"""
Auto-loader selection based on manifest format field or file extension.

Provides intelligent loader selection without explicit loader specification.
"""

from pathlib import Path
from typing import Optional, Any, TYPE_CHECKING
import logging

from .registry import get_loader, is_loader_registered
from .types import ModelFormat

if TYPE_CHECKING:
    from .base import BaseModelLoader

logger = logging.getLogger(__name__)

# Format to loader mapping
FORMAT_TO_LOADER: dict[str, str] = {
    "gguf": "gguf",
    "safetensors": "diffusers",  # Default to diffusers for safetensors
    "onnx": "onnx",
    "pytorch": "hf",
    "hf-snapshot": "hf",
    "diffusion": "diffusers",
}

# Extension-based fallback
EXTENSION_TO_LOADER: dict[str, str] = {
    ".gguf": "gguf",
    ".onnx": "onnx",
    ".safetensors": "diffusers",
    ".pt": "hf",
    ".pth": "hf",
    ".bin": "hf",
}

# Category-based defaults
CATEGORY_TO_LOADER: dict[str, str] = {
    "llm": "gguf",
    "embedding": "gguf",
    "voice": "whisper",
    "diffusion": "diffusers",
    "multimodal": "hf",
    "tools": "onnx",
}


def get_auto_loader(
    model_id: str,
    manifest_path: Optional[str] = None,
    **init_kwargs: Any,
) -> "BaseModelLoader":
    """
    Automatically select and return appropriate loader for a model.

    Selection priority:
    1. Manifest `format` field (if model in manifest)
    2. File extension (for direct paths)
    3. Manifest `category` field (fallback)
    4. Default to "hf" loader

    Args:
        model_id: Model ID from manifest or direct path
        manifest_path: Optional custom manifest path
        **init_kwargs: Arguments passed to loader constructor

    Returns:
        Instantiated loader appropriate for the model

    Example:
        >>> loader = get_auto_loader("whisper-large-v3-turbo")
        >>> model = await loader.load("whisper-large-v3-turbo")

        >>> # Works with paths too
        >>> loader = get_auto_loader("/path/to/model.onnx")
        >>> model = await loader.load("/path/to/model.onnx")
    """
    loader_name: Optional[str] = None

    # Try to get manifest entry
    try:
        from .loader import ModelLoader

        path_loader = ModelLoader(manifest_path=manifest_path)
        entry = path_loader.get_model_entry(model_id)

        if entry:
            # Priority 1: Explicit format field
            if entry.format:
                loader_name = FORMAT_TO_LOADER.get(entry.format)
                if loader_name:
                    logger.debug(
                        f"Selected loader '{loader_name}' from format '{entry.format}'"
                    )

            # Priority 3: Category fallback
            if not loader_name and entry.category:
                loader_name = CATEGORY_TO_LOADER.get(entry.category)
                if loader_name:
                    logger.debug(
                        f"Selected loader '{loader_name}' from category '{entry.category}'"
                    )
    except Exception as e:
        logger.debug(f"Failed to get manifest entry: {e}")

    # Priority 2: Extension-based (for direct paths)
    if not loader_name:
        path = Path(model_id)
        if path.suffix:
            loader_name = EXTENSION_TO_LOADER.get(path.suffix.lower())
            if loader_name:
                logger.debug(
                    f"Selected loader '{loader_name}' from extension '{path.suffix}'"
                )

    # Default fallback
    if not loader_name:
        loader_name = "hf"
        logger.debug(f"Using default loader 'hf'")

    # Verify loader exists
    if not is_loader_registered(loader_name):
        logger.warning(
            f"Loader '{loader_name}' not registered, falling back to 'hf'"
        )
        loader_name = "hf"

    return get_loader(loader_name, **init_kwargs)


def detect_format_from_path(path: str) -> Optional[ModelFormat]:
    """
    Detect model format from file path.

    Args:
        path: Path to model file or directory

    Returns:
        Detected ModelFormat or None
    """
    p = Path(path)

    # File extension detection
    ext = p.suffix.lower()
    if ext == ".gguf":
        return "gguf"
    elif ext == ".onnx":
        return "onnx"
    elif ext == ".safetensors":
        return "safetensors"
    elif ext in (".pt", ".pth", ".bin"):
        return "pytorch"

    # Directory detection
    if p.is_dir():
        # Check for diffusion pipeline
        if (p / "model_index.json").exists():
            return "diffusion"
        # Check for sharded safetensors
        if (p / "model.safetensors.index.json").exists():
            return "safetensors"
        # Check for HuggingFace cache
        if p.name.startswith("models--"):
            return "hf-snapshot"
        # Check for ONNX
        if list(p.glob("*.onnx")):
            return "onnx"
        # Default to safetensors for directories with config.json
        if (p / "config.json").exists():
            return "safetensors"

    return None


def get_loader_for_format(
    format: ModelFormat,
    **init_kwargs: Any,
) -> "BaseModelLoader":
    """
    Get a loader instance for a specific format.

    Args:
        format: Model format
        **init_kwargs: Arguments passed to loader constructor

    Returns:
        Instantiated loader

    Raises:
        KeyError: If no loader registered for format
    """
    loader_name = FORMAT_TO_LOADER.get(format)
    if not loader_name:
        raise KeyError(f"No loader registered for format '{format}'")

    return get_loader(loader_name, **init_kwargs)


def get_loader_for_category(
    category: str,
    **init_kwargs: Any,
) -> "BaseModelLoader":
    """
    Get a loader instance for a model category.

    Args:
        category: Model category (llm, embedding, voice, diffusion, multimodal)
        **init_kwargs: Arguments passed to loader constructor

    Returns:
        Instantiated loader

    Raises:
        KeyError: If no loader registered for category
    """
    loader_name = CATEGORY_TO_LOADER.get(category)
    if not loader_name:
        raise KeyError(f"No loader registered for category '{category}'")

    return get_loader(loader_name, **init_kwargs)