"""Database Migration Tests.

This module tests the database migration system for the codex-lens index,
ensuring that forward and backward compatibility is maintained across schema versions.

Test Coverage:
- Forward migrations: Old schema to new schema
- Backward compatibility: New code can read old schemas
- Migration rollback capabilities
- Data integrity during migrations
- Edge cases (empty databases, corrupted data, etc.)
"""

import pytest
import sqlite3
from pathlib import Path
import tempfile
import json


class TestForwardMigrations:
    """Test upgrading from older schema versions to newer ones."""

    def test_v0_to_v1_migration(self):
        """Test migration from schema v0 to v1."""
        pytest.skip("Requires migration infrastructure setup")

    def test_v1_to_v2_migration(self):
        """Test migration from schema v1 to v2."""
        pytest.skip("Requires migration infrastructure setup")

    def test_migration_preserves_data(self):
        """Test that migration preserves existing data."""
        pytest.skip("Requires migration infrastructure setup")

    def test_migration_adds_new_columns(self):
        """Test that new columns are added with correct defaults."""
        pytest.skip("Requires migration infrastructure setup")


class TestBackwardCompatibility:
    """Test that newer code can read and work with older database schemas."""

    def test_new_code_reads_old_schema(self):
        """Test that current code can read old schema databases."""
        pytest.skip("Requires old schema fixture")

    def test_new_code_writes_to_old_schema(self):
        """Test that current code handles writes to old schema gracefully."""
        pytest.skip("Requires old schema fixture")

    def test_old_code_rejects_new_schema(self):
        """Test that old code fails appropriately on new schemas."""
        pytest.skip("Requires old code fixture")


class TestMigrationRollback:
    """Test rollback capabilities for failed migrations."""

    def test_failed_migration_rolls_back(self):
        """Test that failed migrations are rolled back completely."""
        pytest.skip("Requires migration infrastructure setup")

    def test_partial_migration_recovery(self):
        """Test recovery from partially completed migrations."""
        pytest.skip("Requires migration infrastructure setup")

    def test_rollback_preserves_original_data(self):
        """Test that rollback restores original state."""
        pytest.skip("Requires migration infrastructure setup")


class TestMigrationEdgeCases:
    """Test migration behavior in edge cases."""

    def test_empty_database_migration(self):
        """Test migration of an empty database."""
        pytest.skip("Requires migration infrastructure setup")

    def test_large_database_migration(self):
        """Test migration of a large database."""
        pytest.skip("Requires migration infrastructure setup")

    def test_corrupted_database_handling(self):
        """Test handling of corrupted databases during migration."""
        pytest.skip("Requires migration infrastructure setup")

    def test_concurrent_migration_protection(self):
        """Test that concurrent migrations are prevented."""
        pytest.skip("Requires migration infrastructure setup")


class TestSchemaVersionTracking:
    """Test schema version tracking and detection."""

    def test_version_table_exists(self):
        """Test that version tracking table exists and is populated."""
        pytest.skip("Requires migration infrastructure setup")

    def test_version_auto_detection(self):
        """Test that schema version is auto-detected from database."""
        pytest.skip("Requires migration infrastructure setup")

    def test_version_update_after_migration(self):
        """Test that version is updated correctly after migration."""
        pytest.skip("Requires migration infrastructure setup")


# TODO: Implement actual tests using pytest fixtures
# The test infrastructure needs:
# - Migration runner fixture that can apply and rollback migrations
# - Old schema fixtures (pre-built databases with known schemas)
# - Temporary database fixtures for isolated testing
# - Mock data generators for various schema versions