[audio] WIP on Gobot audio support using mpg123, based on code from @colemanserious

Signed-off-by: deadprogram <ron@hybridgroup.com>

README.md

@@ -98,6 +98,7 @@ Gobot has a extensible system for connecting to hardware devices. The following
 
 - [Ardrone](http://ardrone2.parrot.com/) <=> [Package](https://github.com/hybridgroup/gobot/tree/master/platforms/ardrone)
 - [Arduino](http://www.arduino.cc/) <=> [Package](https://github.com/hybridgroup/gobot/tree/master/platforms/firmata)
+- Audio <=> [Package](https://github.com/hybridgroup/gobot/tree/master/platforms/audio)
 - [Beaglebone Black](http://beagleboard.org/Products/BeagleBone+Black/) <=> [Package](https://github.com/hybridgroup/gobot/tree/master/platforms/beaglebone)
 - [Bebop](http://www.parrot.com/usa/products/bebop-drone/) <=> [Package](https://github.com/hybridgroup/gobot/tree/master/platforms/bebop)
 - [C.H.I.P](http://www.nextthing.co/pages/chip) <=> [Package](https://github.com/hybridgroup/gobot/tree/master/platforms/chip)

examples/audio.go

@@ -0,0 +1,31 @@
+package main
+
+import (
+	"time"
+
+	"github.com/hybridgroup/gobot"
+	"github.com/hybridgroup/gobot/platforms/audio"
+)
+
+func main() {
+	gbot := gobot.NewGobot()
+
+	e := audio.NewAudioAdaptor("sound")
+	laser := audio.NewAudioDriver(e, "laser", nil)
+
+	work := func() {
+		gobot.Every(1*time.Second, func() {
+			laser.Sound("./examples/laser.mp3")
+		})
+	}
+
+	robot := gobot.NewRobot("soundBot",
+		[]gobot.Connection{e},
+		[]gobot.Device{laser},
+		work,
+	)
+
+	gbot.AddRobot(robot)
+
+	gbot.Start()
+}

platforms/audio/audio_adaptor.go

@@ -0,0 +1,60 @@
+// Based on aplay audio adaptor written by @colemanserious (https://github.com/colemanserious)
+package audio
+
+import (
+	"errors"
+	"github.com/hybridgroup/gobot"
+	"log"
+	"os"
+	"os/exec"
+)
+
+var _ gobot.Adaptor = (*AudioAdaptor)(nil)
+
+type AudioAdaptor struct {
+	name string
+}
+
+func NewAudioAdaptor(name string) *AudioAdaptor {
+	return &AudioAdaptor{
+		name: name,
+	}
+}
+
+func (a *AudioAdaptor) Name() string { return a.name }
+
+func (a *AudioAdaptor) Connect() []error { return nil }
+
+func (a *AudioAdaptor) Finalize() []error { return nil }
+
+func (a *AudioAdaptor) Sound(fileName string) []error {
+
+	var errorsList []error
+	var err error
+
+	if fileName == "" {
+		log.Println("Require filename for MP3 file.")
+		errorsList = append(errorsList, errors.New("Requires filename for MP3 file."))
+		return errorsList
+	}
+
+	_, err = os.Open(fileName)
+	if err != nil {
+		log.Println(err)
+		errorsList = append(errorsList, err)
+		return errorsList
+	}
+
+	// command to play a MP3 file
+	cmd := exec.Command("mpg123", fileName)
+	err = cmd.Run()
+
+	if err != nil {
+		log.Println(err)
+		errorsList = append(errorsList, err)
+		return errorsList
+	}
+
+	// Need to return to fulfill function sig, even though returning an empty
+	return nil
+}

platforms/audio/audio_adaptor_test.go

@@ -0,0 +1,28 @@
+// Based on aplay audio adaptor written by @colemanserious (https://github.com/colemanserious)
+package audio
+
+import (
+	"os/exec"
+	"testing"
+
+	"github.com/hybridgroup/gobot/gobottest"
+)
+
+func TestAudioAdaptor(t *testing.T) {
+	a := NewAudioAdaptor("tester")
+
+	gobottest.Assert(t, a.Name(), "tester")
+
+	gobottest.Assert(t, len(a.Connect()), 0)
+
+	_, err := exec.LookPath("mpg123")
+	numErrsForTest := 0
+	if err != nil {
+		numErrsForTest = 1
+	}
+	gobottest.Assert(t, len(a.Sound("../resources/foo.wav")), numErrsForTest)
+
+	gobottest.Assert(t, len(a.Connect()), 0)
+
+	gobottest.Assert(t, len(a.Finalize()), 0)
+}

platforms/audio/audio_driver.go

@@ -0,0 +1,73 @@
+// Based on aplay audio adaptor written by @colemanserious (https://github.com/colemanserious)
+
+package audio
+
+import (
+	"fmt"
+	"github.com/hybridgroup/gobot"
+	"time"
+)
+
+var _ gobot.Driver = (*AudioDriver)(nil)
+
+type AudioDriver struct {
+	name       string
+	connection gobot.Connection
+	interval   time.Duration
+	halt       chan bool
+	gobot.Eventer
+	gobot.Commander
+	queue chan string
+}
+
+func NewAudioDriver(a *AudioAdaptor, name string, queue chan string) *AudioDriver {
+	d := &AudioDriver{
+		name:       name,
+		connection: a,
+		interval:   500 * time.Millisecond,
+		queue:      queue,
+		halt:       make(chan bool, 0),
+		Eventer:    gobot.NewEventer(),
+		Commander:  gobot.NewCommander(),
+	}
+	return d
+}
+
+func (d *AudioDriver) Name() string { return d.name }
+
+func (d *AudioDriver) Connection() gobot.Connection {
+	return d.connection
+}
+
+func (d *AudioDriver) Sound(fileName string) []error {
+	return d.Connection().(*AudioAdaptor).Sound(fileName)
+}
+
+func (d *AudioDriver) adaptor() *AudioAdaptor {
+	return d.Connection().(*AudioAdaptor)
+}
+
+func (d *AudioDriver) Start() (err []error) {
+	go d.serve(d.queue)
+	return
+}
+
+func (d *AudioDriver) Halt() (err []error) {
+	return
+}
+
+// Use semaphore to control how many sounds might be playing at a time
+var sem = make(chan int, 1)
+
+// See example at https://golang.org/doc/effective_go.html#concurrency
+// Purpose: receive messages on channel, but throttle execution of playing
+func (d *AudioDriver) serve(queue chan string) {
+	for req := range queue {
+		sem <- 1
+		go func(req string) {
+			fmt.Printf("Playing sound %v\n", req)
+			d.Sound(req)
+			<-sem
+		}(req)
+	}
+}

platforms/audio/audio_driver_test.go

@@ -0,0 +1,28 @@
+// Based on aplay audio adaptor written by @colemanserious (https://github.com/colemanserious)
+
+package audio
+
+import (
+	"os/exec"
+	"testing"
+
+	"github.com/hybridgroup/gobot/gobottest"
+)
+
+func TestAudioDriver(t *testing.T) {
+	d := NewAudioDriver(NewAudioAdaptor("conn"), "dev", nil)
+
+	gobottest.Assert(t, d.Name(), "dev")
+	gobottest.Assert(t, d.Connection().Name(), "conn")
+
+	gobottest.Assert(t, len(d.Start()), 0)
+
+	gobottest.Assert(t, len(d.Halt()), 0)
+
+	_, err := exec.LookPath("mpg123")
+	numErrsForTest := 0
+	if err != nil {
+		numErrsForTest = 1
+	}
+	gobottest.Assert(t, len(d.Sound("../resources/foo.mp3")), numErrsForTest)
+}