"""Auto-merge scene duplicates wykryte przez identical phash.

Bug-report 2026-05-13 (e5e83b5e): user na PerformerScenes widzi masę scen z
identycznymi miniaturkami (same content re-uploaded z różnymi tytułami). phash
fingerprint pozwala wykryć dokładne duplikaty.

Conservative heuristic — auto-merge tylko gdy:
1. Identical phash (hamming = 0)
2. Same primary performer (≥1 wspólny performer)
3. Similar duration (within 30s, lub jeden ma None duration)

Inne duplicate kandydaci (różne performerzy, hamming 1-5) → wymagają manual review,
nie auto-merge (false-positive ryzyko).

Keep policy: scena z większą liczbą `external_refs` (canonical TPDB/StashDB)
przejmuje content od mniejszej (orphan tube → canonical merge).

Run: `python /srv/scripts/phash_dedup_scenes.py [--dry-run]`
"""
from __future__ import annotations

import argparse
import logging
import sys

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

sys.path.insert(0, "/srv")
from app.db import SessionLocal
from app.models.scene import (
    Scene,
    SceneExternalRef,
    SceneFingerprint,
    ScenePerformer,
)
from app.resolve.scene_merge import merge_scenes

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


def _scene_signals(session: Session, scene_id) -> tuple[int, int, set]:
    """Zwraca (n_external_refs, duration_sec, performer_ids_set) dla weighting."""
    n_refs = session.execute(
        select(func.count()).select_from(SceneExternalRef).where(SceneExternalRef.scene_id == scene_id)
    ).scalar_one()
    duration = session.execute(
        select(Scene.duration_sec).where(Scene.id == scene_id)
    ).scalar_one_or_none() or 0
    performers = set(
        session.execute(
            select(ScenePerformer.performer_id).where(ScenePerformer.scene_id == scene_id)
        ).scalars().all()
    )
    return (n_refs, duration, performers)


def main() -> None:
    ap = argparse.ArgumentParser()
    ap.add_argument("--dry-run", action="store_true", help="Print planned merges, don't execute")
    ap.add_argument("--max-pairs", type=int, default=1000, help="Limit pairs per run")
    args = ap.parse_args()

    # Read-only session dla bucket listy. Każdy merge dostaje fresh session
    # żeby exception nie zostawiał głównej w PendingRollbackError state.
    with SessionLocal() as read_session:
        buckets = read_session.execute(
            select(SceneFingerprint.value, func.array_agg(SceneFingerprint.scene_id))
            .where(SceneFingerprint.kind == "phash")
            .where(SceneFingerprint.value != "0")
            .group_by(SceneFingerprint.value)
            .having(func.count(SceneFingerprint.scene_id.distinct()) > 1)
        ).all()

    log.info("found %d phash buckets with duplicates", len(buckets))

    merged = 0
    skipped_diff_performer = 0
    skipped_diff_duration = 0
    skipped_no_performer = 0

    for value, scene_ids in buckets:
        scene_ids = list(set(scene_ids))
        if len(scene_ids) < 2:
            continue

        # Fresh session per bucket — signals + ranking.
        with SessionLocal() as bucket_session:
            sigs = {sid: _scene_signals(bucket_session, sid) for sid in scene_ids}

        sorted_ids = sorted(
            scene_ids,
            key=lambda sid: (-sigs[sid][0], -sigs[sid][1]),
        )
        keep_id = sorted_ids[0]
        keep_sig = sigs[keep_id]

        for drop_id in sorted_ids[1:]:
            if merged >= args.max_pairs:
                log.info("reached max-pairs limit, stopping")
                break
            drop_sig = sigs[drop_id]

            if keep_sig[2] and drop_sig[2]:
                if not (keep_sig[2] & drop_sig[2]):
                    skipped_diff_performer += 1
                    continue
            elif not keep_sig[2] and not drop_sig[2]:
                skipped_no_performer += 1
                continue

            if keep_sig[1] and drop_sig[1]:
                if abs(keep_sig[1] - drop_sig[1]) > 30:
                    skipped_diff_duration += 1
                    continue

            if args.dry_run:
                log.info("DRY: merge %s ← %s (phash=%s)", keep_id, drop_id, value)
                merged += 1
                continue

            # Fresh session per merge — exception nie psuje innych iteracji.
            with SessionLocal() as merge_session:
                try:
                    merge_scenes(
                        merge_session, keep_id=keep_id, drop_id=drop_id,
                        resolved_by="phash-dedup-script",
                    )
                    merge_session.commit()
                    log.info("merged %s ← %s (phash=%s)", keep_id, drop_id, value)
                    merged += 1
                    # Re-fetch keep_sig — może mieć nowych performerów po merge
                    # (drop's performers przenoszą się do keep). Bez tego kolejny
                    # drop_id w buckecie testowany przeciwko STARYCH performers.
                    with SessionLocal() as refresh:
                        keep_sig = _scene_signals(refresh, keep_id)
                except Exception as e:
                    merge_session.rollback()
                    log.warning("merge fail %s ← %s: %s", keep_id, drop_id, e)

        if merged >= args.max_pairs:
            break

    log.info(
        "done merged=%d skipped_perf=%d skipped_dur=%d skipped_noperf=%d",
        merged, skipped_diff_performer, skipped_diff_duration, skipped_no_performer,
    )
    # Nonzero exit gdy nic NIE zmergowano mimo że buckety istniały — sygnał
    # dla cron/systemd że run zakończył się "soft failure" (np. wszystkie pary
    # blokowane przez heuristic). Operacyjnie warto wiedzieć.
    if buckets and merged == 0:
        sys.exit(2)


if __name__ == "__main__":
    main()