import hashlib
import logging
import re
from typing import Optional
from django.core.cache import cache

logger = logging.getLogger(__name__)

# Cache duration for YouTube stream URLs (3 hours = 10,800 seconds)
YOUTUBE_STREAM_CACHE_TTL = 3 * 3600


def normalize_youtube_url(url: str) -> str:
    """
    Extract YouTube 11-character video ID and return clean canonical URL.
    Strips tracking parameters (like ?si=...) and converts short/embed links to standard watch URL.
    """
    if not url:
        return url
    
    match = re.search(r'(?:v=|\/|embed\/|v\/|^)([0-9A-Za-z_-]{11})(?:[\?&/]|$)', url)
    if match:
        video_id = match.group(1)
        return f"https://www.youtube.com/watch?v={video_id}"
    return url


def _get_cache_key(youtube_url: str) -> str:
    url_hash = hashlib.md5(youtube_url.strip().encode('utf-8')).hexdigest()
    return f"yt_stream_url_{url_hash}"


def get_youtube_stream_url(youtube_url: str) -> Optional[str]:
    """
    Extract direct playable stream URL from a YouTube video URL using yt-dlp.
    Caches the extracted URL in Django cache for 3 hours to minimize calls to YouTube.
    
    Returns direct stream URL string if successful, or None if extraction fails.
    """
    if not youtube_url or not isinstance(youtube_url, str):
        return None

    youtube_url = youtube_url.strip()
    if not youtube_url:
        return None

    cache_key = _get_cache_key(youtube_url)
    cached_url = cache.get(cache_key)
    if cached_url:
        return cached_url

    clean_url = normalize_youtube_url(youtube_url)

    try:
        import yt_dlp

        ydl_opts = {
            'format': 'best[ext=mp4]/bestvideo[ext=mp4]+bestaudio[ext=m4a]/best',
            'quiet': True,
            'no_warnings': True,
            'skip_download': True,
            'nocheckcertificate': True,
            'extractor_args': {
                'youtube': {
                    'player_client': ['android', 'ios', 'web', 'mweb'],
                }
            }
        }

        with yt_dlp.YoutubeDL(ydl_opts) as ydl:
            info = ydl.extract_info(clean_url, download=False)
            if not info:
                return None

            if 'entries' in info:
                info = info['entries'][0]

            stream_url = info.get('url')
            if stream_url:
                cache.set(cache_key, stream_url, YOUTUBE_STREAM_CACHE_TTL)
                return stream_url
    except Exception as e:
        logger.error(f"Failed to extract YouTube stream URL for '{youtube_url}': {e}")

    return None


def clear_youtube_stream_cache(youtube_url: str) -> None:
    """
    Clear cached stream URL for a given YouTube URL.
    """
    if youtube_url:
        cache_key = _get_cache_key(youtube_url)
        cache.delete(cache_key)