jQuery.extend({
	historyCurrentHash: undefined,
	historyCallback: undefined,
	historyIframeSrc: undefined,
	historyNeedIframe: jQuery.browser.msie && (jQuery.browser.version < 8 || document.documentMode < 8),
	
	historyInit: function(callback, src){
		jQuery.historyCallback = callback;
		if (src) jQuery.historyIframeSrc = src;
		var current_hash = location.hash.replace(/\?.*$/, '');
		
		jQuery.historyCurrentHash = current_hash;
		if (jQuery.historyNeedIframe) {
			// To stop the callback firing twice during initilization if no hash present
			if (jQuery.historyCurrentHash == '') {
				jQuery.historyCurrentHash = '#';
			}
		
			// add hidden iframe for IE
			jQuery("body").prepend('<iframe id="jQuery_history" style="display: none;"'+
				' src="javascript:false;"></iframe>'
			);
			var ihistory = jQuery("#jQuery_history")[0];
			var iframe = ihistory.contentWindow.document;
			iframe.open();
			iframe.close();
			iframe.location.hash = current_hash;
		}
		else if (jQuery.browser.safari) {
			// etablish back/forward stacks
			jQuery.historyBackStack = [];
			jQuery.historyBackStack.length = history.length;
			jQuery.historyForwardStack = [];
			jQuery.lastHistoryLength = history.length;
			
			jQuery.isFirst = true;
		}
		if(current_hash)
			jQuery.historyCallback(current_hash.replace(/^#/, ''));
		setInterval(jQuery.historyCheck, 100);
	},
	
	historyAddHistory: function(hash) {
		// This makes the looping function do something
		jQuery.historyBackStack.push(hash);
		
		jQuery.historyForwardStack.length = 0; // clear forwardStack (true click occured)
		this.isFirst = true;
	},
	
	historyCheck: function(){
		if (jQuery.historyNeedIframe) {
			// On IE, check for location.hash of iframe
			var ihistory = jQuery("#jQuery_history")[0];
			var iframe = ihistory.contentDocument || ihistory.contentWindow.document;
			var current_hash = iframe.location.hash.replace(/\?.*$/, '');
			if(current_hash != jQuery.historyCurrentHash) {
			
				location.hash = current_hash;
				jQuery.historyCurrentHash = current_hash;
				jQuery.historyCallback(current_hash.replace(/^#/, ''));
				
			}
		} else if (jQuery.browser.safari) {
			if(jQuery.lastHistoryLength == history.length && jQuery.historyBackStack.length > jQuery.lastHistoryLength) {
				jQuery.historyBackStack.shift();
			}
			if (!jQuery.dontCheck) {
				var historyDelta = history.length - jQuery.historyBackStack.length;
				jQuery.lastHistoryLength = history.length;
				
				if (historyDelta) { // back or forward button has been pushed
					jQuery.isFirst = false;
					if (historyDelta < 0) { // back button has been pushed
						// move items to forward stack
						for (var i = 0; i < Math.abs(historyDelta); i++) jQuery.historyForwardStack.unshift(jQuery.historyBackStack.pop());
					} else { // forward button has been pushed
						// move items to back stack
						for (var i = 0; i < historyDelta; i++) jQuery.historyBackStack.push(jQuery.historyForwardStack.shift());
					}
					var cachedHash = jQuery.historyBackStack[jQuery.historyBackStack.length - 1];
					if (cachedHash != undefined) {
						jQuery.historyCurrentHash = location.hash.replace(/\?.*$/, '');
						jQuery.historyCallback(cachedHash);
					}
				} else if (jQuery.historyBackStack[jQuery.historyBackStack.length - 1] == undefined && !jQuery.isFirst) {
					// back button has been pushed to beginning and URL already pointed to hash (e.g. a bookmark)
					// document.URL doesn't change in Safari
					if (location.hash) {
						var current_hash = location.hash;
						jQuery.historyCallback(location.hash.replace(/^#/, ''));
					} else {
						var current_hash = '';
						jQuery.historyCallback('');
					}
					jQuery.isFirst = true;
				}
			}
		} else {
			// otherwise, check for location.hash
			var current_hash = location.hash.replace(/\?.*$/, '');
			if(current_hash != jQuery.historyCurrentHash) {
				jQuery.historyCurrentHash = current_hash;
				jQuery.historyCallback(current_hash.replace(/^#/, ''));
			}
		}


	},
	historyLoad: function(hash){
		var newhash;
		hash = decodeURIComponent(hash.replace(/\?.*$/, ''));
		
		if (jQuery.browser.safari) {
			newhash = hash;
		}
		else {
			newhash = '#' + hash;
			location.hash = newhash;
		}
		jQuery.historyCurrentHash = newhash;
		
		if (jQuery.historyNeedIframe) {
			var ihistory = jQuery("#jQuery_history")[0];
			var iframe = ihistory.contentWindow.document;
			iframe.open();
			iframe.close();
			iframe.location.hash = newhash;
			jQuery.lastHistoryLength = history.length;
			jQuery.historyCallback(hash);
		}
		else if (jQuery.browser.safari) {
			jQuery.dontCheck = true;
			// Manually keep track of the history values for Safari
			this.historyAddHistory(hash);
			
			// Wait a while before allowing checking so that Safari has time to update the "history" object
			// correctly (otherwise the check loop would detect a false change in hash).
			var fn = function() {jQuery.dontCheck = false;};
			window.setTimeout(fn, 200);
			jQuery.historyCallback(hash);
			// N.B. "location.hash=" must be the last line of code for Safari as execution stops afterwards.
			//      By explicitly using the "location.hash" command (instead of using a variable set to "location.hash") the
			//      URL in the browser and the "history" object are both updated correctly.
			location.hash = newhash;
		}
		else {
		  jQuery.historyCallback(hash);
		}
	}
});

jQuery.fn.tabs = function(settings){
	//configurable options
	var o = $.extend({
		trackState: false, //track tabs in history, url hash, back button, page load
		srcPath: 'jQuery.history.blank.html',
		autoRotate: false,
		alwaysScrollToTop: true
	},settings);
	
	return $(this).each(function(){
		//reference to tabs container
		var tabs = $(this);

		//set app mode
		if( !$('body').is('[role]') ){ $('body').attr('role','application'); }
		
		//nav is first ul
		var tabsNav = tabs.find('ul:first');
		
		//body is nav's next sibling
		var tabsBody = $(tabsNav.find('a:eq(0)').attr('href')).parent();
		
		var tabIDprefix = 'tab-';

		var tabIDsuffix = '-enhanced';
		
		//add class to nav, tab body
		tabsNav
			.addClass('tabs-nav')
			.attr('role','tablist');
			
		tabsBody
			.addClass('tabs-body');
		
		//find tab panels, add class and aria
		tabsBody.find('>div').each(function(){
			$(this)
				.addClass('tabs-panel')
				.attr('role','tabpanel')
				.attr('aria-hidden', true)
				.attr('aria-labelledby', tabIDprefix + $(this).attr('id'))
				.attr('id', $(this).attr('id') + tabIDsuffix);
		});
		
		//set role of each tab
		tabsNav.find('li').each(function(){
			$(this)
				.attr('role','tab')
				.attr('id', tabIDprefix+$(this).find('a').attr('href').split('#')[1]);
		});

		//switch selected on click
		tabsNav.find('a').attr('tabindex','-1');
		
		//generic select tab function
		function selectTab(tab,fromHashChange){
			if(o.trackState && !fromHashChange){ 
				$.historyLoad(tab.attr('href').replace('#','') ); 
			}
			else{	
				//unselect tabs
				tabsNav.find('li.tabs-selected')
					.removeClass('tabs-selected')
					.find('a')
						.attr('tabindex','-1')
						.removeClass('selected');
				//set selected tab item	
				tab
					.attr('tabindex','0')
					.parent()
					.addClass('tabs-selected')
					.find('a')
						.addClass('selected');
				//unselect  panels
				tabsBody.find('div.tabs-panel-selected').attr('aria-hidden',true).removeClass('tabs-panel-selected');
				//select active panel
				$( tab.attr('href') + tabIDsuffix ).addClass('tabs-panel-selected').attr('aria-hidden',false);

			}
		};			

			
		tabsNav.find('a')
			.click(function(){
				selectTab($(this));
				$(this).focus();
				return false;
			})
			.keydown(function(event){
				var currentTab = $(this).parent();
				var ret = true;
				switch(event.keyCode){
					case 37://left
					case 38://up
						if(currentTab.prev().size() > 0){
							selectTab(currentTab.prev().find('a'));
							currentTab.prev().find('a').eq(0).focus();
							ret = false;
						}
					break;
					case 39: //right
					case 40://down
						if(currentTab.next().size() > 0){
							selectTab(currentTab.next().find('a'));
							currentTab.next().find('a').eq(0).focus();
							ret = false;
						}
					break;
					case 36: //home key
						selectTab(tabsNav.find('li:first a'));
						tabsNav.find('li:first a').eq(0).focus();
						ret = false;
					break;
					case 35://end key
						selectTab(tabsNav.find('li:last a'));
						tabsNav.find('li:last a').eq(0).focus();
						ret = false;
					break;
				}
				return ret;
			});
			
		//if tabs are rotating, stop them upon user events	
		tabs.bind('click keydown focus',function(){
			if(o.autoRotate){ clearInterval(tabRotator); }
		});
		
		//function to select a tab from the url hash
		function selectTabFromHash(hash){
			var currHash = hash || window.location.hash;
			var hashedTab = tabsNav.find('a[href=#'+ currHash.replace('#','') +']');
		    if( hashedTab.size() > 0){
		    	selectTab(hashedTab,true);	
		    }
		    else {
		    	selectTab( tabsNav.find('a:first'),true);
		    }
		    //return true/false
		    return !!hashedTab.size();
		}
		
		//if state tracking is enabled, set up the callback
		if(o.trackState){ $.historyInit(selectTabFromHash, o.srcPath); }
		
		
		//set tab from hash at page load, if no tab hash, select first tab
		selectTabFromHash(null,true);

		//auto rotate tabs
		if(o.autoRotate){
			var tabRotator = setInterval(function(){
				var currentTabLI = tabsNav.find('li.tabs-selected');
				var nextTab = currentTabLI.next();
				if(nextTab.length){
					selectTab(nextTab.find('a'),false );
				}
				else{
					selectTab( tabsNav.find('a:first'),false );
				}
			}, o.autoRotate);
		}
		
		if(o.alwaysScrollToTop){
			$(window)[0].scrollTo(0,0);
		}
		

	});
};