// from http://www.mediawiki.org/wiki/Extension:Javascript_Slideshow/slideshow.js

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) + ')';
  }
}