"""
Migration Generator Agent

Generates database migration files for schema changes, supporting
multiple ORM frameworks and database systems.
"""

from typing import Any, Dict, List
from agents.base import BaseAgent


class MigrationGeneratorAgent(BaseAgent):
    """
    Generates database migration files.

    Supports:
    - Alembic (SQLAlchemy)
    - Django migrations
    - TypeORM migrations
    - Sequelize migrations
    - Flyway
    - Liquibase
    """

    def __init__(self):
        super().__init__(
            name='migration-generator',
            description='Generate database migration files',
            category='engineering',
            version='1.0.0',
            tags=['database', 'migrations', 'schema', 'versioning']
        )

    async def execute(self, params: Dict[str, Any]) -> Dict[str, Any]:
        """
        Generate database migration.

        Args:
            params: {
                'migration_tool': 'alembic|django|typeorm|sequelize|flyway|liquibase',
                'database_type': 'postgresql|mysql|sqlite',
                'change_type': 'create_table|alter_table|drop_table|add_column|custom',
                'changes': List[Dict],   # Schema changes
                'options': {
                    'auto_detect': bool,
                    'reversible': bool,
                    'add_data_migration': bool,
                    'dry_run': bool
                }
            }

        Returns:
            {
                'status': 'success|failed',
                'migration_files': List[str],
                'changes': List[Dict],
                'reversible': bool,
                'sql_preview': str
            }
        """
        migration_tool = params.get('migration_tool', 'alembic')
        database_type = params.get('database_type', 'postgresql')
        change_type = params.get('change_type', 'create_table')
        changes = params.get('changes', [])
        options = params.get('options', {})

        self.logger.info(
            f"Generating {migration_tool} migration for {change_type}"
        )

        # Mock migration generation
        migration_changes = [
            {
                'operation': 'create_table',
                'table': 'users',
                'columns': [
                    {'name': 'id', 'type': 'UUID', 'primary_key': True},
                    {'name': 'email', 'type': 'VARCHAR(255)', 'unique': True},
                    {'name': 'created_at', 'type': 'TIMESTAMP'}
                ]
            },
            {
                'operation': 'add_column',
                'table': 'products',
                'column': {'name': 'sku', 'type': 'VARCHAR(100)', 'unique': True}
            },
            {
                'operation': 'create_index',
                'table': 'orders',
                'index_name': 'idx_orders_user_id',
                'columns': ['user_id']
            },
            {
                'operation': 'add_foreign_key',
                'table': 'orders',
                'column': 'user_id',
                'references': 'users.id',
                'on_delete': 'CASCADE'
            }
        ]

        sql_preview = """
-- Migration: 001_add_user_system
-- Created: 2025-11-16 00:00:00

-- Upgrade
CREATE TABLE users (
    id UUID PRIMARY KEY,
    email VARCHAR(255) UNIQUE NOT NULL,
    created_at TIMESTAMP DEFAULT NOW()
);

ALTER TABLE products
ADD COLUMN sku VARCHAR(100) UNIQUE;

CREATE INDEX idx_orders_user_id ON orders(user_id);

ALTER TABLE orders
ADD CONSTRAINT fk_orders_user_id
FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE;

-- Downgrade
ALTER TABLE orders DROP CONSTRAINT fk_orders_user_id;
DROP INDEX idx_orders_user_id;
ALTER TABLE products DROP COLUMN sku;
DROP TABLE users;
"""

        return {
            'status': 'success',
            'migration_tool': migration_tool,
            'database_type': database_type,
            'migration_files': [
                'migrations/001_add_user_system.py',
                'migrations/001_add_user_system_downgrade.py'
            ],
            'migration_name': '001_add_user_system',
            'changes': migration_changes,
            'total_operations': len(migration_changes),
            'reversible': options.get('reversible', True),
            'auto_detected': options.get('auto_detect', False),
            'sql_preview': sql_preview.strip(),
            'estimated_time': '0.5s',
            'tables_affected': ['users', 'products', 'orders'],
            'safety_checks': [
                'No data loss detected',
                'All changes are reversible',
                'Foreign keys properly constrained',
                'Indexes optimized for queries'
            ],
            'warnings': [
                'Adding unique constraint may fail if duplicate data exists',
                'Foreign key will prevent deletion of referenced users'
            ],
            'next_steps': [
                'Review migration SQL',
                'Test on development database',
                'Backup production database',
                'Run migration with --dry-run first',
                'Apply migration'
            ]
        }

    def validate_params(self, params: Dict[str, Any]) -> bool:
        """Validate migration generation parameters."""
        valid_tools = [
            'alembic', 'django', 'typeorm',
            'sequelize', 'flyway', 'liquibase'
        ]
        migration_tool = params.get('migration_tool', 'alembic')

        if migration_tool not in valid_tools:
            self.logger.error(f"Unsupported migration tool: {migration_tool}")
            return False

        valid_change_types = [
            'create_table', 'alter_table', 'drop_table',
            'add_column', 'custom'
        ]
        change_type = params.get('change_type', 'create_table')

        if change_type not in valid_change_types:
            self.logger.error(f"Invalid change type: {change_type}")
            return False

        return True
