var SlideList = new Class({
  initialize: function(menu, options) {
    this.setOptions(this.getOptions(), options);

    this.menu = $(menu), this.current = this.menu.getElement('li.current');

    this.menu.getElements('li').each(function(item){
      item.addEvent('mouseover', function(){ this.moveBg(item); }.bind(this));
      item.addEvent('mouseout', function(){ this.moveBg(this.current); }.bind(this));
      item.addEvent('click', function(event){ this.clickItem(event, item); }.bind(this));
    }.bind(this));

    this.back = new Element('li').addClass('background').adopt(new Element('div').addClass('left')).injectInside(this.menu);
    this.back.fx = this.back.effects(this.options);
    if(this.current) {
      this.setCurrent(this.current);
    }
    else
    {
      this.setCurrent(this.menu.getElement('li'));
    }
  },

  setCurrent: function(el, effect){
    this.back.setStyles({left: (el.offsetLeft)+'px', width: (el.offsetWidth)+'px'});
    (effect) ? this.back.effect('opacity').set(0).start(1) : this.back.setOpacity(1);
    this.current = el;
  },

  getOptions: function(){
    return {
      transition: Fx.Transitions.sineInOut,
      duration: 500, wait: false,
      onClick: Class.empty
    };
  },

  clickItem: function(event, item) {
    if(!this.current) this.setCurrent(item, true);
    this.current = item;
    this.options.onClick(new Event(event), item);
  },

  moveBg: function(to) {
    if(!this.current) return;
    this.back.fx.custom({
      left: [this.back.offsetLeft, to.offsetLeft],
      width: [this.back.offsetWidth, to.offsetWidth]
    });
  }
});

SlideList.implement(new Options);