pi-rfid-jukebox/jukebox/children.js

"use strict";

// TODO: These should really be their own individual classes. Are
// there enough commonalities to warrant a base class?

const spawn = require('child_process').spawn;

const EventEmitter = require('events').EventEmitter;

const TAGREADER = 'tagreader';
const MP3PLAYER = 'mpg321';

class ChildEmitter extends EventEmitter {
  constructor(process) {
    super();

    this.childProcess = process;

    this.childProcess.on('error', function(err) {
      this.emit('process_error', err);
    });

    this.childProcess.on('close', function(code, signal) {
      this.emit('close', code, signal);
    });

    this.childProcess.stdout.on('data', (data) => {
      var s = data.toString(), lines = s.split(/\n/g);
      for (var i = 0, l = lines.length; i < l; i++) {
        this.emit('message', lines[i]);
      }
    });

    this.childProcess.stderr.on('data', (data) => {
      this.emit('error', data);
    });
  }

  kill() {
    this.childProcess.kill();
  }

  send(message) {
    this.childProcess.stdin.write(message);
  }
}

function launchChild(name, command) {
  var cmd = command[0],
    args = command.slice(1);

  return spawn(cmd, args);
}

exports.init = function(config) {
  // Set up tag reader
  var tagreader = launchChild(TAGREADER, config.tag_reader);
  exports.tagreader = new ChildEmitter(tagreader);

  // set up mp3 player
  var mp3player = launchChild(MP3PLAYER, config.mpg321);
  exports.mp3player = new ChildEmitter(mp3player);
};

exports.exitHandler = function(options, err) {
  console.log('[player] closing children');
  if (err) console.log(err.stack);

  module.exports.tagreader.kill();
  module.exports.mp3player.kill();

  if (options.exit) {
    process.exit();
  }
};

// vim:set ts=2 sw=2 et: