"""
Template for generated migration tests.
This file is used as a template and populated with actual migration data.
"""
from django.test import TestCase
from django.db import connection
from django.db.migrations.executor import MigrationExecutor
from django.db.migrations.state import ProjectState
from django.core.management import call_command
from django.test.utils import override_settings


class {migration_class_name}(TestCase):
    """
    Test migration: {app_label}.{migration_name}

    Auto-generated test for migration validation.

    Migration Details:
    - App: {app_label}
    - Migration: {migration_name}
    - Dependencies: {dependencies}
    - Operations: {operations}

    This test validates that the migration:
    1. Executes successfully in forward direction
    2. Can be rolled back (if reversible)
    3. Produces expected database schema changes
    """

    migrate_from = None
    migrate_to = '{migration_name}'
    django_application = '{app_label}'

    def setUp(self):
        """Set up test environment for migration testing."""
        self.executor = MigrationExecutor(connection)
        self.app_label = '{app_label}'
        self.migration_name = '{migration_name}'
        self.migration_key = (self.app_label, self.migration_name)

        # Store original migration state
        self.original_applied = self.executor.loader.applied_migrations.copy()

    def tearDown(self):
        """Clean up after migration tests."""
        # Reset to original migration state if needed
        super().tearDown()

    def test_migration_exists(self):
        """Test that the migration file exists and is loadable."""
        try:
            migration = self.executor.loader.get_migration(*self.migration_key)
            self.assertIsNotNone(migration, f"Migration {{self.migration_key}} should exist")
            self.assertEqual(migration.app_label, self.app_label)
        except KeyError:
            self.fail(f"Migration {{self.migration_key}} not found in migration loader")

    def test_migration_dependencies(self):
        """Test that migration dependencies are properly defined."""
        migration = self.executor.loader.get_migration(*self.migration_key)

        # Verify dependencies exist
        for dep_app, dep_name in migration.dependencies:
            try:
                dep_migration = self.executor.loader.get_migration(dep_app, dep_name)
                self.assertIsNotNone(dep_migration,
                                     f"Dependency {{(dep_app, dep_name)}} should exist")
            except KeyError:
                self.fail(f"Dependency {{(dep_app, dep_name)}} not found")

    def test_migration_forward(self):
        """Test forward migration execution."""
        # Get the migration
        migration = self.executor.loader.get_migration(*self.migration_key)

        # Get state before migration
        dependencies = [
            key for key in self.executor.loader.graph.nodes
            if key < self.migration_key
        ]
        state_before = self.executor.loader.project_state(dependencies)

        # Apply migration to get new state
        state_after = migration.mutate_state(state_before, preserve=False)

        # Basic assertions
        self.assertIsInstance(state_after, ProjectState)
        self.assertIsNotNone(state_after.models)

        # Verify migration operations completed
        self.assertEqual(len(migration.operations), len([op for op in migration.operations]))

        # TODO: Add specific assertions for your migration
        # Uncomment and modify these examples based on your migration:

        # Test model creation
        # if 'CreateModel' in '{operations}':
        #     # Check if new models exist in state
        #     model_names = [model._meta.object_name.lower() 
        #                   for model in state_after.models.get((self.app_label,), {{}}).values()]
        #     self.assertIn('your_model_name', model_names, 
        #                  "New model should be created")

        # Test field addition
        # if 'AddField' in '{operations}':
        #     # Verify field was added to model
        #     model_key = (self.app_label, 'your_model_name')
        #     if model_key in state_after.models:
        #         model = state_after.models[model_key]
        #         field_names = [field.name for field in model._meta.get_fields()]
        #         self.assertIn('your_field_name', field_names,
        #                      "New field should be added to model")

        # Test field removal
        # if 'RemoveField' in '{operations}':
        #     # Verify field was removed from model
        #     model_key = (self.app_label, 'your_model_name')
        #     if model_key in state_after.models:
        #         model = state_after.models[model_key]
        #         field_names = [field.name for field in model._meta.get_fields()]
        #         self.assertNotIn('removed_field_name', field_names,
        #                         "Field should be removed from model")

        # Test index creation
        # if hasattr(migration, 'operations'):
        #     for operation in migration.operations:
        #         if hasattr(operation, 'index'):
        #             # Test index-related operations
        #             pass

    def test_migration_backward(self):
        """Test migration rollback capability."""
        migration = self.executor.loader.get_migration(*self.migration_key)

        # Check if migration is reversible
        if getattr(migration, 'irreversible', False):
            self.skipTest(f"Migration {{self.migration_key}} is marked as irreversible")

        # Check for irreversible operations
        irreversible_ops = []
        for op in migration.operations:
            if getattr(op, 'irreversible', False):
                irreversible_ops.append(op.__class__.__name__)

        if irreversible_ops:
            self.skipTest(f"Migration contains irreversible operations: {{irreversible_ops}}")

        # Get dependencies to rollback to
        dependencies = migration.dependencies
        if not dependencies:
            self.skipTest("No dependencies to rollback to")

        # Test that each operation can be reversed
        for operation in migration.operations:
            # Most operations should have a reverse operation
            if hasattr(operation, 'database_backwards'):
                self.assertTrue(
                    callable(operation.database_backwards),
                    f"Operation {{operation.__class__.__name__}} should have database_backwards method"
                )

        # TODO: Add specific rollback tests
        # Example: Test that rolling back removes created models/fields

        pass

    def test_migration_sql_generation(self):
        """Test that migration generates valid SQL."""
        migration = self.executor.loader.get_migration(*self.migration_key)

        # Get schema editor for SQL generation
        schema_editor = connection.schema_editor()

        # Test that operations can generate SQL without errors
        for operation in migration.operations:
            try:
                # This tests that the operation can generate SQL
                # without actually executing it
                if hasattr(operation, 'database_forwards'):
                    # Most operations should be able to generate forward SQL
                    self.assertTrue(
                        callable(operation.database_forwards),
                        f"Operation {{operation.__class__.__name__}} should have database_forwards method"
                    )
            except Exception as e:
                self.fail(f"Operation {{operation.__class__.__name__}} failed SQL generation: {{e}}")

    def test_migration_atomic_operations(self):
        """Test that migration operations are atomic."""
        migration = self.executor.loader.get_migration(*self.migration_key)

        # Check if migration is set to be atomic
        atomic = getattr(migration, 'atomic', True)

        # Most migrations should be atomic unless explicitly set otherwise
        if not atomic:
            # Log warning for non-atomic migrations
            import warnings
            warnings.warn(f"Migration {{self.migration_key}} is not atomic", UserWarning)

        # Verify atomic setting is boolean
        self.assertIsInstance(atomic, bool, "Migration atomic setting should be boolean")

    def test_migration_performance(self):
        """Basic performance test for migration execution."""
        import time

        migration = self.executor.loader.get_migration(*self.migration_key)

        # Get state before migration
        dependencies = [
            key for key in self.executor.loader.graph.nodes
            if key < self.migration_key
        ]
        state_before = self.executor.loader.project_state(dependencies)

        # Time the migration state mutation
        start_time = time.time()
        state_after = migration.mutate_state(state_before, preserve=False)
        end_time = time.time()

        execution_time = end_time - start_time

        # Basic performance check - migrations should complete quickly in tests
        # Adjust this threshold based on your migration complexity
        max_time = 5.0  # 5 seconds
        self.assertLess(execution_time, max_time,
                        f"Migration took {{execution_time:.2f}}s, expected < {{max_time}}s")

    # TODO: Add custom test methods specific to your migration
    # Examples:

    # def test_data_migration_preserves_data(self):
    #     """Test that data migrations preserve existing data."""
    #     # Create test data before migration
    #     # Apply migration
    #     # Verify data is preserved/transformed correctly
    #     pass

    # def test_migration_handles_edge_cases(self):
    #     """Test migration behavior with edge cases."""
    #     # Test with empty tables
    #     # Test with large datasets
    #     # Test with null values
    #     # Test with duplicate data
    #     pass

    # def test_migration_constraints(self):
    #     """Test that migration properly handles database constraints."""
    #     # Test foreign key constraints
    #     # Test unique constraints
    #     # Test check constraints
    #     pass

    # def test_migration_indexes(self):
    #     """Test that migration properly manages database indexes."""
    #     # Test index creation
    #     # Test index removal
    #     # Test index modifications
    #     pass
