"""One-off backfill for downloads made before per-asset channel URLs + poster fallbacks existed.

Fills `media_assets.uploader_url` (re-extracting metadata for YouTube/Facebook sources, so an
auto-detected channel becomes a clickable link) and `poster_path` (an ffmpeg frame for
thumbnail-less sources, so the card / watch page / link preview still shows an image). Best-effort
and safe to re-run: it only touches assets still missing the field, and only re-fetches YouTube /
Facebook sources (a direct media URL like a reddit HLS manifest carries no channel and its signed
URL may have expired — those just get a locally-generated poster instead).

Run once per environment:
    docker exec siftlode-worker-1 python -c "from app.downloads import backfill; print(backfill.run())"
"""
import logging
from urllib.parse import urlparse

import yt_dlp
from sqlalchemy import select

from app.config import settings
from app.db import SessionLocal
from app.downloads import edit as editmod
from app.downloads import formats, service
from app.models import MediaAsset
from app.worker import _uploader_url

log = logging.getLogger("siftlode.backfill")


def _should_refetch(asset: MediaAsset) -> bool:
    """Only YouTube + Facebook sources have a derivable channel URL worth a network round-trip."""
    if asset.source_kind == "youtube":
        return True
    if asset.source_kind == "url":
        host = urlparse(asset.source_ref).netloc.lower()
        return "facebook.com" in host or "fb.watch" in host
    return False


def _extract_meta(url: str) -> dict | None:
    """Metadata-only yt-dlp extraction, trying the same client sets as the worker (YouTube needs the
    POT/player-client strategy even just to extract)."""
    client_sets = [
        c for c in (settings.player_client_list, settings.player_client_fallback_list) if c
    ] or [None]
    for clients in client_sets:
        opts = formats.build_ydl_opts(
            {}, "%(id)s.%(ext)s", lambda d: None, settings.download_pot_base_url, clients
        )
        opts["skip_download"] = True
        try:
            with yt_dlp.YoutubeDL(opts) as ydl:
                info = ydl.extract_info(url, download=False)
            if info:
                return info
        except Exception as exc:  # noqa: BLE001 — best-effort backfill, keep going
            log.info("meta extract failed for %s (%s): %s", url, clients, str(exc)[:100])
    return None


def run() -> dict:
    filled_url = filled_poster = 0
    with SessionLocal() as db:
        assets = (
            db.execute(
                select(MediaAsset).where(
                    MediaAsset.status == "ready", MediaAsset.rel_path.is_not(None)
                )
            )
            .scalars()
            .all()
        )
        for a in assets:
            if a.uploader_url is None and _should_refetch(a):
                url = a.source_webpage_url or service.source_url(a.source_kind, a.source_ref)
                info = _extract_meta(url)
                uu = _uploader_url(info) if info else None
                if uu:
                    a.uploader_url = uu
                    filled_url += 1
                    log.info("asset %s uploader_url <- %s", a.id, uu)
            if a.poster_path is None:
                # Record a self-hosted poster for every download (the reliable og:image source):
                # ensure_poster returns the existing <base>.jpg thumbnail sidecar, or cuts a frame.
                rel = editmod.ensure_poster(a, settings.download_root)
                if rel:
                    a.poster_path = rel
                    filled_poster += 1
                    log.info("asset %s poster <- %s", a.id, rel)
            db.commit()
    result = {
        "assets": len(assets),
        "filled_uploader_url": filled_url,
        "filled_poster": filled_poster,
    }
    log.info("backfill done: %s", result)
    return result