From bc5159e272b0e42857ca3cf220d8f226a0c41655 Mon Sep 17 00:00:00 2001
From: Frode Petterson <frode.andre.petterson@gmail.com>
Date: Mon, 10 Nov 2014 11:31:23 +0100
Subject: [PATCH] Added event dispatcher.

---
 h5p.classes.php            |   1 +
 js/h5p-event-dispatcher.js | 135 +++++++++++++++++++++++++++++++++++++
 2 files changed, 136 insertions(+)
 create mode 100644 js/h5p-event-dispatcher.js

diff --git a/h5p.classes.php b/h5p.classes.php
index 827903a..d0fd2c8 100644
--- a/h5p.classes.php
+++ b/h5p.classes.php
@@ -1534,6 +1534,7 @@ class H5PCore {
   public static $scripts = array(
     'js/jquery.js',
     'js/h5p.js',
+    'js/h5p-event-dispatcher.js',
   );
   public static $adminScripts = array(
     'js/jquery.js',
diff --git a/js/h5p-event-dispatcher.js b/js/h5p-event-dispatcher.js
new file mode 100644
index 0000000..147024d
--- /dev/null
+++ b/js/h5p-event-dispatcher.js
@@ -0,0 +1,135 @@
+/** @namespace H5P */
+var H5P = H5P || {};
+
+H5P.EventDispatcher = (function () {
+
+  /**
+   * The base of the event system.
+   * Inherit this class if you want your H5P to dispatch events.
+   * @class
+   */
+  function EventDispatcher() {
+    var self = this;
+
+    /**
+     * Keep track of events and listeners for each event.
+     * @private
+     * @type {Object}
+     */
+    var events = {};
+
+    /**
+     * Add new event listener.
+     *
+     * @public
+     * @throws {TypeError} listener must be a function
+     * @param {String} type Event type
+     * @param {Function} listener Event listener
+     */
+    self.on = function (type, listener) {
+      if (!(listener instanceof Function)) {
+        throw TypeError('listener must be a function');
+      }
+
+      // Trigger event before adding to avoid recursion
+      self.trigger('newListener', type, listener);
+
+      if (!events[type]) {
+        // First
+        events[type] = [listener];
+      }
+      else {
+        // Append
+        events[type].push(listener);
+      }
+    };
+
+    /**
+     * Add new event listener that will be fired only once.
+     *
+     * @public
+     * @throws {TypeError} listener must be a function
+     * @param {String} type Event type
+     * @param {Function} listener Event listener
+     */
+    self.once = function (type, listener) {
+      if (!(listener instanceof Function)) {
+        throw TypeError('listener must be a function');
+      }
+
+      var once = function () {
+        self.off(type, once);
+        listener.apply(self, arguments);
+      };
+
+      self.on(type, once);
+    };
+
+    /**
+     * Remove event listener.
+     * If no listener is specified, all listeners will be removed.
+     *
+     * @public
+     * @throws {TypeError} listener must be a function
+     * @param {String} type Event type
+     * @param {Function} [listener] Event listener
+     */
+    self.off = function (type, listener) {
+      if (listener !== undefined && !(listener instanceof Function)) {
+        throw TypeError('listener must be a function');
+      }
+
+      if (events[type] === undefined) {
+        return;
+      }
+
+      if (listener === undefined) {
+        // Remove all listeners
+        delete events[type];
+        self.trigger('removeListener', type);
+        return;
+      }
+
+      // Find specific listener
+      for (var i = 0; i < events[type].length; i++) {
+        if (events[type][i] === listener) {
+          events[type].unshift(i, 1);
+          self.trigger('removeListener', type, listener);
+          break;
+        }
+      }
+
+      // Clean up empty arrays
+      if (!events[type].length) {
+        delete events[type];
+      }
+    };
+
+    /**
+     * Dispatch event.
+     *
+     * @public
+     * @param {String} type Event type
+     * @param {...*} args
+     */
+    self.trigger = function (type, args) {
+      if (events[type] === undefined) {
+        return;
+      }
+
+      // Copy all arguments except the first
+      args = [];
+      var i;
+      for (i = 1; i < arguments.length; i++) {
+        args.push(arguments[i]);
+      }
+
+      // Call all listeners
+      for (i = 0; i < events[type].length; i++) {
+        events[type][i].apply(self, args);
+      }
+    };
+  }
+
+  return EventDispatcher;
+})();