Add text-to-speech support. (#13)

Reviewed-on: #13
Co-authored-by: Anna Rose Wiggins <annabunches@gmail.com>
Co-committed-by: Anna Rose Wiggins <annabunches@gmail.com>

cmd/joyful/tts.go

@@ -0,0 +1,135 @@
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"os/exec"
+	"strconv"
+	"time"
+
+	"git.annabunches.net/annabunches/joyful/internal/logger"
+	"github.com/ebitengine/oto/v3"
+	flag "github.com/spf13/pflag"
+)
+
+type TTSOptions struct {
+	Disabled bool
+	Voice    string
+	Volume   int
+	Pitch    int
+	Range    int
+	Speed    int
+}
+
+type TTS struct {
+	options *TTSOptions
+	otoCtx  *oto.Context
+	phrases map[string][]byte
+}
+
+const (
+	playbackCheckIntervalMs = 100
+)
+
+// TODO: make most of this configurable via file
+func addTTSFlags() *TTSOptions {
+	ops := &TTSOptions{}
+
+	flag.BoolVar(&ops.Disabled, "no-tts", false, "Disable text-to-speech.")
+	flag.StringVar(&ops.Voice, "tts-voice", "en", "Which voice to use for TTS; see 'espeak --voices' for a full list of options.")
+	flag.IntVar(&ops.Volume, "tts-volume", 100, "Text to speech volume")
+	flag.IntVar(&ops.Pitch, "tts-pitch", 50, "Text to speech volume")
+	flag.IntVar(&ops.Range, "tts-range", 50, "Text to speech volume")
+	flag.IntVar(&ops.Range, "tts-speed", 175, "Text to speech speaking speed (in words per minute)")
+
+	return ops
+}
+
+func makeOtoContext() (*oto.Context, error) {
+	op := &oto.NewContextOptions{
+		SampleRate:   22050,
+		ChannelCount: 1,
+		Format:       oto.FormatSignedInt16LE,
+	}
+
+	otoCtx, readyChan, err := oto.NewContext(op)
+	if err != nil {
+		return nil, err
+	}
+	<-readyChan // wait for initialization
+
+	return otoCtx, nil
+}
+
+func newTTS(ops *TTSOptions) (*TTS, error) {
+	if ops.Disabled {
+		return nil, nil
+	}
+
+	context, err := makeOtoContext()
+	if err != nil {
+		return nil, err
+	}
+
+	return &TTS{
+		options: ops,
+		otoCtx:  context,
+		phrases: make(map[string][]byte),
+	}, nil
+}
+
+func (t *TTS) AddMessage(msg string) {
+	// TODO: need to get lots of input validation in here
+	// We execute `espeak-ng` directly because extant libraries produce terrible output
+	// compared to the command-line utility. This also gives us a chance to
+	cmd := exec.Command(
+		"espeak-ng", "--stdout",
+		"-v", t.options.Voice,
+		"-a", strconv.Itoa(t.options.Volume),
+		"-p", strconv.Itoa(t.options.Pitch),
+		"-P", strconv.Itoa(t.options.Range),
+		"-s", strconv.Itoa(t.options.Speed),
+		msg,
+	)
+
+	wavData, err := cmd.Output()
+	if err != nil {
+		logger.LogError(err, "Failed to create TTS data")
+		return
+	}
+
+	t.phrases[msg] = wavData
+}
+
+// "Say" generates TTS audio and plays it in a go routine
+func (t *TTS) Say(msg string) error {
+	if _, ok := t.phrases[msg]; !ok {
+		return fmt.Errorf("tried to play non-buffered phrase '%s'", msg)
+	}
+
+	go func(buf []byte) {
+		buffer := bytes.NewBuffer(buf)
+		player := t.otoCtx.NewPlayer(buffer)
+
+		volume := 0.0
+		player.SetVolume(volume)
+		player.Play()
+
+		// Gradually ramp up the volume to avoid harsh clicks
+		for player.Volume() < 1.0 {
+			volume += 0.01
+			if volume > 1.0 {
+				volume = 1.0
+			}
+
+			player.SetVolume(volume)
+			time.Sleep(1 * time.Millisecond)
+		}
+
+		for player.IsPlaying() {
+			time.Sleep(playbackCheckIntervalMs * time.Millisecond)
+		}
+	}(t.phrases[msg])
+
+	return nil
+}