/*
* Original from: http://brainerror.net/scripts/javascript/blendtrans/demo.html
*
* Edits by ASC:
*   - Removed unnecessary OO code that caused MSIE to choke
*   - Added pause between setting bg image and setting opacity to zero to
*     prevent MSIE image flash
*   - Increased opacity check argument to 103 for completely smooth fade
*
*/

//find next image
function nextImage(o) {
    do o = o.nextSibling;
    while (o && o.tagName != 'IMG');
    return o;
}

//find first image inside an element
function firstChildImage(o) {

    o = o.firstChild;

    while (o && o.tagName != 'IMG') {
        o = o.nextSibling;
    }

    return o;
}

//set the opacity of an element to a specified value
function setOpacity(obj, o) {

    obj.style.opacity = (o / 100);
    obj.style.MozOpacity = (o / 100);
    obj.style.KhtmlOpacity = (o / 100);
    obj.style.filter = 'alpha(opacity=' + o + ')';
}

//make image invisible and set next one as current image
function getNextImage(image) {

    if (next = nextImage(image)) {
        image.style.display = 'none';
        image.style.zIndex = 0;

        next.style.display = 'block';
        next.style.zIndex = 100;

    } else {
        //if there is not a next image, get the first image again
        next = firstChildImage(image.parentNode);
    }

    return next;
}

//set default values for parameters and starting image
function blendImages(id, speed, pause, caption) {

    if (speed == null) {
        speed = 30;
    }

    if (pause == null) {
        pause = 1500;
    }

    var blend = document.getElementById(id);

    var image = firstChildImage(blend);

    startBlending(image, speed, pause, caption);
}

//make image a block-element and set the caption
function startBlending(image, speed, pause, caption) {

    image.style.display = 'block';

    if (caption != null) {
        document.getElementById(caption).innerHTML = image.alt;
    }

    continueFadeImage(image, 0, speed, pause, caption);
}

// ASC: copied from http://www.sean.co.uk/a/webdesign/javascriptdelay.shtm
function pausecomp(millis) {
    var date = new Date();
    var curDate = null;

    do { curDate = new Date(); }
    while (curDate - date < millis);
}

//set an increased opacity and check if the image is done blending
function continueFadeImage(image, opacity, speed, pause, caption) {

    opacity = opacity + 3;

    if (opacity < 103) {

        setTimeout(function() { fadeImage(image, opacity, speed, pause, caption) }, speed);

    } else {
        //if the image is done, set it to the background and make it transparent
        image.parentNode.style.backgroundImage = "url(" + image.src + ")";

        // ASC: pause 1sec here to prevent MSIE image flash ...
        var paws = pause - 1000;
        if (paws < 0) {
            paws = 0;
        }
        pausecomp(1000);

        setOpacity(image, 0);
        //get the next image and start blending it again
        image = getNextImage(image);
        setTimeout(function() { startBlending(image, speed, pause, caption) }, paws);
    }
}

//set the opacity to a new value and continue the fading
function fadeImage(image, opacity, speed, pause, caption) {
    setOpacity(image, opacity);
    continueFadeImage(image, opacity, speed, pause, caption);
}