// cycles through from 1 to number of tabs and switches them all off, then switches one back 
function tabswitch(current, maxtabs, tab_prefix) {

	for (var i=1; i < maxtabs + 1; i++)  	{
		document.getelementById(tab_prefix+i).classname='';

	}

	document.getElementById(tab_prefix+current).classname = 'current';
	
}



// CSS helper functions
CSS = {
    // Adds a class to an element.
    AddClass: function (e, c) {
        if (!e.className.match(new RegExp("\\b" + c + "\\b", "i")))
            e.className += (e.className ? " " : "") + c;
    },

    // Removes a class from an element.
    RemoveClass: function (e, c) {
        e.className = e.className.replace(new RegExp(" \\b" + c + "\\b|\\b" + c + "\\b ?", "gi"), "");
    }
};

// Functions for handling tabs.
Tabs = {
    // Changes to the tab with the specified ID.
    GoTo: function (contentId, skipReplace) {
        // This variable will be true if a tab for the specified
        // content ID was found.
        var foundTab = false;

        // Get the NavBar element.
        var toc= document.getElementById("navbar");
        if (toc) {
            var lis = toc.getElementsByTagName("li");
            for (var j = 0; j < lis.length; j++) {
                var li = lis[j];

                // Give the current tab link the class "current" and
                // remove the class from any other links.
                if (li.id == contentid) {

                    CSS.AddClass(li, "current");
                    foundTab = true;
                    break;
                    } else {
                        CSS.RemoveClass(li, "current");
                    }
              
            }
        }

    },

    OnClickHandler: function (e) {
        // Stop the event (to stop it from scrolling or
        // making an entry in the history).
        if (!e) e = window.event;
        if (e.preventDefault) e.preventDefault(); else e.returnValue = false;

        // Get the name of the anchor of the link that was clicked.
        Tabs.GoTo(this.hash.substring(1));
    },

    Init: function () {
        if (!document.getElementsByTagName) return;

        // Attach an onclick event to all the anchor links on the page.
        var anchors = document.getElementsByTagName("a");
        for (var i = 0; i < anchors.length; i++) {
            var a = anchors[i];
            if (a.hash) a.onclick = Tabs.OnClickHandler;
        }

        var contentId;
        if (window.location.hash) contentId = window.location.hash.substring(1);

        var divs = document.getElementsByTagName("div");
        for (var i = 0; i < divs.length; i++) {
            var div = divs[i];

            if (div.className.match(/\bcontent\b/i)) {
                if (!contentId) contentId = div.id;
                div.id = "_" + div.id;
            }
        }

        if (contentId) Tabs.GoTo(contentId, true);
    }
};

// Hook up the OnLoad event to the tab initialization function.
window.onload = Tabs.Init;

// Hide the content while waiting for the onload event to trigger.
var contentId = window.location.hash || "#Introduction";

if (document.createStyleSheet) {
    var style = document.createStyleSheet();
    style.addRule("div.content", "display: none;");
    style.addRule("div" + contentId, "display: block;");
} else {
    var head = document.getElementsByTagName("head")[0];
    if (head) {
        var style = document.createElement("style");
        style.setAttribute("type", "text/css");
        style.appendChild(document.createTextNode("div.content { display: none; }"));
		style.appendChild(document.createTextNode("div" + contentId + " { display: block; }"));
        head.appendChild(style);
    }
}