Refactor default listen port

If both tls-cert-file and tls-key-file are set, assume the intent to use
TLS.

If TLS is enabled, default to port 8443. Otherwise, 8080.

Author: dwrz

llama-swap.go

@@ -28,7 +28,7 @@ var (
 func main() {
 	// Define a command-line flag for the port
 	configPath := flag.String("config", "config.yaml", "config file name")
-	listenStr := flag.String("listen", ":8080", "listen ip/port")
+	listenStr := flag.String("listen", "", "listen ip/port")
 	certFile := flag.String("tls-cert-file", "", "TLS certificate file")
 	keyFile := flag.String("tls-key-file", "", "TLS key file")
 	showVersion := flag.Bool("version", false, "show version of build")
@@ -41,12 +41,6 @@ func main() {
 		os.Exit(0)
 	}
 
-	if (*certFile != "" && *keyFile == "") ||
-		(*certFile == "" && *keyFile != "") {
-		fmt.Println("Error: Both --tls-cert-file and --tls-key-file must be provided for TLS.")
-		os.Exit(1)
-	}
-
 	conf, err := config.LoadConfig(*configPath)
 	if err != nil {
 		fmt.Printf("Error loading config: %v\n", err)
@@ -63,6 +57,24 @@ func main() {
 		gin.SetMode(gin.ReleaseMode)
 	}
 
+	// Validate TLS flags.
+	var useTLS bool
+	if (*certFile != "" && *keyFile == "") ||
+		(*certFile == "" && *keyFile != "") {
+		fmt.Println("Error: Both --tls-cert-file and --tls-key-file must be provided for TLS.")
+		os.Exit(1)
+	} else {
+		useTLS = true
+	}
+	// Set default ports.
+	if *listenStr == "" {
+		defaultPort := ":8080"
+		if useTLS {
+			defaultPort = ":8443"
+		}
+		listenStr = &defaultPort
+	}
+
 	// Setup channels for server management
 	exitChan := make(chan struct{})
 	sigChan := make(chan os.Signal, 1)
@@ -177,7 +189,7 @@ func main() {
 	// Start server
 	go func() {
 		var err error
-		if *certFile != "" && *keyFile != "" {
+		if useTLS {
 			fmt.Printf("llama-swap listening with TLS on https://%s\n", *listenStr)
 			err = srv.ListenAndServeTLS(*certFile, *keyFile)
 		} else {