// JavaScript Document

/* general variables */
var timeout = 8000;
var galleryId = 'RandomImage'; /* change this to the ID of the gallery list */
var	gallery; /* this will be the object reference to the list later on */
var galleryImages; /* array that will hold all child elements of the list */
var currentImage; /* keeps track of which image should currently be showing */
var previousImage;
var preInitTimer;
preInit();

/* functions */

function preInit() {
	/* an inspired kludge that - in most cases - manages to initially hide the image gallery list
	   before even onload is triggered (at which point it's normally too late, and the whole list already
	   appeared to the user before being remolded) */
	if ((document.getElementById)&&(gallery=document.getElementById(galleryId))) {
		gallery.style.visibility = "hidden";
		if (typeof preInitTimer != 'undefined') clearTimeout(preInitTimer); /* thanks to Steve Clay http://mrclay.org/ for this small Opera fix */
	} else {
		preInitTimer = setTimeout("preInit()",2);
	}
}

function fader(imageNumber,opacity) {
	/* helper function to deal specifically with images and the cross-browser differences in opacity handling */
	var obj=galleryImages[imageNumber];
	if (obj.style) {
		if (obj.style.MozOpacity!=null) {  
			/* Mozilla's pre-CSS3 proprietary rule */
			obj.style.MozOpacity = (opacity/100) - .001;
		} else if (obj.style.opacity!=null) {
			/* CSS3 compatible */
			obj.style.opacity = (opacity/100) - .001;
		} else if (obj.style.filter!=null) {
			/* IE's proprietary filter */
			obj.style.filter = "alpha(opacity="+opacity+")";
		}
	}
}

function fadeInit() {
	if (document.getElementById) {
		preInit(); /* shouldn't be necessary, but IE can sometimes get ahead of itself and trigger fadeInit first */
		galleryImages = new Array;
		var node = gallery.firstChild;
		while (node) {
			if (node.nodeType==1) {
				galleryImages.push(node);
			}
			node = node.nextSibling;
		}
		for(i=0;i<galleryImages.length;i++) {
			galleryImages[i].style.position='absolute';
			galleryImages[i].style.top=0;
			galleryImages[i].style.zIndex=0;
			/* set their opacity to transparent */
			fader(i,0);
		}
		/* make the list visible again */
		gallery.style.visibility = 'visible';
		/* initialise a few parameters to get the cycle going */
		currentImage=0;
		previousImage=galleryImages.length-1;
		opacity=100;
		fader(currentImage,100);
		/* start the whole crossfade process after a pause */
		window.setTimeout("crossfade(100)", timeout);
	}
}

function crossfade(opacity) {
		if (opacity < 101) {
			/* current image not faded up fully yet...so increase its opacity */
			fader(currentImage,opacity);
			 fader(previousImage,100-opacity); 
			opacity += 5;
			window.setTimeout("crossfade("+ opacity +")", 30);
		} else {
			/* make the previous image - which is now covered by the current one fully - transparent */
			fader(previousImage,0);
			
			/* current image is now previous image, as we advance in the list of images */
			previousImage=currentImage;
			/*randomly select an image. To step through the array sequentially use: currentImage +=1;*/
			var ran = Math.floor( 1 + Math.random() * galleryImages.length-1 );
			//in case the same image is selected twice
			
			if(ran==0){
				if(currentImage == ran)
					currentImage = ran+1;
					else
					currentImage=ran
			}
			else{
				if(currentImage == ran)
					currentImage = ran-1;
					else
					currentImage=ran
			}
			/*when stepping through the array the following code creates a loop
			if (currentImage>=galleryImages.length) {
				// start over from first image if we cycled through all images in the list 
				currentImage=0;
			} 
			/* make sure the current image is on top of the previous one */
			galleryImages[previousImage].style.zIndex = 0;
			galleryImages[currentImage].style.zIndex = 0.5;
			/* and start the crossfade after a pause */
			opacity=0;
			window.setTimeout("crossfade("+opacity+")", timeout);
		}
		
}

/* initialise fader by hiding image object first */
addEvent(window,'load',fadeInit)



/* 3rd party helper functions */

/* addEvent handler for IE and other browsers */
function addEvent(elm, evType, fn, useCapture) 
// addEvent and removeEvent
// cross-browser event handling for IE5+,  NS6 and Mozilla
// By Scott Andrew
{
 if (elm.addEventListener){
   elm.addEventListener(evType, fn, useCapture);
   return true;
 } else if (elm.attachEvent){
   var r = elm.attachEvent("on"+evType, fn);
   return r;
 }
}