/**
 *
 * @param HTMLElement element : Objet HTML à modifier
 * @param int opacity : opacité à atteindre
 * @param int duration : Durée de l'aniamtion de l'opacité en millisecondes
 * @param int steps : nombre d'étapes de modification de l'opacité
 * @param int curOpacity : opacité actuel 
 *
 */
var counter = 0;
var setOpactityModifier = function(element, opacity, duration, steps, curOpacity)
{
  if(typeof element.opacityEffect == 'undefined')
    element.opacityEffect = new Object();
  /*
  if(element.opacityEffect.timer == null || typeof element.opacityEffect.timer == 'undefined')
  {
  */
    /*
    opacity = opacity || 100; //in percent
    duration = duration || 1000;//in milliseconds
    steps = steps || 25; //frames * speed
    curOpacity = curOpacity || 0; //in percent
    */
    var opPerSteps = (opacity - curOpacity) / steps;
    
    element.opacityEffect = {
      curOpacity : curOpacity, 
      opacity : opacity,
      opPerSteps : opPerSteps
    }
    element.opacityEffect.timer = setInterval(
      (function()
      {
        return function()
        {
          var opacityEffect = element.opacityEffect,
          opacity = opacityEffect.opacity,
          curOpacity = opacityEffect.curOpacity,
          opPerSteps = opacityEffect.opPerSteps,
          eStyle = element.style,
          newOpacity = curOpacity + opPerSteps;//in %
          element.opacityEffect.curOpacity = newOpacity;
          if((newOpacity >= opacity && opPerSteps >= 0) || (newOpacity <= opacity && opPerSteps <= 0))
          {
            newOpacity = opacity;
            clearInterval(opacityEffect.timer);//clear Timer
            opacityEffect.timer = null;
            /* //delete [Object].porperty not work with IE 
            delete element.opacityEffect; //del effectModifier and parameters
            */
          }
          if(typeof document.body.style.filter != 'undefined')//IE
            //eStyle.filter = 'alpha(opacity=' + newOpacity + ')';
            //document.body.style.filter = 'alpha(opacity=' + newOpacity + ')';
            //IE la grosse merde ! il chie dans tout les sens !
            element.style.filter = 'alpha(opacity=' + newOpacity + ')';
          else//else for others webbrowsers (whitout opera ... ?)
            eStyle.opacity = newOpacity / 100;
          //alert(eStyle.filter);
        }
      })(), duration / steps
    );
  //}
};

var curElement;
function displayWords()
{
  if(curElement.parentNode.lastChild == curElement)
    curElement = curElement.parentNode.firstChild;
  else
    curElement = curElement.nextSibling;
  setOpactityModifier(curElement, 100, 1000, 25, 0);
  curElement.style.visibility = 'visible';
  setTimeout(function()
  {
    setOpactityModifier(curElement, 0, 1000, 25, 100);
    setTimeout(function()
    {
      curElement.style.visibility = 'hidden';
      displayWords();
    }, 1000);
  }, 1000)
}


//On éxecute la fonction onLoad au lancement de la page
window.onload = function()
{
  //donc on est sur la home page  
  if(document.getElementById('index'))
  {
    curElement = document.getElementById('problems').lastChild;
    displayWords();
    
    //document.body.style.filter = 'alpha(opacity=50)';
  }

};