Facebook Video Downloader(HD Support)

// Copyright (c) 2011,2012 Karthic Kumaran <karthic@fastmail.in>
//
// Permission to use, copy, modify, and distribute this software for any
// purpose with or without fee is hereby granted, provided that the above
// copyright notice and this permission notice appear in all copies.
//
// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
// ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
// ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
// OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
// 
// ==UserScript==
// @name           Facebook Video Downloader
// @namespace      K3
// @description    Download link for Facebook Videos
// @include        http://*facebook.com/video/*
// @include        https://*facebook.com/video/*
// @include        https://*facebook.com/photo.php*
// @include        https://*facebook.com/photo.php*
// @require        https://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js
// ==/UserScript==

//Code for detecting chrome from http://davidwalsh.name/detecting-google-chrome-javascript
//Code for adding jquery from http://erikvold.com/blog/index.cfm/2010/6/14/using-jquery-with-a-user-script via http://stackoverflow.com/questions/2246901/how-can-i-use-jquery-in-greasemonkey-scripts-in-google-chrome

function addJQuery(callback) {
  var script = document.createElement("script");
  
  script.setAttribute("src", "https://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js");
  script.addEventListener('load', function() {
    var script = document.createElement("script");
 
    script.textContent = "(" + callback.toString() + ")();";
 
    document.body.appendChild(script);
  }, false);
  
  document.body.appendChild(script);
}

function main() {
 var script_tags = document.getElementsByTagName('script');
 var i = null;
 var id = '#fbPhotoPageActions';
 var temp = null;
 var found = false;
 
 function decode(url) {
  url = url.substring(url.indexOf(","),url.indexOf(";"));
  url = url.substring(url.indexOf('"'),url.indexOf(")"));
  url = url.substring(url.indexOf('"'));
  url = url.substring(1,url.length-1);
 
  url = url.replace(/\\u00253A/g,":");
  url = url.replace(/\\u00252F/g,'/');
  url = url.replace(/\\u00253F/g,"?");
  url = url.replace(/\\u00253D/g,"=");
  url = url.replace(/\\u002526/g,"&");
 
  return url;
 }
 
 for(i in script_tags){
  temp = script_tags[i];
  temp = temp.innerHTML;
  
  if(temp.search(/video_src/) != -1){
   var video_url = temp;
   var download_link = document.createElement('a');
 
   download_link.setAttribute('target','_blank');
   download_link.setAttribute('title','Download this video');
    
   video_url = video_url.substring(video_url.indexOf("video_src"),video_url.indexOf("motion_log"));
   video_url = decode(video_url);
   download_link.setAttribute('href',video_url);
 
   download_link.innerHTML = "Download Low Quality<br />";
    
   $(id).prepend(download_link);
   found = true;
  }
  
  if(temp.search(/highqual_src/) != -1){
   var hd_video_url = temp;
   var hd_download_link = document.createElement('a');
   
   hd_download_link.setAttribute('target','_blank');
   hd_download_link.setAttribute('title','Download this video');
    
   hd_video_url = hd_video_url.substring(hd_video_url.indexOf("highqual_src"),hd_video_url.indexOf("lowqual_src"));
   hd_video_url = decode(hd_video_url);
   hd_download_link.setAttribute('href',hd_video_url);
    
   hd_download_link.innerHTML = "Download High Quality<br />";
   
   $(id).prepend(hd_download_link);
   found = true;
  }
  
  if(found === true) {
   break;
  }
 }
}

if((navigator.userAgent.toLowerCase().indexOf('chrome') > -1) === true) {
 addJQuery(main);
} else {
 main();
}