import json
from typing import Optional

from fastapi import APIRouter, BackgroundTasks, Depends, HTTPException
from pydantic import BaseModel
from sqlalchemy.orm import Session
from sqlalchemy import text

from ..auth_utils import get_current_user
from ..database import get_db
from ..models import Channel, DiscoveryQueue, User, UserChannel, UserSettings
from ..services.discovery import run_full_discovery

router = APIRouter()


class PreviewVideo(BaseModel):
    thumbnail_url: str
    title: str


class DiscoveryItem(BaseModel):
    id: int
    channel_id: int
    youtube_channel_id: str
    name: str
    description: Optional[str]
    thumbnail_url: Optional[str]
    subscriber_count: Optional[int] = None
    score: float
    source: Optional[str]
    recent_video_titles: list[str] = []
    preview_videos: list[PreviewVideo] = []

    model_config = {"from_attributes": True}


@router.get("", response_model=list[DiscoveryItem])
def list_discovery(
    offset: int = 0,
    limit: int = 50,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    rows = db.execute(
        text("""
            SELECT dq.id, dq.channel_id, dq.score, dq.source, dq.preview_json,
                   c.youtube_channel_id, c.name, c.description, c.thumbnail_url, c.subscriber_count
            FROM discovery_queue dq
            JOIN channels c ON dq.channel_id = c.id
            WHERE dq.user_id = :user_id AND dq.seen = 0
              AND dq.channel_id NOT IN (
                  SELECT channel_id FROM user_channels
                  WHERE user_id = :user_id AND status IN ('followed', 'dismissed')
              )
            ORDER BY dq.score DESC
            LIMIT :limit OFFSET :offset
        """),
        {"user_id": current_user.id, "limit": limit * 3, "offset": offset},
    ).mappings().all()

    # Load negative affinity tags and use them to filter channels already in the queue
    neg_affinity = {
        r["tag"] for r in db.execute(
            text("SELECT tag FROM user_tag_affinity WHERE user_id = :user_id AND score < -2"),
            {"user_id": current_user.id},
        ).mappings().all()
    }
    if neg_affinity and rows:
        channel_ids_csv = ",".join(str(r["channel_id"]) for r in rows)
        vtag_rows = db.execute(
            text(f"SELECT channel_id, tags FROM videos WHERE channel_id IN ({channel_ids_csv}) AND tags IS NOT NULL LIMIT 1000")
        ).mappings().all()
        neg_hit: dict[int, int] = {}
        for vr in vtag_rows:
            try:
                for tag in json.loads(vr["tags"] or "[]"):
                    if isinstance(tag, str) and tag.lower().strip() in neg_affinity:
                        neg_hit[vr["channel_id"]] = neg_hit.get(vr["channel_id"], 0) + 1
            except (json.JSONDecodeError, TypeError):
                pass
        rows = [r for r in rows if neg_hit.get(r["channel_id"], 0) < 3]

    rows = rows[:limit]
    items = []
    for row in rows:
        row = dict(row)
        video_rows = db.execute(
            text("""
                SELECT title, youtube_video_id FROM videos
                WHERE channel_id = :channel_id
                ORDER BY published_at DESC
                LIMIT 3
            """),
            {"channel_id": row["channel_id"]},
        ).fetchall()
        row["recent_video_titles"] = [r[0] for r in video_rows]

        if video_rows:
            row["preview_videos"] = [
                {
                    "thumbnail_url": f"https://i.ytimg.com/vi/{r[1]}/hqdefault.jpg",
                    "title": r[0],
                }
                for r in video_rows
            ]
        else:
            try:
                row["preview_videos"] = json.loads(row.get("preview_json") or "[]")
            except (json.JSONDecodeError, TypeError):
                row["preview_videos"] = []

        items.append(DiscoveryItem(**row))
    return items


@router.post("/{channel_id}/follow", status_code=204)
def follow_discovery(
    channel_id: int,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    channel = db.query(Channel).filter(Channel.id == channel_id).first()
    if not channel:
        raise HTTPException(status_code=404, detail="Channel not found")

    uc = db.query(UserChannel).filter_by(user_id=current_user.id, channel_id=channel_id).first()
    if uc:
        uc.status = "followed"
    else:
        db.add(UserChannel(user_id=current_user.id, channel_id=channel_id, status="followed"))

    dq = db.query(DiscoveryQueue).filter_by(user_id=current_user.id, channel_id=channel_id).first()
    if dq:
        dq.seen = True
    db.commit()


@router.post("/{channel_id}/dismiss", status_code=204)
def dismiss_discovery(
    channel_id: int,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    uc = db.query(UserChannel).filter_by(user_id=current_user.id, channel_id=channel_id).first()
    if uc:
        uc.status = "dismissed"
    else:
        db.add(UserChannel(user_id=current_user.id, channel_id=channel_id, status="dismissed"))

    dq = db.query(DiscoveryQueue).filter_by(user_id=current_user.id, channel_id=channel_id).first()
    if dq:
        dq.seen = True
    db.commit()


@router.post("/refresh", status_code=202)
def refresh_discovery(
    background_tasks: BackgroundTasks,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    s = db.query(UserSettings).filter_by(user_id=current_user.id).first()
    regions_str = (s.discovery_regions if s and s.discovery_regions else "US,SE")
    regions = [r.strip().upper() for r in regions_str.split(",") if r.strip()]
    background_tasks.add_task(run_full_discovery, db, current_user.id, regions)
    from .channels import _enrich_missing_task
    background_tasks.add_task(_enrich_missing_task, 20)
    return {"detail": "Discovery refresh started"}


@router.get("/videos", response_model=list[dict])
def discovery_videos(
    offset: int = 0,
    limit: int = 50,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    """2 recent videos from every channel in the discovery queue that has indexed content.
    Ordered by channel score so the best-matched channels surface first.
    Channels fall out naturally when dismissed or followed."""
    rows = db.execute(
        text("""
            SELECT * FROM (
                SELECT v.id, v.youtube_video_id, v.title, v.thumbnail_url,
                       v.duration_seconds, v.published_at,
                       c.id AS channel_id, c.name AS channel_name,
                       c.youtube_channel_id AS channel_youtube_id,
                       dq.score,
                       ROW_NUMBER() OVER (
                           PARTITION BY c.id ORDER BY v.published_at DESC NULLS LAST
                       ) AS rn
                FROM videos v
                JOIN channels c ON v.channel_id = c.id
                JOIN discovery_queue dq ON c.id = dq.channel_id
                WHERE dq.user_id = :user_id AND dq.seen = 0
                  AND dq.channel_id NOT IN (
                      SELECT channel_id FROM user_channels
                      WHERE user_id = :user_id AND status IN ('followed', 'dismissed')
                  )
            )
            WHERE rn <= 2
            ORDER BY score DESC, rn ASC, RANDOM()
            LIMIT :limit OFFSET :offset
        """),
        {"user_id": current_user.id, "limit": limit, "offset": offset},
    ).mappings().all()
    return [dict(r) for r in rows]


@router.post("/videos/{youtube_video_id}/dismiss", status_code=204)
def dismiss_discovery_video(
    youtube_video_id: str,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    """Dismiss all discovery for the channel that owns this video."""
    from ..models import Video
    video = db.query(Video).filter_by(youtube_video_id=youtube_video_id).first()
    if not video or not video.channel_id:
        raise HTTPException(status_code=404, detail="Video not found")

    channel_id = video.channel_id
    uc = db.query(UserChannel).filter_by(user_id=current_user.id, channel_id=channel_id).first()
    if uc:
        uc.status = "dismissed"
    else:
        db.add(UserChannel(user_id=current_user.id, channel_id=channel_id, status="dismissed"))

    dq = db.query(DiscoveryQueue).filter_by(user_id=current_user.id, channel_id=channel_id).first()
    if dq:
        dq.seen = True

    from ..routers.videos import _update_affinity
    _update_affinity(db, current_user.id, video, -3.0)

    db.commit()


@router.get("/community", response_model=list[dict])
def community_shelf(
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    """Channels downloaded by other users, weighted by count."""
    rows = db.execute(
        text("""
            SELECT c.id, c.youtube_channel_id, c.name, c.thumbnail_url,
                   COUNT(DISTINCT d.user_id) AS downloader_count,
                   v.title AS latest_title, v.thumbnail_url AS latest_thumbnail
            FROM downloads d
            JOIN videos v ON d.video_id = v.id
            JOIN channels c ON v.channel_id = c.id
            WHERE d.user_id != :user_id
              AND d.status = 'complete'
              AND v.id NOT IN (
                  SELECT uv.video_id FROM user_videos uv
                  WHERE uv.user_id = :user_id AND (uv.watched = 1 OR uv.downloaded = 1)
              )
            GROUP BY c.id
            ORDER BY downloader_count DESC
            LIMIT 20
        """),
        {"user_id": current_user.id},
    ).mappings().all()
    return [dict(r) for r in rows]