var counter = 1;
var timeToFade = 250.0; //Transition time OF FADE in milliseconds
var timeToTransition = 5000.0; //Transition time BETWEEN fades in milliseconds

function swapCtrl() {
	curtain('image-slide');
	setTimeout("curtain('image-slide')", 150);
	var imgs = document.getElementById('image-slide').getElementsByTagName("img");
	switch (counter) {
		case imgs.length:
			setTimeout("swap('" + imgs[counter - 1].id + "')", 100);
			setTimeout("swap('" + imgs[0].id + "')", 100);
			counter = 1;
			break;
		default:
			setTimeout("swap('" + imgs[counter -1].id + "')", 100);
			setTimeout("swap('" + imgs[counter].id + "')", 100);
			counter = counter + 1;
			break;
	}
	clearTimeout(t);
	t = setTimeout("swapCtrl()", timeToTransition);
}

function curtain(eid) {
	fade('image-slide');
}

function swap(eid) {
	var element = document.getElementById(eid);
	if (element == null)
		return;
	if (element.style.display == 'none') {
		element.style.display = 'block';
	}
	else {
		element.style.display = 'none';
	}
}

function advance() {
    swapCtrl();
}

function retreat() {
    curtain('image-slide');
    setTimeout("curtain('image-slide')", 150);
    var imgs = document.getElementById('image-slide').getElementsByTagName("img");
    switch (counter) {
        case 1:
            setTimeout("swap('" + imgs[0].id + "')", 100);
            setTimeout("swap('" + imgs[imgs.length-1].id + "')", 100);
            counter = imgs.length;
            break;
        default:
            setTimeout("swap('" + imgs[counter - 1].id + "')", 100);
            setTimeout("swap('" + imgs[counter - 2].id + "')", 100);
            counter = counter - 1;
            break;
    }
    clearTimeout(t);
    t = setTimeout("swapCtrl()", timeToTransition);
}

/* Fade Effect */
function fade(eid) {
	var element = document.getElementById(eid);
	if (element == null)
		return;

	if (element.FadeState == null) {
		if (element.style.opacity == null
        || element.style.opacity == ''
        || element.style.opacity == '1') {
			element.FadeState = 2;
		}
		else {
			element.FadeState = -2;
		}
	}

	if (element.FadeState == 1 || element.FadeState == -1) {
		element.FadeState = element.FadeState == 1 ? -1 : 1;
		element.FadeTimeLeft = timeToFade - element.FadeTimeLeft;
	}
	else {
		element.FadeState = element.FadeState == 2 ? -1 : 1;
		element.FadeTimeLeft = timeToFade;
		setTimeout("animateFade(" + new Date().getTime() + ",'" + eid + "')", 0);
	}
}

function animateFade(lastTick, eid) {
	var curTick = new Date().getTime();
	var elapsedTicks = curTick - lastTick;

	var element = document.getElementById(eid);

	if (element.FadeTimeLeft <= elapsedTicks) {
		element.style.opacity = element.FadeState == 1 ? '1' : '0';
		element.style.filter = 'alpha(opacity = '
        + (element.FadeState == 1 ? '100' : '0') + ')';
		element.FadeState = element.FadeState == 1 ? 2 : -2;
		return;
	}

	element.FadeTimeLeft -= elapsedTicks;
	var newOpVal = element.FadeTimeLeft / timeToFade;
	if (element.FadeState == 1)
		newOpVal = 1 - newOpVal;

	element.style.opacity = newOpVal;
	element.style.filter = 'alpha(opacity = ' + (newOpVal * 100) + ')';

	setTimeout("animateFade(" + curTick + ",'" + eid + "')", 0);
}

addLoadEvent(function () {
	if (document.getElementById('image-slide')) {
		t = setTimeout("swapCtrl()", timeToTransition);
	}
});