Make the serial communication work

agent.go

@@ -1,36 +1,44 @@
 package main
 
-// Create a new virtual serial device:
-// socat PTY,link=/dev/ttyS10 PTY,link=/dev/ttyS11
-
 import (
 	"log"
 	"os"
 	"path"
+	"errors"
 
 	"github.com/fsnotify/fsnotify"
-	"github.com/tarm/serial"
 	"github.com/mkideal/cli"
+	"github.com/tarm/serial"
 )
 
-// TODO: Make the error code optional (as a parameter)
-func stop() {
+func stop(exitCode int) {
 	log.Println("Have a nice day.")
-	os.Exit(0)
+	os.Exit(exitCode)
 }
 
-func waitAndExecuteCommandsFromDevice(device string) {
-	config := &serial.Config{Name: device, Baud: 115200}
-	serial, err := serial.OpenPort(config)
-
-	if err != nil {
-		log.Fatal(err)
+type message struct {
+	msgType byte
+	data []byte
 }
 
-	log.Printf("Open the connection to the n3rdpad over %s", device)
+const (
+	MSG_TYPE_ANSWER_OK = 0x01
+	MSG_TYPE_ANSWER_NOOK = 0x02
+	MSG_TYPE_AGENTID = 0x03
+	MSG_TYPE_CONFIG = 0x04
+)
 
-	// Read from serial
-	buffer := make([]byte, 128)
+func decodeByteString(bytes []byte, num int) (msg message, err error) {
+	if bytes[0] == 0x3c && bytes[1] == 0x3e &&
+		bytes[num-1] == 0x0A && bytes[num-2] == 0x0D {
+		return message{msgType: bytes[2], data: bytes[3:num-2]}, nil
+	}
+
+	return message{msgType: 0x00, data: make([]byte, 1)}, errors.New("Can't decode the byte array.")
+}
+
+func waitAndExecuteCommandsFromDevice(serial *serial.Port) {
+	buffer := make([]byte, 40)
 	for {
 		num, err := serial.Read(buffer)
 
@@ -38,12 +46,21 @@ func waitAndExecuteCommandsFromDevice(device string) {
 			log.Fatal(err)
 		}
 
-		// TODO: Do something with the incomind commands
-		log.Printf("%q", buffer[:num])
+		input, err := decodeByteString(buffer, num)
+		if err != nil {
+			log.Fatal(err)
+		} else {
+			switch (input.msgType) {
+			case MSG_TYPE_AGENTID:
+				log.Printf("Key pressed: %d", input.data[0])
+			default:
+				log.Fatal("Can't recognize the message type.")
+			}
+		}
 	}
 }
 
-func watchForConfigChanges(configFile string) {
+func watchForConfigChanges(configFile string, serial *serial.Port) {
 	watcher, err := fsnotify.NewWatcher()
 	if err != nil {
 		log.Fatal(err)
@@ -72,7 +89,7 @@ func watchForConfigChanges(configFile string) {
 					}
 				}
 
-				// Some editors have a feature calles "swap save" (like vim), which
+				// Some editors have a feature called "swap save" (like vim), which
 				// will trigger a simple WRITE event, instead it wil trigger RENAME
 				// -> CHMOD -> REMOVE in that order. So we lost track of the file.
 				// To prevent this, we add the file again, if it exist after a
@@ -82,13 +99,13 @@ func watchForConfigChanges(configFile string) {
 						watcher.Add(event.Name)
 					} else {
 						log.Fatal("Lost the configuration file. We stop now.")
-						stop()
+						stop(1)
 					}
 				}
 			case err := <-watcher.Errors:
 				log.Println("We have the following problem with the configuration file: ", err)
 				log.Println("Try the fix this problem by yourself and restart the agent.")
-				stop()
+				stop(2)
 			}
 		}
 	}()
@@ -117,16 +134,28 @@ func main() {
 		}
 		if args.Device == "" {
 			log.Fatal("You need to specify the serial device with the --device parameter.")
-			stop();
+			stop(3)
 		}
 
 		if !args.Help {
 			// Start up the application
 			log.Println("Using the configuration file", configFile)
-			go watchForConfigChanges(configFile)
-			waitAndExecuteCommandsFromDevice(args.Device)
 
-			stop()
+			// Open the serial connection
+			config := &serial.Config{Name: args.Device, Baud: 115200}
+			serial, err := serial.OpenPort(config)
+
+			if err != nil {
+				log.Fatal(err)
+				return nil
+			}
+
+			log.Printf("Open the connection to the n3rdpad over %s", args.Device)
+
+			go watchForConfigChanges(configFile, serial)
+			waitAndExecuteCommandsFromDevice(serial)
+
+			stop(0)
 		}
 
 		return nil