import logging
from google.adk.sessions import DatabaseSessionService
from app.config import settings

logger = logging.getLogger(__name__)

# Global service instance
_session_service: DatabaseSessionService | None = None


async def init_session_service() -> None:
    """Initialize the database session service on application startup."""
    global _session_service
    if _session_service is None:
        logger.info(f"Initializing DatabaseSessionService with {settings.DATABASE_URL}...")
        _session_service = DatabaseSessionService(db_url=settings.DATABASE_URL)
        logger.info("DatabaseSessionService initialized successfully")


async def close_session_service() -> None:
    """Cleanup session service resources on application shutdown."""
    global _session_service
    if _session_service:
        _session_service = None
        logger.info("DatabaseSessionService closed")


def get_session_service() -> DatabaseSessionService:
    """
    Get the session service instance for dependency injection.
    
    Raises:
        RuntimeError: If service is not initialized.
    """
    if _session_service is None:
        raise RuntimeError("Session service not initialized. Application may not have started properly.")
    return _session_service