var $ = function (id)
{
  return "string" == typeof id ? document.getElementById(id) : id;
};

var Extend = function(destination, source)
{
  for (var property in source)
  {
    destination[property] = source[property];
  }

  return destination;
}

var CurrentStyle = function(element)
{
  return element.currentStyle || document.defaultView.getComputedStyle(element, null);
}

var Bind = function(object, fun) 
{
  var args = Array.prototype.slice.call(arguments).slice(2);
  return function() 
  {
    return fun.apply(object, args.concat(Array.prototype.slice.call(arguments)));
  }
}

var Tween = 
{
  Quart: 
  {
    easeOut: function(t,b,c,d)
    {
      return -c * ((t=t/d-1)*t*t*t - 1) + b;
    }
  },
  Back: 
  {
    easeOut: function(t,b,c,d,s)
    {
      if (s == undefined) s = 1.70158;
        return c*((t=t/d-1)*t*((s+1)*t + s) + 1) + b;
    }
  },
  Bounce:
  {
    easeOut: function(t,b,c,d)
    {
      if ((t/=d) < (1/2.75)) 
      {
        return c*(7.5625*t*t) + b;
      }
      else if (t < (2/2.75))
      {
        return c*(7.5625*(t-=(1.5/2.75))*t + .75) + b;
      }
      else if (t < (2.5/2.75))
      {
        return c*(7.5625*(t-=(2.25/2.75))*t + .9375) + b;
      }
      else
      {
        return c*(7.5625*(t-=(2.625/2.75))*t + .984375) + b;
      }
    }
  }
}

//容器对象,滑动对象,切换数量
var SlideTrans = function(container, slider, count, options)
{
  this._slider = $(slider);
  this._container = $(container);//容器对象
  this._timer = null;//定时器
  this._count = Math.abs(count);//切换数量
  this._target = 0;//目标值
  this._t = this._b = this._c = 0;//tween参数
  this.Index = 0;//当前索引
  this.SetOptions(options);
  this.Auto = !!this.options.Auto;
  this.Duration = Math.abs(this.options.Duration);
  this.Time = Math.abs(this.options.Time);
  this.Pause = Math.abs(this.options.Pause);
  this.Tween = this.options.Tween;
  this.onStart = this.options.onStart;
  this.onFinish = this.options.onFinish;
  var bVertical = !!this.options.Vertical;
  this._css = bVertical ? "top" : "left";//方向
  //样式设置
  var p = CurrentStyle(this._container).position;
  p == "relative" || p == "absolute" || (this._container.style.position = "relative");
  this._container.style.overflow = "hidden";
  this._slider.style.position = "absolute";
  this.Change = this.options.Change ? this.options.Change :
  this._slider[bVertical ? "offsetHeight" : "offsetWidth"] / this._count;
};
SlideTrans.prototype = {
  //设置默认属性
  SetOptions: function(options)
  {
    this.options = {
      //默认值
      Vertical:	true,//是否垂直方向（方向不能改）
      Auto:		true,//是否自动
      Change:		0,//改变量
      Duration:	50,//滑动持续时间
      Time:		10,//滑动延时
      Pause:		2000,//停顿时间(Auto为true时有效)
      onStart:	function(){},//开始转换时执行
      onFinish:	function(){},//完成转换时执行
      Tween:		Tween.Quart.easeOut//tween算子
    };
    
    Extend(this.options, options || {});
  },
  //开始切换
  Run: function(index)
  {
    //修正index
    index == undefined && (index = this.Index);
    index < 0 && (index = this._count - 1) || index >= this._count && (index = 0);
    //设置参数
    this._target = -Math.abs(this.Change) * (this.Index = index);
    this._t = 0;
    this._b = parseInt(CurrentStyle(this._slider)[this.options.Vertical ? "top" : "left"]);
    this._c = this._target - this._b;
    this.onStart();
    this.Move();
  },
  //移动
  Move: function()
  {
    clearTimeout(this._timer);
    //未到达目标继续移动否则进行下一次滑动
    if (this._c && this._t < this.Duration) 
    {
      this.MoveTo(Math.round(this.Tween(this._t++, this._b, this._c, this.Duration)));
      this._timer = setTimeout(Bind(this, this.Move), this.Time);
    }
    else
    {
      this.MoveTo(this._target);
      this.Auto && (this._timer = setTimeout(Bind(this, this.Next), this.Pause));
    }
  },
  //移动到
  MoveTo: function(i)
  {
    this._slider.style[this._css] = i + "px";
  },
  //下一个
  Next: function()
  {
    this.Run(++this.Index);
  },
  //上一个
  Previous: function()
  {
    this.Run(--this.Index);
  },
  //停止
  Stop: function()
  {
    clearTimeout(this._timer); this.MoveTo(this._target);
  }
};