dndmusicbot/mpd.go

package main

import (
	"bytes"
	"context"
	"log"
	"os"
	"os/exec"
	"strconv"
	"syscall"
	"text/template"
	"time"

	"github.com/faiface/beep"
	"github.com/kataras/go-events"
	"github.com/steino/gompd/v2/mpd"
)

type MPD struct {
	file int
	f    beep.Format
}

func init() {
	log.Println("mpd.go loading..")

	f, err := os.Create(config.GetString("mpd.config"))
	if err != nil {
		log.Fatal(err)
	}

	t, err := template.New("mpd.tmpl").ParseFiles("tmpl/mpd.tmpl")
	if err != nil {
		log.Fatal(err)
	}

	err = t.Execute(f, config.GetStringMapString("mpd"))
	if err != nil {
		log.Fatal(err)
	}

	f.Close()

	pidstr, err := os.ReadFile(config.GetString("mpd.pid"))
	if err != nil && os.IsNotExist(err) {
		pid, _ := strconv.Atoi(string(bytes.TrimSpace(pidstr)))
		proc, err := os.FindProcess(pid)
		switch err {
		case nil:
			log.Println(proc.Kill())
		case os.ErrProcessDone:
			log.Println("Pid alreadt finished, doing nothing.")
		default:
			log.Fatal(err)
		}
	} else if err != nil {
		log.Fatal(err)
	}

	ctx, cancel := context.WithCancel(context.Background())

	app.mpdc = cancel

	cmd := exec.CommandContext(
		ctx,
		config.GetString("mpd.cmd"),
		"--no-daemon",
		config.GetString("mpd.config"),
		"-v",
	)

	cmd.Stdout = os.Stdout
	cmd.Stderr = os.Stderr

	go func() {
		err := cmd.Run()
		if err != nil {
			log.Println(err)
		}
		cancel()
	}()

	// wait for mpd to start.
	time.Sleep(2 * time.Second)

	app.mpd, err = mpd.Dial("unix", config.GetString("mpd.sock"))
	if err != nil {
		log.Fatal(err)
	}

	app.mpd.Repeat(true)
	app.mpd.Random(true)

	err = app.mpd.EnableOutput(0)
	if err != nil {
		log.Fatal(err)
	}

	app.mpdw, err = mpd.NewWatcher("unix", config.GetString("mpd.sock"), "")
	if err != nil {
		log.Fatal(err)
	}

	go func() {
		for {
			select {
			case ev := <-app.mpdw.Event:
				app.events.Emit(events.EventName(ev))
			case err := <-app.mpdw.Error:
				log.Println(err)
				return
			}
		}
	}()

	log.Println("mpd.go done.")
}

func NewMPD() (*MPD, error) {
	out := new(MPD)

	f, err := syscall.Open(config.GetString("mpd.fifo"), syscall.O_CREAT|syscall.O_RDONLY|syscall.O_CLOEXEC|syscall.O_NONBLOCK, 0644)
	if err != nil {
		return nil, err
	}

	out.f = beep.Format{
		SampleRate:  beep.SampleRate(sampleRate),
		NumChannels: channels,
		Precision:   2,
	}

	out.file = f

	return out, nil
}

func (m *MPD) Err() error {
	return nil
}

func (m *MPD) Stream(samples [][2]float64) (n int, ok bool) {
	tmp := make([]byte, m.f.NumChannels+2)

	for i := range samples {
		dn, err := syscall.Read(m.file, tmp)
		if dn == len(tmp) {
			samples[i], _ = m.f.DecodeSigned(tmp)
			ok = true
		}
		if err != nil {
			samples[i] = [2]float64{}
			ok = true
			break
		}
	}

	return len(samples), ok
}