var slideshowDivs = [];
var currentDivIndexes = [];
 
function getChildDivs(id) {
        var parent = document.getElementById(id);
        var spacer = document.getElementById(id + '-spacer');
        var childDivs = [];
        var childDivCount = 0;
        var i;
        var maxHeight = 0;
        var maxWidth = 0;
        for (i=0; i < parent.childNodes.length; i++) {
                var child = parent.childNodes[i];
                if (child.tagName == 'DIV') {
                        childDivs[childDivCount++] = child;
                        if (maxHeight < child.offsetHeight) {
                                maxHeight = child.offsetHeight
                        }
                        if (maxWidth < child.offsetWidth) {
                                maxWidth = child.offsetWidth
                        }
                        child.style.position = 'absolute';
                        //child.style.height = '0px';
                        //child.style.width = '0px';
                        //child.style.overflow = 'visible';
                        hide(child);
                }
        }
        parent.style.position = 'absolute';
        spacer.style.height = maxHeight + 'px';
        spacer.style.width = maxWidth + 'px';
 
        return childDivs;
}
 
function getInitialDivIndex(id, sequence) {
        var index = -1;
        if (sequence == 'forward') {
          index = 0;
        } else if (sequence == 'backward') {
          index = (slideshowDivs[id].length)-1;
        } else if (sequence == 'random') {
                index = Math.floor(Math.random()*slideshowDivs[id].length);
        }
        show(slideshowDivs[id][index]);
        return index;
}
 
function getNextDivIndex(id, sequence) {
        var index = -1;
        if (sequence == 'forward') {
                index = currentDivIndexes[id] + 1;
                if (index == slideshowDivs[id].length) {
                        index = 0;
                }
        } else if (sequence == 'backward') {
                index = currentDivIndexes[id] - 1;
                if (index == -1) {
                        index = slideshowDivs[id].length - 1;
                }
        } else if (sequence == 'random') {
                index = currentDivIndexes[id];
                if (slideshowDivs[id].length > 1) {
                        while (index == currentDivIndexes[id]) {
                                index = Math.floor(Math.random()*slideshowDivs[id].length);
                        }
                }
        }
 
        return index;
}
 
function getNode(id, index) {
        return slideshowDivs[id][index];
}
 
function doTransition(currentNode, newNode, transition) {
        if (transition == 'cut') {
                hide(currentNode);
                show(newNode);
        } else if (transition == 'fade') {
                currentNode.style.zIndex = 2;
                setOpacity(newNode,0);
                newNode.style.zIndex = 1;
                var fadeTransition = new Effect.Parallel([
                        new Effect.Opacity(currentNode, {from: 1.0, to: 0.0}),
                        new Effect.Opacity(newNode, {from: 0.0, to: 1.0})
                        ], {duration: 1.0, afterFinish: function() { currentNode.style.zIndex = 0; }});
        } else if (transition == 'blindDown') {
                currentNode.style.zIndex = 1;
                newNode.style.zIndex = 2;
                new Effect.BlindDown(newNode, {duration: 1.0});
        }
}
 
function slideshow(id, sequence, transition) {
        var newIndex = getNextDivIndex(id, sequence);
        doTransition(getNode(id, currentDivIndexes[id]), getNode(id, newIndex), transition);
        currentDivIndexes[id] = newIndex;
}
 
function startSlideshow(id, refresh, sequence, transition) {
        slideshowDivs[id] = getChildDivs(id);
        if (slideshowDivs[id].length > 0) {
                currentDivIndexes[id] = getInitialDivIndex(id, sequence);
                setInterval("slideshow('" + id + "', '" + sequence + "', '" + transition + "');", refresh);
        }
}
 
function hide(node) {
   if (node != null) {
                setOpacity(node, 0);
                node.style.zIndex = 0;
        }
}
 
function show(node) {
   if (node != null) {
                setOpacity(node, 1);
                node.style.zIndex = 1;
        }
}
 
function setOpacity(node, value) {
   if (node != null) {
                node.style.opacity = value;
                node.style.filter = 'alpha(opacity = ' + (value * 100) + ')';
        }
}