Add optional TLS support (#340)

* Add optional TLS support

Introduce HTTPS support with net/http Server.ListenAndServeTLS.

This should enable the option of serving via HTTPS without a reverse
proxy.

Add two flags:
- tls-cert-file (path to the TLS certificate file)
- tls-key-file (path to the TLS private key file)

Both flags must be supplied together; otherwise exit with error.

If both flags are present, call srv.ListenAndServeTLS.
If not, fall back to the existing srv.ListenAndServe (HTTP); no changes
to existing non‑TLS behavior.

llama-swap.go

@@ -28,7 +28,9 @@ 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")
 	watchConfig := flag.Bool("watch-config", false, "Automatically reload config file on change")
 
@@ -55,6 +57,23 @@ func main() {
 		gin.SetMode(gin.ReleaseMode)
 	}
 
+	// Validate TLS flags.
+	var useTLS = (*certFile != "" && *keyFile != "")
+	if (*certFile != "" && *keyFile == "") ||
+		(*certFile == "" && *keyFile != "") {
+		fmt.Println("Error: Both --tls-cert-file and --tls-key-file must be provided for TLS.")
+		os.Exit(1)
+	}
+
+	// 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)
@@ -167,9 +186,16 @@ func main() {
 	}()
 
 	// Start server
-	fmt.Printf("llama-swap listening on %s\n", *listenStr)
 	go func() {
-		if err := srv.ListenAndServe(); err != nil && err != http.ErrServerClosed {
+		var err error
+		if useTLS {
+			fmt.Printf("llama-swap listening with TLS on https://%s\n", *listenStr)
+			err = srv.ListenAndServeTLS(*certFile, *keyFile)
+		} else {
+			fmt.Printf("llama-swap listening on http://%s\n", *listenStr)
+			err = srv.ListenAndServe()
+		}
+		if err != nil && err != http.ErrServerClosed {
 			log.Fatalf("Fatal server error: %v\n", err)
 		}
 	}()