Add drive mode flag and switching

rover/main.go

@@ -10,7 +10,6 @@ import (
 )
 
 const (
-	gamepadChanBufSize = 16
 	// Logitech gamepad codes
 	codeLeftAnalogX  = 0
 	codeLeftAnalogY  = 1
@@ -31,6 +30,9 @@ const (
 	codeLogitech     = 316
 	codeLeftAnalog   = 317
 	codeRightAnalog  = 318
+)
+
+const (
 	// event types
 	button = iota
 	axisX
@@ -38,6 +40,8 @@ const (
 	axisZ
 )
 
+const gamepadChanBufSize = 16
+
 type event struct {
 	code  int
 	value int32
@@ -65,14 +69,49 @@ type gamepadEvents struct {
 	back, start, logitech         chan event
 }
 
+const (
+	// drive modes
+	tank = iota
+	joystick
+)
+
+const driveModeCount = 2
+
+type driveMode int
+
+func (d driveMode) String() string {
+	switch d {
+	case tank:
+		return "tank"
+	case joystick:
+		return "joystick"
+	default:
+		return "unknown"
+	}
+}
+
+func (d *driveMode) Set(value string) error {
+	switch value {
+	case "tank":
+		*d = tank
+	case "joystick":
+		*d = joystick
+	default:
+		return fmt.Errorf("unknown drive mode: %v", value)
+	}
+	return nil
+}
+
 func main() {
 	var (
 		gamepad string
 		listen  string
+		mode    driveMode
 	)
 
 	flag.StringVar(&gamepad, "gamepad", "/dev/input/event0", "the gamepad device path")
 	flag.StringVar(&listen, "listen", "localhost:8080", "the HTTP listen address and port")
+	flag.Var(&mode, "mode", "the drive mode (default \"tank\")")
 	flag.Parse()
 
 	if !evdev.IsInputDevice(gamepad) {
@@ -98,13 +137,15 @@ func main() {
 		logitech:    make(chan event, gamepadChanBufSize),
 	}
 
-	go control(events)
+	go control(mode, events)
 	go gamepadRead(device, events)
 
+	log.Print("HTTP server started")
 	log.Fatalf("error listening and serving: %v", http.ListenAndServe(listen, nil))
 }
 
-func control(events *gamepadEvents) {
+func control(mode driveMode, events *gamepadEvents) {
+	log.Printf("control loop started (drive mode: %v)", mode)
 	for {
 		select {
 		case e := <-events.leftAnalog:
@@ -130,12 +171,17 @@ func control(events *gamepadEvents) {
 		case e := <-events.start:
 			log.Println("start", e)
 		case e := <-events.logitech:
-			log.Println("logitech", e)
+			if e.value > 0 {
+				mode++
+				mode %= driveModeCount
+				log.Printf("switched drive mode: %v", mode)
+			}
 		}
 	}
 }
 
 func gamepadRead(device *evdev.InputDevice, events *gamepadEvents) {
+	log.Print("gamepad read loop started")
 	for {
 		e, err := device.ReadOne()
 		if err != nil {