From 83e2740d68ec11904dabf3b867f32661c20da560 Mon Sep 17 00:00:00 2001
From: Virgil <virgil@lethean.io>
Date: Fri, 3 Apr 2026 20:32:04 +0000
Subject: [PATCH] Add HTTP health endpoint

---
 http_server.go  | 85 +++++++++++++++++++++++++++++++++++++++++++++++++
 service_test.go | 46 ++++++++++++++++++++++++++
 2 files changed, 131 insertions(+)
 create mode 100644 http_server.go

diff --git a/http_server.go b/http_server.go
new file mode 100644
index 0000000..47098fb
--- /dev/null
+++ b/http_server.go
@@ -0,0 +1,85 @@
+package dns
+
+import (
+	"context"
+	"encoding/json"
+	"net"
+	"net/http"
+	"strconv"
+	"time"
+)
+
+// HTTPServer owns the health endpoint listener and server.
+type HTTPServer struct {
+	listener net.Listener
+	server   *http.Server
+}
+
+func (server *HTTPServer) Address() string {
+	if server == nil || server.listener == nil {
+		return ""
+	}
+	return server.listener.Addr().String()
+}
+
+func (server *HTTPServer) Close() error {
+	if server == nil {
+		return nil
+	}
+	shutdownContext, cancel := context.WithTimeout(context.Background(), 2*time.Second)
+	defer cancel()
+
+	if server.server != nil {
+		if err := server.server.Shutdown(shutdownContext); err != nil {
+			_ = server.server.Close()
+			return err
+		}
+		return nil
+	}
+
+	if server.listener != nil {
+		return server.listener.Close()
+	}
+	return nil
+}
+
+// ServeHTTPHealth starts a minimal HTTP server exposing GET /health.
+//
+//	service.ServeHTTPHealth("127.0.0.1", 5554)
+func (service *Service) ServeHTTPHealth(bind string, port int) (*HTTPServer, error) {
+	if bind == "" {
+		bind = "127.0.0.1"
+	}
+
+	address := net.JoinHostPort(bind, strconv.Itoa(port))
+	listener, err := net.Listen("tcp", address)
+	if err != nil {
+		return nil, err
+	}
+
+	mux := http.NewServeMux()
+	mux.HandleFunc("/health", func(responseWriter http.ResponseWriter, request *http.Request) {
+		if request.Method != http.MethodGet {
+			responseWriter.WriteHeader(http.StatusMethodNotAllowed)
+			return
+		}
+
+		responseWriter.Header().Set("Content-Type", "application/json")
+		_ = json.NewEncoder(responseWriter).Encode(service.Health())
+	})
+
+	server := &http.Server{
+		Handler: mux,
+	}
+
+	httpServer := &HTTPServer{
+		listener: listener,
+		server:   server,
+	}
+
+	go func() {
+		_ = server.Serve(listener)
+	}()
+
+	return httpServer, nil
+}
diff --git a/service_test.go b/service_test.go
index bb4dc65..d015c40 100644
--- a/service_test.go
+++ b/service_test.go
@@ -4,6 +4,7 @@ import (
 	"context"
 	"encoding/json"
 	"errors"
+	"io"
 	"net/http"
 	"net/http/httptest"
 	"strings"
@@ -300,6 +301,51 @@ func TestServiceHealthUsesChainTreeRootAfterDiscovery(t *testing.T) {
 	}
 }
 
+func TestServiceServeHTTPHealthReturnsJSON(t *testing.T) {
+	service := NewService(ServiceOptions{
+		Records: map[string]NameRecords{
+			"gateway.charon.lthn": {
+				A: []string{"10.10.10.10"},
+			},
+		},
+	})
+
+	httpServer, err := service.ServeHTTPHealth("127.0.0.1", 0)
+	if err != nil {
+		t.Fatalf("expected health HTTP server to start: %v", err)
+	}
+	defer func() {
+		_ = httpServer.Close()
+	}()
+
+	response, err := http.Get("http://" + httpServer.Address() + "/health")
+	if err != nil {
+		t.Fatalf("expected health endpoint to respond: %v", err)
+	}
+	defer func() {
+		_ = response.Body.Close()
+	}()
+
+	if response.StatusCode != http.StatusOK {
+		t.Fatalf("unexpected health status: %d", response.StatusCode)
+	}
+
+	var payload map[string]any
+	body, err := io.ReadAll(response.Body)
+	if err != nil {
+		t.Fatalf("expected health payload: %v", err)
+	}
+	if err := json.Unmarshal(body, &payload); err != nil {
+		t.Fatalf("expected health JSON: %v", err)
+	}
+	if payload["status"] != "ready" {
+		t.Fatalf("expected ready health status, got %#v", payload["status"])
+	}
+	if payload["names_cached"] != float64(1) {
+		t.Fatalf("expected one cached name, got %#v", payload["names_cached"])
+	}
+}
+
 func TestServiceDiscoverReplacesRecordsFromDiscoverer(t *testing.T) {
 	records := []map[string]NameRecords{
 		{
-- 
2.45.3