"""Image storage utilities for managing image files and directory structure."""
import re
import uuid
from pathlib import Path
from typing import List, Optional
from urllib.parse import quote

# Root directory for all images
IMAGES_ROOT = Path("images")


def sanitize_filename(filename: str) -> str:
    """
    Sanitize a filename by removing unsafe characters and limiting length.

    Args:
        filename: The original filename to sanitize

    Returns:
        A sanitized filename safe for filesystem storage

    Raises:
        ValueError: If filename is empty or becomes empty after sanitization
    """
    if not filename or not filename.strip():
        raise ValueError("Filename cannot be empty")

    # Remove path traversal attempts (/, \, ..)
    sanitized = re.sub(r'[/\\]', '', filename)
    sanitized = sanitized.replace('..', '')

    # Remove null bytes and control characters
    sanitized = re.sub(r'[\x00-\x1f\x7f]', '', sanitized)

    # Remove other unsafe characters but keep dots for extension, dashes, underscores
    # Allow: alphanumeric, dots, dashes, underscores
    sanitized = re.sub(r'[^a-zA-Z0-9._\-]', '', sanitized)

    # Convert to lowercase
    sanitized = sanitized.lower()

    # Check if filename is now empty or only dots
    if not sanitized or re.match(r'^\.+$', sanitized):
        raise ValueError("Filename cannot be empty after sanitization")

    # Limit to 255 characters (filesystem limit)
    if len(sanitized) > 255:
        # Try to preserve extension if present
        if '.' in sanitized:
            parts = sanitized.rsplit('.', 1)
            name_part = parts[0][:251]  # Leave room for .ext
            ext_part = parts[1]
            sanitized = f"{name_part}.{ext_part}"
        else:
            sanitized = sanitized[:255]

    return sanitized


def get_unique_filename(
    item_name: str,
    category: str,
    existing_files: List[str],
    variant: str = "original"
) -> str:
    """
    Generate a unique filename with collision handling.

    If a file with the sanitized name already exists, appends a UUID suffix.
    Format: {name}_{uuid_first_8}_{variant}.jpg

    Args:
        item_name: The item/product name
        category: The category name
        existing_files: List of existing filenames in the category directory
        variant: The image variant (original, thumb, etc.)

    Returns:
        A unique filename string
    """
    # Sanitize the item name
    sanitized_name = sanitize_filename(item_name)

    # Build the base filename without UUID
    base_filename = f"{sanitized_name}_{variant}.jpg"

    # Check for collision (case-insensitive)
    existing_lower = [f.lower() for f in existing_files]

    if base_filename.lower() not in existing_lower:
        # No collision
        return base_filename

    # Collision detected - add UUID suffix
    uuid_suffix = str(uuid.uuid4()).replace('-', '')[:8]
    unique_filename = f"{sanitized_name}_{uuid_suffix}_{variant}.jpg"

    return unique_filename


def ensure_image_directories() -> None:
    """
    Ensure image storage directories exist on startup.

    Creates /images/ root and category-specific subdirectories.
    """
    # Create root images directory
    IMAGES_ROOT.mkdir(parents=True, exist_ok=True)

    # Create category subdirectories
    try:
        categories = get_categories()
        for category in categories:
            cat_dir = IMAGES_ROOT / category
            cat_dir.mkdir(parents=True, exist_ok=True)
    except Exception:
        # If get_categories fails (e.g., DB not ready), just create root
        # Categories will be created on-demand in save_image
        pass


def save_image(
    file_bytes: bytes,
    category: str,
    filename_base: str,
    variant: str = "original"
) -> str:
    """
    Save an image file to the storage directory.

    Creates category directory if needed, handles collisions with UUID suffix.

    Args:
        file_bytes: The image file content as bytes
        category: The category name (e.g., "networking")
        filename_base: The base filename without extension (e.g., "SFP-LR")
        variant: The image variant (original, thumb, etc.)

    Returns:
        The relative path to the saved image (e.g., "/images/networking/sfp-lr_original.jpg")

    Raises:
        ValueError: If category or filename_base is invalid
    """
    if not category or not category.strip():
        raise ValueError("Category cannot be empty")

    if not filename_base or not filename_base.strip():
        raise ValueError("Filename base cannot be empty")

    # Sanitize category
    sanitized_category = sanitize_filename(category)

    # Create category directory
    cat_dir = IMAGES_ROOT / sanitized_category
    cat_dir.mkdir(parents=True, exist_ok=True)

    # Get existing files in the category
    existing_files = [f.name for f in cat_dir.iterdir() if f.is_file()]

    # Get unique filename
    unique_filename = get_unique_filename(filename_base, sanitized_category, existing_files, variant)

    # Write file
    file_path = cat_dir / unique_filename
    file_path.write_bytes(file_bytes)

    # Return relative path with forward slashes
    relative_path = f"/images/{sanitized_category}/{unique_filename}"
    return relative_path


def get_categories() -> List[str]:
    """
    Get list of categories from the database.

    This is a stub that will be called from ensure_image_directories.
    In production, this should query the database for categories.

    Returns:
        List of category names
    """
    # This will be implemented to query the database
    # For now, return empty list (handled in ensure_image_directories)
    return []