Add GetMaxAPIVersion to get max supported API

Author: lucacome

client/nginx.go

@@ -610,6 +610,23 @@ func versionSupported(n int) bool {
 	return false
 }
 
+// GetMaxAPIVersion returns the maximum API version supported by the server and the client.
+func (client *NginxClient) GetMaxAPIVersion() (int, error) {
+	serverVersions, err := client.getAPIVersions(client.httpClient, client.apiEndpoint)
+	if err != nil {
+		return 0, fmt.Errorf("failed to get max API version: %w", err)
+	}
+
+	maxServerVersion := slices.Max(*serverVersions)
+	maxClientVersion := slices.Max(supportedAPIVersions)
+
+	if maxServerVersion > maxClientVersion {
+		return maxClientVersion, nil
+	}
+
+	return maxServerVersion, nil
+}
+
 func (client *NginxClient) getAPIVersions(httpClient *http.Client, endpoint string) (*versions, error) {
 	ctx, cancel := context.WithTimeout(context.Background(), client.ctxTimeout)
 	defer cancel()

client/nginx_test.go

@@ -752,3 +752,67 @@ func TestGetStats_SSL(t *testing.T) {
 		t.Fatalf("SSL stats: expected %v, actual %v", testStats, stats.SSL)
 	}
 }
+
+func TestGetMaxAPIVersionServer(t *testing.T) {
+	t.Parallel()
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		switch {
+		case r.RequestURI == "/":
+			_, err := w.Write([]byte(`[4, 5, 6, 7]`))
+			if err != nil {
+				t.Fatalf("unexpected error: %v", err)
+			}
+		default:
+			_, err := w.Write([]byte(`{}`))
+			if err != nil {
+				t.Fatalf("unexpected error: %v", err)
+			}
+		}
+	}))
+	defer ts.Close()
+
+	c, err := NewNginxClient(ts.URL)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	maxVer, err := c.GetMaxAPIVersion()
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if maxVer != 7 {
+		t.Fatalf("expected 7, got %v", maxVer)
+	}
+}
+
+func TestGetMaxAPIVersionClient(t *testing.T) {
+	t.Parallel()
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		switch {
+		case r.RequestURI == "/":
+			_, err := w.Write([]byte(`[4, 5, 6, 7, 8, 9, 25]`))
+			if err != nil {
+				t.Fatalf("unexpected error: %v", err)
+			}
+		default:
+			_, err := w.Write([]byte(`{}`))
+			if err != nil {
+				t.Fatalf("unexpected error: %v", err)
+			}
+		}
+	}))
+	defer ts.Close()
+
+	c, err := NewNginxClient(ts.URL)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	maxVer, err := c.GetMaxAPIVersion()
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if maxVer != c.apiVersion {
+		t.Fatalf("expected %v, got %v", c.apiVersion, maxVer)
+	}
+}

docker/Dockerfile

@@ -1,4 +1,4 @@
-# syntax=docker/dockerfile:1.7
+# syntax=docker/dockerfile:1.8
 FROM debian:12-slim
 
 LABEL maintainer="NGINX Docker Maintainers <integrations@nginx.com>"