From 3d76205c809a5e08af4178e97e67182436306318 Mon Sep 17 00:00:00 2001
From: Annika Backstrom <annika@sixohthree.com>
Date: Sun, 9 Apr 2017 09:41:17 -0400
Subject: [PATCH] Move child process handling into its own module

---
 jukebox/children.js | 73 +++++++++++++++++++++++++++++++++++++++++++++
 player.js           | 70 ++++++++++++++-----------------------------
 2 files changed, 96 insertions(+), 47 deletions(-)
 create mode 100644 jukebox/children.js

diff --git a/jukebox/children.js b/jukebox/children.js
new file mode 100644
index 0000000..7494517
--- /dev/null
+++ b/jukebox/children.js
@@ -0,0 +1,73 @@
+const spawn = require('child_process').spawn;
+
+const EventEmitter = require('events').EventEmitter;
+
+const TAGREADER = 'tagreader';
+const MP3PLAYER = 'mpg321';
+
+const child_processes = new Map();
+
+function launchChild(name, command) {
+  var cmd = command[0],
+    args = command.slice(1);
+
+  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;
+
+  // 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.exitHandler = function(options, err) {
+  console.log('[player] closing children');
+  if (err) console.log(err.stack);
+
+  child_processes.forEach((p) => {
+    p.kill();
+  });
+
+  if (options.exit) {
+    process.exit();
+  }
+};
+
+// vim:set ts=2 sw=2 et:
diff --git a/player.js b/player.js
index 9de1f6e..df8c7b9 100644
--- a/player.js
+++ b/player.js
@@ -2,9 +2,6 @@
 const config = require('./config.json')
 
 const glob = require('glob');
-const spawn = require('child_process').spawn;
-const tag_reader = spawn(config.tag_reader[0], config.tag_reader.slice(1));
-const player = spawn(config.mpg321[0], config.mpg321.slice(1));
 
 const express = require('express');
 const logger = require('morgan')
@@ -12,6 +9,8 @@ const mustache = require('mustache');
 
 const readFileSync = require('fs').readFileSync;
 
+const children = require('./jukebox/children');
+
 var app = express();
 var server = require('http').createServer();
 
@@ -28,37 +27,32 @@ mustache.parse(log_tpl);
 
 var play_log = [];
 
-function exitHandler(options, err) {
-  console.log('[player] closing children');
-  if (err) console.log(err.stack);
-  tag_reader.kill();
-  player.kill();
-  if (options.exit) {
-    process.exit();
-  }
+children.init(config);
+
+process.on('exit', children.exitHandler.bind(null));
+process.on('SIGINT', children.exitHandler.bind(null, {exit:true}));
+
+function setupChildLogging(name, child) {
+  child.on('process_error', (err) => {
+    console.log(`[${name}] error=${err}`);
+  });
+
+  child.on('close', (code, signal) => {
+    console.log(`[${name}] process closed:code=${code} signal=${signal}`);
+  });
+
+  child.on('error', (data) => {
+    console.log(`[${name}] stderr: ${data}`);
+  });
 }
 
-process.on('exit', exitHandler.bind(null));
-process.on('SIGINT', exitHandler.bind(null, {exit:true}));
+setupChildLogging('tagreader', children.tagreader);
+setupChildLogging('mp3player', children.mp3player);
 
-tag_reader.on('error', function(err) {
-  console.log(`[tag_reader] error=${err}`);
+children.tagreader.on('message', (data) => {
+  processLine(data);
 });
 
-player.on('error', function(err) {
-  console.log(`[mpg321] error=${err}`);
-});
-
-tag_reader.on('close', function(code, signal) {
-  console.log(`[tag_reader] process closed:code=${code} signal=${signal}`);
-});
-
-player.on('close', function(code, signal) {
-  console.log(`[mpg321] process closed:code=${code} signal=${signal}`);
-});
-
-// player.stdin.write("GAIN 100");
-
 var last_tag = null;
 var debounce_until = 0;
 
@@ -115,24 +109,6 @@ function processLine(data) {
   });
 }
 
-tag_reader.stdout.on('data', (data) => {
-  var s = data.toString(), lines = s.split(/\n/g);
-  for (var i = 0, l = lines.length; i < l; i++) {
-    processLine(lines[i]);
-  }
-});
-
-tag_reader.stderr.on('data', (data) => {
-  console.log(`[tag_reader:stderr] ${data}`);
-});
-
-player.stderr.on('data', (data) => {
-  if (String(data).substr(0, 3) === "@F ") {
-    return;
-  }
-  console.log(`[mpg321] stderr ${data}`);
-});
-
 app.use(logger('dev'))
 app.use(express.static(__dirname + '/static'))