"""Operational endpoints used by Docker/Kubernetes probes and by humans."""

from __future__ import annotations

from typing import Any

from django.conf import settings
from django.db import connection
from drf_spectacular.utils import extend_schema
from rest_framework import status
from rest_framework.permissions import AllowAny
from rest_framework.request import Request
from rest_framework.response import Response
from rest_framework.views import APIView

from apps.search.backends import get_search_backend


class LivenessView(APIView):
    """Cheap check: the process is up and can answer HTTP."""

    permission_classes = [AllowAny]
    authentication_classes: list = []
    throttle_classes: list = []

    @extend_schema(tags=["health"], responses={200: dict})
    def get(self, request: Request) -> Response:  # noqa: ARG002
        return Response({"status": "ok", "service": settings.SERVICE_NAME})


class ReadinessView(APIView):
    """
    Deep check: verifies every dependency the API needs to serve traffic.

    Returns 503 when any dependency is down so an orchestrator stops routing
    traffic to this instance.
    """

    permission_classes = [AllowAny]
    authentication_classes: list = []
    throttle_classes: list = []

    @extend_schema(tags=["health"], responses={200: dict, 503: dict})
    def get(self, request: Request) -> Response:  # noqa: ARG002
        checks: dict[str, Any] = {
            "database": _check(_database),
            "search": _check(_search),
        }
        healthy = all(c["healthy"] for c in checks.values())
        return Response(
            {"status": "ok" if healthy else "degraded", "checks": checks},
            status=status.HTTP_200_OK if healthy else status.HTTP_503_SERVICE_UNAVAILABLE,
        )


def _check(fn) -> dict[str, Any]:  # noqa: ANN001
    try:
        detail = fn()
    except Exception as exc:  # noqa: BLE001 - health checks must never raise
        return {"healthy": False, "detail": str(exc)[:200]}
    return {"healthy": True, "detail": detail}


def _database() -> str:
    with connection.cursor() as cursor:
        cursor.execute("SELECT 1")
        cursor.fetchone()
    return "reachable"


def _search() -> str:
    backend = get_search_backend()
    backend.ping()
    return f"{backend.name} reachable"