/**
* @author Ryan Johnson <http://saucytiger.com/>
* @copyright 2008 PersonalGrid Corporation <http://personalgrid.com/>
* @package LivePipe UI
* @license MIT
* @url http://livepipe.net/control/scrollbar
* @require prototype.js, slider.js, livepipe.js
*/
 
if(typeof(Prototype) == "undefined")
  throw "Control.ScrollBar requires Prototype to be loaded.";
if(typeof(Control.Slider) == "undefined")
  throw "Control.ScrollBar requires Control.Slider to be loaded.";
if(typeof(Object.Event) == "undefined")
  throw "Control.ScrollBar requires Object.Event to be loaded.";
 
Control.ScrollBar = Class.create({
  initialize: function(container,track,options){
    this.enabled = false;
    this.notificationTimeout = false;
    this.container = $(container);
    this.boundMouseWheelEvent = this.onMouseWheel.bindAsEventListener(this);
    this.boundResizeObserver = this.onWindowResize.bind(this);
    this.track = $(track);
    this.handle = this.track.firstDescendant();
    this.options = Object.extend({
      active_class_name: 'scrolling',
      apply_active_class_name_to: this.container,
      notification_timeout_length: 125,
      handle_minimum_height: 25,
      scroll_to_smoothing: 0.01,
      scroll_to_steps: 15,
      proportional: true,
      slider_options: {}
    },options || {});
    this.slider = new Control.Slider(this.handle,this.track,Object.extend({
      axis: 'vertical',
      onSlide: this.onChange.bind(this),
      onChange: this.onChange.bind(this)
    },this.options.slider_options));
    this.recalculateLayout();
    Event.observe(window,'resize',this.boundResizeObserver);
    this.handle.observe('mousedown',function(){
     if(this.auto_sliding_executer)
          this.auto_sliding_executer.stop();
    }.bind(this));
  },
  destroy: function(){
    Event.stopObserving(window,'resize',this.boundResizeObserver);
  },
  enable: function(){
    this.enabled = true;
    this.container.observe('mouse:wheel',this.boundMouseWheelEvent);
    this.slider.setEnabled();
    this.track.show();
    if(this.options.active_class_name)
      $(this.options.apply_active_class_name_to).addClassName(this.options.active_class_name);
    this.notify('enabled');
  },
  disable: function(){
    this.enabled = false;
    this.container.stopObserving('mouse:wheel',this.boundMouseWheelEvent);
    this.slider.setDisabled();
    this.track.hide();
    if(this.options.active_class_name)
      $(this.options.apply_active_class_name_to).removeClassName(this.options.active_class_name);
    this.notify('disabled');
    this.reset();
  },
  reset: function(){
    this.slider.setValue(0);
  },
  recalculateLayout: function(){
    if(this.container.scrollHeight <= this.container.offsetHeight)
      this.disable();
    else{
      this.slider.trackLength = this.slider.maximumOffset() - this.slider.minimumOffset();
      if(this.options.proportional){
        this.handle.style.height = Math.max(this.container.offsetHeight * (this.container.offsetHeight / this.container.scrollHeight),this.options.handle_minimum_height) + 'px';
        this.slider.handleLength = this.handle.style.height.replace(/px/,'');
      }
      this.enable();
    }
  },
  onWindowResize: function(){
    this.recalculateLayout();
    this.scrollBy(0);
  },
  onMouseWheel: function(event){
   if(this.auto_sliding_executer)
      this.auto_sliding_executer.stop();
    this.slider.setValueBy(-(event.memo.delta / 20)); //put in math to account for the window height
    event.stop();
    return false;
  },
  onChange: function(value){
    this.container.scrollTop = Math.round(value / this.slider.maximum * (this.container.scrollHeight - this.container.offsetHeight));
    if(this.notification_timeout)
      window.clearTimeout(this.notificationTimeout);
    this.notificationTimeout = window.setTimeout(function(){
      this.notify('change',value);
    }.bind(this),this.options.notification_timeout_length);
  },
  getCurrentMaximumDelta: function(){
    return this.slider.maximum * (this.container.scrollHeight - this.container.offsetHeight);
  },
  getDeltaToElement: function(element){
    return this.slider.maximum * ((element.positionedOffset().top + (element.getHeight() / 2)) - (this.container.getHeight() / 2));
  },
  scrollTo: function(y,animate){
    var current_maximum_delta = this.getCurrentMaximumDelta();
    if(y == 'top')
      y = 0;
    else if(y == 'bottom')
      y = current_maximum_delta;
    else if(typeof(y) != "number")
      y = this.getDeltaToElement($(y));
    if(this.enabled){
      y = Math.max(0,Math.min(y,current_maximum_delta));
      if(this.auto_sliding_executer)
        this.auto_sliding_executer.stop();
      var target_value = y / current_maximum_delta;
      var original_slider_value = this.slider.value;
      var delta = (target_value - original_slider_value) * current_maximum_delta;
      if(animate){
        this.auto_sliding_executer = new PeriodicalExecuter(function(){
          if(Math.round(this.slider.value * 100) / 100 < Math.round(target_value * 100) / 100 || Math.round(this.slider.value * 100) / 100 > Math.round(target_value * 100) / 100){
            this.scrollBy(delta / this.options.scroll_to_steps);
          }else{
            this.auto_sliding_executer.stop();
            this.auto_sliding_executer = null;
            if(typeof(animate) == "function")
              animate();
          }      
        }.bind(this),this.options.scroll_to_smoothing);
      }else
        this.scrollBy(delta);
    }else if(typeof(animate) == "function")
      animate();
  },
  scrollBy: function(y){
    if(!this.enabled)
      return false;
    this.slider.setValueBy(y / this.getCurrentMaximumDelta());
  }
});
Object.Event.extend(Control.ScrollBar);