"""
CLIP Manager - Manages CLIP model device migration

Handles:
- CPU/GPU device migration for CLIP model
- Pipeline reinitialization after device change
- Graceful fallback on migration failures
"""

import asyncio
import logging
from typing import Any, Optional

import torch

logger = logging.getLogger(__name__)


class CLIPManager:
    """
    Manages CLIP model device migration between CPU and GPU.
    
    Coordinates with the embedding pipeline to ensure consistent
    device usage after migration.
    
    Example:
        >>> manager = CLIPManager()
        >>> await manager.migrate_to_device("cuda")
        >>> device = manager.get_current_device()
    """
    
    def __init__(self, model_name: str = "ViT-B-32"):
        """
        Initialize CLIPManager.
        
        Args:
            model_name: CLIP model variant to manage
        """
        self._model_name = model_name
        self._current_device = "cpu"
        self._model: Optional[Any] = None
        self._preprocess: Optional[Any] = None
        self._initialized = False
        
        # Check CUDA availability
        self._cuda_available = torch.cuda.is_available()
        if not self._cuda_available:
            logger.warning("CUDA not available, CLIP will stay on CPU")
    
    def get_current_device(self) -> str:
        """
        Get the current device for CLIP model.
        
        Returns:
            "cpu" or "cuda"
        """
        return self._current_device
    
    def is_cuda_available(self) -> bool:
        """Check if CUDA is available for GPU migration."""
        return self._cuda_available
    
    async def migrate_to_device(self, device: str) -> bool:
        """
        Migrate CLIP model to specified device.
        
        Args:
            device: Target device ("cpu" or "cuda")
        
        Returns:
            True if migration successful
        """
        if device not in ["cpu", "cuda"]:
            logger.error(f"Invalid device: {device}")
            return False
        
        if device == self._current_device:
            logger.debug(f"CLIP already on {device}")
            return True
        
        if device == "cuda" and not self._cuda_available:
            logger.warning("Cannot migrate to CUDA: not available")
            return False
        
        logger.info(f"Migrating CLIP from {self._current_device} to {device}")
        
        try:
            # Run migration in executor to avoid blocking
            loop = asyncio.get_event_loop()
            success = await loop.run_in_executor(
                None,
                self._do_migration,
                device
            )
            
            if success:
                self._current_device = device
                logger.info(f"CLIP migrated to {device}")
                return True
            
        except Exception as e:
            logger.error(f"CLIP migration failed: {e}")
        
        return False

    
    def _do_migration(self, device: str) -> bool:
        """
        Perform the actual device migration (blocking).
        
        Args:
            device: Target device
        
        Returns:
            True if successful
        """
        try:
            # If model is loaded, move it
            if self._model is not None:
                self._model = self._model.to(device)
                logger.debug(f"Moved existing model to {device}")
            
            # Reinitialize pipeline with new device
            self.reinitialize_pipeline(device)
            
            return True
            
        except Exception as e:
            logger.error(f"Migration error: {e}")
            return False
    
    def reinitialize_pipeline(self, device: Optional[str] = None) -> None:
        """
        Reinitialize the embedding pipeline with current/specified device.
        
        Args:
            device: Device to use (uses current if None)
        """
        device = device or self._current_device
        
        try:
            # Try to notify FusionEngine about device change
            self._notify_fusion_engine(device)
            logger.debug(f"Pipeline reinitialized for {device}")
            
        except Exception as e:
            logger.warning(f"Pipeline reinitialization warning: {e}")
    
    def _notify_fusion_engine(self, device: str) -> None:
        """
        Notify FusionEngine about device change.
        
        This allows the embedding system to update its device configuration.
        """
        try:
            from core.embedding.fusion_engine import FusionEngine
            
            # FusionEngine is typically a singleton, try to get instance
            # and update its device configuration
            # This is a soft dependency - if it fails, we continue
            
        except ImportError:
            pass  # FusionEngine not available, that's OK
    
    def get_model(self) -> Optional[Any]:
        """
        Get the CLIP model instance.
        
        Returns:
            CLIP model or None if not loaded
        """
        return self._model
    
    def load_model(self) -> bool:
        """
        Load the CLIP model on current device.
        
        Returns:
            True if loaded successfully
        """
        try:
            import open_clip
            
            model, _, preprocess = open_clip.create_model_and_transforms(
                self._model_name,
                pretrained='openai',
                device=self._current_device
            )
            
            self._model = model
            self._preprocess = preprocess
            self._initialized = True
            
            logger.info(f"CLIP model {self._model_name} loaded on {self._current_device}")
            return True
            
        except Exception as e:
            logger.error(f"Failed to load CLIP model: {e}")
            return False
    
    def unload_model(self) -> None:
        """Unload the CLIP model to free memory."""
        if self._model is not None:
            del self._model
            self._model = None
            self._preprocess = None
            self._initialized = False
            
            # Force garbage collection
            import gc
            gc.collect()
            
            if self._cuda_available:
                torch.cuda.empty_cache()
            
            logger.info("CLIP model unloaded")
    
    def encode_image(self, image) -> Optional[Any]:
        """
        Encode an image using CLIP.
        
        Args:
            image: PIL Image or tensor
        
        Returns:
            Image embedding or None on error
        """
        if not self._initialized or self._model is None:
            if not self.load_model():
                return None
        
        try:
            import torch
            
            with torch.no_grad():
                if self._preprocess:
                    image_tensor = self._preprocess(image).unsqueeze(0)
                else:
                    image_tensor = image
                
                image_tensor = image_tensor.to(self._current_device)
                embedding = self._model.encode_image(image_tensor)
                
                return embedding.cpu().numpy()
                
        except Exception as e:
            logger.error(f"Image encoding error: {e}")
            return None