// Favicon.js - Change favicon dynamically [http://ajaxify.com/run/favicon].
// Copyright (c) 2006 Michael Mahemoff. Only works in Firefox and Opera.
// Background and MIT License notice at end of file, see the homepage for more.

// 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]
}

// BACKGROUND
// The main point of this script is to give you a means of alerting the user
// something has happened while your application is in a background tab. Serves
// a similar task to notifications in the operating system taskbar. A secondary
// function is to support favicon animation.
//
// This script works by DOM manipulation. After a call, there will be exactly one
// "rel='icon'" link and one "rel='shortcut icon'" link under the head element.
// Both of these are required for portability reasons. It would be nice  (from
// a performance perspective) if we could just update an existing link, if it
// already exists, but it turns out we can't. Firefox (and others?) will ignore
// changes to the link's attributes; it's only interested in a new link being
// added. So we have to delete and re-add in all cases.