// JavaScript Document
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;
}

function addEventHandler(oTarget, sEventType, fnHandler) {
	if (oTarget.addEventListener) {
		oTarget.addEventListener(sEventType, fnHandler, false);
	} else if (oTarget.attachEvent) {
		oTarget.attachEvent("on" + sEventType, fnHandler);
	} else {
		oTarget["on" + sEventType] = fnHandler;
	}
};


var Scroller = Class.create();
Scroller.prototype = {
  initialize: function(idScroller, idScrollMid, options) {
    var oScroll = this, oScroller = $(idScroller), oScrollMid = $(idScrollMid);
	
	this.heightScroller = oScroller.offsetHeight;
	this.heightList = oScrollMid.offsetHeight;
	
	if(this.heightList <= this.heightScroller) return;
	
	oScroller.style.overflow = "hidden";
	oScrollMid.appendChild(oScrollMid.cloneNode(true));
	
	this.oScroller = oScroller;	
	this.timer = null;
	
	this.SetOptions(options);
	
	this.side = 1;//1是上 -1是下
	switch (this.options.Side) {
		case "down" :
			this.side = -1;
			break;
		case "up" :
		default :
			this.side = 1;
	}
	
	addEventHandler(oScrollMid , "mouseover", function() { oScroll.Stop(); });
	addEventHandler(oScrollMid , "mouseout", function() { oScroll.Start(); });
	
	if(this.options.PauseStep <= 0 || this.options.PauseHeight <= 0) this.options.PauseStep = this.options.PauseHeight = 0;
	this.Pause = 0;
	
	this.Start();
  },
  //设置默认属性
  SetOptions: function(options) {
    this.options = {//默认值
	  Step:			1,//每次变化的px量
	  Time:			20,//速度(越大越慢)
	  Side:			"up",//滚动方向:"up"是上，"down"是下
	  PauseHeight:	0,//隔多高停一次
	  PauseStep:	1000//停顿时间(PauseHeight大于0该参数才有效)
    };
    Object.extend(this.options, options || {});
  },
  //滚动
  Scroll: function() {
	var iScroll = this.oScroller.scrollTop, iHeight = this.heightList, time = this.options.Time, oScroll = this, iStep = this.options.Step * this.side;
	
	if(this.side > 0){
		if(iScroll >= (iHeight * 2 - this.heightScroller)){ iScroll -= iHeight; }
	} else {
		if(iScroll <= 0){ iScroll += iHeight; }
	}
	
	if(this.options.PauseHeight > 0){
		if(this.Pause >= this.options.PauseHeight){
			time = this.options.PauseStep;
			this.Pause = 0;
		} else {
			this.Pause += Math.abs(iStep);
			this.oScroller.scrollTop = iScroll + iStep;
		}
	} else { this.oScroller.scrollTop = iScroll + iStep; }
	
	this.timer = window.setTimeout(function(){ oScroll.Scroll(); }, time);
  },
  //开始
  Start: function() {
	this.Scroll();
  },
  //停止
  Stop: function() {
	clearTimeout(this.timer);
  }
};