"""Flask web application for YouTube RSS feed parsing."""

import os
from flask import Flask, render_template, request, jsonify, redirect, url_for, flash, send_file
from flask_login import LoginManager, login_user, logout_user, login_required, current_user
from feed_parser import YouTubeFeedParser
from database import init_db, get_db_session
from models import Channel, VideoEntry, DownloadStatus, User
from download_service import download_video, download_videos_batch
from sqlalchemy import desc


app = Flask(__name__)
app.secret_key = os.getenv("SECRET_KEY", "dev-secret-key-change-in-production")

# Configure Flask-Login
login_manager = LoginManager()
login_manager.init_app(app)
login_manager.login_view = "login"
login_manager.login_message = "Please log in to access this page."
login_manager.login_message_category = "info"


@login_manager.user_loader
def load_user(user_id):
    """Load user by ID for Flask-Login."""
    with get_db_session() as session:
        user = session.query(User).get(int(user_id))
        if user:
            # Expire the user from this session so it can be used in request context
            session.expunge(user)
        return user

# Default channel ID for demonstration
DEFAULT_CHANNEL_ID = "UCtTWOND3uyl4tVc_FarDmpw"


# Initialize database on app startup
with app.app_context():
    init_db()


# ============================================================================
# Authentication Routes
# ============================================================================

@app.route("/register", methods=["GET", "POST"])
def register():
    """User registration page."""
    if current_user.is_authenticated:
        return redirect(url_for("index"))

    if request.method == "POST":
        username = request.form.get("username")
        email = request.form.get("email")
        password = request.form.get("password")
        confirm_password = request.form.get("confirm_password")

        # Validation
        if not username or not email or not password:
            flash("All fields are required", "error")
            return render_template("register.html")

        if password != confirm_password:
            flash("Passwords do not match", "error")
            return render_template("register.html")

        if len(password) < 8:
            flash("Password must be at least 8 characters long", "error")
            return render_template("register.html")

        try:
            with get_db_session() as session:
                # Check if username or email already exists
                existing_user = session.query(User).filter(
                    (User.username == username) | (User.email == email)
                ).first()

                if existing_user:
                    if existing_user.username == username:
                        flash("Username already taken", "error")
                    else:
                        flash("Email already registered", "error")
                    return render_template("register.html")

                # Create new user
                user = User(username=username, email=email)
                user.set_password(password)
                session.add(user)
                session.commit()

                flash("Registration successful! Please log in.", "success")
                return redirect(url_for("login"))

        except Exception as e:
            flash(f"Registration failed: {str(e)}", "error")
            return render_template("register.html")

    return render_template("register.html")


@app.route("/login", methods=["GET", "POST"])
def login():
    """User login page."""
    if current_user.is_authenticated:
        return redirect(url_for("index"))

    if request.method == "POST":
        username = request.form.get("username")
        password = request.form.get("password")
        remember = request.form.get("remember") == "on"

        if not username or not password:
            flash("Please enter both username and password", "error")
            return render_template("login.html")

        try:
            with get_db_session() as session:
                user = session.query(User).filter_by(username=username).first()

                if user and user.check_password(password):
                    # Expunge user from session before login
                    session.expunge(user)
                    login_user(user, remember=remember)
                    flash(f"Welcome back, {user.username}!", "success")

                    # Redirect to next page if specified
                    next_page = request.args.get("next")
                    return redirect(next_page) if next_page else redirect(url_for("index"))
                else:
                    flash("Invalid username or password", "error")

        except Exception as e:
            flash(f"Login failed: {str(e)}", "error")

    return render_template("login.html")


@app.route("/logout")
@login_required
def logout():
    """Log out the current user."""
    logout_user()
    flash("You have been logged out", "info")
    return redirect(url_for("login"))


# ============================================================================
# Frontend Routes
# ============================================================================

@app.route("/", methods=["GET"])
@login_required
def index():
    """Render the dashboard with all videos sorted by date."""
    try:
        with get_db_session() as session:
            # Query videos for current user's channels, sorted by published date (newest first)
            videos = session.query(VideoEntry).join(Channel).filter(
                Channel.user_id == current_user.id
            ).order_by(desc(VideoEntry.published_at)).all()

            return render_template("dashboard.html", videos=videos)
    except Exception as e:
        flash(f"Error loading videos: {str(e)}", "error")
        return render_template("dashboard.html", videos=[])


@app.route("/channels", methods=["GET"])
@login_required
def channels_page():
    """Render the channels management page."""
    try:
        with get_db_session() as session:
            channels = session.query(Channel).filter_by(
                user_id=current_user.id
            ).order_by(desc(Channel.last_fetched_at)).all()
            return render_template("channels.html", channels=channels)
    except Exception as e:
        flash(f"Error loading channels: {str(e)}", "error")
        return render_template("channels.html", channels=[])


@app.route("/downloads", methods=["GET"])
@login_required
def downloads_page():
    """Render the downloads page showing all download jobs."""
    try:
        with get_db_session() as session:
            # Get all videos for current user's channels with download activity
            # Order by: downloading first, then pending, then failed, then completed
            # Within each status, order by download_started_at or created_at
            videos = session.query(VideoEntry).join(Channel).filter(
                Channel.user_id == current_user.id
            ).order_by(
                # Custom sort: downloading=0, pending=1, failed=2, completed=3
                desc(VideoEntry.download_status == DownloadStatus.DOWNLOADING),
                desc(VideoEntry.download_status == DownloadStatus.PENDING),
                desc(VideoEntry.download_status == DownloadStatus.FAILED),
                desc(VideoEntry.download_started_at),
                desc(VideoEntry.created_at)
            ).all()

            return render_template("downloads.html", videos=videos)
    except Exception as e:
        flash(f"Error loading downloads: {str(e)}", "error")
        return render_template("downloads.html", videos=[])


@app.route("/add-channel", methods=["GET", "POST"])
@login_required
def add_channel_page():
    """Render the add channel page and handle channel subscription."""
    if request.method == "GET":
        return render_template("add_channel.html")

    # Handle POST - add new channel
    channel_id = request.form.get("channel_id")
    if not channel_id:
        flash("Channel ID is required", "error")
        return redirect(url_for("add_channel_page"))

    # Validate channel ID format (should start with UC or UU)
    channel_id = channel_id.strip()
    if not channel_id.startswith(("UC", "UU")):
        flash("Invalid channel ID format. Channel IDs should start with UC or UU.", "error")
        return redirect(url_for("add_channel_page"))

    try:
        # Fetch feed using parser
        parser = YouTubeFeedParser(channel_id)
        result = parser.fetch_feed()

        if result is None:
            flash("Failed to fetch feed from YouTube. Please check the channel ID.", "error")
            return redirect(url_for("add_channel_page"))

        # Save to database with current user
        with get_db_session() as session:
            channel = parser.save_to_db(session, result, current_user.id)
            channel_title = channel.title
            video_count = len(result["entries"])

        flash(f"Successfully subscribed to {channel_title}! Added {video_count} videos.", "success")
        return redirect(url_for("channels_page"))

    except Exception as e:
        flash(f"Error subscribing to channel: {str(e)}", "error")
        return redirect(url_for("add_channel_page"))


@app.route("/watch/<int:video_id>", methods=["GET"])
@login_required
def watch_video(video_id: int):
    """Render the video watch page."""
    try:
        with get_db_session() as session:
            # Only allow user to watch videos from their own channels
            video = session.query(VideoEntry).join(Channel).filter(
                VideoEntry.id == video_id,
                Channel.user_id == current_user.id
            ).first()

            if not video:
                flash("Video not found", "error")
                return redirect(url_for("index"))

            return render_template("watch.html", video=video)
    except Exception as e:
        flash(f"Error loading video: {str(e)}", "error")
        return redirect(url_for("index"))


@app.route("/api/feed", methods=["GET"])
def get_feed():
    """API endpoint to fetch YouTube channel feed and save to database.

    Query parameters:
        channel_id: YouTube channel ID (optional, uses default if not provided)
        save: Whether to save to database (default: true)

    Returns:
        JSON response with feed data or error message
    """
    channel_id = request.args.get("channel_id", DEFAULT_CHANNEL_ID)
    save_to_db = request.args.get("save", "true").lower() == "true"

    parser = YouTubeFeedParser(channel_id)
    result = parser.fetch_feed(filter_shorts=True)

    if result is None:
        return jsonify({"error": "Failed to fetch feed"}), 500

    # Save to database if requested
    if save_to_db:
        try:
            with get_db_session() as session:
                parser.save_to_db(session, result)
        except Exception as e:
            return jsonify({"error": f"Failed to save to database: {str(e)}"}), 500

    return jsonify(result)


@app.route("/api/channels", methods=["GET"])
def get_channels():
    """API endpoint to list all tracked channels.

    Returns:
        JSON response with list of channels
    """
    try:
        with get_db_session() as session:
            channels = session.query(Channel).all()
            return jsonify({
                "channels": [
                    {
                        "id": ch.id,
                        "channel_id": ch.channel_id,
                        "title": ch.title,
                        "link": ch.link,
                        "last_fetched": ch.last_fetched.isoformat(),
                        "video_count": len(ch.videos)
                    }
                    for ch in channels
                ]
            })
    except Exception as e:
        return jsonify({"error": f"Failed to fetch channels: {str(e)}"}), 500


@app.route("/api/history/<channel_id>", methods=["GET"])
def get_history(channel_id: str):
    """API endpoint to get video history for a specific channel.

    Args:
        channel_id: YouTube channel ID

    Query parameters:
        limit: Maximum number of videos to return (default: 50)

    Returns:
        JSON response with channel info and video history
    """
    limit = request.args.get("limit", "50")
    try:
        limit = int(limit)
    except ValueError:
        limit = 50

    try:
        with get_db_session() as session:
            channel = session.query(Channel).filter_by(
                channel_id=channel_id
            ).first()

            if not channel:
                return jsonify({"error": "Channel not found"}), 404

            videos = session.query(VideoEntry).filter_by(
                channel_id=channel.id
            ).order_by(VideoEntry.created_at.desc()).limit(limit).all()

            return jsonify({
                "channel": {
                    "channel_id": channel.channel_id,
                    "title": channel.title,
                    "link": channel.link,
                    "last_fetched": channel.last_fetched.isoformat()
                },
                "videos": [video.to_dict() for video in videos],
                "total_videos": len(channel.videos)
            })
    except Exception as e:
        return jsonify({"error": f"Failed to fetch history: {str(e)}"}), 500


@app.route("/api/download/<int:video_id>", methods=["POST"])
@login_required
def trigger_download(video_id: int):
    """Trigger video download for a specific video.

    Args:
        video_id: Database ID of the VideoEntry

    Returns:
        JSON response with task information
    """
    try:
        with get_db_session() as session:
            # Only allow downloading videos from user's own channels
            video = session.query(VideoEntry).join(Channel).filter(
                VideoEntry.id == video_id,
                Channel.user_id == current_user.id
            ).first()

            if not video:
                return jsonify({"status": "error", "message": "Video not found"}), 404

            # Check if already downloaded or downloading
            if video.download_status == DownloadStatus.COMPLETED:
                return jsonify({
                    "status": "success",
                    "message": "Video already downloaded"
                })

            if video.download_status == DownloadStatus.DOWNLOADING:
                return jsonify({
                    "status": "success",
                    "message": "Video is already downloading"
                })

            # Queue download task
            task = download_video.delay(video_id)

            return jsonify({
                "status": "success",
                "video_id": video_id,
                "task_id": task.id,
                "message": "Download started"
            })
    except Exception as e:
        return jsonify({"status": "error", "message": f"Failed to queue download: {str(e)}"}), 500


@app.route("/api/download/status/<int:video_id>", methods=["GET"])
def get_download_status(video_id: int):
    """Get download status for a specific video.

    Args:
        video_id: Database ID of the VideoEntry

    Returns:
        JSON response with download status
    """
    try:
        with get_db_session() as session:
            video = session.query(VideoEntry).filter_by(id=video_id).first()
            if not video:
                return jsonify({"error": "Video not found"}), 404

            return jsonify({
                "video_id": video_id,
                "title": video.title,
                "download_status": video.download_status.value,
                "download_path": video.download_path,
                "download_started_at": video.download_started_at.isoformat() if video.download_started_at else None,
                "download_completed_at": video.download_completed_at.isoformat() if video.download_completed_at else None,
                "download_error": video.download_error,
                "file_size": video.file_size
            })
    except Exception as e:
        return jsonify({"error": f"Failed to fetch download status: {str(e)}"}), 500


@app.route("/api/download/batch", methods=["POST"])
def trigger_batch_download():
    """Trigger batch download for multiple videos.

    Query parameters:
        channel_id: Download all pending videos for this channel (optional)
        status: Filter by download status (default: pending)

    Request body (alternative to query params):
        video_ids: List of video IDs to download

    Returns:
        JSON response with batch task information
    """
    try:
        with get_db_session() as session:
            # Check if video_ids provided in request body
            data = request.get_json(silent=True)
            if data and 'video_ids' in data:
                video_ids = data['video_ids']
            else:
                # Filter by channel and/or status
                channel_id = request.args.get("channel_id")
                status_str = request.args.get("status", "pending")

                try:
                    status = DownloadStatus(status_str)
                except ValueError:
                    return jsonify({"error": f"Invalid status: {status_str}"}), 400

                query = session.query(VideoEntry).filter_by(download_status=status)

                if channel_id:
                    channel = session.query(Channel).filter_by(
                        channel_id=channel_id
                    ).first()
                    if not channel:
                        return jsonify({"error": "Channel not found"}), 404
                    query = query.filter_by(channel_id=channel.id)

                videos = query.all()
                video_ids = [v.id for v in videos]

            if not video_ids:
                return jsonify({"message": "No videos to download", "total_queued": 0})

            # Queue batch download task
            task = download_videos_batch.delay(video_ids)

            return jsonify({
                "task_id": task.id,
                "total_queued": len(video_ids),
                "video_ids": video_ids,
                "message": "Batch download queued successfully"
            })
    except Exception as e:
        return jsonify({"error": f"Failed to queue batch download: {str(e)}"}), 500


@app.route("/api/videos/refresh/<int:channel_id>", methods=["POST"])
@login_required
def refresh_channel_videos(channel_id: int):
    """Refresh videos for a specific channel by fetching latest from RSS feed.

    Args:
        channel_id: Database ID of the Channel

    Returns:
        JSON response with number of new videos found
    """
    try:
        with get_db_session() as session:
            # Only allow refresh for user's own channels
            channel = session.query(Channel).filter_by(
                id=channel_id,
                user_id=current_user.id
            ).first()

            if not channel:
                return jsonify({"status": "error", "message": "Channel not found"}), 404

            # Fetch latest feed
            parser = YouTubeFeedParser(channel.channel_id)
            result = parser.fetch_feed()

            if result is None:
                return jsonify({"status": "error", "message": "Failed to fetch feed"}), 500

            # Count existing videos before save
            existing_count = len(channel.video_entries)

            # Save to database (upsert logic will handle duplicates)
            parser.save_to_db(session, result, current_user.id)

            # Count after save
            session.refresh(channel)
            new_count = len(channel.video_entries) - existing_count

            return jsonify({
                "status": "success",
                "channel_id": channel_id,
                "new_videos": max(0, new_count),  # Ensure non-negative
                "total_videos": len(channel.video_entries),
                "message": f"Found {max(0, new_count)} new videos"
            })
    except Exception as e:
        return jsonify({"status": "error", "message": f"Failed to refresh channel: {str(e)}"}), 500


@app.route("/api/video/stream/<int:video_id>", methods=["GET"])
@login_required
def stream_video(video_id: int):
    """Stream a downloaded video file.

    Args:
        video_id: Database ID of the VideoEntry

    Query parameters:
        download: If set to 1, force download instead of streaming

    Returns:
        Video file stream or error
    """
    try:
        with get_db_session() as session:
            # Only allow streaming videos from user's own channels
            video = session.query(VideoEntry).join(Channel).filter(
                VideoEntry.id == video_id,
                Channel.user_id == current_user.id
            ).first()

            if not video:
                return jsonify({"error": "Video not found"}), 404

            if video.download_status != DownloadStatus.COMPLETED or not video.download_path:
                return jsonify({"error": "Video not downloaded yet"}), 404

            # Check if file exists
            if not os.path.exists(video.download_path):
                return jsonify({"error": "Video file not found on disk"}), 404

            # Check if download is requested
            as_attachment = request.args.get("download") == "1"

            return send_file(
                video.download_path,
                mimetype="video/mp4",
                as_attachment=as_attachment,
                download_name=f"{video.title}.mp4" if as_attachment else None
            )
    except Exception as e:
        return jsonify({"error": f"Failed to stream video: {str(e)}"}), 500


def main():
    """CLI entry point for testing feed parser."""
    parser = YouTubeFeedParser(DEFAULT_CHANNEL_ID)
    result = parser.fetch_feed()

    if result is None:
        print("Failed to retrieve RSS feed")
        return

    print(f"Feed Title: {result['feed_title']}")
    print(f"Feed Link: {result['feed_link']}")

    for entry in result['entries']:
        print(f"\nEntry Title: {entry['title']}")
        print(f"Entry Link: {entry['link']}")


if __name__ == "__main__":
    main()