// USAGE:
// * favicon.change("/icon/active.ico");  (Optional 2nd arg is new title.)
// * favicon.animate(new Array("icon1.ico", "icon2.ico", ...));
//     Tip: Use "" as the last element to make an empty icon between cycles.
//     To stop the animation, call change() and pass in the new arg.
//     (Optional 2nd arg is animation pause in millis, overwrites the default.)
// * favicon.defaultPause = 5000;

var favicon = {

// -- "PUBLIC" ----------------------------------------------------------------

defaultPause: 2000,

change: function(iconURL, optionalDocTitle) {
  clearTimeout(this.loopTimer);
  if (optionalDocTitle) {
    document.title = optionalDocTitle;
  }
  this.addLink(iconURL, true);
},

animate: function(iconSequence, optionalDelay) {
  this.preloadIcons(iconSequence);
  this.iconSequence = iconSequence;
  this.sequencePause = (optionalDelay) ?  optionalDelay : this.defaultPause;
  favicon.index = 0;
  favicon.change(iconSequence[0]);
  this.loopTimer = setInterval(function() {
    favicon.index = (favicon.index+1) % favicon.iconSequence.length;
    favicon.addLink(favicon.iconSequence[favicon.index], false);
  }, favicon.sequencePause);
},

// -- "PRIVATE" ---------------------------------------------------------------

loopTimer: null,

preloadIcons: function(iconSequence) {
  var dummyImageForPreloading = document.createElement("img");
  for (var i=0; i<iconSequence.length; i++) {
    dummyImageForPreloading.src = iconSequence[i];
  }
},

addLink: function(iconURL) {
  var link = document.createElement("link");
  link.type = "image/x-icon";
  link.rel = "shortcut icon";
  link.href = iconURL;
  this.removeLinkIfExists();
  this.docHead.appendChild(link);
},

removeLinkIfExists: function() {
  var links = this.docHead.getElementsByTagName("link");
  for (var i=0; i<links.length; i++) {
    var link = links[i];
    if (link.type=="image/x-icon" && link.rel=="shortcut icon") {
      this.docHead.removeChild(link);
      return; // Assuming only one match at most.
    }
  }
},

docHead:document.getElementsByTagName("head")[0]
}