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

var Class = {
  create: function() {
		return function() {
		  this.initialize.apply(this, arguments);
		}
  }
}

Object.extend = function(destination, source) {
	for (var property in source) {
		destination[property] = source[property];
	}
	return destination;
}

var TransformView = Class.create();
TransformView.prototype = {
  //容器对象,滑动对象,切换参数,切换数量
  initialize: function(container, slider, parameter, count, options) {
		if(parameter <= 0 || count <= 0) return;
		var oContainer = $(container), oSlider = $(slider), oThis = this;
	
		this.Index = 0;//当前索引
		
		this._timer = null;//定时器
		this._slider = oSlider;//滑动对象
		this._parameter = parameter;//切换参数
		this._count = count || 0;//切换数量
		this._target = 0;//目标参数
		
		this.SetOptions(options);
		
		this.Up = !!this.options.Up;
		this.Step = Math.abs(this.options.Step);
		this.Time = Math.abs(this.options.Time);
		this.Auto = !!this.options.Auto;
		this.Pause = Math.abs(this.options.Pause);
		this.onStart = this.options.onStart;
		this.onFinish = this.options.onFinish;
		
		oContainer.style.overflow = "hidden";
		oContainer.style.position = "relative";
		
		oSlider.style.position = "absolute";
		oSlider.style.top = oSlider.style.left = 0;
  },
  //设置默认属性
  SetOptions: function(options) {
		this.options = {//默认值
			Up:			true,//是否向上(否则向左)
			Step:		5,//滑动变化率
			Time:		10,//滑动延时
			Gap:		7,//两个图片直接的间隔
			Auto:		true,//是否自动转换
			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
		};
		Object.extend(this.options, options || {});
  },
  //开始切换设置
  Start: function() {
		if(this.Index < 0){
			this.Index = this._count - 1;
		} else if (this.Index >= this._count){ this.Index = 0; }
		
		this._target = -1 * this._parameter * this.Index;
		this.onStart();
		this.Move();
  },
  //移动
  Move: function() {
		clearTimeout(this._timer);
		var oThis = this, style = this.Up ? "top" : "left", iNow = parseInt(this._slider.style[style]) || 0, iStep = this.GetStep(this._target, iNow);
		
		if (iStep != 0) {
			this._slider.style[style] = (iNow + iStep) + "px";
			this._timer = setTimeout(function(){ oThis.Move(); }, this.Time);
		} else {
			this._slider.style[style] = this._target + "px";
			this.onFinish();
			if (this.Auto) { this._timer = setTimeout(function(){ oThis.Index++; oThis.Start(); }, this.Pause); }
		}
  },
  //获取步长
  GetStep: function(iTarget, iNow) {
		var iStep = (iTarget - iNow) / this.Step;
		if (iStep == 0) return 0;
		if (Math.abs(iStep) < 1) return (iStep > 0 ? 1 : -1);
		return iStep;
  },
  //停止
  Stop: function(iTarget, iNow) {
		clearTimeout(this._timer);
		this._slider.style[this.Up ? "top" : "left"] = this._target + "px";
  }
};