"""Phase 4-A study_question_jobs consumer — APScheduler 1분 간격.

study 도메인 전용 큐 (processing_queue 와 분리). BATCH_SIZE=1 — MLX 26B 가
deep_summary 와 같은 Semaphore(1) 게이트를 공유하므로 GPU 부하 통제.

stage 별 worker dispatch:
  - kind='explanation': study_explanation_worker.run_explanation_job (Phase 4-A)
  - kind='session_summary': Phase 4-B 예약, 1차 미구현 — pending 만 보면 즉시 skipped 처리
"""

from __future__ import annotations

from datetime import datetime, timedelta, timezone

from sqlalchemy import select, update
from sqlalchemy.exc import SQLAlchemyError

from core.database import async_session
from core.config import settings
from core.utils import setup_logger
from models.study_question_job import StudyQuestionJob
from workers.study_explanation_worker import run_explanation_job

logger = setup_logger("study_queue_consumer")

# 한 사이클에 한 row 씩 — MLX 게이트 직렬화 + GPU 부하 예측 가능.
BATCH_SIZE = 1
# processing 상태로 STALE_MINUTES 이상 방치된 job 은 worker 가 죽었다고 보고 pending 복구.
STALE_MINUTES = 10


async def reset_stale_study_jobs() -> None:
    """processing 으로 STALE_MINUTES 이상 방치된 job 을 pending 으로 복구.

    partial unique idx 가 (qid, kind) WHERE status IN ('pending','processing') 이라
    같은 qid 의 다른 pending 이 동시에 있을 일이 거의 없음 (enqueue 가 on_conflict_do_nothing).
    그래도 안전하게 update 만 — 충돌 시 IntegrityError 는 단건 단위 catch.
    """
    cutoff = datetime.now(timezone.utc) - timedelta(minutes=STALE_MINUTES)
    try:
        async with async_session() as session:
            stmt = (
                update(StudyQuestionJob)
                .where(
                    StudyQuestionJob.status == "processing",
                    StudyQuestionJob.started_at.is_not(None),
                    StudyQuestionJob.started_at < cutoff,
                )
                .values(status="pending", started_at=None)
            )
            result = await session.execute(stmt)
            await session.commit()
            n = result.rowcount or 0
            if n > 0:
                logger.warning("study_jobs_stale_reset count=%s", n)
    except SQLAlchemyError as e:
        logger.exception("study_jobs_stale_reset_failed: %s", e)


async def consume_study_queue() -> None:
    """APScheduler 진입점. pending job BATCH_SIZE 만큼 처리."""
    # 생성 LLM 홀드: env(study_explanation_enabled) 와 별개의 self-contained 게이트.
    # pending 은 그대로 유지 (Mac mini derived-worker 흡수 경로도 본 게이트와 무관).
    if "study_explanation" in settings.pipeline_held_stages:
        logger.debug("study_explanation 보류 (pipeline.held_stages)")
        return
    await reset_stale_study_jobs()

    async with async_session() as session:
        rows = (
            await session.execute(
                select(StudyQuestionJob)
                .where(StudyQuestionJob.status == "pending")
                .order_by(StudyQuestionJob.id.asc())
                .limit(BATCH_SIZE)
            )
        ).scalars().all()

    for job_row in rows:
        # 각 job 마다 독립 세션 — 한 job 실패가 다른 job 에 전염 X.
        async with async_session() as s:
            try:
                # 같은 row 를 fresh load (lock 회피, 세션 격리)
                job = await s.get(StudyQuestionJob, job_row.id)
                if job is None or job.status != "pending":
                    continue  # 다른 cycle 에서 이미 처리

                if job.kind == "explanation":
                    if not settings.study_explanation_enabled:
                        # PR-MacMini-Derived-Worker-1: explanation owner = Mac mini.
                        # status/attempts 변경하지 않고 pending 그대로 유지 → Mac mini worker 가 흡수.
                        logger.info("skip explanation owner=macmini job_id=%s qid=%s", job.id, job.study_question_id)
                        continue
                    await run_explanation_job(s, job)
                elif job.kind == "session_summary":
                    # Phase 4-B 미구현 — 즉시 skipped 처리 (lost in queue 방지)
                    job.status = "skipped"
                    job.error_code = "unknown"
                    job.error_message = "session_summary not implemented in Phase 4-A"
                    job.completed_at = datetime.now(timezone.utc)
                    logger.info("study_job_unsupported_kind id=%s kind=%s", job.id, job.kind)
                else:
                    job.status = "skipped"
                    job.error_code = "unknown"
                    job.error_message = f"unknown kind: {job.kind!r}"
                    job.completed_at = datetime.now(timezone.utc)
                    logger.warning("study_job_unknown_kind id=%s kind=%s", job.id, job.kind)

                await s.commit()
                logger.info(
                    "study_job_processed id=%s qid=%s kind=%s status=%s error_code=%s attempts=%s",
                    job.id, job.study_question_id, job.kind, job.status, job.error_code,
                    job.attempts,
                )
            except Exception as e:
                # worker 안에서 잡지 못한 catastrophic 실패 — 세션 rollback 후 다음 cycle 재처리.
                # study_explanation_worker 가 catch-all except 를 가지므로 여기 도달은 드묾.
                await s.rollback()
                logger.exception("study_job_outer_failed job_id=%s: %s", job_row.id, e)