// JavaScript Document

function load(){
	fadePrep('otherPreference','preference_Other');
	addListener(document.getElementById('preference_Other'),'click',fadeOther);
	fadePrep('dpWhichFriend','dpFriend');
	addListener(document.getElementById('dpFriend'),'click',fadeFriend);
	fadePrep('dpOtherStudOrg','dpStudOrg');
	addListener(document.getElementById('dpStudOrg'),'click',fadeStudOrg);
}

function addListener(element, type, expression, bubbling)
{
	bubbling = bubbling || false;
	
	if(window.addEventListener)	{ // Standard
		element.addEventListener(type, expression, bubbling);
		return true;
	} else if(window.attachEvent) { // IE
		element.attachEvent('on' + type, expression);
		return true;
	} else return false;
}

function fadeOther(){
	fade('otherPreference');
	postFade('otherPreference','preference_Other');
}

function fadeFriend(){
	fade('dpWhichFriend');
	postFade('dpWhichFriend','dpFriend');
}

function fadeStudOrg(){
	fade('dpOtherStudOrg');
	postFade('dpOtherStudOrg','dpStudOrg');
}


function fadePrep(elem,check){
	elem = document.getElementById(elem);
	if(document.getElementById(check).checked == false){
		elem.style.position="relative";
		elem.style.backgroundColor="transparent";
		elem.style.opacity="0";
		elem.style.filter="alpha(opacity=0)";
		elem.FadeState=-2;
	} else { elem.FadeState=2; }
}

function postFade(fadeElem,check){
	fadeElem = document.getElementById(fadeElem);
	fadeElem.value='';
	if(document.getElementById(check).checked){ fadeElem.disabled = false; fadeElem.focus(); }
	else { fadeElem.disabled = true; }
}

// fade script from http://www.switchonthecode.com/tutorials/javascript-tutorial-simple-fade-animation
var TimeToFade = 300.0;

function fade(eid)
{
  var element = document.getElementById(eid);
  if(element == null)
    return;
   
  if(element.FadeState == null)
  {
    if(element.style.opacity == null
        || element.style.opacity == ''
        || element.style.opacity == '1')
    {
      element.FadeState = 2;
    }
    else
    {
      element.FadeState = -2;
    }
  }
   
  if(element.FadeState == 1 || element.FadeState == -1)
  {
    element.FadeState = element.FadeState == 1 ? -1 : 1;
    element.FadeTimeLeft = TimeToFade - element.FadeTimeLeft;
  }
  else
  {
    element.FadeState = element.FadeState == 2 ? -1 : 1;
    element.FadeTimeLeft = TimeToFade;
    setTimeout("animateFade(" + new Date().getTime() + ",'" + eid + "')", 33);
  }  
}

function animateFade(lastTick, eid)
{  
  var curTick = new Date().getTime();
  var elapsedTicks = curTick - lastTick;
 
  var element = document.getElementById(eid);
 
  if(element.FadeTimeLeft <= elapsedTicks)
  {
    element.style.opacity = element.FadeState == 1 ? '1' : '0';
    element.style.filter = 'alpha(opacity = '
        + (element.FadeState == 1 ? '100' : '0') + ')';
    element.FadeState = element.FadeState == 1 ? 2 : -2;
    return;
  }
 
  element.FadeTimeLeft -= elapsedTicks;
  var newOpVal = element.FadeTimeLeft/TimeToFade;
  if(element.FadeState == 1)
    newOpVal = 1 - newOpVal;

  element.style.opacity = newOpVal;
  element.style.filter = 'alpha(opacity = ' + (newOpVal*100) + ')';
 
  setTimeout("animateFade(" + curTick + ",'" + eid + "')", 33);
}