"""
Image and video processing utilities for thumbnail generation
"""
import os
import subprocess
from PIL import Image
from django.conf import settings


def create_thumbnail(image_path, size=(300, 300), quality=85, format='WEBP'):
    """
    Create a thumbnail for an uploaded image
    
    Args:
        image_path: Absolute path to original image
        size: Tuple of (width, height) for thumbnail max dimensions
        quality: Image quality (1-95 for JPEG, 1-100 for WebP)
        format: Output format ('WEBP', 'JPEG', 'PNG')
    
    Returns:
        Absolute path to thumbnail file
    
    Raises:
        ValueError: If image cannot be processed
        FileNotFoundError: If original image doesn't exist
    """
    if not os.path.exists(image_path):
        raise FileNotFoundError(f"Original image not found: {image_path}")
    
    try:
        # Open and process image
        img = Image.open(image_path)
        
        # Convert RGBA to RGB if needed (for JPEG/WebP compatibility)
        if img.mode in ('RGBA', 'LA', 'P'):
            background = Image.new('RGB', img.size, (255, 255, 255))
            if img.mode == 'RGBA':
                background.paste(img, mask=img.split()[-1])
            else:
                background.paste(img)
            img = background
        
        # Create thumbnail maintaining aspect ratio
        img.thumbnail(size, Image.Resampling.LANCZOS)
        
        # Generate thumbnail path
        base, ext = os.path.splitext(image_path)
        
        # Choose extension based on format
        if format.upper() == 'WEBP':
            thumb_path = f"{base}_thumb.webp"
            img.save(thumb_path, 'WEBP', quality=quality, method=6)
        elif format.upper() == 'JPEG':
            thumb_path = f"{base}_thumb.jpg"
            img.save(thumb_path, 'JPEG', quality=quality, optimize=True)
        elif format.upper() == 'PNG':
            thumb_path = f"{base}_thumb.png"
            img.save(thumb_path, 'PNG', optimize=True)
        else:
            # Default to WebP
            thumb_path = f"{base}_thumb.webp"
            img.save(thumb_path, 'WEBP', quality=quality, method=6)
        
        return thumb_path
        
    except Exception as e:
        raise ValueError(f"Failed to create thumbnail: {str(e)}")


def get_image_dimensions(image_path):
    """
    Get dimensions of an image
    
    Args:
        image_path: Path to image file
    
    Returns:
        Tuple of (width, height) or None if error
    """
    try:
        with Image.open(image_path) as img:
            return img.size
    except Exception:
        return None


def is_image_file(file_path):
    """
    Check if a file is an image based on extension and content
    
    Args:
        file_path: Path to file
    
    Returns:
        Boolean indicating if file is an image
    """
    image_extensions = {'.jpg', '.jpeg', '.png', '.gif', '.webp', '.bmp', '.tiff'}
    ext = os.path.splitext(file_path)[1].lower()
    
    if ext not in image_extensions:
        return False
    
    try:
        with Image.open(file_path) as img:
            img.verify()
        return True
    except Exception:
        return False


def is_video_file(file_path):
    """
    Check if a file is a video based on extension
    
    Args:
        file_path: Path to file
    
    Returns:
        Boolean indicating if file is a video
    """
    video_extensions = {'.mp4', '.avi', '.mov', '.mkv', '.flv', '.wmv', '.webm', '.m4v'}
    ext = os.path.splitext(file_path)[1].lower()
    return ext in video_extensions


def extract_video_thumbnail(video_path, time_offset='00:00:01', size=(300, 300), quality=85):
    """
    Extract a frame from video as thumbnail using FFmpeg
    
    Args:
        video_path: Absolute path to video file
        time_offset: Time position to extract frame (default: 1 second)
        size: Tuple of (width, height) for thumbnail max dimensions
        quality: JPEG quality (1-31 for FFmpeg, lower is better, we convert to FFmpeg scale)
    
    Returns:
        Absolute path to thumbnail file or None if failed
    
    Raises:
        FileNotFoundError: If video file doesn't exist
        ValueError: If FFmpeg is not installed or extraction fails
    """
    if not os.path.exists(video_path):
        raise FileNotFoundError(f"Video file not found: {video_path}")
    
    # Check if FFmpeg is available
    try:
        subprocess.run(['ffmpeg', '-version'], 
                      stdout=subprocess.PIPE, 
                      stderr=subprocess.PIPE, 
                      timeout=5)
    except (subprocess.TimeoutExpired, FileNotFoundError):
        raise ValueError("FFmpeg is not installed or not available in PATH")
    
    try:
        # Generate output path
        base, ext = os.path.splitext(video_path)
        output_path = f"{base}_thumb.jpg"
        
        # Convert quality (85 -> 2 in FFmpeg scale)
        # FFmpeg uses 1-31 where lower is better, opposite of our 0-100 scale
        ffmpeg_quality = max(1, min(31, int((100 - quality) * 31 / 100)))
        
        # FFmpeg command to extract frame
        cmd = [
            'ffmpeg',
            '-ss', time_offset,              # Seek to time position (before input for speed)
            '-i', video_path,                # Input video
            '-vframes', '1',                 # Extract 1 frame
            '-vf', f'scale={size[0]}:-1',   # Scale to width, maintain aspect ratio
            '-q:v', str(ffmpeg_quality),     # Quality
            '-y',                            # Overwrite output
            output_path
        ]
        
        result = subprocess.run(
            cmd,
            stdout=subprocess.PIPE,
            stderr=subprocess.PIPE,
            timeout=15  # 15 second timeout
        )
        
        if result.returncode == 0 and os.path.exists(output_path):
            return output_path
        else:
            error_msg = result.stderr.decode('utf-8', errors='ignore')
            raise ValueError(f"FFmpeg extraction failed: {error_msg[:200]}")
        
    except subprocess.TimeoutExpired:
        raise ValueError("Video thumbnail extraction timed out (>15s)")
    except Exception as e:
        raise ValueError(f"Failed to extract video thumbnail: {str(e)}")