"""离线检测定时调度器

使用 APScheduler 在 Django 进程中启动后台线程，每 30 秒检测一次终端心跳超时。
"""
import logging

from apscheduler.schedulers.background import BackgroundScheduler
from django.utils.timezone import now

logger = logging.getLogger(__name__)

CHECK_INTERVAL_SECONDS = 30  # 检测间隔：30 秒

_scheduler: BackgroundScheduler | None = None


def _check_offline_terminals():
    """检测超时心跳的终端(3 分钟内未心跳)，标记为离线并推送 WebSocket 通知"""
    from datetime import timedelta

    from apps.core.models import AiSmartTerminal

    HEARTBEAT_TIMEOUT = timedelta(minutes=3)
    threshold = now() - HEARTBEAT_TIMEOUT

    offline_terminals = AiSmartTerminal.objects.filter(
        online_status=1,
        last_heartbeat_time__isnull=False,
        last_heartbeat_time__lt=threshold,
    )

    if not offline_terminals.exists():
        return

    offline_list = list(offline_terminals.values("stcd", "stnm"))
    count = offline_terminals.update(online_status=0)

    logger.warning("标记 %d 个终端为离线:", count)
    for t in offline_list:
        logger.warning("  - %s (%s)", t["stcd"], t["stnm"])

    # WebSocket 推送离线通知
    try:
        from asgiref.sync import async_to_sync
        from channels.layers import get_channel_layer

        channel_layer = get_channel_layer()
        if channel_layer is not None:
            async_to_sync(channel_layer.group_send)(
                "terminal_status",
                {
                    "type": "terminal.status",
                    "data": {
                        "event": "offline",
                        "count": count,
                        "terminals": offline_list,
                    },
                },
            )
    except Exception:
        logger.exception("WebSocket 推送失败")


def start_offline_checker():
    """启动离线检测后台调度器（仅在主进程中启动一次）"""
    global _scheduler
    if _scheduler is not None:
        return  # 已启动，避免重复

    _scheduler = BackgroundScheduler(daemon=True)
    _scheduler.add_job(
        _check_offline_terminals,
        "interval",
        seconds=CHECK_INTERVAL_SECONDS,
        id="check_terminal_offline",
        replace_existing=True,
    )
    _scheduler.start()
    logger.info("离线检测调度器已启动，每 %d 秒检测一次", CHECK_INTERVAL_SECONDS)