"""告警相关 Celery 任务"""
import traceback
from datetime import datetime
from sqlalchemy import func, case
from app.core.celery_app import celery_app
from app.core.database import SessionLocal


@celery_app.task(queue='h3c_onu_ms', ignore_result=True)
def check_school_offline_alerts():
    """
    检查是否有学校全部离线（在线率为 0%），如有则发送企业微信告警。
    该任务在每次全量状态检查完成后异步调用。
    """
    from app.models.device import ONUDevice, DeviceStatusHistory
    from app.services.wechat_service import send_wechat_markdown

    db = SessionLocal()
    try:
        # 每台设备最新状态的子查询
        latest_subq = (
            db.query(
                DeviceStatusHistory.onu_device_id,
                func.max(DeviceStatusHistory.checked_at).label("max_checked_at")
            )
            .group_by(DeviceStatusHistory.onu_device_id)
            .subquery()
        )
        latest_status_subq = (
            db.query(
                DeviceStatusHistory.onu_device_id,
                DeviceStatusHistory.status
            )
            .join(
                latest_subq,
                (DeviceStatusHistory.onu_device_id == latest_subq.c.onu_device_id) &
                (DeviceStatusHistory.checked_at == latest_subq.c.max_checked_at)
            )
            .subquery()
        )

        # 按学校聚合在线率，只查询在线数为 0 的学校
        rows = (
            db.query(
                ONUDevice.school_name,
                ONUDevice.region,
                func.count().label("total"),
                func.sum(case((latest_status_subq.c.status == 'online', 1), else_=0)).label("online"),
            )
            .outerjoin(latest_status_subq, ONUDevice.id == latest_status_subq.c.onu_device_id)
            .group_by(ONUDevice.school_name, ONUDevice.region)
            .having(
                func.sum(case((latest_status_subq.c.status == 'online', 1), else_=0)) == 0
            )
            .all()
        )

        if not rows:
            return {"alerted": False, "reason": "没有全离线的学校"}

        # 构造告警消息
        now_str = datetime.now().strftime("%Y-%m-%d %H:%M:%S")
        lines = [
            "## <font color=\"warning\">[告警] 学校全部离线</font>",
            f"> 检查时间：{now_str}",
            "> 以下学校所有设备均处于离线状态：",
            "",
        ]
        for row in rows:
            school = row.school_name or "未知"
            region = row.region or "未知"
            total = int(row.total or 0)
            if total > 0:
                lines.append(f"- **{school}**（{region}）: {total} 台设备全离线")

        content = "\n".join(lines)
        send_wechat_markdown(content)
        return {"alerted": True, "schools": len(rows)}
    except Exception as e:
        return {"alerted": False, "error": str(e), "traceback": traceback.format_exc()}
    finally:
        db.close()