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: 4000,//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
 };
 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);
 }
};