function createPopup(url, width, height)
{
  document.popup = new Popup(url, width, height);
  document.popup.show();
}

function destroyPopup()
{
  document.popup.hide();
}


function Popup(newURL, newWidth, newHeight) 
{
  document.PopperdePopup = this;
  
  this.id           = 'popupeddiv';
  this.overlayId    = 'overlayeddiv';
  this.url          = newURL;
  this.width        = newWidth;
  this.height       = newHeight;
  this.windowWidth  = -1;
  this.windowHeight = -1;
  this.scrollLeft   = 0;
  this.scrollTop    = 0;
  this.body         = null;
  this.iframe       = '<iframe id="popupediframe" style="position: absolute; z-index: -1; filter: mask(); border: 0; margin: 0; padding: 0; top: 0; left: 0; width: 100px; height: 100px; overflow: hidden;"></iframe>';
  this.iframeid     = 'popupediframe';

  if (typeof(_Popup_prototype_called) == 'undefined')
  {
    _Popup_prototype_called = true;
    Popup.prototype.show    = show;
    Popup.prototype.hide    = hide;
    Popup.prototype.repaint = repaint;
    
    Popup.prototype.showOverlay = showOverlay;
    Popup.prototype.hideOverlay = hideOverlay;
    Popup.prototype.getPageSize = getPageSize;
    Popup.prototype.getScrollPosition = getScrollPosition;
    
    if (window.addEventListener)
    { // Standard
      window.addEventListener('resize', repaint, false);
      window.addEventListener('scroll', repaint, false);
    }
    else if (window.attachEvent)
    { // IE
      window.attachEvent('onresize', repaint);
      window.attachEvent('onscroll', repaint);
    }
  }

  

  function getPageSize() 
  { 
    if (self.innerHeight)
    { // Standard
      this.windowWidth  = self.innerWidth;
      this.windowHeight = self.innerHeight;
      
      // BUG: in firefox the width and height are a bit too big when scrollbars are visible.
    }
    else if (document.documentElement && document.documentElement.clientHeight)
    { // Explorer 6 Strict Mode
      this.windowWidth  = document.documentElement.clientWidth;
      this.windowHeight = document.documentElement.clientHeight;
    }
    else if (document.body)
    { // other Explorers
      this.windowWidth  = document.body.clientWidth;
      this.windowHeight = document.body.clientHeight;
    }
  }
  
  function getScrollPosition()
  {
    this.scrollTop  = typeof window.pageYOffset != 'undefined' ? window.pageYOffset : document.documentElement.scrollTop;
    this.scrollLeft = typeof window.pageXOffset != 'undefined' ? window.pageXOffset : document.documentElement.scrollLeft;

    this.scrollTop  = document.body.scrollTop > 0 ? document.body.scrollTop : this.scrollTop;
    this.scrollLeft = document.body.scrollLeft > 0 ? document.body.scrollLeft : this.scrollLeft;
  }
  
  function getMaxZIndex()
  {
    var maxZIndex = 0;
    var elements  = document.getElementsByTagName('*');
  
    for (i = 0; i < elements.length; i++)
    {
      var element = elements[i];
      var zindex;

      if (element.currentStyle)
        zindex = element.currentStyle.zIndex;
      else if (document.defaultView)
        zindex = document.defaultView.getComputedStyle(element, null).getPropertyValue('z-index');

      if (!isNaN(zindex))
      {
        if (zindex > maxZIndex)
          maxZIndex = zindex;
      }
    }

    return ++maxZIndex;
  }

  function setOpacity(obj, opacity)
  {
    opacity = (opacity == 100) ? 99.999 : opacity;
    // IE/Win
    obj.style.filter = 'alpha(opacity:' + opacity + ')';
    // Safari<1.2, Konqueror
    obj.style.KHTMLopacity = opacity/100;
    // Older Mozilla and Firefox
    obj.style.Mozopacity = opacity/100;
    // Safari 1.2, newer Firefox and Mozilla, CSS3
    obj.style.opacity = opacity/100;
  }

  function showOverlay()
  {
    // Create div.
    var newDiv = document.createElement('div');
    newDiv.setAttribute('id', this.overlayId);

    // Style new div.
    newDiv.style.position         = 'absolute';
    newDiv.style.left             = this.scrollLeft + 'px';
    newDiv.style.top              = this.scrollTop + 'px';
    newDiv.style.width            = this.windowWidth + 'px';
    newDiv.style.height           = this.windowHeight + 'px';
    newDiv.style.zIndex           = getMaxZIndex();
    newDiv.style.backgroundColor  = '#CCCCCC';
    newDiv.style.visibility       = 'visible';
    setOpacity(newDiv, 50);
    document.body.appendChild(newDiv);
  }
  
  function hideOverlay()
  {
    // Remove div.
    var overlayDiv = document.getElementById(this.overlayId);
    document.body.removeChild(overlayDiv);
  }
  
  
  
  function show() 
  {
    var popupDiv = document.getElementById(this.id);
    if (popupDiv != null) return;

    this.getPageSize();
    this.getScrollPosition();
    this.showOverlay();
  
    var separator = (this.url.indexOf('?') == -1 ? '?' : '&');
    var url       = this.url + separator + 'nocache=' + new Date().getTime();
  
    // Get content.
    ajaxConnection = new AJAXConnection(url);
    ajaxConnection.get();
    this.body = this.iframe + ajaxConnection.getResponseText();
    
    // Create div.
    var newDiv = document.createElement('div');
    document.body.appendChild(newDiv);
    newDiv.setAttribute('id', this.id);
    newDiv.innerHTML = this.body;
    
    // Style new div.
    newDiv.style.display    = 'block';
    newDiv.style.visibility = 'visible';
    newDiv.style.position   = 'absolute';
    if (this.width == null || this.height == null)
    {
      // Get size of popup content.
      this.width  = newDiv.offsetWidth;
      this.height = newDiv.offsetHeight;
    }
    newDiv.style.left       = ((this.windowWidth / 2) - (this.width / 2)) + this.scrollLeft + 'px';
    newDiv.style.top        = ((this.windowHeight / 2) - (this.height / 2)) + this.scrollTop + 'px';
    newDiv.style.zIndex     = getMaxZIndex();
    // Set size to helper iframe.
    document.getElementById(this.iframeid).style.width  = this.width + 'px';
    document.getElementById(this.iframeid).style.height = this.height + 'px';
  }
  
  function hide()
  {
    this.hideOverlay();
    
    // Remove div.
    var popupDiv = document.getElementById(this.id);
    document.body.removeChild(popupDiv);
  }
  
  function repaint()
  { // BUG: in firefox it's possible to keep scrolling.
    var p = document.PopperdePopup;
    p.getPageSize();
    p.getScrollPosition();

    // Resize and relocate overlay div.
    var overlayDiv = document.getElementById(p.overlayId);
    if (overlayDiv != null)
    {
      overlayDiv.style.left   = p.scrollLeft + 'px';
      overlayDiv.style.top    = p.scrollTop + 'px';
      overlayDiv.style.width  = p.windowWidth + 'px';
      overlayDiv.style.height = p.windowHeight + 'px';
    }
    
    // Relocate popup div.
    var popupDiv = document.getElementById(p.id);
    if (popupDiv != null)
    {
      if (p.width == null || p.height == null)
      {
        // Get width of popup content.
        p.width  = popupDiv.offsetWidth;
        p.height = popupDiv.offsetHeight;
      }
      popupDiv.style.left = ((p.windowWidth / 2) - (p.width / 2)) + 'px';
      popupDiv.style.top  = ((p.windowHeight / 2) - (p.height / 2)) + 'px';
    }
  }
}