import yt_dlp
import os
import sys
import tempfile

def download_video(url, output_dir=None):
    """Downloads a video from the given URL to a temporary location or specified output directory.

    Args:
        url (str): The URL of the video to download.
        output_dir (str, optional): Directory to save the downloaded file. If None, uses a temporary directory.

    Returns:
        str: The absolute path to the downloaded video file, or None if download fails.
    """
    if output_dir and not os.path.isdir(output_dir):
        print(f"Error: Output directory '{output_dir}' for download does not exist or is not a directory.", file=sys.stderr)
        return None

    temp_dir = None
    if not output_dir:
        temp_dir = tempfile.TemporaryDirectory() # Create a temporary directory
        output_dir = temp_dir.name

    ydl_opts = {
        'format': 'bestvideo[ext!=webm]+bestaudio[ext!=webm]/best[ext!=webm]', # Prioritize non-webm formats
        'outtmpl': os.path.join(output_dir, '%(title)s.%(ext)s'),
        'noplaylist': True, # Only download single video, not entire playlist
                'progress_hooks': [lambda d: sys.stdout.write(f"Downloading: {d['filename']} - {d['status']}" + '\r') if d['status'] == 'downloading' else None],
        'postprocessors': [{
            'key': 'FFmpegVideoConvertor',
            'preferedformat': 'mp4',
        }],
        'quiet': True, # Suppress yt-dlp output unless error
        'no_warnings': True,
    }

    downloaded_file_path = None
    try:
        with yt_dlp.YoutubeDL(ydl_opts) as ydl:
            info_dict = ydl.extract_info(url, download=True)
            downloaded_file_path = ydl.prepare_filename(info_dict)
            # yt-dlp might return a path with a different extension if format conversion happened
            # We need to find the actual downloaded file
            base, ext = os.path.splitext(downloaded_file_path)
            if not os.path.exists(downloaded_file_path):
                # Try common extensions if the exact path isn't found
                for common_ext in ['.mp4', '.mkv', '.webm', '.flv']:
                    if os.path.exists(base + common_ext):
                        downloaded_file_path = base + common_ext
                        break
            
            if not os.path.exists(downloaded_file_path):
                print(f"Error: Downloaded file not found at expected path: {downloaded_file_path}", file=sys.stderr)
                return None

    except yt_dlp.utils.DownloadError as e:
        print(f"Error downloading video: {e}", file=sys.stderr)
        return None
    except Exception as e:
        print(f"An unexpected error occurred during download: {e}", file=sys.stderr)
        return None
    finally:
        if temp_dir: # Clean up temporary directory if it was created
            # The file might have been moved by yt-dlp, so we only clean up if it's empty
            if not os.listdir(temp_dir.name):
                temp_dir.cleanup()
            else:
                print(f"Warning: Temporary directory {temp_dir.name} not empty, not cleaning up automatically.", file=sys.stderr)

    return downloaded_file_path