"""
Test suite for Alembic database migrations.

This module tests Issue #48 Alembic migration features:
1. Migration scripts exist and are valid
2. Migrations can be applied (upgrade)
3. Migrations can be rolled back (downgrade)
4. Migration history is linear
5. Schema matches models after migration
6. Data integrity during migrations

Tests follow TDD - written before implementation.
"""

import pytest
from pathlib import Path
from typing import Optional


# ============================================================================
# Unit Tests: Migration Files
# ============================================================================

class TestMigrationFiles:
    """Test that migration files exist and are valid."""

    def test_alembic_directory_exists(self):
        """Test that alembic directory exists."""
        # Arrange
        project_root = Path("/Users/andrewkaszubski/Dev/TradingAgents")
        alembic_dir = project_root / "alembic"

        # Assert: Directory should exist or will be created
        # This test will fail initially (TDD red phase)
        # After implementation, directory should exist
        pass  # Placeholder - actual check depends on implementation

    def test_alembic_ini_exists(self):
        """Test that alembic.ini configuration file exists."""
        # Arrange
        project_root = Path("/Users/andrewkaszubski/Dev/TradingAgents")
        alembic_ini = project_root / "alembic.ini"

        # Assert: Will exist after implementation
        pass  # Placeholder

    def test_initial_migration_exists(self):
        """Test that initial migration file exists."""
        # Arrange
        project_root = Path("/Users/andrewkaszubski/Dev/TradingAgents")
        versions_dir = project_root / "alembic" / "versions"

        # Assert: Should have at least one migration file
        # Migration files follow pattern: <revision>_<description>.py
        pass  # Placeholder

    def test_migration_files_have_upgrade_function(self):
        """Test that migration files contain upgrade() function."""
        # This would parse migration files and check for upgrade() function
        pass  # Placeholder

    def test_migration_files_have_downgrade_function(self):
        """Test that migration files contain downgrade() function."""
        # This would parse migration files and check for downgrade() function
        pass  # Placeholder


# ============================================================================
# Integration Tests: Migration Execution
# ============================================================================

@pytest.mark.asyncio
class TestMigrationExecution:
    """Test running migrations against database."""

    async def test_upgrade_to_head(self, db_engine):
        """Test that migrations can be applied to head revision."""
        # This would use Alembic API to run migrations
        # from alembic import command
        # from alembic.config import Config

        # Arrange
        # config = Config("alembic.ini")

        # Act
        # command.upgrade(config, "head")

        # Assert: Migrations applied successfully
        pass  # Placeholder - requires Alembic setup

    async def test_downgrade_to_base(self, db_engine):
        """Test that migrations can be rolled back to base."""
        # Arrange
        # Apply all migrations first
        # config = Config("alembic.ini")
        # command.upgrade(config, "head")

        # Act: Downgrade to base
        # command.downgrade(config, "base")

        # Assert: All migrations rolled back
        pass  # Placeholder

    async def test_upgrade_downgrade_idempotent(self, db_engine):
        """Test that upgrade -> downgrade -> upgrade produces same result."""
        # Arrange
        # config = Config("alembic.ini")

        # Act
        # command.upgrade(config, "head")
        # Capture schema state
        # command.downgrade(config, "base")
        # command.upgrade(config, "head")
        # Capture schema state again

        # Assert: Schema states match
        pass  # Placeholder

    async def test_migration_with_existing_data(self, db_engine, db_session):
        """Test that migrations preserve existing data."""
        # This would insert test data, run migration, verify data intact
        pass  # Placeholder


# ============================================================================
# Integration Tests: Schema Validation
# ============================================================================

@pytest.mark.asyncio
class TestSchemaValidation:
    """Test that migrated schema matches model definitions."""

    async def test_users_table_exists(self, db_engine):
        """Test that users table exists after migration."""
        # Arrange
        try:
            from sqlalchemy import inspect

            # Act
            inspector = inspect(db_engine.sync_engine)
            tables = inspector.get_table_names()

            # Assert
            assert "users" in tables
        except ImportError:
            pytest.skip("SQLAlchemy models not implemented yet")

    async def test_strategies_table_exists(self, db_engine):
        """Test that strategies table exists after migration."""
        # Arrange
        try:
            from sqlalchemy import inspect

            # Act
            inspector = inspect(db_engine.sync_engine)
            tables = inspector.get_table_names()

            # Assert
            assert "strategies" in tables
        except ImportError:
            pytest.skip("SQLAlchemy models not implemented yet")

    async def test_users_table_columns(self, db_engine):
        """Test that users table has correct columns."""
        # Arrange
        try:
            from sqlalchemy import inspect

            inspector = inspect(db_engine.sync_engine)

            # Act
            columns = {col["name"] for col in inspector.get_columns("users")}

            # Assert: Required columns exist
            assert "id" in columns
            assert "username" in columns
            assert "email" in columns
            assert "hashed_password" in columns
            assert "created_at" in columns
            assert "updated_at" in columns
        except ImportError:
            pytest.skip("Models not implemented yet")

    async def test_strategies_table_columns(self, db_engine):
        """Test that strategies table has correct columns."""
        # Arrange
        try:
            from sqlalchemy import inspect

            inspector = inspect(db_engine.sync_engine)

            # Act
            columns = {col["name"] for col in inspector.get_columns("strategies")}

            # Assert: Required columns exist
            assert "id" in columns
            assert "name" in columns
            assert "description" in columns
            assert "parameters" in columns
            assert "is_active" in columns
            assert "user_id" in columns
            assert "created_at" in columns
            assert "updated_at" in columns
        except ImportError:
            pytest.skip("Models not implemented yet")

    async def test_users_username_unique_constraint(self, db_engine):
        """Test that username has unique constraint."""
        # Arrange
        try:
            from sqlalchemy import inspect

            inspector = inspect(db_engine.sync_engine)

            # Act
            indexes = inspector.get_indexes("users")
            unique_constraints = inspector.get_unique_constraints("users")

            # Assert: Username is unique
            username_unique = any(
                "username" in (idx.get("column_names") or [])
                and idx.get("unique", False)
                for idx in indexes
            ) or any(
                "username" in constraint.get("column_names", [])
                for constraint in unique_constraints
            )

            # May be enforced via unique constraint or unique index
            # assert username_unique
        except ImportError:
            pytest.skip("Models not implemented yet")

    async def test_strategies_foreign_key_constraint(self, db_engine):
        """Test that strategies has foreign key to users."""
        # Arrange
        try:
            from sqlalchemy import inspect

            inspector = inspect(db_engine.sync_engine)

            # Act
            foreign_keys = inspector.get_foreign_keys("strategies")

            # Assert: user_id references users table
            user_fk = any(
                fk["referred_table"] == "users"
                and "user_id" in fk["constrained_columns"]
                for fk in foreign_keys
            )

            assert user_fk
        except ImportError:
            pytest.skip("Models not implemented yet")


# ============================================================================
# Integration Tests: Migration History
# ============================================================================

class TestMigrationHistory:
    """Test migration history and versioning."""

    def test_migration_history_linear(self):
        """Test that migration history forms a linear chain."""
        # This would check that each migration has exactly one parent
        # (no branches in migration history)
        pass  # Placeholder

    def test_migration_revision_ids_unique(self):
        """Test that migration revision IDs are unique."""
        # Parse all migration files and check revision IDs
        pass  # Placeholder

    def test_migration_down_revision_valid(self):
        """Test that down_revision references exist."""
        # Check that each migration's down_revision points to valid revision
        pass  # Placeholder

    def test_no_duplicate_migrations(self):
        """Test that no duplicate migration files exist."""
        # Check for duplicate revision IDs or timestamps
        pass  # Placeholder


# ============================================================================
# Edge Cases: Migrations
# ============================================================================

@pytest.mark.asyncio
class TestMigrationEdgeCases:
    """Test edge cases in migration handling."""

    async def test_migration_with_empty_database(self, db_engine):
        """Test running migrations on empty database."""
        # This is the normal case but worth testing explicitly
        pass  # Placeholder

    async def test_migration_rollback_on_error(self, db_engine):
        """Test that failed migration rolls back changes."""
        # This would require intentionally failing migration
        pass  # Placeholder

    async def test_concurrent_migration_attempts(self):
        """Test behavior when multiple processes try to migrate simultaneously."""
        # Alembic uses locking to prevent concurrent migrations
        pass  # Placeholder

    async def test_partial_migration_recovery(self):
        """Test recovery from partially applied migration."""
        # Edge case: migration fails halfway through
        pass  # Placeholder


# ============================================================================
# Utility Tests: Alembic Commands
# ============================================================================

class TestAlembicCommands:
    """Test Alembic command-line functionality."""

    def test_alembic_current_command(self):
        """Test 'alembic current' shows current revision."""
        # Would execute: alembic current
        # and verify output
        pass  # Placeholder

    def test_alembic_history_command(self):
        """Test 'alembic history' shows migration history."""
        # Would execute: alembic history
        # and verify output format
        pass  # Placeholder

    def test_alembic_heads_command(self):
        """Test 'alembic heads' shows head revision."""
        # Would execute: alembic heads
        # and verify single head
        pass  # Placeholder

    def test_alembic_branches_command(self):
        """Test 'alembic branches' shows no branches."""
        # Would execute: alembic branches
        # Should return empty (linear history)
        pass  # Placeholder


# ============================================================================
# Documentation Tests
# ============================================================================

class TestMigrationDocumentation:
    """Test that migrations are properly documented."""

    def test_migration_files_have_docstrings(self):
        """Test that migration files have docstrings."""
        # Parse migration files and check for module docstrings
        pass  # Placeholder

    def test_migration_descriptions_meaningful(self):
        """Test that migration descriptions are meaningful."""
        # Check that revision messages are not generic
        # e.g., not just "initial" or "update"
        pass  # Placeholder

    def test_alembic_readme_exists(self):
        """Test that alembic directory has README."""
        # Arrange
        project_root = Path("/Users/andrewkaszubski/Dev/TradingAgents")
        readme = project_root / "alembic" / "README"

        # Assert: README should exist
        # (Alembic generates this by default)
        pass  # Placeholder