from django.conf import settings
from django.db import connection, OperationalError
from django.core.cache import cache
from django.http import HttpResponse
from rest_framework.decorators import api_view, permission_classes, authentication_classes
from rest_framework.permissions import AllowAny
from rest_framework.response import Response
from rest_framework import status


@api_view(["GET"])
@authentication_classes([])
@permission_classes([AllowAny])
def healthcheck(request):
    """Liveness + readiness probe endpoint. Returns 200 when all dependencies are reachable."""
    checks = {}
    overall_ok = True

    # Database
    try:
        connection.ensure_connection()
        checks["db"] = "ok"
    except OperationalError as exc:
        checks["db"] = f"error: {exc}"
        overall_ok = False

    # Cache / Redis
    try:
        key = "_healthcheck"
        cache.set(key, "1", timeout=5)
        assert cache.get(key) == "1"
        checks["cache"] = "ok"
    except Exception as exc:
        checks["cache"] = f"error: {exc}"
        overall_ok = False

    http_status = status.HTTP_200_OK if overall_ok else status.HTTP_503_SERVICE_UNAVAILABLE
    return Response(
        {"status": "ok" if overall_ok else "degraded", "checks": checks},
        status=http_status,
    )


@api_view(["GET"])
@authentication_classes([])
@permission_classes([AllowAny])
def metrics(request):
    """Prometheus metrics scrape endpoint.

    Restricted to internal networks via METRICS_ALLOWED_HOSTS setting (checked
    at the reverse-proxy level in prod). Returns 403 when the feature flag is
    off so the endpoint is a no-op in environments where it is not configured.
    """
    if not getattr(settings, "METRICS_ENABLED", False):
        return HttpResponse(status=403)

    from prometheus_client import generate_latest, CONTENT_TYPE_LATEST
    return HttpResponse(generate_latest(), content_type=CONTENT_TYPE_LATEST)