"""Bulk thumbnail backfill dla scen bez miniatury.

Pętla: dla każdej sceny z `dead_at IS NULL` playback_sources i 0 z thumbnail_url,
fetch tube page (pierwszy alive playback) → extract_thumbnail_url() → update
WSZYSTKIE alive sources tej sceny (idempotent).

Bug-reports 2026-05-10 (b2a656fe, 3876a8ce): user "Brak miniaturek" na Scenes
listingu. Mobile używa `playback_sources.find(s.thumbnail_url)` — bez backfill
~133k scen pokazuje placeholder.

Run: `python /srv/scripts/backfill_scene_thumbnails.py --batch 100 --limit 50000`
"""
from __future__ import annotations

import argparse
import logging
import sys
import time

import httpx
from sqlalchemy import select, func
from sqlalchemy.orm import Session

sys.path.insert(0, "/srv")
from app.db import SessionLocal
from app.extractors._fetch import browser_get
from app.extractors._models import TubePageError
from app.extractors.thumb_extract import extract_thumbnail_url
from app.models.playback_source import PlaybackSource

log = logging.getLogger("backfill_thumbnails")
logging.basicConfig(
    level=logging.INFO,
    format="%(asctime)s %(levelname)s %(message)s",
)

# Narrow exception set — wcześniej `(TubePageError, Exception)` łapało wszystko
# włącznie z KeyboardInterrupt + MemoryError + maskowało connection pool failures
# jak transient retry'owalne.
NET_EXC = (TubePageError, httpx.HTTPError, OSError, ValueError)


def _scenes_missing_thumb(session: Session, batch: int, after_id, origin: str | None = None) -> list[tuple]:
    """Cursor-based pagination po scene_id > after_id.

    NIE używamy offset (skip-rows bug: gdy scena w batch'u N nie zostanie
    przeprocesowana, offset += batch zignoruje ją w batchu N+1). Cursor by
    scene_id gwarantuje monotonic forward progress: niezależnie czy update
    się udał czy failem zostawił thumbnail=NULL, następny batch zaczyna od
    scene_id > MAX(processed_in_this_batch). Failed scenes są poza
    zasięgiem do nextrun.
    """
    q = (
        select(
            PlaybackSource.scene_id,
            func.array_agg(PlaybackSource.id).label("ps_ids"),
            func.array_agg(PlaybackSource.page_url).label("page_urls"),
            func.array_agg(PlaybackSource.origin).label("origins"),
        )
        .where(
            PlaybackSource.dead_at.is_(None),
            PlaybackSource.origin == origin if origin else PlaybackSource.origin.like("tube:%"),
        )
        .group_by(PlaybackSource.scene_id)
        .having(func.bool_and(PlaybackSource.thumbnail_url.is_(None)))
        .order_by(PlaybackSource.scene_id)
        .limit(batch)
    )
    if after_id is not None:
        q = q.where(PlaybackSource.scene_id > after_id)
    rows = session.execute(q).all()
    return [
        (r.scene_id, list(zip(r.ps_ids, r.page_urls, r.origins, strict=False)))
        for r in rows
    ]


def main() -> None:
    ap = argparse.ArgumentParser()
    ap.add_argument("--batch", type=int, default=100, help="scenes per DB query batch")
    ap.add_argument("--limit", type=int, default=10_000, help="max scenes to attempt")
    ap.add_argument("--sleep", type=float, default=0.5, help="seconds between fetches")
    ap.add_argument("--origin", type=str, default=None, help="filter by exact origin (e.g. tube:0dayxxcom)")
    args = ap.parse_args()

    total = ok = fail = 0
    cursor = None

    while total < args.limit:
        with SessionLocal() as session:
            batch = _scenes_missing_thumb(session, batch=args.batch, after_id=cursor, origin=args.origin)
            if not batch:
                log.info("no more scenes to process (cursor=%s, done)", cursor)
                break
            # Advance cursor PRZED przetwarzaniem — w razie crash następny run
            # zacznie za tym batchem, nie powtórzy go w pętli infinite.
            cursor = batch[-1][0]

            for scene_id, sources in batch:
                total += 1
                sp = session.begin_nested()
                try:
                    thumb = None
                    update_src_id = None
                    for ps_id, page_url, origin in sources:
                        if not page_url:
                            continue
                        try:
                            r = browser_get(page_url, timeout=10.0, follow_redirects=True)
                        except NET_EXC as e:
                            log.debug("fetch fail %s: %s", page_url, e)
                            continue
                        if r.status_code >= 400:
                            continue
                        thumb = extract_thumbnail_url(r.text)
                        if thumb:
                            update_src_id = ps_id
                            break
                        time.sleep(args.sleep)

                    if not thumb or update_src_id is None:
                        sp.rollback()
                        fail += 1
                        continue

                    # Update tylko źródła z którego thumb pochodzi (single playback).
                    session.execute(
                        PlaybackSource.__table__.update()
                        .where(PlaybackSource.id == update_src_id)
                        .where(PlaybackSource.thumbnail_url.is_(None))
                        .values(thumbnail_url=thumb)
                    )
                    sp.commit()
                    ok += 1
                except Exception as e:
                    sp.rollback()
                    log.warning("scene %s unexpected: %s", scene_id, e)
                    fail += 1

                if total % 50 == 0:
                    session.commit()
                    log.info(
                        "progress total=%d ok=%d fail=%d cursor=%s",
                        total, ok, fail, cursor,
                    )

            session.commit()

    log.info("done total=%d ok=%d fail=%d", total, ok, fail)


if __name__ == "__main__":
    main()