add client-side setup for DJ feature.

app/assets/javascripts/application.js

@@ -11,4 +11,5 @@
 //= require tabs
 //= require follow
 //= require report
-//= require custom-playlist-settings
+//= require custom-playlist-settings
+//= require dj

app/assets/javascripts/dj.js

@@ -0,0 +1,62 @@
+/*jshint browser:true undef:true strict:false jquery:true*/
+/*global io */
+
+var exports = window.Tubalr || {};
+
+window.Tubalr = (function(exports) {
+  var DJ = function(username, opts) {
+    opts = opts || {};
+
+    this.username = username;
+
+    this.server   = opts.server || 'localhost';
+    this.port     = opts.port   || 8900;
+
+    this.socket   = io.connect(this.server, {port: this.port});
+    this.onUpdate = opts.onUpdate || function() {};
+  };
+
+  DJ.prototype.startBroadcasting = function(videoId, videoElapsed) {
+    if (!this.broadcasting) {
+      this.broadcasting = true;
+      this.socket.emit('start', {
+        from: this.username,
+        id:   videoId,
+        at:   videoElapsed
+      });
+    }
+  };
+
+  DJ.prototype.stopBroadcasting = function() {
+    if (this.broadcasting) {
+      this.broadcasting = false;
+
+      this.socket.emit('stop', {
+        from: this.username
+      });
+    }
+  };
+
+  DJ.prototype.updateBroadcast = function(videoId, videoElapsed) {
+    if (this.broadcasting) {
+      this.socket.emit('change', {
+        from: this.username,
+        id:   videoId,
+        at:   videoElapsed
+      });
+    }
+  };
+
+  DJ.prototype.listenTo = function(who) {
+    var self = this;
+
+    this.socket.on('dj-' + who, function(msg) {
+      self.onUpdate(msg);
+    });
+
+    this.socket.emit('subscribe', {target: who});
+  };
+
+  exports.DJ = DJ;
+  return exports;
+})(exports);