//********** 图片切换 S## **********//
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
		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";
  }
};
//********** 图片切换 E## **********//