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:                13000,//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);
  }
};