"""就绪探针：MySQL / Redis / Milvus 必须是真实探测结果。

B3 修复：原先 ``checks["milvus"] = True`` 是硬编码，健康检查永远报告 Milvus 正常，
属于误导性探针。现在改为真实探测（连接 + ``get_server_version``），并满足：

- 探测有超时（默认 2s），超时返回 ``False`` + ``timeout`` 状态；
- 外部依赖不可用时不抛异常，只返回 ``False`` + 明确状态，整体降级为 ``degraded``；
- pymilvus 是可选依赖（且无类型存根），缺失时返回 ``False`` + ``client_missing``。
"""

import asyncio
from typing import Any

from sqlalchemy import text

from app.core.config import get_settings
from app.infrastructure.db import SessionFactory

MILVUS_PROBE_TIMEOUT_SECONDS = 2.0


def _create_milvus_client(uri: str, token: str) -> Any:
    """延迟导入并建连：pymilvus 为可选依赖，缺失时由调用方转为明确状态。"""
    from pymilvus import AsyncMilvusClient  # type: ignore[import-untyped]

    return AsyncMilvusClient(uri=uri, token=token or None)


class HealthService:
    def __init__(self, *, milvus_timeout_seconds: float = MILVUS_PROBE_TIMEOUT_SECONDS) -> None:
        self._milvus_timeout_seconds = milvus_timeout_seconds

    async def ready(self) -> dict[str, Any]:
        checks: dict[str, bool] = {}
        probes: dict[str, str] = {}
        try:
            async with SessionFactory() as session:
                await session.execute(text("SELECT 1"))
            checks["mysql"] = True
        except Exception:
            checks["mysql"] = False
            probes["mysql"] = "unavailable"
        checks["redis"] = await self._redis_ready()
        milvus_ready, milvus_state = await self._milvus_ready()
        checks["milvus"] = milvus_ready
        probes["milvus"] = milvus_state
        return {
            "status": "ready" if all(checks.values()) else "degraded",
            "checks": checks,
            "probes": probes,
        }

    async def _redis_ready(self) -> bool:
        client = None
        try:
            from redis.asyncio import Redis

            settings = get_settings()
            client = Redis.from_url(
                settings.redis_url,
                socket_connect_timeout=settings.redis_connect_timeout_seconds,
                socket_timeout=settings.redis_connect_timeout_seconds,
                decode_responses=True,
            )
            return bool(await client.ping())
        except Exception:
            return False
        finally:
            if client is not None:
                try:
                    await client.aclose()
                except Exception:
                    pass

    async def _milvus_ready(self) -> tuple[bool, str]:
        """真实探测 Milvus：状态取值 ok / unavailable / client_missing / timeout。"""
        settings = get_settings()
        client: Any = None
        try:
            async with asyncio.timeout(self._milvus_timeout_seconds):
                client = await asyncio.to_thread(
                    _create_milvus_client, settings.milvus_uri, settings.milvus_token
                )
                await client.get_server_version()
            return True, "ok"
        except TimeoutError:
            return False, "timeout"
        except ImportError:
            return False, "client_missing"
        except Exception:
            return False, "unavailable"
        finally:
            await self._close_milvus_client(client)

    @staticmethod
    async def _close_milvus_client(client: Any) -> None:
        if client is None:
            return
        try:
            await client.close()
        except Exception:
            pass