Delete Facebook messages

// 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          Delete Facebook messages
// @namespace     K3
// @description   Selectively delete facebook messages with one click
// @include       http://www.facebook.com/messages/*
// @include       https://www.facebook.com/messages/*
// @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 myTimer = null;
 
 function setup_modal(overlay_html) {
  var msgdiv = document.createElement("div");
  var maskdiv = document.createElement("div");
  
  function restore_refresh() { 
   $('body').css({'overflow':'auto'}); 
   location.reload(); 
  }

  function delete_msg(tid) {
   var xmlHttp = new XMLHttpRequest();
   var url = "https://www.facebook.com/ajax/messaging/async.php?action=delete&tids=";
   var url_end = "&_a=1";
   
   if(xmlHttp !== null) {
    xmlHttp.open("GET",url + tid + url_end,true);
    xmlHttp.send();
   } else {
    alert("Error sending command to server");
   }
  }

  msgdiv.id = "modal";
  msgdiv.className = "window";
  msgdiv.innerHTML = overlay_html;
    
  maskdiv.id = "mask";
    
  $("body").append(msgdiv);
  $("body").append(maskdiv);
  $('body').css({'overflow':'hidden'});
      
  $('#mask').css({'width':'100%','height':$('#modal').height()*2});
  $('#mask').fadeIn(1000);   
  $('#mask').fadeTo("slow",0.9); 
    
  $('#modal').css('border','1px solid white');
  $('#modal').css('top', 20);
  $('#modal').css('left', $(window).width()/2-$('#modal').width()/2);
  $('#modal').fadeIn(2000);
    
  $('.delete_msg_button').click(function (e) {
   e.preventDefault();
   delete_msg($(this).attr('id'));
   $(this).parent().parent().hide();
  });
    
  $('.window .close').click(function (e) {
   e.preventDefault();
   $('#mask').click();
  });    
  
  $(document).keyup(function(e) {
   if (e.keyCode == 27) { $('#mask').click(); }
  });
     
  $('#mask').click(function () {
   $(this).hide();
   $('.window').hide();
   restore_refresh();
  });  
 }
 
 function extract_messages() {
  var messages = null;
  var overlay_html = null;
  var i = null;
  var msg = null;
  var tid = null;
  var name = null;
  var snippet = null;
  var pic = null;
  
  messages = document.getElementsByClassName('threadLink');
  overlay_html = "<style>\
       .msg_box {\
        background-color: #ffffff;\
        border: 1px solid red;\
        padding: 15px;\
        margin-bottom: 10px;\
       }\
       .msg_authors {\
        color: #3B5998;\
        font-size: 16px;\
        font-weight: bold;\
        margin-right: 10px;\
       }\
       #mask {\
        position:absolute;\
        z-index:9000;\
        background-color:#000;\
        display:none;\
        top:0;\
        left:0;\
       }\
       .window {\
        position:absolute;\
        width:440px;\
        height:200px;\
        display:none;\
        z-index:9999;\
        padding:20px;\
       }\
       #modal {\
        overflow:auto;\
        display:none;\
        width:70%;\
        height:86%;\
       }\
       .close {\
        font-size: 25px;\
        color: white;\
       }\
      </style>\
      <a class=\"close\">Close</a><br />";
     
  if(messages === null) {
   return null;
  }
  
  for(i in messages) {
   msg = messages[i];
    
   if(msg !== null && msg.href) {
    tid = msg.href.substring(msg.href.indexOf("tid=") + 4);
     
    name = msg.innerHTML.substring(msg.innerHTML.indexOf('class="authors"') + 16);
    name = name.substring(0,name.indexOf("<"));
     
    snippet = msg.innerHTML.substring(msg.innerHTML.indexOf("<div class=\"snippet"));
    snippet = snippet.substring(0,snippet.indexOf("</div>") + 6);
     
    pic = msg.innerHTML.substring(msg.innerHTML.indexOf(">") + 1);
    pic = pic.substring(0,pic.indexOf("<div"));
     
    overlay_html = overlay_html.concat("<div class=\"msg_box\">");
     overlay_html = overlay_html.concat(pic + "<span class=\"msg_authors\">" + name + ": </span><br/>");
     overlay_html = overlay_html.concat("<span class=\"snippet\">" + snippet + "</snippet><br/><br/>");
     overlay_html = overlay_html.concat("<button type=\"button\" class=\"delete_msg_button\" id=" + tid + ">Delete</button>");
    overlay_html = overlay_html.concat("</div>");
    overlay_html = overlay_html.concat("<div style=\"clear:both;\">&nbsp;</div>");
   }
  }
    
  return overlay_html;
 }
 
 function setup_delete_button(toolbar) {
   var search = toolbar.nextSibling;
  var button = document.createElement("a");
  var toolbar_parent = toolbar.parentNode;

  button.id = "delete_messages_button";
  button.className = "uiToolbarItem uiButton";
  button.innerHTML = "<span class=\"uiButtonText\">Delete Messages</span>";

  toolbar_parent.removeChild(search);
  toolbar_parent.appendChild(button);
  toolbar_parent.appendChild(search);

  $('#delete_messages_button').click(function () {
   var overlay_html = null;
   
   overlay_html = extract_messages();
   
   if(overlay_html === null) {
    alert("Not able to extract messages");
    location.reload();
   } else {
    setup_modal(overlay_html);
   }
  }); 
 }

 function repeat_search() {
  var toolbar = null;
  
  toolbar = document.getElementsByClassName('uiToolbarItem uiButton')[0];
  
  if(toolbar !== null) {
   if(toolbar.parentNode.innerHTML.search("Delete Messages") === -1) {
    setup_delete_button(toolbar);
   }
  }
 }
 
 myTimer = window.setInterval(repeat_search,1000);
}

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