Fix: send messages to mp3 player

Also reworking the structure of the child processes: they are now
subclasses of EventEmitter, wrapping some process-specific
functionality. The next logical step here would be be distinct modules
for the MP3Player and TagReader children.

bin/mpg321-dummy

@@ -1,5 +1,5 @@
 #!/bin/bash
 
 while read line ; do
-    echo "OK"
+    echo "running $line"
 done

jukebox/children.js

@@ -1,3 +1,8 @@
+"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;
@@ -5,7 +10,40 @@ const EventEmitter = require('events').EventEmitter;
 const TAGREADER = 'tagreader';
 const MP3PLAYER = 'mpg321';
 
-const child_processes = new Map();
+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],
@@ -14,56 +52,22 @@ function launchChild(name, command) {
   return spawn(cmd, args);
 }
 
-function setupEmitter(name, emitter, child) {
-  exports[name] = emitter;
-
-  child.on('error', function(err) {
-    emitter.emit('process_error', err);
-  });
-
-  child.on('close', function(code, signal) {
-    emitter.emit('close', code, signal);
-  });
-
-  child.stdout.on('data', (data) => {
-    var s = data.toString(), lines = s.split(/\n/g);
-    for (var i = 0, l = lines.length; i < l; i++) {
-      emitter.emit('message', lines[i]);
-    }
-  });
-
-  child.stderr.on('data', (data) => {
-    emitter.emit('error', data);
-  });
-
-  return emitter;
-}
-
 exports.init = function(config) {
   // Set up tag reader
   var tagreader = launchChild(TAGREADER, config.tag_reader);
-  var tagreader_emitter = new EventEmitter();
-  setupEmitter(TAGREADER, tagreader_emitter, tagreader);
-
-  child_processes.set(TAGREADER, tagreader);
-  exports.tagreader = tagreader_emitter;
+  exports.tagreader = new ChildEmitter(tagreader);
 
   // set up mp3 player
   var mp3player = launchChild(MP3PLAYER, config.mpg321);
-  var mp3player_emitter = new EventEmitter();
-  setupEmitter(MP3PLAYER, mp3player_emitter, mp3player);
-
-  child_processes.set(MP3PLAYER, mp3player);
-  exports.mp3player = mp3player_emitter;
+  exports.mp3player = new ChildEmitter(mp3player);
 };
 
 exports.exitHandler = function(options, err) {
   console.log('[player] closing children');
   if (err) console.log(err.stack);
 
-  child_processes.forEach((p) => {
-    p.kill();
-  });
+  module.exports.tagreader.kill();
+  module.exports.mp3player.kill();
 
   if (options.exit) {
     process.exit();

player.js

@@ -46,6 +46,12 @@ children.tagreader.on('message', (data) => {
   processLine(data);
 });
 
+if (config.debug) {
+  children.mp3player.on('message', (data) => {
+    console.log(`[mp3player] stdout: ${data}`);
+  });
+}
+
 var last_tag = null;
 var debounce_until = 0;
 
@@ -97,7 +103,7 @@ function processLine(data) {
     debounce_until = Date.now() / 1000 + wait_sec;
     if (action) {
       console.log(`[action] [${action}] for [${last_tag}]`);
-      player.stdin.write(action + "\n");
+      children.mp3player.send(action + "\n");
     }
   });
 }