"""YouTube RSS feed parser module.

This module handles fetching and parsing YouTube channel RSS feeds,
with filtering capabilities to exclude unwanted content like Shorts.
"""

from datetime import datetime
import feedparser
from typing import Dict, List, Optional
import re

from sqlalchemy.orm import Session
from sqlalchemy.exc import IntegrityError

from models import Channel, VideoEntry


class FeedEntry:
    """Represents a single entry in a YouTube RSS feed."""

    def __init__(self, title: str, video_url: str, video_id: str,
                 published_at: datetime, thumbnail_url: Optional[str] = None,
                 description: Optional[str] = None):
        self.title = title
        self.video_url = video_url
        self.video_id = video_id
        self.published_at = published_at
        self.thumbnail_url = thumbnail_url
        self.description = description

    def to_dict(self) -> Dict:
        """Convert entry to dictionary."""
        return {
            "title": self.title,
            "video_url": self.video_url,
            "video_id": self.video_id,
            "published_at": self.published_at.isoformat(),
            "thumbnail_url": self.thumbnail_url,
            "description": self.description
        }


class YouTubeFeedParser:
    """Parser for YouTube channel RSS feeds."""

    BASE_URL = "https://www.youtube.com/feeds/videos.xml"

    def __init__(self, channel_id: str):
        """Initialize parser with a YouTube channel ID.

        Args:
            channel_id: The YouTube channel ID to fetch feeds from
        """
        self.channel_id = channel_id
        self.url = f"{self.BASE_URL}?channel_id={channel_id}"

    def fetch_feed(self, filter_shorts: bool = True) -> Optional[Dict]:
        """Fetch and parse the RSS feed.

        Args:
            filter_shorts: If True, exclude YouTube Shorts from results

        Returns:
            Dictionary containing feed metadata and entries, or None if fetch fails
        """
        feed = feedparser.parse(self.url)

        if feed.status != 200:
            return None

        entries = []
        for entry in feed.entries:
            if filter_shorts and "shorts" in entry.link.lower():
                continue

            # Extract video ID from URL
            video_id = self._extract_video_id(entry.link)
            if not video_id:
                continue

            # Get thumbnail URL (YouTube provides this in media:group)
            thumbnail_url = None
            if hasattr(entry, 'media_thumbnail') and entry.media_thumbnail:
                thumbnail_url = entry.media_thumbnail[0]['url']

            # Get description
            description = None
            if hasattr(entry, 'summary'):
                description = entry.summary

            # Parse published date
            published_at = datetime(*entry.published_parsed[:6])

            entries.append(FeedEntry(
                title=entry.title,
                video_url=entry.link,
                video_id=video_id,
                published_at=published_at,
                thumbnail_url=thumbnail_url,
                description=description
            ))

        return {
            "feed_title": feed.feed.title,
            "feed_link": feed.feed.link,
            "rss_url": self.url,
            "entries": [entry.to_dict() for entry in entries]
        }

    @staticmethod
    def _extract_video_id(url: str) -> Optional[str]:
        """Extract video ID from YouTube URL.

        Args:
            url: YouTube video URL

        Returns:
            Video ID or None if not found
        """
        # Match patterns like: youtube.com/watch?v=VIDEO_ID
        match = re.search(r'[?&]v=([a-zA-Z0-9_-]{11})', url)
        if match:
            return match.group(1)

        # Match patterns like: youtu.be/VIDEO_ID
        match = re.search(r'youtu\.be/([a-zA-Z0-9_-]{11})', url)
        if match:
            return match.group(1)

        return None

    def save_to_db(self, db_session: Session, feed_data: Dict, user_id: int) -> Channel:
        """Save feed data to the database.

        Args:
            db_session: SQLAlchemy database session
            feed_data: Dictionary containing feed metadata and entries (from fetch_feed)
            user_id: ID of the user subscribing to this channel

        Returns:
            The Channel model instance

        This method uses upsert logic:
        - Updates existing channel if it exists for this user
        - Creates new channel if it doesn't exist
        - Only inserts new video entries (ignores duplicates based on video_id and channel_id)
        """
        # Get or create channel for this user
        channel = db_session.query(Channel).filter_by(
            user_id=user_id,
            channel_id=self.channel_id
        ).first()

        if channel:
            # Update existing channel
            channel.title = feed_data["feed_title"]
            channel.link = feed_data["feed_link"]
            channel.rss_url = feed_data["rss_url"]
            channel.last_fetched_at = datetime.utcnow()
        else:
            # Create new channel
            channel = Channel(
                user_id=user_id,
                channel_id=self.channel_id,
                title=feed_data["feed_title"],
                link=feed_data["feed_link"],
                rss_url=feed_data["rss_url"],
                last_fetched_at=datetime.utcnow()
            )
            db_session.add(channel)
            db_session.flush()  # Get the channel ID

        # Add video entries (ignore duplicates)
        for entry_data in feed_data["entries"]:
            # Check if video already exists for this channel
            existing = db_session.query(VideoEntry).filter_by(
                channel_id=channel.id,
                video_id=entry_data["video_id"]
            ).first()

            if not existing:
                # Parse published_at if it's a string
                published_at = entry_data["published_at"]
                if isinstance(published_at, str):
                    published_at = datetime.fromisoformat(published_at.replace('Z', '+00:00'))

                video = VideoEntry(
                    channel_id=channel.id,
                    video_id=entry_data["video_id"],
                    title=entry_data["title"],
                    video_url=entry_data["video_url"],
                    thumbnail_url=entry_data.get("thumbnail_url"),
                    description=entry_data.get("description"),
                    published_at=published_at,
                    created_at=datetime.utcnow()
                )
                db_session.add(video)

        db_session.commit()
        return channel