"""
Database configuration for BackgroundFX Pro.

Handles PostgreSQL, MongoDB, and other database connections.
"""

from dataclasses import dataclass, field
from typing import Optional, Dict, Any
from sqlalchemy import create_engine, Engine
from sqlalchemy.orm import sessionmaker, Session
from sqlalchemy.pool import QueuePool, NullPool
import pymongo
from pymongo import MongoClient
import logging

logger = logging.getLogger(__name__)


@dataclass
class DatabaseConfig:
    """Database configuration settings."""
    
    # PostgreSQL settings
    postgres_url: str = "postgresql://user:password@localhost/backgroundfx"
    postgres_pool_size: int = 20
    postgres_max_overflow: int = 40
    postgres_pool_timeout: int = 30
    postgres_pool_recycle: int = 3600
    postgres_echo: bool = False
    postgres_echo_pool: bool = False
    
    # MongoDB settings
    mongodb_url: str = "mongodb://localhost:27017/backgroundfx"
    mongodb_database: str = "backgroundfx"
    mongodb_max_pool_size: int = 50
    mongodb_min_pool_size: int = 10
    mongodb_max_idle_time: int = 60000  # milliseconds
    mongodb_server_selection_timeout: int = 30000  # milliseconds
    
    # Connection retry settings
    max_retries: int = 3
    retry_delay: int = 1  # seconds
    
    # Query settings
    query_timeout: int = 30  # seconds
    slow_query_threshold: float = 1.0  # seconds
    log_slow_queries: bool = True
    
    # Migration settings
    auto_migrate: bool = False
    migration_directory: str = "migrations"


class PostgreSQLManager:
    """Manages PostgreSQL database connections."""
    
    def __init__(self, config: DatabaseConfig):
        self.config = config
        self._engine: Optional[Engine] = None
        self._session_factory: Optional[sessionmaker] = None
    
    @property
    def engine(self) -> Engine:
        """Get or create database engine."""
        if self._engine is None:
            self._engine = self._create_engine()
        return self._engine
    
    @property
    def session_factory(self) -> sessionmaker:
        """Get or create session factory."""
        if self._session_factory is None:
            self._session_factory = sessionmaker(
                bind=self.engine,
                expire_on_commit=False
            )
        return self._session_factory
    
    def _create_engine(self) -> Engine:
        """Create SQLAlchemy engine with connection pooling."""
        # Determine pool class based on environment
        if self.config.postgres_pool_size == 0:
            poolclass = NullPool
            pool_kwargs = {}
        else:
            poolclass = QueuePool
            pool_kwargs = {
                'pool_size': self.config.postgres_pool_size,
                'max_overflow': self.config.postgres_max_overflow,
                'pool_timeout': self.config.postgres_pool_timeout,
                'pool_recycle': self.config.postgres_pool_recycle,
            }
        
        engine = create_engine(
            self.config.postgres_url,
            poolclass=poolclass,
            echo=self.config.postgres_echo,
            echo_pool=self.config.postgres_echo_pool,
            pool_pre_ping=True,  # Verify connections before using
            **pool_kwargs
        )
        
        logger.info(f"PostgreSQL engine created with pool size: {self.config.postgres_pool_size}")
        return engine
    
    def get_session(self) -> Session:
        """Get a new database session."""
        return self.session_factory()
    
    def healthcheck(self) -> bool:
        """Check database health."""
        try:
            with self.engine.connect() as conn:
                result = conn.execute("SELECT 1")
                return result.scalar() == 1
        except Exception as e:
            logger.error(f"PostgreSQL healthcheck failed: {e}")
            return False
    
    def close(self):
        """Close all database connections."""
        if self._engine:
            self._engine.dispose()
            logger.info("PostgreSQL connections closed")


class MongoDBManager:
    """Manages MongoDB connections."""
    
    def __init__(self, config: DatabaseConfig):
        self.config = config
        self._client: Optional[MongoClient] = None
        self._database = None
    
    @property
    def client(self) -> MongoClient:
        """Get or create MongoDB client."""
        if self._client is None:
            self._client = self._create_client()
        return self._client
    
    @property
    def database(self):
        """Get MongoDB database."""
        if self._database is None:
            self._database = self.client[self.config.mongodb_database]
        return self._database
    
    def _create_client(self) -> MongoClient:
        """Create MongoDB client with connection pooling."""
        client = MongoClient(
            self.config.mongodb_url,
            maxPoolSize=self.config.mongodb_max_pool_size,
            minPoolSize=self.config.mongodb_min_pool_size,
            maxIdleTimeMS=self.config.mongodb_max_idle_time,
            serverSelectionTimeoutMS=self.config.mongodb_server_selection_timeout,
            retryWrites=True,
            retryReads=True
        )
        
        # Verify connection
        client.admin.command('ping')
        logger.info(f"MongoDB client created for database: {self.config.mongodb_database}")
        
        return client
    
    def get_collection(self, name: str):
        """Get a MongoDB collection."""
        return self.database[name]
    
    def healthcheck(self) -> bool:
        """Check MongoDB health."""
        try:
            self.client.admin.command('ping')
            return True
        except Exception as e:
            logger.error(f"MongoDB healthcheck failed: {e}")
            return False
    
    def close(self):
        """Close MongoDB connection."""
        if self._client:
            self._client.close()
            logger.info("MongoDB connection closed")


class DatabaseManager:
    """Central database manager for all database connections."""
    
    def __init__(self, config: DatabaseConfig):
        self.config = config
        self.postgres = PostgreSQLManager(config)
        self.mongodb = MongoDBManager(config)
    
    def initialize(self):
        """Initialize all database connections."""
        logger.info("Initializing database connections...")
        
        # Initialize PostgreSQL
        if self.postgres.healthcheck():
            logger.info("PostgreSQL connection established")
        else:
            logger.error("Failed to connect to PostgreSQL")
        
        # Initialize MongoDB
        if self.mongodb.healthcheck():
            logger.info("MongoDB connection established")
        else:
            logger.error("Failed to connect to MongoDB")
    
    def healthcheck(self) -> Dict[str, bool]:
        """Check health of all databases."""
        return {
            'postgresql': self.postgres.healthcheck(),
            'mongodb': self.mongodb.healthcheck()
        }
    
    def close_all(self):
        """Close all database connections."""
        self.postgres.close()
        self.mongodb.close()
        logger.info("All database connections closed")
    
    def get_stats(self) -> Dict[str, Any]:
        """Get database statistics."""
        stats = {}
        
        # PostgreSQL stats
        if self.postgres._engine:
            pool = self.postgres.engine.pool
            stats['postgresql'] = {
                'size': pool.size() if hasattr(pool, 'size') else None,
                'checked_in': pool.checkedin() if hasattr(pool, 'checkedin') else None,
                'overflow': pool.overflow() if hasattr(pool, 'overflow') else None,
                'total': pool.total() if hasattr(pool, 'total') else None
            }
        
        # MongoDB stats
        if self.mongodb._client:
            stats['mongodb'] = self.mongodb.client.server_info()
        
        return stats


def create_database_config(settings: Any) -> DatabaseConfig:
    """
    Create database configuration from settings.
    
    Args:
        settings: Application settings
        
    Returns:
        DatabaseConfig instance
    """
    return DatabaseConfig(
        postgres_url=settings.database_url,
        postgres_pool_size=settings.database_pool_size,
        postgres_max_overflow=settings.database_max_overflow,
        postgres_echo=settings.database_echo,
        mongodb_url=settings.mongodb_url,
        mongodb_database=settings.mongodb_database
    )


# Global database manager instance
db_manager: Optional[DatabaseManager] = None


def initialize_databases(settings: Any):
    """
    Initialize global database manager.
    
    Args:
        settings: Application settings
    """
    global db_manager
    config = create_database_config(settings)
    db_manager = DatabaseManager(config)
    db_manager.initialize()
    return db_manager


def get_db_manager() -> DatabaseManager:
    """Get global database manager instance."""
    if db_manager is None:
        raise RuntimeError("Database manager not initialized")
    return db_manager