"""
File Utilities
==============

File I/O operations for Nano Banana Streamlit.
Handles image saving/loading, metadata management, and filename generation.
"""

import json
import hashlib
import re
from datetime import datetime
from pathlib import Path
from typing import Optional, Dict, Any, Tuple, Union
from PIL import Image

from config.settings import Settings
from utils.logging_utils import get_logger


logger = get_logger(__name__)


# =============================================================================
# FILENAME UTILITIES
# =============================================================================

def sanitize_filename(name: str) -> str:
    """
    Sanitize a string to be safe for use as a filename.

    Removes or replaces unsafe characters.

    Args:
        name: Raw filename string

    Returns:
        Sanitized filename safe for all operating systems
    """
    # Remove/replace unsafe characters
    safe = re.sub(r'[<>:"/\\|?*]', '_', name)

    # Remove leading/trailing spaces and dots
    safe = safe.strip('. ')

    # Limit length (leave room for timestamp and extension)
    max_len = 100
    if len(safe) > max_len:
        safe = safe[:max_len]

    # If empty after sanitization, use default
    if not safe:
        safe = "generated"

    return safe


def generate_timestamp_filename(
    base_name: str,
    extension: str = "png"
) -> str:
    """
    Generate a filename with timestamp.

    Format: {base_name}_{YYYYMMDD_HHMMSS}.{extension}

    Args:
        base_name: Base name for file (will be sanitized)
        extension: File extension (default: "png")

    Returns:
        Filename string with timestamp
    """
    safe_name = sanitize_filename(base_name)
    timestamp = datetime.now().strftime("%Y%m%d_%H%M%S")
    return f"{safe_name}_{timestamp}.{extension}"


def get_unique_filename(directory: Path, base_name: str, extension: str = "png") -> Path:
    """
    Generate a unique filename in a directory.

    If file exists, appends a number: _1, _2, etc.

    Args:
        directory: Directory where file will be saved
        base_name: Base name for file
        extension: File extension

    Returns:
        Path object with unique filename
    """
    safe_name = sanitize_filename(base_name)
    timestamp = datetime.now().strftime("%Y%m%d_%H%M%S")

    # Try without counter first
    filename = f"{safe_name}_{timestamp}.{extension}"
    path = directory / filename

    if not path.exists():
        return path

    # Add counter if file exists
    counter = 1
    while True:
        filename = f"{safe_name}_{timestamp}_{counter}.{extension}"
        path = directory / filename
        if not path.exists():
            return path
        counter += 1


# =============================================================================
# IMAGE SAVE/LOAD
# =============================================================================

def ensure_pil_image(obj: Union[Image.Image, str, Path], context: str = "") -> Image.Image:
    """
    Ensure the provided object is a PIL Image.

    Accepts a PIL Image directly, or a string/Path pointing to an image file.

    Args:
        obj: PIL Image, file path string, or Path
        context: Optional context string for clearer error messages

    Returns:
        PIL Image object

    Raises:
        TypeError: If the object cannot be converted to an Image
        FileNotFoundError: If a provided path does not exist
        IOError: If the path cannot be opened as an image
    """
    if isinstance(obj, Image.Image):
        return obj

    # Handle path-like inputs
    if isinstance(obj, (str, Path)):
        p = Path(obj)
        if not p.exists():
            raise FileNotFoundError(f"Image path not found: {p} {('['+context+']') if context else ''}")
        try:
            image = Image.open(p)
            image.load()  # Validate/load into memory
            return image
        except Exception as e:
            raise IOError(f"Cannot open image at {p}: {e} {('['+context+']') if context else ''}")

    raise TypeError(
        f"Expected PIL Image or path-like, got {type(obj).__name__} {('['+context+']') if context else ''}"
    )

def save_image(
    image: Image.Image,
    directory: Path,
    base_name: str,
    metadata: Optional[Dict[str, Any]] = None
) -> Tuple[Path, Optional[Path]]:
    """
    Save an image and optionally its metadata.

    Args:
        image: PIL Image to save
        directory: Directory to save in
        base_name: Base name for files
        metadata: Optional metadata dictionary to save as JSON

    Returns:
        Tuple of (image_path, metadata_path)
        metadata_path is None if metadata not provided
    """
    # Ensure directory exists
    directory.mkdir(parents=True, exist_ok=True)

    # Generate unique filename
    image_path = get_unique_filename(directory, base_name, "png")

    # Save image (uncompressed PNG for maximum quality)
    try:
        # Normalize/validate input to avoid 'str' object errors
        image = ensure_pil_image(image, context="save_image")
        image.save(image_path, format="PNG", compress_level=0)
        logger.info(f"Saved image: {image_path}")
    except Exception as e:
        logger.error(f"Failed to save image (type={type(image).__name__}): {e}")
        raise

    # Save metadata if provided
    metadata_path = None
    if metadata is not None:
        metadata_path = image_path.with_suffix(".json")
        try:
            save_metadata(metadata_path, metadata)
            logger.info(f"Saved metadata: {metadata_path}")
        except Exception as e:
            logger.error(f"Failed to save metadata: {e}")
            # Don't raise - image is saved, metadata is optional

    return image_path, metadata_path


def load_image(file_path: Path) -> Image.Image:
    """
    Load an image from disk.

    Args:
        file_path: Path to image file

    Returns:
        PIL Image object

    Raises:
        FileNotFoundError: If file doesn't exist
        IOError: If file can't be read as image
    """
    if not file_path.exists():
        raise FileNotFoundError(f"Image not found: {file_path}")

    try:
        image = Image.open(file_path)
        logger.debug(f"Loaded image: {file_path}")
        return image
    except Exception as e:
        logger.error(f"Failed to load image {file_path}: {e}")
        raise IOError(f"Cannot read image: {e}")


# =============================================================================
# METADATA MANAGEMENT
# =============================================================================

def save_metadata(file_path: Path, metadata: Dict[str, Any]):
    """
    Save metadata dictionary as JSON.

    Args:
        file_path: Path for JSON file
        metadata: Dictionary to save

    Raises:
        IOError: If write fails
    """
    try:
        with open(file_path, 'w', encoding='utf-8') as f:
            json.dump(metadata, f, indent=2, ensure_ascii=False)
    except Exception as e:
        logger.error(f"Failed to save metadata to {file_path}: {e}")
        raise IOError(f"Cannot write metadata: {e}")


def load_metadata(file_path: Path) -> Dict[str, Any]:
    """
    Load metadata from JSON file.

    Args:
        file_path: Path to JSON file

    Returns:
        Metadata dictionary

    Raises:
        FileNotFoundError: If file doesn't exist
        json.JSONDecodeError: If file is not valid JSON
    """
    if not file_path.exists():
        raise FileNotFoundError(f"Metadata file not found: {file_path}")

    try:
        with open(file_path, 'r', encoding='utf-8') as f:
            metadata = json.load(f)
        logger.debug(f"Loaded metadata: {file_path}")
        return metadata
    except json.JSONDecodeError as e:
        logger.error(f"Invalid JSON in {file_path}: {e}")
        raise
    except Exception as e:
        logger.error(f"Failed to load metadata from {file_path}: {e}")
        raise IOError(f"Cannot read metadata: {e}")


def create_generation_metadata(
    prompt: str,
    backend: str,
    aspect_ratio: str,
    temperature: float,
    input_images: Optional[list] = None,
    generation_time: Optional[float] = None,
    **kwargs
) -> Dict[str, Any]:
    """
    Create a standard metadata dictionary for a generation.

    Args:
        prompt: Generation prompt
        backend: Backend used
        aspect_ratio: Aspect ratio used
        temperature: Temperature used
        input_images: Optional list of input image paths
        generation_time: Optional time taken (seconds)
        **kwargs: Additional custom fields

    Returns:
        Metadata dictionary
    """
    metadata = {
        "timestamp": datetime.now().isoformat(),
        "prompt": prompt,
        "backend": backend,
        "aspect_ratio": aspect_ratio,
        "temperature": temperature,
        "version": "2.0.0-streamlit"
    }

    if input_images:
        metadata["input_images"] = input_images

    if generation_time is not None:
        metadata["generation_time_seconds"] = round(generation_time, 2)

    # Add any custom fields
    metadata.update(kwargs)

    return metadata


# =============================================================================
# IMAGE HASHING (for metadata)
# =============================================================================

def compute_image_hash(image: Image.Image) -> str:
    """
    Compute SHA-256 hash of image data.

    Useful for detecting if input images have changed.

    Args:
        image: PIL Image

    Returns:
        Hex string of SHA-256 hash
    """
    # Convert to bytes
    img_bytes = image.tobytes()

    # Compute hash
    hash_obj = hashlib.sha256(img_bytes)
    return hash_obj.hexdigest()


# =============================================================================
# DIRECTORY UTILITIES
# =============================================================================

def ensure_directory_exists(directory: Path):
    """
    Ensure a single directory exists.

    Creates the directory (and any parent directories) if it doesn't exist.

    Args:
        directory: Path to directory to ensure exists
    """
    directory.mkdir(parents=True, exist_ok=True)
    logger.debug(f"Ensured directory exists: {directory}")


def ensure_output_directories():
    """
    Ensure all output directories exist.

    Creates directories defined in Settings if they don't exist.
    """
    directories = [
        Settings.OUTPUT_DIR,
        Settings.CHARACTER_SHEETS_DIR,
        Settings.WARDROBE_CHANGES_DIR,
        Settings.COMPOSITIONS_DIR,
        Settings.STANDARD_DIR
    ]

    for directory in directories:
        directory.mkdir(parents=True, exist_ok=True)
        logger.debug(f"Ensured directory exists: {directory}")


def get_output_directory_for_type(generation_type: str) -> Path:
    """
    Get the appropriate output directory for a generation type.

    Args:
        generation_type: Type of generation
            ("character_sheet", "wardrobe", "composition", "standard")

    Returns:
        Path to output directory

    Raises:
        ValueError: If generation_type is unknown
    """
    mapping = {
        "character_sheet": Settings.CHARACTER_SHEETS_DIR,
        "wardrobe": Settings.WARDROBE_CHANGES_DIR,
        "composition": Settings.COMPOSITIONS_DIR,
        "standard": Settings.STANDARD_DIR
    }

    if generation_type not in mapping:
        raise ValueError(f"Unknown generation type: {generation_type}")

    return mapping[generation_type]


def list_recent_generations(
    generation_type: str,
    count: int = 10
) -> list:
    """
    List recent generation files in a directory.

    Args:
        generation_type: Type of generation
        count: Number of recent files to return

    Returns:
        List of (image_path, metadata_path) tuples, newest first
    """
    directory = get_output_directory_for_type(generation_type)

    # Get all PNG files
    png_files = sorted(
        directory.glob("*.png"),
        key=lambda p: p.stat().st_mtime,
        reverse=True
    )

    # Limit to count
    png_files = png_files[:count]

    # Pair with metadata files
    results = []
    for png_path in png_files:
        json_path = png_path.with_suffix(".json")
        results.append((png_path, json_path if json_path.exists() else None))

    return results