import json
import threading as _threading
from datetime import datetime, timedelta
from typing import Optional

from fastapi import APIRouter, BackgroundTasks, Depends, HTTPException, status
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, ChannelGroup, ChannelGroupMember, Download, User, UserChannel, UserSettings, UserVideo, Video
from ..services import ytdlp

router = APIRouter()

_tasks: dict = {}
_tasks_lock = _threading.Lock()


class ChannelOut(BaseModel):
    id: int
    youtube_channel_id: str
    name: str
    description: Optional[str]
    thumbnail_url: Optional[str]
    banner_url: Optional[str]
    crawled_at: Optional[datetime]
    status: Optional[str]
    auto_download: Optional[bool] = None
    subscriber_count: Optional[int] = None
    video_count: int = 0
    unwatched_count: int = 0
    watched_count: int = 0
    downloaded_count: int = 0
    last_published_at: Optional[datetime] = None
    new_count: int = 0
    latest_video_id: Optional[str] = None
    latest_video_title: Optional[str] = None
    muted_until: Optional[datetime] = None
    upload_frequency_days: Optional[float] = None
    notes: Optional[str] = ""

    model_config = {"from_attributes": True}


class ChannelGroupOut(BaseModel):
    id: int
    name: str
    channel_ids: list[int] = []

    model_config = {"from_attributes": True}


class VideoOut(BaseModel):
    id: int
    youtube_video_id: str
    title: str
    thumbnail_url: Optional[str]
    duration_seconds: Optional[int]
    published_at: Optional[datetime]
    channel_id: Optional[int] = None
    channel_name: Optional[str] = None
    channel_youtube_id: Optional[str] = None
    is_downloaded: bool = False
    is_watched: bool = False
    queued: bool = False
    view_count: Optional[int] = None

    model_config = {"from_attributes": True}



def _get_channel_or_404(db: Session, channel_id: int) -> Channel:
    c = db.query(Channel).filter(Channel.id == channel_id).first()
    if not c:
        raise HTTPException(status_code=404, detail="Channel not found")
    return c


def _index_channels_batch(channel_ids: list[int], user_id: int, delay: float = 1.5):
    for cid in channel_ids:
        _index_channel_task(cid, user_id)


def _index_channel_task(channel_id: int, user_id: int, max_videos: int = 30):
    from ..database import SessionLocal
    db = SessionLocal()
    try:
        channel = db.query(Channel).filter_by(id=channel_id).first()
        if not channel:
            return

        result = ytdlp.fetch_channel_metadata(channel.youtube_channel_id, max_videos=max_videos, polite=True)
        if not result:
            return

        ch_data = result.get("channel", {})
        if ch_data:
            for k, v in ch_data.items():
                if hasattr(channel, k) and v is not None and v != "":
                    setattr(channel, k, v)
        channel.crawled_at = datetime.utcnow()
        db.merge(channel)

        new_video_ids = []
        for vdata in result.get("videos", []):
            yt_id = vdata.get("youtube_video_id")
            if not yt_id:
                continue
            existing = db.query(Video).filter_by(youtube_video_id=yt_id).first()
            if not existing:
                new_video = Video(
                    youtube_video_id=yt_id,
                    channel_id=channel.id,
                    title=vdata.get("title", ""),
                    description=vdata.get("description"),
                    thumbnail_url=vdata.get("thumbnail_url"),
                    duration_seconds=vdata.get("duration_seconds"),
                    published_at=vdata.get("published_at"),
                    tags=vdata.get("tags"),
                    category=vdata.get("category"),
                )
                db.add(new_video)
                db.flush()
                new_video_ids.append((yt_id, new_video.id))
            else:
                # Backfill missing metadata on existing videos
                if existing.published_at is None and vdata.get("published_at"):
                    existing.published_at = vdata["published_at"]
                if not existing.title and vdata.get("title"):
                    existing.title = vdata["title"]
                if not existing.thumbnail_url and vdata.get("thumbnail_url"):
                    existing.thumbnail_url = vdata["thumbnail_url"]
                if not existing.duration_seconds and vdata.get("duration_seconds"):
                    existing.duration_seconds = vdata["duration_seconds"]
                if not existing.description and vdata.get("description"):
                    existing.description = vdata["description"]
        db.commit()

        # Auto-download new videos if setting says to
        if new_video_ids and user_id:
            uc = db.query(UserChannel).filter_by(user_id=user_id, channel_id=channel.id).first()
            user_settings = db.query(UserSettings).filter_by(user_id=user_id).first()
            global_auto = user_settings.auto_download_on_sync if user_settings else False
            channel_auto = uc.auto_download if uc and uc.auto_download is not None else global_auto

            if channel_auto:
                quality = user_settings.preferred_quality if user_settings else "best"
                subtitle_langs = (user_settings.subtitle_langs or "") if user_settings else ""
                from ..routers.downloads import _on_progress, _on_complete, _on_error
                for yt_id, vid_id in new_video_ids:
                    existing_dl = db.query(Download).filter_by(
                        user_id=user_id, video_id=vid_id
                    ).filter(Download.status.in_(["pending", "downloading", "complete"])).first()
                    if not existing_dl:
                        dl = Download(user_id=user_id, video_id=vid_id, status="pending")
                        db.add(dl)
                        db.flush()
                        import threading
                        t = threading.Thread(
                            target=ytdlp.start_download,
                            args=(yt_id, dl.id, _on_progress, _on_complete, _on_error, quality, subtitle_langs),
                            daemon=True,
                        )
                        t.start()
                db.commit()
    except Exception:
        db.rollback()
    finally:
        db.close()


def _discovery_task(user_id: int):
    from ..database import SessionLocal
    from ..services.discovery import run_full_discovery
    db = SessionLocal()
    try:
        run_full_discovery(db, user_id)
    except Exception:
        pass
    finally:
        db.close()


def _enrich_missing_task(limit: int = 20):
    """Fetch full metadata for videos missing description, published_at, or view_count."""
    from ..database import SessionLocal
    import time
    db = SessionLocal()
    try:
        rows = db.execute(
            text("""
                SELECT v.id, v.youtube_video_id FROM videos v
                WHERE v.description IS NULL OR v.published_at IS NULL OR v.view_count IS NULL
                ORDER BY
                    (EXISTS (SELECT 1 FROM user_channels uc
                             WHERE uc.channel_id = v.channel_id AND uc.status = 'followed')) DESC,
                    (EXISTS (SELECT 1 FROM discovery_queue dq
                             WHERE dq.channel_id = v.channel_id)) DESC,
                    v.id DESC
                LIMIT :limit
            """),
            {"limit": limit},
        ).mappings().all()
        for row in rows:
            try:
                meta = ytdlp.fetch_video_metadata(row["youtube_video_id"], polite=True)
                if meta:
                    vid = db.query(Video).filter_by(id=row["id"]).first()
                    if vid:
                        if meta.get("description") is not None:
                            vid.description = meta["description"] or ""
                        if not vid.published_at and meta.get("published_at"):
                            vid.published_at = meta["published_at"]
                        if vid.view_count is None and meta.get("view_count") is not None:
                            vid.view_count = meta["view_count"]
                        if not vid.tags and meta.get("tags"):
                            vid.tags = meta["tags"]
                        if not vid.category and meta.get("category"):
                            vid.category = meta["category"]
                        if not vid.chapters and meta.get("chapters"):
                            vid.chapters = meta["chapters"]
                        db.commit()
            except Exception:
                db.rollback()
    finally:
        db.close()


@router.get("/feed", response_model=list[VideoOut])
def channel_feed(
    limit: int = 24,
    offset: int = 0,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    rows = db.execute(
        text("""
            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,
                   COALESCE(uv.downloaded, 0) AS is_downloaded,
                   COALESCE(uv.watched, 0) AS is_watched,
                   COALESCE(uv.queued, 0) AS queued
            FROM videos v
            JOIN channels c ON v.channel_id = c.id
            JOIN user_channels uc ON c.id = uc.channel_id AND uc.user_id = :user_id AND uc.status = 'followed'
            LEFT JOIN user_videos uv ON v.id = uv.video_id AND uv.user_id = :user_id
            ORDER BY v.published_at DESC
            LIMIT :limit OFFSET :offset
        """),
        {"user_id": current_user.id, "limit": limit, "offset": offset},
    ).mappings().all()
    return [VideoOut(**dict(r)) for r in rows]


@router.post("/sync-all", status_code=202)
def sync_all_channels(
    background_tasks: BackgroundTasks,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    # Only sync channels not touched in the last 6 hours to avoid hammering YouTube
    channels = db.execute(
        text("""
            SELECT c.id FROM channels c
            JOIN user_channels uc ON c.id = uc.channel_id
            WHERE uc.user_id = :uid AND uc.status = 'followed'
              AND (c.crawled_at IS NULL OR c.crawled_at < datetime('now', '-6 hours'))
            ORDER BY COALESCE(c.crawled_at, '1970-01-01') ASC
        """),
        {"uid": current_user.id},
    ).mappings().all()

    if channels:
        ids = [row["id"] for row in channels]
        background_tasks.add_task(_index_channels_batch, ids, current_user.id)
        background_tasks.add_task(_discovery_task, current_user.id)

    background_tasks.add_task(_enrich_missing_task, 30)

    return {"indexing": len(channels)}


@router.get("/rss")
def rss_feed(
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    from fastapi.responses import Response
    rows = db.execute(
        text("""
            SELECT v.youtube_video_id, v.title, v.description, v.published_at,
                   c.name AS channel_name, c.youtube_channel_id
            FROM videos v
            JOIN channels c ON v.channel_id = c.id
            JOIN user_channels uc ON c.id = uc.channel_id AND uc.user_id = :uid AND uc.status = 'followed'
            WHERE v.published_at IS NOT NULL
            ORDER BY v.published_at DESC
            LIMIT 100
        """),
        {"uid": current_user.id},
    ).mappings().all()

    def esc(s):
        if not s:
            return ""
        return str(s).replace("&", "&amp;").replace("<", "&lt;").replace(">", "&gt;").replace('"', "&quot;")

    items = []
    for r in rows:
        pub = r["published_at"]
        pub_str = pub.strftime("%a, %d %b %Y %H:%M:%S +0000") if pub else ""
        yt_id = r["youtube_video_id"]
        items.append(f"""    <item>
      <title>{esc(r['title'])}</title>
      <link>https://www.youtube.com/watch?v={yt_id}</link>
      <description>{esc(r['description'] or '')}</description>
      <author>{esc(r['channel_name'])}</author>
      <pubDate>{pub_str}</pubDate>
      <guid>https://www.youtube.com/watch?v={yt_id}</guid>
    </item>""")

    xml = f"""<?xml version="1.0" encoding="UTF-8"?>
<rss version="2.0">
  <channel>
    <title>YTContinue — Following</title>
    <link>https://www.youtube.com/</link>
    <description>Latest videos from your followed channels</description>
{chr(10).join(items)}
  </channel>
</rss>"""
    return Response(content=xml, media_type="application/rss+xml; charset=utf-8")


@router.get("/tasks")
def get_active_tasks(current_user: User = Depends(get_current_user)):
    with _tasks_lock:
        return list(_tasks.values())


@router.post("/mark-seen", status_code=204)
def mark_channels_seen(
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    db.execute(
        text("UPDATE user_channels SET last_seen_at = :now WHERE user_id = :uid AND status = 'followed'"),
        {"now": datetime.utcnow(), "uid": current_user.id},
    )
    db.commit()


@router.get("", response_model=list[ChannelOut])
def list_channels(
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    uid = current_user.id

    # Step 1 — channel rows + user_channel metadata (fast, no video stats)
    ch_rows = db.execute(
        text("""
            SELECT c.id, c.youtube_channel_id, c.name, c.description,
                   c.thumbnail_url, c.banner_url, c.subscriber_count, c.crawled_at,
                   uc.status, uc.auto_download, uc.muted_until, uc.notes, uc.last_seen_at
            FROM channels c
            JOIN user_channels uc ON c.id = uc.channel_id
            WHERE uc.user_id = :uid AND uc.status = 'followed'
        """),
        {"uid": uid},
    ).mappings().all()

    if not ch_rows:
        return []

    id_csv = ",".join(str(r["id"]) for r in ch_rows)
    last_seen = {r["id"]: r["last_seen_at"] for r in ch_rows}

    # Step 2 — aggregated video stats for all channels in one query
    vstats = {
        r["channel_id"]: r
        for r in db.execute(
            text(f"""
                SELECT v.channel_id,
                       COUNT(*) AS video_count,
                       MAX(v.published_at) AS last_published_at,
                       julianday(MAX(v.published_at)) - julianday(MIN(v.published_at)) AS date_span_days,
                       SUM(CASE WHEN COALESCE(uv.watched,   0) = 0 THEN 1 ELSE 0 END) AS unwatched_count,
                       SUM(CASE WHEN uv.watched    = 1 THEN 1 ELSE 0 END) AS watched_count,
                       SUM(CASE WHEN uv.downloaded = 1 THEN 1 ELSE 0 END) AS downloaded_count
                FROM videos v
                LEFT JOIN user_videos uv ON uv.video_id = v.id AND uv.user_id = :uid
                WHERE v.channel_id IN ({id_csv})
                GROUP BY v.channel_id
            """),
            {"uid": uid},
        ).mappings().all()
    }

    # Step 3 — new-video count per channel (videos indexed after last_seen_at)
    new_counts = {
        r["channel_id"]: r["new_count"]
        for r in db.execute(
            text(f"""
                SELECT v.channel_id, COUNT(*) AS new_count
                FROM videos v
                JOIN user_channels uc
                    ON uc.channel_id = v.channel_id
                    AND uc.user_id = :uid
                WHERE v.channel_id IN ({id_csv})
                  AND (uc.last_seen_at IS NULL OR v.indexed_at > uc.last_seen_at)
                GROUP BY v.channel_id
            """),
            {"uid": uid},
        ).mappings().all()
    }

    # Step 4 — latest video id + title per channel (derived-table join, no correlated subquery)
    latest = {
        r["channel_id"]: r
        for r in db.execute(
            text(f"""
                SELECT v.channel_id,
                       v.youtube_video_id AS latest_video_id,
                       v.title            AS latest_video_title
                FROM videos v
                JOIN (
                    SELECT channel_id, MAX(published_at) AS max_pub
                    FROM videos
                    WHERE channel_id IN ({id_csv})
                    GROUP BY channel_id
                ) m ON v.channel_id = m.channel_id AND v.published_at = m.max_pub
                GROUP BY v.channel_id
            """),
        ).mappings().all()
    }

    # Merge and build response
    result = []
    for r in ch_rows:
        cid = r["id"]
        vs = vstats.get(cid) or {}
        vc = vs.get("video_count") or 0
        newest = vs.get("last_published_at")
        span = vs.get("date_span_days")
        freq = (span / (vc - 1.0)) if (vc >= 2 and span is not None) else None

        result.append(ChannelOut(
            id=cid,
            youtube_channel_id=r["youtube_channel_id"],
            name=r["name"],
            description=r["description"],
            thumbnail_url=r["thumbnail_url"],
            banner_url=r.get("banner_url"),
            subscriber_count=r.get("subscriber_count"),
            crawled_at=r.get("crawled_at"),
            status=r["status"],
            auto_download=r.get("auto_download"),
            muted_until=r.get("muted_until"),
            notes=r.get("notes") or "",
            video_count=vc,
            last_published_at=newest,
            unwatched_count=vs.get("unwatched_count") or 0,
            watched_count=vs.get("watched_count") or 0,
            downloaded_count=vs.get("downloaded_count") or 0,
            new_count=new_counts.get(cid, 0),
            latest_video_id=latest.get(cid, {}).get("latest_video_id"),
            latest_video_title=latest.get(cid, {}).get("latest_video_title"),
            upload_frequency_days=freq,
        ))

    result.sort(key=lambda c: c.last_published_at or datetime.min, reverse=True)
    return result


# ── Channel Groups (must be before /{channel_id} to avoid route shadowing) ───

@router.get("/groups", response_model=list[ChannelGroupOut])
def list_groups(
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    groups = db.query(ChannelGroup).filter_by(user_id=current_user.id).all()
    result = []
    for g in groups:
        members = db.query(ChannelGroupMember).filter_by(group_id=g.id).all()
        result.append(ChannelGroupOut(id=g.id, name=g.name, channel_ids=[m.channel_id for m in members]))
    return result


@router.post("/groups", response_model=ChannelGroupOut, status_code=201)
def create_group(
    body: dict,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    name = (body.get("name") or "").strip()
    if not name:
        raise HTTPException(status_code=400, detail="name required")
    g = ChannelGroup(user_id=current_user.id, name=name)
    db.add(g)
    db.commit()
    db.refresh(g)
    return ChannelGroupOut(id=g.id, name=g.name, channel_ids=[])


@router.delete("/groups/{group_id}", status_code=204)
def delete_group(
    group_id: int,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    g = db.query(ChannelGroup).filter_by(id=group_id, user_id=current_user.id).first()
    if not g:
        raise HTTPException(status_code=404, detail="Group not found")
    db.delete(g)
    db.commit()


@router.patch("/groups/{group_id}", response_model=ChannelGroupOut)
def rename_group(
    group_id: int,
    body: dict,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    g = db.query(ChannelGroup).filter_by(id=group_id, user_id=current_user.id).first()
    if not g:
        raise HTTPException(status_code=404, detail="Group not found")
    name = (body.get("name") or "").strip()
    if name:
        g.name = name
        db.commit()
    members = db.query(ChannelGroupMember).filter_by(group_id=g.id).all()
    return ChannelGroupOut(id=g.id, name=g.name, channel_ids=[m.channel_id for m in members])


@router.post("/groups/{group_id}/channels/{channel_id}", status_code=204)
def add_channel_to_group(
    group_id: int,
    channel_id: int,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    g = db.query(ChannelGroup).filter_by(id=group_id, user_id=current_user.id).first()
    if not g:
        raise HTTPException(status_code=404, detail="Group not found")
    existing = db.query(ChannelGroupMember).filter_by(group_id=group_id, channel_id=channel_id).first()
    if not existing:
        db.add(ChannelGroupMember(group_id=group_id, channel_id=channel_id))
        db.commit()


@router.delete("/groups/{group_id}/channels/{channel_id}", status_code=204)
def remove_channel_from_group_route(
    group_id: int,
    channel_id: int,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    m = db.query(ChannelGroupMember).filter_by(group_id=group_id, channel_id=channel_id).first()
    if m:
        db.delete(m)
        db.commit()


class BulkChannelBody(BaseModel):
    channel_ids: list[int]
    action: str  # "mute" | "unmute" | "unfollow"


@router.post("/bulk-action", status_code=200)
def bulk_channel_action(
    body: BulkChannelBody,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    if not body.channel_ids:
        return {"ok": True}
    placeholders = ",".join(str(int(i)) for i in body.channel_ids)
    if body.action == "mute":
        db.execute(
            text(f"""
                UPDATE user_channels SET muted_until = :until
                WHERE user_id = :user_id AND channel_id IN ({placeholders})
            """),
            {"until": datetime.utcnow() + timedelta(days=30), "user_id": current_user.id},
        )
    elif body.action == "unmute":
        db.execute(
            text(f"UPDATE user_channels SET muted_until = NULL WHERE user_id = :user_id AND channel_id IN ({placeholders})"),
            {"user_id": current_user.id},
        )
    elif body.action == "unfollow":
        db.execute(
            text(f"DELETE FROM user_channels WHERE user_id = :user_id AND channel_id IN ({placeholders})"),
            {"user_id": current_user.id},
        )
    db.commit()
    return {"ok": True}


@router.get("/{channel_id}", response_model=ChannelOut)
def get_channel(
    channel_id: int,
    background_tasks: BackgroundTasks,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    row = db.execute(
        text("""
            SELECT c.*, uc.status, uc.auto_download, uc.muted_until,
                   (SELECT COUNT(*) FROM videos WHERE channel_id = c.id) AS video_count,
                   (SELECT MAX(v.published_at) FROM videos v WHERE v.channel_id = c.id) AS last_published_at,
                   (SELECT COUNT(*) FROM videos v
                    LEFT JOIN user_videos uv ON v.id = uv.video_id AND uv.user_id = :user_id
                    WHERE v.channel_id = c.id AND COALESCE(uv.watched, 0) = 0) AS unwatched_count,
                   (SELECT COUNT(*) FROM videos v
                    JOIN user_videos uv ON v.id = uv.video_id AND uv.user_id = :user_id
                    WHERE v.channel_id = c.id AND uv.watched = 1) AS watched_count,
                   (SELECT COUNT(*) FROM videos v
                    JOIN user_videos uv ON v.id = uv.video_id AND uv.user_id = :user_id
                    WHERE v.channel_id = c.id AND uv.downloaded = 1) AS downloaded_count,
                   0 AS new_count,
                   (SELECT v.youtube_video_id FROM videos v
                    WHERE v.channel_id = c.id ORDER BY v.published_at DESC LIMIT 1) AS latest_video_id,
                   (SELECT v.title FROM videos v
                    WHERE v.channel_id = c.id ORDER BY v.published_at DESC LIMIT 1) AS latest_video_title
            FROM channels c
            LEFT JOIN user_channels uc ON c.id = uc.channel_id AND uc.user_id = :user_id
            WHERE c.id = :channel_id
        """),
        {"user_id": current_user.id, "channel_id": channel_id},
    ).mappings().first()
    if not row:
        raise HTTPException(status_code=404, detail="Channel not found")

    # Re-index in the background if stale (not crawled in the last hour)
    stale = True
    try:
        crawled_at_raw = row.get("crawled_at")
        if crawled_at_raw:
            crawled_at = (
                crawled_at_raw if isinstance(crawled_at_raw, datetime)
                else datetime.fromisoformat(str(crawled_at_raw))
            )
            stale = (datetime.utcnow() - crawled_at).total_seconds() > 3600
    except Exception:
        pass
    if stale:
        background_tasks.add_task(_index_channel_task, channel_id, current_user.id)

    return ChannelOut(**dict(row))


@router.get("/{channel_id}/videos", response_model=list[VideoOut])
def get_channel_videos(
    channel_id: int,
    sort: str = "newest",
    offset: int = 0,
    limit: int = 60,
    q: str = "",
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    _get_channel_or_404(db, channel_id)
    params: dict = {"user_id": current_user.id, "channel_id": channel_id, "limit": limit, "offset": offset}
    q_clause = ""
    if q.strip():
        q_clause = "AND (v.title LIKE :q OR v.description LIKE :q)"
        params["q"] = f"%{q.strip()}%"

    order = {
        "newest":   "v.published_at DESC NULLS LAST",
        "oldest":   "v.published_at ASC NULLS LAST",
        "title":    "v.title ASC",
        "unwatched":"COALESCE(uv.watched, 0) ASC, v.published_at DESC NULLS LAST",
        "popular":  "v.view_count DESC NULLS LAST",
    }.get(sort, "v.published_at DESC NULLS LAST")
    view_count_clause = "AND v.view_count IS NOT NULL" if sort == "popular" else ""
    rows = db.execute(
        text(f"""
            SELECT v.id, v.youtube_video_id, v.title, v.thumbnail_url,
                   v.duration_seconds, v.published_at, v.view_count,
                   COALESCE(uv.downloaded, 0) AS is_downloaded,
                   COALESCE(uv.watched, 0) AS is_watched
            FROM videos v
            LEFT JOIN user_videos uv ON v.id = uv.video_id AND uv.user_id = :user_id
            WHERE v.channel_id = :channel_id {view_count_clause} {q_clause}
            ORDER BY {order}
            LIMIT :limit OFFSET :offset
        """),
        params,
    ).mappings().all()
    return [VideoOut(**dict(r)) for r in rows]


@router.post("/{channel_id}/fetch-popular", status_code=status.HTTP_202_ACCEPTED)
def fetch_popular_videos(
    channel_id: int,
    background_tasks: BackgroundTasks,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    """Fetch the channel's most popular videos from YouTube and index them."""
    channel = _get_channel_or_404(db, channel_id)
    background_tasks.add_task(_fetch_popular_task, channel_id, channel.youtube_channel_id, channel.name or "")
    return {"detail": "Fetching popular videos"}


def _fetch_popular_task(channel_id: int, youtube_channel_id: str, channel_name: str = ""):
    """Half-and-half popular fetch.

    Phase 1 (fast): flat-playlist crawl of the full channel → store any
    new videos in DB (title, duration, thumbnail). No individual requests.

    Phase 2 (sequential, polite): fetch each video's watch page one at a time
    with a 2-second pause between requests to avoid cookie invalidation.
    Prioritises videos missing view_count; caps at 100 per run.
    """
    import time
    from ..database import SessionLocal

    task_id = f"popular-{channel_id}"
    label = f"Popular fetch — {channel_name}" if channel_name else "Popular fetch"

    # Phase 1 — flat-playlist: crawl all channel videos quickly
    with _tasks_lock:
        _tasks[task_id] = {
            "id": task_id,
            "label": label,
            "phase": "Crawling channel…",
            "total": 0,
            "done": 0,
            "started_at": datetime.utcnow().isoformat(),
        }

    if youtube_channel_id.startswith("@"):
        url = f"https://www.youtube.com/{youtube_channel_id}/videos"
    else:
        url = f"https://www.youtube.com/channel/{youtube_channel_id}/videos"

    stdout, _, _ = ytdlp._run([
        "yt-dlp", url,
        "--dump-json", "--flat-playlist",
        "--quiet",
        *ytdlp._cookie_args(),
    ], timeout=120)

    flat_entries = []
    for line in stdout.splitlines():
        line = line.strip()
        if not line:
            continue
        try:
            info = json.loads(line)
            yt_id = info.get("id")
            if yt_id:
                flat_entries.append({
                    "id": yt_id,
                    "title": info.get("title", ""),
                    "duration": info.get("duration"),
                })
        except json.JSONDecodeError:
            continue

    # Store any new videos from the flat crawl
    if flat_entries:
        db = SessionLocal()
        try:
            channel = db.query(Channel).filter_by(id=channel_id).first()
            if channel:
                for entry in flat_entries:
                    if not db.query(Video).filter_by(youtube_video_id=entry["id"]).first():
                        try:
                            db.add(Video(
                                youtube_video_id=entry["id"],
                                channel_id=channel_id,
                                title=entry["title"],
                                thumbnail_url=ytdlp._stable_thumbnail(entry["id"]),
                                duration_seconds=entry["duration"],
                                tags="[]",
                            ))
                            db.commit()
                        except Exception:
                            db.rollback()
        finally:
            db.close()

    # Phase 2 — sequential fetches with a polite delay to avoid cookie invalidation
    db = SessionLocal()
    try:
        rows = db.execute(
            text("""
                SELECT youtube_video_id FROM videos
                WHERE channel_id = :cid
                ORDER BY (view_count IS NULL) DESC, RANDOM()
                LIMIT 100
            """),
            {"cid": channel_id},
        ).mappings().all()
        video_ids = [r["youtube_video_id"] for r in rows]
    finally:
        db.close()

    if not video_ids:
        with _tasks_lock:
            _tasks.pop(task_id, None)
        return

    with _tasks_lock:
        if task_id in _tasks:
            _tasks[task_id]["phase"] = "Enriching view counts…"
            _tasks[task_id]["total"] = len(video_ids)
            _tasks[task_id]["done"] = 0

    try:
        for yt_id in video_ids:
            try:
                meta = ytdlp.fetch_video_metadata(yt_id, polite=True)
                if meta:
                    db = SessionLocal()
                    try:
                        vid = db.query(Video).filter_by(youtube_video_id=yt_id).first()
                        if vid:
                            if meta.get("view_count") is not None:
                                vid.view_count = meta["view_count"]
                            if not vid.published_at and meta.get("published_at"):
                                vid.published_at = meta["published_at"]
                            db.commit()
                    except Exception:
                        db.rollback()
                    finally:
                        db.close()
            except Exception:
                pass
            with _tasks_lock:
                if task_id in _tasks:
                    _tasks[task_id]["done"] += 1
    finally:
        with _tasks_lock:
            _tasks.pop(task_id, None)


@router.post("/{channel_id}/search", status_code=status.HTTP_202_ACCEPTED)
def search_channel_youtube(
    channel_id: int,
    q: str,
    background_tasks: BackgroundTasks,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    """Search YouTube within this channel and index matching videos."""
    channel = _get_channel_or_404(db, channel_id)
    background_tasks.add_task(_search_channel_task, channel_id, channel.youtube_channel_id, q, current_user.id)
    return {"detail": "Search started"}


def _search_channel_task(channel_id: int, youtube_channel_id: str, q: str, user_id: int):
    """Fetch videos matching q from YouTube for this channel and index them."""
    from ..database import SessionLocal
    from urllib.parse import quote
    db = SessionLocal()
    try:
        url = f"https://www.youtube.com/channel/{youtube_channel_id}/search?query={quote(q)}"
        result = ytdlp.fetch_channel_metadata(youtube_channel_id, max_videos=100, polite=True)
        if not result:
            return
        # Filter results by query match (yt-dlp fetches all; we filter titles locally)
        q_lower = q.lower()
        matched = [v for v in result.get("videos", []) if q_lower in (v.get("title") or "").lower()]
        if not matched:
            matched = result.get("videos", [])[:30]
        channel = db.query(Channel).filter_by(id=channel_id).first()
        if not channel:
            return
        for vdata in matched:
            yt_id = vdata.get("youtube_video_id")
            if not yt_id:
                continue
            existing = db.query(Video).filter_by(youtube_video_id=yt_id).first()
            if not existing:
                db.add(Video(
                    youtube_video_id=yt_id,
                    channel_id=channel.id,
                    title=vdata.get("title", ""),
                    description=vdata.get("description"),
                    thumbnail_url=vdata.get("thumbnail_url"),
                    duration_seconds=vdata.get("duration_seconds"),
                    published_at=vdata.get("published_at"),
                    tags=vdata.get("tags"),
                    category=vdata.get("category"),
                ))
        db.commit()
    except Exception:
        db.rollback()
    finally:
        db.close()


@router.get("/{channel_id}/random", response_model=VideoOut)
def get_random_channel_video(
    channel_id: int,
    unwatched_only: bool = True,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    _get_channel_or_404(db, channel_id)
    unwatched_clause = "AND COALESCE(uv.watched, 0) = 0" if unwatched_only else ""
    row = db.execute(
        text(f"""
            SELECT v.id, v.youtube_video_id, v.title, v.thumbnail_url,
                   v.duration_seconds, v.published_at, v.view_count,
                   c.id AS channel_id, c.name AS channel_name, c.youtube_channel_id AS channel_youtube_id,
                   COALESCE(uv.downloaded, 0) AS is_downloaded,
                   COALESCE(uv.watched, 0) AS is_watched,
                   COALESCE(uv.queued, 0) AS queued
            FROM videos v
            JOIN channels c ON v.channel_id = c.id
            LEFT JOIN user_videos uv ON v.id = uv.video_id AND uv.user_id = :user_id
            WHERE v.channel_id = :channel_id {unwatched_clause}
            ORDER BY RANDOM()
            LIMIT 1
        """),
        {"user_id": current_user.id, "channel_id": channel_id},
    ).mappings().first()
    if not row:
        raise HTTPException(status_code=404, detail="No videos found")
    return VideoOut(**dict(row))


@router.get("/{channel_id}/in-progress", response_model=list[VideoOut])
def get_channel_in_progress(
    channel_id: int,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    _get_channel_or_404(db, channel_id)
    rows = db.execute(
        text("""
            SELECT v.id, v.youtube_video_id, v.title, v.thumbnail_url,
                   v.duration_seconds, v.published_at, v.view_count,
                   c.id AS channel_id, c.name AS channel_name, c.youtube_channel_id AS channel_youtube_id,
                   COALESCE(uv.downloaded, 0) AS is_downloaded,
                   COALESCE(uv.watched, 0) AS is_watched,
                   COALESCE(uv.queued, 0) AS queued
            FROM videos v
            JOIN channels c ON v.channel_id = c.id
            JOIN user_videos uv ON v.id = uv.video_id AND uv.user_id = :user_id
            WHERE v.channel_id = :channel_id
              AND uv.watch_progress_seconds > 30
              AND COALESCE(uv.watched, 0) = 0
            ORDER BY uv.watch_progress_seconds DESC
            LIMIT 6
        """),
        {"user_id": current_user.id, "channel_id": channel_id},
    ).mappings().all()
    return [VideoOut(**dict(r)) for r in rows]


@router.post("/{channel_id}/follow", status_code=status.HTTP_204_NO_CONTENT)
def follow_channel(
    channel_id: int,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    _get_channel_or_404(db, channel_id)
    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"))
    db.commit()


@router.delete("/{channel_id}/follow", status_code=status.HTTP_204_NO_CONTENT)
def unfollow_channel(
    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:
        db.delete(uc)
        db.commit()


@router.patch("/{channel_id}/auto-download", status_code=200)
def set_channel_auto_download(
    channel_id: int,
    body: dict,
    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 not uc:
        raise HTTPException(status_code=404, detail="Not following this channel")
    value = body.get("auto_download")  # True / False / None
    uc.auto_download = value
    db.commit()
    return {"auto_download": uc.auto_download}


@router.post("/{channel_id}/index", status_code=status.HTTP_202_ACCEPTED)
def index_channel(
    channel_id: int,
    background_tasks: BackgroundTasks,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    _get_channel_or_404(db, channel_id)
    background_tasks.add_task(_index_channel_task, channel_id, current_user.id, 100)
    return {"detail": "Indexing started"}


@router.post("/{channel_id}/index-full", status_code=status.HTTP_202_ACCEPTED)
def index_channel_full(
    channel_id: int,
    background_tasks: BackgroundTasks,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    _get_channel_or_404(db, channel_id)
    background_tasks.add_task(_index_channel_task, channel_id, current_user.id, 0)
    return {"detail": "Full index started"}


@router.post("/{channel_id}/explore", status_code=status.HTTP_202_ACCEPTED)
def explore_channel_older(
    channel_id: int,
    page: int = 2,
    background_tasks: BackgroundTasks = None,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    """Fetch a page of older videos from this channel (page 1 = newest 30, page 2 = next 100, etc.)."""
    _get_channel_or_404(db, channel_id)
    start = 1 if page <= 1 else (30 + (page - 2) * 100 + 1)
    background_tasks.add_task(_index_channel_explore_task, channel_id, current_user.id, start, 100)
    return {"detail": f"Fetching older videos (page {page})", "start": start}


def _index_channel_explore_task(channel_id: int, user_id: int, start_video: int, count: int):
    from ..database import SessionLocal
    db = SessionLocal()
    try:
        channel = db.query(Channel).filter_by(id=channel_id).first()
        if not channel:
            return
        result = ytdlp.fetch_channel_metadata(channel.youtube_channel_id, max_videos=count, start_video=start_video, polite=True)
        if not result:
            return
        for vdata in result.get("videos", []):
            yt_id = vdata.get("youtube_video_id")
            if not yt_id:
                continue
            if not db.query(Video).filter_by(youtube_video_id=yt_id).first():
                db.add(Video(
                    youtube_video_id=yt_id,
                    channel_id=channel.id,
                    title=vdata.get("title", ""),
                    description=vdata.get("description"),
                    thumbnail_url=vdata.get("thumbnail_url"),
                    duration_seconds=vdata.get("duration_seconds"),
                    published_at=vdata.get("published_at"),
                    tags=vdata.get("tags"),
                    category=vdata.get("category"),
                ))
        db.commit()
    except Exception:
        db.rollback()
    finally:
        db.close()


@router.post("/follow-bulk", status_code=200)
def follow_bulk(
    body: dict,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    """Follow a large list of channel handles/IDs without hitting YouTube.

    Creates stub Channel records for unknowns and UserChannel rows immediately.
    Metadata (name, thumbnail, videos) fills in when the user hits Sync All.
    """
    handles = body.get("handles", [])
    if not handles or not isinstance(handles, list):
        raise HTTPException(status_code=400, detail="handles list required")

    followed = 0
    already = 0
    created = 0

    for handle in handles:
        handle = str(handle).strip()
        if not handle:
            continue

        channel = db.query(Channel).filter_by(youtube_channel_id=handle).first()
        if not channel:
            # Stub — name defaults to handle, filled in on next index
            channel = Channel(
                youtube_channel_id=handle,
                name=handle.lstrip("@"),
            )
            db.add(channel)
            db.flush()
            created += 1

        uc = db.query(UserChannel).filter_by(
            user_id=current_user.id, channel_id=channel.id
        ).first()
        if uc:
            if uc.status != "followed":
                uc.status = "followed"
                followed += 1
            else:
                already += 1
        else:
            db.add(UserChannel(
                user_id=current_user.id,
                channel_id=channel.id,
                status="followed",
            ))
            followed += 1

    db.commit()
    return {"followed": followed, "already_following": already, "new_channels": created}


@router.patch("/{channel_id}/notes", status_code=200)
def update_channel_notes(
    channel_id: int,
    body: dict,
    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 not uc:
        raise HTTPException(status_code=404, detail="Not following this channel")
    uc.notes = body.get("notes", "") or ""
    db.commit()
    return {"ok": True}


@router.post("/{channel_id}/mute", status_code=204)
def mute_channel(
    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 not uc:
        raise HTTPException(status_code=404, detail="Not following this channel")
    uc.muted_until = datetime.utcnow() + timedelta(days=30)
    db.commit()


@router.delete("/{channel_id}/mute", status_code=204)
def unmute_channel(
    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.muted_until = None
        db.commit()


@router.post("/follow-by-url", status_code=status.HTTP_201_CREATED)
def follow_by_url(
    body: dict,
    background_tasks: BackgroundTasks,
    db: Session = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    yt_channel_id = body.get("youtube_channel_id") or body.get("channel_id")
    if not yt_channel_id:
        raise HTTPException(status_code=400, detail="youtube_channel_id required")

    channel = db.query(Channel).filter_by(youtube_channel_id=yt_channel_id).first()
    if not channel:
        meta = ytdlp.fetch_channel_metadata(yt_channel_id, max_videos=30, polite=True)
        if not meta or not meta.get("channel"):
            raise HTTPException(status_code=404, detail="Channel not found on YouTube")
        ch_data = meta["channel"]
        channel = Channel(**{k: v for k, v in ch_data.items() if hasattr(Channel, k)})
        channel.crawled_at = datetime.utcnow()
        db.add(channel)
        db.flush()

        for vdata in meta.get("videos", []):
            yt_id = vdata.get("youtube_video_id")
            if not yt_id:
                continue
            if not db.query(Video).filter_by(youtube_video_id=yt_id).first():
                db.add(Video(
                    youtube_video_id=yt_id,
                    channel_id=channel.id,
                    title=vdata.get("title", ""),
                    description=vdata.get("description"),
                    thumbnail_url=vdata.get("thumbnail_url"),
                    duration_seconds=vdata.get("duration_seconds"),
                    published_at=vdata.get("published_at"),
                    tags=vdata.get("tags"),
                    category=vdata.get("category"),
                ))
        db.commit()
        db.refresh(channel)

    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"))
    db.commit()

    background_tasks.add_task(_discovery_task, current_user.id)

    return {"channel_id": channel.id, "name": channel.name}