/*
http://blog.makezine.com/archive/2008/05/detect_which_sites_a_web_user.html
Aza Raskin's SocialHistory Javascript library allows you to do something incredibly cool: detect which sites your web users have visited on a per-user basis. The javascript runtime isn't supposed to be privy to the information in a user's browser history, but there's an information backchannel common to all major browsers which allows you to effectively interrogate the browsing history and determine if a particular URL has been visited before.

It works by creating an anchor link to the site in question and applying a CSS style to the link, specifying a different display property for "a:visited". By reading the computed style back from the anchor element, you can then determine the property's value, and consequently if the user had visited the URL or not.

This could probably be used for a number of devious purposes, but Aza's concept for the SocialHistory library is actually really useful. By querying the default URLs that belong to all the major social network sites, you can figure out which sites a particular user visits and custom tailor any social badges that you display. If they use del.icio.us, you show a del.icio.us link. If they visit Digg, you show the Digg button. It's an awesome feature made possible by a pretty freaky security leak.

Now, it's not perfect. It requires that you query the exact URLs that a user may have visited. You can't figure out everywhere they've been, how frequently, or in what order, only whether a particular URL that you know about has been visited before. On the other hand, it's a pretty useful tool considering you aren't even supposed to be able to do this.
*/
/*
http://code.google.com/p/aza/source/browse/trunk/SocialHistory/SocialHistory.js
 * Social Limit - Only the social you care about.
 *
 * Enables your site to know which social bookmarking badges to display to your
 * visitors. It tells you all social sites the user has gone to, or you can 
 * query for a specific one.
 * 
 * For example:
 * 
 *    var sl = SocialHistory();
 *    alert( sl.doesVisit("Digg") ); // Returns true/false, -1 if unknown.
 *    var listOfVisitedSites = sl.visitedSites();
 *    var checkedSites = sl.checkedSites();
 *
 * If you want to add more sites to check, you can pass that in as a dictionary
 * to History:
 *
 *    var more = { "Humanized": "http://humanized.com",
 *                 "Azarask.in": ["http://azarask.in", "http://azarask.in/blog"]
 *               };
 *    var sl = SocialHistory(more);
 *    alert( sl.doesVisit("Humanized") );
 *
 * For a list of built-in sites, see the sites variable below.
 *
 * Copyright (c) 2008 Aza Raskin (http://azarask.in/blog)
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 *
 */
var SocialHistory = function(moreSites) {
  
  var sites = {
    "Digg": ["http://digg.com", "http://digg.com/login"],
    "Reddit": ["http://reddit.com", "http://reddit.com/new/", "http://reddit.com/controversial/", "http://reddit.com/top/", "http://reddit.com/r/reddit.com/", "http://reddit.com/r/programming/"],
    "StumbleUpon": ["http://stumbleupon.com"],
    "Yahoo Buzz": ["http://buzz.yahoo.com"],
    "Facebook": ["http://facebook.com/home.php", "http://facebook.com", "https://login.facebook.com/login.php"],
    "Del.icio.us": ["https://secure.del.icio.us/login", "http://del.icio.us/"],
    "MySpace": ["http://www.myspace.com/"],
    "Technorati": ["http://www.technorati.com"],
    "Newsvine": ["https://www.newsvine.com", "https://www.newsvine.com/_tools/user/login"],
    "Songza": ["http://songza.com"],
    "Slashdot": ["http://slashdot.org/"],
    "Ma.gnolia": ["http://ma.gnolia.com/"],
    "Blinklist": ["http://www.blinklist.com"],
    "Furl": ["http://furl.net", "http://furl.net/members/login"],
    "Mister Wong": ["http://www.mister-wong.com"],
    "Current": ["http://current.com", "http://current.com/login.html"],
    "Menaeme": ["http://meneame.net", "http://meneame.net/login.php"],
    "Oknotizie": ["http://oknotizie.alice.it", "http://oknotizie.alice.it/login.html.php"],
    "Diigo": ["http://www.diigo.com/", "https://secure.diigo.com/sign-in"],
    "Funp": ["http://funp.com", "http://funp.com/account/loginpage.php"],
    "Blogmarks": ["http://blogmarks.net"],
    "Yahoo Bookmarks": ["http://bookmarks.yahoo.com"],
    "Xanga": ["http://xanga.com"],
    "Blogger": ["http://blogger.com"],
    "Last.fm": ["http://www.last.fm/", "https://www.last.fm/login/"],
    "N4G": ["http://www.n4g.com"],
    "Faves": ["http://faves.com", "http://faves.com/home", "https://secure.faves.com/signIn"],
    "Simpy": ["http://www.simpy.com", "http://www.simpy.com/login"],
    "Yigg": ["http://www.yigg.de"],
    "Kirtsy": ["http://www.kirtsy.com", "http://www.kirtsy.com/login.php"],
    "Fark": ["http://www.fark.com", "http://cgi.fark.com/cgi/fark/users.pl?self=1"],
    "Mixx": ["https://www.mixx.com/login/dual", "http://www.mixx.com"],
    "Google Bookmarks": ["http://www.google.com/bookmarks", "http://www.google.com/ig/add?moduleurl=bookmarks.xml&hl=en"],
    "Subbmitt": ["http://subbmitt.com/"]
  };
  
  for( var site in moreSites ) {
    // If we don't have the site, create the URL list.
    if( typeof( sites[site] ) == "undefined" ) sites[site] = [];
    
    // If the value is string, just push that onto the URL list.
    if( typeof( moreSites[site] ) == "string" )
      sites[site].push( moreSites[site] );
    else
      sites[site] = sites[site].concat( moreSites[site] );
  }
  
  var visited = {};

  function getStyle(el, scopeDoc,styleProp) {
    if (el.currentStyle)
      var y = el.currentStyle[styleProp];
    else if (window.getComputedStyle)
      var y = scopeDoc.defaultView.getComputedStyle(el,null).getPropertyValue(styleProp);
    return y;
  }
  
  function remove( el ) {
    el.parentNode.removeChild( el );
  }
  
  // Code inspired by:
  // bindzus.wordpress.com/2007/12/24/adding-dynamic-contents-to-iframes
  function createIframe() {
    var iframe = document.createElement("iframe");
    iframe.style.position = "absolute";
    iframe.style.visibility = "hidden";

    document.body.appendChild(iframe);

    // Firefox, Opera
    if(iframe.contentDocument) iframe.doc = iframe.contentDocument;
    // Internet Explorer
    else if(iframe.contentWindow) iframe.doc = iframe.contentWindow.document;

    // Magic: Force creation of the body (which is null by default in IE).
    // Also force the styles of visited/not-visted links.
    iframe.doc.open();
        iframe.doc.write('<style>');
        iframe.doc.write("a{color: #000000; display:none;}");   
        iframe.doc.write("a:visited {color: #FF0000; display:inline;}");        
        iframe.doc.write('</style>');
    iframe.doc.close();
    
    // Return the iframe: iframe.doc contains the iframe.
    return iframe;
  }  

  var iframe = createIframe();
  
  function embedLinkInIframe( href, text ) {
    var a = iframe.doc.createElement("a");
    a.href = href;
    a.innerHTML = site;
    iframe.doc.body.appendChild( a );
  }
  
  for( var site in sites ) {
    var urls = sites[site];
    for( var i=0; i<urls.length; i++ ) {
      // You have to create elements in the scope of the iframe for IE.
      embedLinkInIframe( urls[i], site );
      
      // Automatically try variations of the URLS with and without the "www"
      if( urls[i].match(/www\./) ){
        var sansWWW = urls[i].replace(/www\./, "");
        embedLinkInIframe( sansWWW, site );
      } else {
        // 2 = 1 for length of string + 1 for slice offset
        var httpLen = urls[i].indexOf("//") + 2;
        var withWWW = urls[i].substring(0, httpLen ) + "www." + urls[i].substring( httpLen );
        embedLinkInIframe( withWWW, site );
      }
      
    }
  }
    
  var links = iframe.doc.body.childNodes;
  for( var i=0; i<links.length; i++) {
    // Handle both Firefox/Safari, and IE (respectively)
    var displayValue = getStyle(links[i], iframe.doc, "display");
    var didVisit = displayValue != "none";
      
    if( didVisit ){
      visited[ links[i].innerHTML ] = true;
    }
  }
  
  remove( iframe );
  
  return new (function(){
    var usedSites = [];
    for( var site in visited ){
      usedSites.push( site );
    }
    
    // Return an array of visited sites.
    this.visitedSites = function() {
      return usedSites;
    }
    
    // Return true/false. If we didn't check the site, return -1.
    this.doesVisit = function( site ) {
      if( typeof( sites[site] ) == "undefined" )
        return -1;
      return typeof( visited[site] ) != "undefined";
    }
    
    var checkedSites = [];
    for( var site in sites ){
      checkedSites.push( site );
    }
    // Return a list of the sites checked.
    this.checkedSites = function(){
      return checkedSites;
    }
  })();
}