"""
Model Manager
=============

Manages model loading states and provides a robust interface for
ensuring models are loaded and validated before generation.

States:
- UNLOADED: No model loaded
- LOADING: Model is being loaded
- READY: Model loaded and validated
- ERROR: Model failed to load
"""

import logging
import threading
import time
from typing import Optional, Callable, Tuple
from enum import Enum
from PIL import Image

from .backend_router import BackendRouter, BackendType
from .character_service import CharacterSheetService


logger = logging.getLogger(__name__)


class ModelState(Enum):
    """Model loading states."""
    UNLOADED = "unloaded"
    LOADING = "loading"
    READY = "ready"
    ERROR = "error"


class ModelManager:
    """
    Manages model loading lifecycle with state tracking.

    Ensures models are fully loaded and validated before allowing generation.
    Provides progress callbacks for UI updates during loading.
    """

    def __init__(self):
        self._state = ModelState.UNLOADED
        self._current_backend: Optional[BackendType] = None
        self._service: Optional[CharacterSheetService] = None
        self._error_message: Optional[str] = None
        self._loading_progress: float = 0.0
        self._loading_message: str = ""
        self._lock = threading.Lock()
        self._cancel_requested = False

    @property
    def state(self) -> ModelState:
        """Current model state."""
        return self._state

    @property
    def is_ready(self) -> bool:
        """Check if model is ready for generation."""
        return self._state == ModelState.READY

    @property
    def is_loading(self) -> bool:
        """Check if model is currently loading."""
        return self._state == ModelState.LOADING

    @property
    def error_message(self) -> Optional[str]:
        """Get error message if in error state."""
        return self._error_message

    @property
    def loading_progress(self) -> float:
        """Get loading progress (0.0 to 1.0)."""
        return self._loading_progress

    @property
    def loading_message(self) -> str:
        """Get current loading status message."""
        return self._loading_message

    @property
    def current_backend(self) -> Optional[BackendType]:
        """Get currently loaded backend."""
        return self._current_backend

    @property
    def service(self) -> Optional[CharacterSheetService]:
        """Get the character sheet service (only valid when ready)."""
        if self._state != ModelState.READY:
            return None
        return self._service

    def get_status_display(self) -> Tuple[str, str]:
        """
        Get status message and color for UI display.

        Returns:
            Tuple of (message, color) where color is a CSS color string
        """
        if self._state == ModelState.UNLOADED:
            return "No model loaded", "#888888"
        elif self._state == ModelState.LOADING:
            pct = int(self._loading_progress * 100)
            return f"Loading... {pct}% - {self._loading_message}", "#FFA500"
        elif self._state == ModelState.READY:
            backend_name = BackendRouter.BACKEND_NAMES.get(
                self._current_backend,
                str(self._current_backend)
            )
            return f"Ready: {backend_name}", "#00AA00"
        elif self._state == ModelState.ERROR:
            return f"Error: {self._error_message}", "#FF0000"
        return "Unknown state", "#888888"

    def request_cancel(self):
        """Request cancellation of current loading operation."""
        self._cancel_requested = True
        logger.info("Model loading cancellation requested")

    def load_model(
        self,
        backend: BackendType,
        api_key: Optional[str] = None,
        steps: int = 4,
        guidance: float = 1.0,
        progress_callback: Optional[Callable[[float, str], None]] = None
    ) -> bool:
        """
        Load a model with progress tracking.

        Args:
            backend: Backend type to load
            api_key: API key for cloud backends
            steps: Default steps for generation
            guidance: Default guidance scale
            progress_callback: Callback for progress updates (progress, message)

        Returns:
            True if model loaded successfully
        """
        with self._lock:
            if self._state == ModelState.LOADING:
                logger.warning("Model is already loading, ignoring request")
                return False

            self._state = ModelState.LOADING
            self._loading_progress = 0.0
            self._loading_message = "Initializing..."
            self._error_message = None
            self._cancel_requested = False

        def update_progress(progress: float, message: str):
            self._loading_progress = progress
            self._loading_message = message
            if progress_callback:
                progress_callback(progress, message)

        try:
            # Step 1: Unload previous model if different backend
            update_progress(0.05, "Checking current model...")

            if self._service and self._current_backend != backend:
                update_progress(0.1, "Unloading previous model...")
                try:
                    if hasattr(self._service, 'router'):
                        self._service.router.unload_local_models()
                except Exception as e:
                    logger.warning(f"Error unloading previous model: {e}")
                self._service = None

            if self._cancel_requested:
                self._state = ModelState.UNLOADED
                return False

            # Step 2: Create service and load model
            backend_name = BackendRouter.BACKEND_NAMES.get(backend, str(backend))
            update_progress(0.15, f"Loading {backend_name}...")

            logger.info(f"Creating CharacterSheetService for {backend.value}")

            # For local models, this will load the model
            # For cloud backends, this just validates the API key
            self._service = CharacterSheetService(
                api_key=api_key,
                backend=backend
            )

            if self._cancel_requested:
                self._state = ModelState.UNLOADED
                self._service = None
                return False

            update_progress(0.7, "Model loaded, configuring...")

            # Step 3: Configure default parameters
            if hasattr(self._service.client, 'default_steps'):
                self._service.client.default_steps = steps
            if hasattr(self._service.client, 'default_guidance'):
                self._service.client.default_guidance = guidance

            update_progress(0.8, "Validating model...")

            # Step 4: Validate model is actually working
            is_valid, error = self._validate_model()

            if not is_valid:
                raise RuntimeError(f"Model validation failed: {error}")

            update_progress(1.0, "Ready!")

            # Success!
            with self._lock:
                self._current_backend = backend
                self._state = ModelState.READY
                self._loading_progress = 1.0
                self._loading_message = "Ready"

            logger.info(f"Model {backend.value} loaded and validated successfully")
            return True

        except Exception as e:
            error_msg = str(e)
            logger.error(f"Failed to load model {backend.value}: {error_msg}", exc_info=True)

            with self._lock:
                self._state = ModelState.ERROR
                self._error_message = self._simplify_error(error_msg)
                self._service = None

            if progress_callback:
                progress_callback(0.0, f"Error: {self._error_message}")

            return False

    def _validate_model(self) -> Tuple[bool, Optional[str]]:
        """
        Validate that the model is actually working.

        For local models, checks that the pipeline is loaded.
        For cloud backends, does a minimal health check.

        Returns:
            Tuple of (is_valid, error_message)
        """
        if self._service is None:
            return False, "Service not initialized"

        try:
            client = self._service.client

            # Check if client has health check method
            if hasattr(client, 'is_healthy'):
                if not client.is_healthy():
                    return False, "Client health check failed"

            # For local models, check pipeline is loaded
            if hasattr(client, '_loaded'):
                if not client._loaded:
                    return False, "Model pipeline not loaded"

            # For FLUX models, verify the pipe exists
            if hasattr(client, 'pipe'):
                if client.pipe is None:
                    return False, "Model pipeline is None"

            return True, None

        except Exception as e:
            return False, str(e)

    def _simplify_error(self, error: str) -> str:
        """Simplify technical error messages for user display."""
        error_lower = error.lower()

        if "cuda out of memory" in error_lower or "out of memory" in error_lower:
            return "Not enough GPU memory. Try a smaller model or close other applications."

        if "api key" in error_lower:
            return "Invalid or missing API key."

        if "connection" in error_lower or "network" in error_lower:
            return "Network connection error. Check your internet connection."

        if "not found" in error_lower and "model" in error_lower:
            return "Model files not found. The model may need to be downloaded."

        if "import" in error_lower:
            return "Missing dependencies. Some required packages are not installed."

        if "meta tensor" in error_lower:
            return "Model loading failed (meta tensor error). Try restarting the application."

        # Truncate long errors
        if len(error) > 100:
            return error[:97] + "..."

        return error

    def unload(self):
        """Unload the current model."""
        with self._lock:
            if self._service:
                try:
                    if hasattr(self._service, 'router'):
                        self._service.router.unload_local_models()
                except Exception as e:
                    logger.warning(f"Error during unload: {e}")
                self._service = None

            self._state = ModelState.UNLOADED
            self._current_backend = None
            self._error_message = None
            self._loading_progress = 0.0
            self._loading_message = ""

        logger.info("Model unloaded")


# Global singleton for model management
_model_manager: Optional[ModelManager] = None


def get_model_manager() -> ModelManager:
    """Get the global ModelManager instance."""
    global _model_manager
    if _model_manager is None:
        _model_manager = ModelManager()
    return _model_manager