var DDSPEED = 10;
var DDTIMER = 15;

dom.event.addEventListener(window, 'load', dropdownInit);

function dropdownInit(){
  var oneDDheader = "";
  var oneDDcontent = "";
  var dropdowns = document.getElementsByClassName('dropdown');
  for(var i = 0; i < dropdowns.length; i++){
    oneDDheader = dropdowns[i].getElementsByTagName("dt")[0];
    oneDDcontent = dropdowns[i].getElementsByTagName("dd")[0];
    var base = oneDDcontent.getAttribute('id').split('-')[0];
    dom.event.addEventListener( oneDDheader, 'mouseover', ddMenu(base,1),true );
    dom.event.addEventListener( oneDDheader, 'mouseout', ddMenu(base,-1) );
    dom.event.addEventListener( oneDDcontent, 'mouseover', cancelHide(base) );
    dom.event.addEventListener( oneDDcontent, 'mouseout', ddMenu(base,-1) );
  }
}

// main function to handle the mouse events //
function ddMenu(id,d){
  return function(ev){
    var h = document.getElementById(id + '-ddheader');
    var c = document.getElementById(id + '-ddcontent');
    clearInterval(c.timer);
    if(d == 1){
      clearTimeout(h.timer);
      if(c.maxh && c.maxh <= c.offsetHeight){return}
      else if(!c.maxh){
        c.style.display = 'block';
        c.style.height = 'auto';
        c.maxh = c.offsetHeight;
        c.style.height = '0px';
      }
      c.timer = setInterval(function(){ddSlide(c,1)},DDTIMER);
    }else{
      h.timer = setTimeout(function(){ddCollapse(c)},50);
    }
  }
}

// collapse the menu //
function ddCollapse(c){
  c.timer = setInterval(function(){ddSlide(c,-1)},DDTIMER);
}

// cancel the collapse if a user rolls over the dropdown //
function cancelHide(id){
  return function(ev){
    var h = document.getElementById(id + '-ddheader');
    var c = document.getElementById(id + '-ddcontent');
    clearTimeout(h.timer);
    clearInterval(c.timer);
    if(c.offsetHeight < c.maxh){
      c.timer = setInterval(function(){ddSlide(c,1)},DDTIMER);
    }
  }
}

// incrementally expand/contract the dropdown and change the opacity //
function ddSlide(c,d){
  var currh = c.offsetHeight;
  var dist;
  if(d == 1){
    dist = (Math.round((c.maxh - currh) / DDSPEED));
  }else{
    dist = (Math.round(currh / DDSPEED));
  }
  if(dist <= 1 && d == 1){
    dist = 1;
  }
  c.style.height = currh + (dist * d) + 'px';
  c.style.opacity = currh / c.maxh;
  c.style.filter = 'alpha(opacity=' + (currh * 100 / c.maxh) + ')';
  if((currh < 2 && d != 1) || (currh > (c.maxh - 2) && d == 1)){
    clearInterval(c.timer);
  }
}