"""健康检查 — 存活探针与就绪探针分离

为什么必须拆开：
- 存活探针（liveness）只回答「进程还活着吗」，绝不能探测外部依赖。
  否则数据库抖一下，编排系统会判定进程已死并反复重启容器，
  把一次依赖故障放大成全站雪崩。
- 就绪探针（readiness）回答「现在能对外服务吗」。依赖不可用时返回 503，
  由负载均衡把该实例摘掉，依赖恢复后自动回来。
"""
from __future__ import annotations

import logging

import anyio
from fastapi import APIRouter
from fastapi.responses import JSONResponse
from sqlalchemy import text

from app.core.config import settings
from app.core.database import AsyncSessionLocal
from app.core.mom_database import mom_engine

logger = logging.getLogger("track.health")

router = APIRouter(tags=["健康检查"])


async def _probe_primary_db() -> bool:
    """主库探活 — 业务强依赖，失败即不就绪"""
    try:
        async with AsyncSessionLocal() as session:
            await session.execute(text("SELECT 1"))
        return True
    except Exception:
        logger.exception("主库探活失败")
        return False


def _probe_mom_db_sync() -> bool:
    try:
        with mom_engine.connect() as conn:
            conn.execute(text("SELECT 1"))
        return True
    except Exception:
        logger.exception("MOM 库探活失败")
        return False


async def _probe_mom_db() -> bool:
    # MOM 用的是同步引擎，放线程池执行，避免阻塞事件循环
    return await anyio.to_thread.run_sync(_probe_mom_db_sync)


async def _collect() -> tuple[bool, dict[str, str]]:
    primary_ok = await _probe_primary_db()
    mom_ok = await _probe_mom_db()
    checks = {
        "database": "ok" if primary_ok else "fail",
        # MOM 是外部只读依赖：挂掉时登录/选料降级，但扫码、流转、看板仍可用。
        # 因此只标记 degraded、不摘流量 —— 否则 MOM 一抖就让在产车间全线停摆。
        "mom_database": "ok" if mom_ok else "degraded",
    }
    return primary_ok, checks


@router.get("/health/live", include_in_schema=False)
async def liveness() -> dict:
    """存活探针：不触碰任何依赖，恒定快速返回"""
    return {"status": "ok"}


@router.get("/health/ready", include_in_schema=False)
async def readiness() -> JSONResponse:
    """就绪探针：主库不可用时返回 503，让负载均衡摘流量"""
    ready, checks = await _collect()
    return JSONResponse(
        {"status": "ready" if ready else "not_ready", "checks": checks},
        status_code=200 if ready else 503,
    )


@router.get("/health", include_in_schema=False)
async def health() -> JSONResponse:
    """兼容旧监控脚本：语义等同就绪探针，并附带版本号"""
    ready, checks = await _collect()
    return JSONResponse(
        {
            "status": "ok" if ready else "unavailable",
            "version": settings.APP_VERSION,
            "checks": checks,
        },
        status_code=200 if ready else 503,
    )