from django.test import TransactionTestCase
from django.db import connection


class MigrationTestBase(TransactionTestCase):
    """
    Contains an extended set of asserts for testing migrations and schema operations.
    """

    available_apps = ["migrations"]

    def get_table_description(self, table):
        with connection.cursor() as cursor:
            return connection.introspection.get_table_description(cursor, table)

    def assertTableExists(self, table):
        with connection.cursor() as cursor:
            self.assertIn(table, connection.introspection.table_names(cursor))

    def assertTableNotExists(self, table):
        with connection.cursor() as cursor:
            self.assertNotIn(table, connection.introspection.table_names(cursor))

    def assertColumnExists(self, table, column):
        self.assertIn(column, [c.name for c in self.get_table_description(table)])

    def assertColumnNotExists(self, table, column):
        self.assertNotIn(column, [c.name for c in self.get_table_description(table)])

    def assertColumnNull(self, table, column):
        self.assertEqual([c.null_ok for c in self.get_table_description(table) if c.name == column][0], True)

    def assertColumnNotNull(self, table, column):
        self.assertEqual([c.null_ok for c in self.get_table_description(table) if c.name == column][0], False)

    def assertIndexExists(self, table, columns, value=True):
        with connection.cursor() as cursor:
            self.assertEqual(
                value,
                any(
                    c["index"]
                    for c in connection.introspection.get_constraints(cursor, table).values()
                    if c['columns'] == list(columns)
                ),
            )

    def assertIndexNotExists(self, table, columns):
        return self.assertIndexExists(table, columns, False)

    def assertFKExists(self, table, columns, to, value=True):
        with connection.cursor() as cursor:
            self.assertEqual(
                value,
                any(
                    c["foreign_key"] == to
                    for c in connection.introspection.get_constraints(cursor, table).values()
                    if c['columns'] == list(columns)
                ),
            )

    def assertFKNotExists(self, table, columns, to, value=True):
        return self.assertFKExists(table, columns, to, False)