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);
      }
    };