//var $ = function (id) {
//	return "string" == typeof id ? document.getElementById(id) : id;
//};
var $id = function (id) {
    return "string" == typeof id ? document.getElementById(id) : id;
};

//var $id = function (id) {
//    return typeof id == "string" ? 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 = $id(slider);
	this._container = $id(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);
	}
};