mixer: implement mute/unmute and setting fader level

1 files changed, 88 insertions, 1 deletions

diff --git a/pkg/mixer/mixer.go b/pkg/mixer/mixer.go
index 235978c..c3040fe 100644
--- a/pkg/mixer/mixer.go
+++ b/pkg/mixer/mixer.go
@@ -22,17 +22,104 @@
 
 package mixer
 
+import (
+	"errors"
+	"strings"
+
+	"github.com/scgolang/midi"
+)
+
+type MixerChannel uint8
+type FaderLevel uint8
+
 type Mixer struct {
+	DevIn  *midi.Device
+	DevOut *midi.Device
+}
+
+// TODO: make this confgurabel
+const (
+	CC_MUTE  = byte(0xB1)
+	CC_FADER = byte(0xB0)
+
+	FaderLevelMax = FaderLevel(0x7F)
+	FaderLevel0db = FaderLevel(0x60)
+	FaderLevelOff = FaderLevel(0x00)
+)
+
+func openDevice(devices []*midi.Device, prefix string) (d *midi.Device, err error) {
+	for _, device := range devices {
+		if strings.HasPrefix(device.Name, prefix) {
+			d = device
+		}
+	}
+	if d == nil {
+		return nil, errors.New("could not find device with prefix " + prefix)
+	}
+	return d, d.Open()
 }
 
 func NewMixer(c Config) (*Mixer, error) {
-	return &Mixer{}, nil
+	devices, err := midi.Devices()
+	if err != nil {
+		return nil, err
+	}
+
+	m := &Mixer{}
+	if m.DevIn, err = openDevice(devices, c.DevIn); err != nil {
+		return nil, err
+	}
+	if m.DevOut, err = openDevice(devices, c.DevOut); err != nil {
+		return nil, err
+	}
+
+	return m, nil
 }
 
 func (m *Mixer) Init() error {
+	// TODO: sync state
 	return nil
 }
 
 func (m *Mixer) Shutdown() error {
+	if m.DevIn != nil {
+		m.DevIn.Close()
+	}
+	if m.DevOut != nil {
+		m.DevOut.Close()
+	}
+	return nil
+}
+
+func (m *Mixer) sendMute(channel byte, value byte) error {
+	n, err := m.DevOut.Write([]byte{CC_MUTE, channel, value})
+	if err != nil {
+		return err
+	}
+	if n != 3 {
+		return errors.New("sending mute command failed.")
+	}
+	return nil
+}
+
+func (m *Mixer) Mute(ch MixerChannel) error {
+	return m.sendMute(byte(ch), 0x7F)
+}
+
+func (m *Mixer) UnMute(ch MixerChannel) error {
+	return m.sendMute(byte(ch), 0x00)
+}
+
+func (m *Mixer) SetLevel(ch MixerChannel, level FaderLevel) error {
+	if level > FaderLevelMax {
+		level = FaderLevelMax
+	}
+	n, err := m.DevOut.Write([]byte{CC_FADER, byte(ch), byte(level)})
+	if err != nil {
+		return err
+	}
+	if n != 3 {
+		return errors.New("setting fader level failed.")
+	}
 	return nil
 }