// JavaScript Document 
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:   false,//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);   
  }   
};