )

        cls.person_binary = Person.objects.create(name="Person", data=b"binary data")
        cls.person_binary_get = Person.objects.get(pk=cls.person_binary.pk)

    @assert_no_queries
    def test_class_attribute_equality(self):
        """Class level test data is equal to instance level test data."""
        self.assertEqual(self.jim_douglas, self.__class__.jim_douglas)
        self.assertEqual(self.person_binary, self.__class__.person_binary)
        self.assertEqual(self.person_binary_get, self.__class__.person_binary_get)

    @assert_no_queries
    def test_class_attribute_identity(self):
        """
        Class level test data is not identical to instance level test data.
        """
        self.assertIsNot(self.jim_douglas, self.__class__.jim_douglas)
        self.assertIsNot(self.person_binary, self.__class__.person_binary)
        self.assertIsNot(self.person_binary_get, self.__class__.person_binary_get)

    @assert_no_queries
    def test_binaryfield_data_type(self):
        self.assertEqual(bytes(self.person_binary.data), b"binary data")
        self.assertEqual(bytes(self.person_binary_get.data), b"binary data")
        self.assertEqual(
            type(self.person_binary_get.data),
            type(self.__class__.person_binary_get.data),
        )
        self.assertEqual(
            type(self.person_binary.data),
            type(self.__class__.person_binary.data),
        )

    @assert_no_queries
    def test_identity_preservation(self):
        """Identity of test data is preserved between accesses."""
        self.assertIs(self.jim_douglas, self.jim_douglas)

    @assert_no_queries
    def test_known_related_objects_identity_preservation(self):
        """Known related objects identity is preserved."""
        self.assertIs(self.herbie.car, self.car)
        self.assertIs(self.herbie.belongs_to, self.jim_douglas)

    def test_repr(self):
        self.assertEqual(
            repr(TestData("attr", "value")),
            "<TestData: name='attr', data='value'>",
        )


class SetupTestDataIsolationTests(TestCase):
    """
    In-memory data isolation is respected for model instances assigned to class
    attributes during setUpTestData.
    """

    @classmethod
    def setUpTestData(cls):
        cls.car = Car.objects.create(name="Volkswagen Beetle")

    def test_book_name_deutsh(self):
        self.assertEqual(self.car.name, "Volkswagen Beetle")
        self.car.name = "VW sKäfer"
        self.car.save()

    def test_book_name_french(self):
        self.assertEqual(self.car.name, "Volkswagen Beetle")
        self.car.name = "Volkswagen Coccinelle"
        self.car.save()