# diagnosis/ai_engine/model_loader.py
"""Singleton pattern for model loading

This loader provides a clean interface for getting the detector instance.
Uses singleton pattern to ensure models are loaded only once.
"""
import logging

logger = logging.getLogger(__name__)

_detector_instance = None

def get_stutter_detector():
    """
    Get or create singleton AdvancedStutterDetector instance.
    
    This ensures models are loaded only once and reused across requests.
    
    Returns:
        AdvancedStutterDetector: The singleton detector instance
        
    Raises:
        ImportError: If the detector class cannot be imported
    """
    global _detector_instance
    
    if _detector_instance is None:
        try:
            from .detect_stuttering import AdvancedStutterDetector
            logger.info("🔄 Initializing detector instance (first call)...")
            _detector_instance = AdvancedStutterDetector()
            logger.info("✅ Detector instance created successfully")
        except ImportError as e:
            logger.error(f"❌ Failed to import AdvancedStutterDetector: {e}")
            raise ImportError("No StutterDetector implementation available in detect_stuttering.py") from e
        except Exception as e:
            logger.error(f"❌ Failed to create detector instance: {e}")
            raise
    
    return _detector_instance

def reset_detector():
    """
    Reset the singleton instance (useful for testing or reloading models).
    
    Note: This will force reloading of models on next get_stutter_detector() call.
    """
    global _detector_instance
    _detector_instance = None
    logger.info("🔄 Detector instance reset")