from __future__ import annotations

import logging
from datetime import datetime, timedelta
from zoneinfo import ZoneInfo

from croniter import croniter

from app.core.logging import setup_logging
from app.db import crud
from app.db.engine import get_session
from app.tasks.celery_app import celery_app
from app.tasks.execute import execute_job


logger = logging.getLogger("connecthub.tasks.dispatcher")


def _floor_to_minute(dt: datetime) -> datetime:
    return dt.replace(second=0, microsecond=0)


@celery_app.task(name="connecthub.dispatcher.tick")
def tick() -> dict[str, int]:
    """
    Beat 每分钟触发一次：
    - 读取 enabled Jobs
    - cron_expr 到点则触发 execute_job
    - last_run_at 防止同一分钟重复触发
    """
    setup_logging()

    session = get_session()
    tz = ZoneInfo("Asia/Shanghai")
    now = datetime.now(tz)
    now_min = _floor_to_minute(now)
    triggered = 0

    try:
        for job in crud.list_enabled_jobs(session):
            last = job.last_run_at
            if last is not None:
                # SQLite 通常存 naive datetime；按 Asia/Shanghai 解释
                if last.tzinfo is None:
                    last_min = _floor_to_minute(last.replace(tzinfo=tz))
                else:
                    last_min = _floor_to_minute(last.astimezone(tz))
                # 防御：若 last_run_at 被错误写成 UTC 等导致“在未来”，则忽略该值避免任务永久不触发
                if last_min > now_min:
                    logger.warning(
                        "job.last_run_at appears in the future (ignored) job_id=%s last_run_at=%s now=%s",
                        job.id,
                        last,
                        now,
                    )
                else:
                    if last_min >= now_min:
                        continue

            # croniter 默认按传入 datetime 计算，这里用 Asia/Shanghai
            base = now_min - timedelta(minutes=1)
            itr = croniter(job.cron_expr, base)
            nxt = itr.get_next(datetime)
            if _floor_to_minute(nxt.replace(tzinfo=tz)) != now_min:
                continue

            execute_job.delay(job_id=job.id)
            # 写入时保留 tz 信息，避免在 PostgreSQL timestamptz 中被误当 UTC 导致“未来 last_run_at”
            crud.update_job_last_run_at(session, job.id, now_min)
            triggered += 1

    except Exception:  # noqa: BLE001
        logger.exception("dispatcher.tick failed")
    finally:
        session.close()

    return {"triggered": triggered}