// 获取编号
var byid = 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 = byid(slider);
	this._container = byid(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);
	}
};