av/cmd/audio-player/looper/main.go

/*
DESCRIPTION
  Looper is a program that loops an audio file.

AUTHORS
  Ella Pietraroia <ella@ausocean.org>
  Scott Barnard <scott@ausocean.org>

LICENSE
  audio player is Copyright (C) 2020 the Australian Ocean Lab (AusOcean)

  It is free software: you can redistribute it and/or modify them
  under the terms of the GNU General Public License as published by the
  Free Software Foundation, either version 3 of the License, or (at your
  option) any later version.

  It is distributed in the hope that it will be useful, but WITHOUT
  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
  for more details.

  You should have received a copy of the GNU General Public License
  in gpl.txt.  If not, see http://www.gnu.org/licenses.
*/

// Audio looper.
package main

import (
	"bytes"
	"flag"
	"io"
	"os"
	"os/exec"
	"sync"

	"bitbucket.org/ausocean/utils/logger"
	"gopkg.in/natefinch/lumberjack.v2"
)

func main() {
	// Command line flags.
	var soundFilePtr = flag.String("path", "", "Location of sound file")
	flag.Parse()

	// Logging constants.
	const (
		logPath      = "/var/log/audiolooper/audiolooper.log"
		logMaxSize   = 500 // MB
		logMaxBackup = 10
		logMaxAge    = 28 // days
		logVerbosity = logger.Debug
		logSuppress  = true
	)

	// Create lumberjack logger to handle logging to file.
	fileLog := &lumberjack.Logger{
		Filename:   logPath,
		MaxSize:    logMaxSize,
		MaxBackups: logMaxBackup,
		MaxAge:     logMaxAge,
	}

	// Create logger that we call methods on to log.
	log := logger.New(logVerbosity, fileLog, logSuppress)

	// Pi model specific initialisation
	initCommand(log)

	// Infinite loop that outputs audio and gathers debug information.
	var numPlays int
	for {
		numPlays++
		log.Log(logger.Debug, "playing audio", "play number", numPlays)

		cmd := exec.Command(audioCmd, *soundFilePtr)

		var stdoutBuf, stderrBuf bytes.Buffer
		stdoutIn, _ := cmd.StdoutPipe()
		stderrIn, _ := cmd.StderrPipe()

		var errStdout, errStderr error
		stdout := io.MultiWriter(os.Stdout, &stdoutBuf)
		stderr := io.MultiWriter(os.Stderr, &stderrBuf)

		err := cmd.Start()
		if err != nil {
			log.Log(logger.Fatal, "cmd.Start() for 'play' failed", "error", err.Error())
		}

		var wg sync.WaitGroup
		wg.Add(1)

		go func() {
			_, errStdout = io.Copy(stdout, stdoutIn)
			wg.Done()
		}()

		_, errStderr = io.Copy(stderr, stderrIn)
		wg.Wait()

		err = cmd.Wait()
		if err != nil {
			log.Log(logger.Fatal, "cmd.Run() for 'play' failed", "error", err.Error())
		}
		if errStdout != nil || errStderr != nil {
			log.Log(logger.Fatal, "failed to capture stdout or stderr")
		}
		outStr, errStr := string(stdoutBuf.Bytes()), string(stderrBuf.Bytes())
		log.Log(logger.Debug, "stdout received", "stdout", outStr)
		log.Log(logger.Debug, "stderr received", "stderr", errStr)
	}
}