var duma = {
	$:function(o){ if(document.getElementById(o)) {return document.getElementById(o);} },
	getStyle:function(o) { return o.currentStyle||document.defaultView.getComputedStyle(o,null); },
	getOffset:function(o) {
		var t = o.offsetTop,h = o.offsetHeight;
		while(o = o.offsetParent) { t += o.offsetTop; }
		return { top:t, height:h };
	},
	bind:function(o,eType,fn) {
		if(o.addEventListener) { o.addEventListener(eType,fn,false); }
		else if(o.attachEvent) { o.attachEvent("on" + eType,fn); }
		else { o["on" + eType] = fn; }
	},
	stopEvent:function(e) {
		e = e || window.event;
		e.stopPropagation && (e.preventDefault(),e.stopPropagation()) || (e.cancelBubble = true,e.returnValue = false);
	}
};
duma.BeautifyScrollBar = function(obj,arrowUpCss,arrowUpActiveCss,handleCss,handleActiveCss,arrowDownCss,arrowDownActiveCss) {
	this.arrowUpInterval;
	this.arrowDownInterval;
	this.barMouseDownInterval;
	this.relY;
	this.obj = duma.$(obj);
	this.area = duma.$(obj + "Area");
	this.bar = duma.$(obj + "Bar");
	this.arrowUp = this.bar.getElementsByTagName("div")[0];
	this.arrowUpCss = arrowUpCss;
	this.arrowUpActiveCss = arrowUpActiveCss;
	this.handle = this.bar.getElementsByTagName("div")[1];
	this.handleCss = handleCss;
	this.handleActiveCss = handleActiveCss;
	this.arrowDown = this.bar.getElementsByTagName("div")[2];
	this.arrowDownCss = arrowDownCss;
	this.arrowDownActiveCss = arrowDownActiveCss;
	this.handleMinHeight = 15;
	this.arrowUpHeight = parseInt(duma.getStyle(this.arrowUp).height);
	this.arrowDownHeight = parseInt(duma.getStyle(this.arrowDown).height);
	this.areaScrollHeight = this.area.scrollHeight;
	this.handleHeight = parseInt(this.area.offsetHeight/this.area.scrollHeight * (this.bar.offsetHeight - this.arrowUpHeight - this.arrowDownHeight));
}
duma.BeautifyScrollBar.prototype = {
	sethandle:function() {				//当内容超多时设置拖拽条子的最小高度
		this.handle.style.top = this.arrowUpHeight + "px";
		if(this.handleHeight > this.handleMinHeight) { this.handle.style.height = this.handleHeight + "px"; }
		else { this.handleHeight = this.handleMinHeight; this.handle.style.height = this.handleMinHeight + "px"; }
	},
	clearArrowUpInterval:function() { clearInterval(this.arrowUpInterval); },
	clearArrowDownInterval:function() { clearInterval(this.arrowDownInterval); },
	clearBarMouseDownInterval:function() { clearInterval(this.barMouseDownInterval); },
	areaScroll:function() {
		this.handle.style.top = this.area.scrollTop/(this.area.scrollHeight - this.area.offsetHeight) * (this.bar.offsetHeight - this.handleHeight - this.arrowUpHeight - this.arrowDownHeight) + this.arrowUpHeight + "px";
	},
	handleMove:function(e) {
		var e = e || window.event;
		this.area.scrollTop = (e.clientY - this.relY - this.arrowUpHeight)/(this.bar.offsetHeight - this.handleHeight - this.arrowUpHeight - this.arrowDownHeight)*(this.area.scrollHeight - this.area.offsetHeight);
	},
	handleMouseDown:function(e) {
		var that = this,e = e || window.event;
		that.relY = e.clientY - that.handle.offsetTop;
		if(that.handle.setCapture) { that.handle.setCapture(); }
		that.handle.className = that.handleActiveCss;
		document.onmousemove = function(event) { that.handleMove(event); };
		document.onmouseup = function() {
			that.handle.className = that.handleCss;
			if(that.handle.releaseCapture){ that.handle.releaseCapture(); }
			document.onmousemove = null;
		};
	},
	barScroll:function(e) {
		var e = e || window.event,eDir;		//设置滚轮事件,e.wheelDelta与e.detail分别兼容IE、W3C，根据返回值的正负来判断滚动方向
		if(e.wheelDelta) { eDir = e.wheelDelta/120; }
		else if(e.detail) { eDir = -e.detail/3; }
		if(eDir > 0) { this.area.scrollTop -= 80; }		//步长设80像素a比较接近window滚动条的滚动速度
		else { this.area.scrollTop += 80; }
		if(this.area.scrollTop > 0 && this.area.scrollTop < this.area.scrollHeight - this.area.offsetHeight){ duma.stopEvent(e); }
	},
	barDown:function(e) {
		var e = e || window.event,that = this,
			eY = e.clientY,
			mStep = this.bar.offsetHeight,
			documentScrollTop = document.documentElement.scrollTop || document.body.scrollTop,
			hOffset = duma.getOffset(this.handle),
			bOffset = duma.getOffset(this.bar);
		if(documentScrollTop + eY < hOffset.top) { this.barMouseDownInterval = setInterval(function(e){
			that.area.scrollTop -= that.area.offsetHeight;
			if(that.area.scrollTop <= (eY + documentScrollTop - bOffset.top - that.arrowUpHeight)/(that.bar.offsetHeight - that.arrowUpHeight - that.arrowDownHeight) * that.area.scrollHeight) { that.clearBarMouseDownInterval(); }
		},80); }
		else if(documentScrollTop + eY > hOffset.top + hOffset.height) { this.barMouseDownInterval = setInterval(function(){
			that.area.scrollTop += that.area.offsetHeight;
			if(that.area.scrollTop >= (eY + documentScrollTop - bOffset.top - that.arrowUpHeight - hOffset.height)/(that.bar.offsetHeight - that.arrowUpHeight - that.arrowDownHeight) * that.area.scrollHeight) { that.clearBarMouseDownInterval(); }
		},80); }
		duma.stopEvent(e);
		duma.bind(this.bar,"mouseup",function(){});
	},
	arrowUpMouseDown:function(e) {
		var that = this;
		this.arrowUpInterval = setInterval(function(){ that.area.scrollTop -= 25; },10);
		this.arrowUp.className = this.arrowUpActiveCss;
		duma.stopEvent(e);
	},
	arrowUpMouseUp:function() { this.clearArrowUpInterval(); this.arrowUp.className = this.arrowUpCss; },
	arrowUpMouseOut:function() { this.clearArrowUpInterval(); this.arrowUp.className = this.arrowUpCss; },
	arrowDownMouseDown:function(e) {
		var that = this;
		this.arrowDownInterval = setInterval(function(){ that.area.scrollTop += 25; },10);
		this.arrowDown.className = this.arrowDownActiveCss;
		duma.stopEvent(e);
	},
	arrowDownMouseUp:function() { this.clearArrowDownInterval(); this.arrowDown.className = this.arrowDownCss; },
	arrowDownMouseOut:function() { this.clearArrowDownInterval(); this.arrowDown.className = this.arrowDownCss; },
	run:function(){
		var that = this;
		this.sethandle();
		this.areaScroll();
		duma.bind(this.obj,"mousewheel",function(event){that.barScroll(event)});
		duma.bind(this.obj,"DOMMouseScroll",function(event){that.barScroll(event)});
		this.area.onscroll = function(){that.areaScroll()};
		this.handle.onmousedown = function(event){that.handleMouseDown(event)};
		this.bar.onmousedown = function(event){that.barDown(event)};
		this.bar.onmouseup = function(){that.clearBarMouseDownInterval()};
		this.bar.onmouseout = function(){that.clearBarMouseDownInterval()};
		this.arrowUp.onmousedown = function(event){that.arrowUpMouseDown(event)};
		this.arrowUp.onmouseup = function(){that.arrowUpMouseUp()};
		this.arrowUp.onmouseout = function(){that.arrowUpMouseOut()};
		this.arrowDown.onmousedown = function(event){that.arrowDownMouseDown(event)};
		this.arrowDown.onmouseup = function(){that.arrowDownMouseUp()};
		this.arrowDown.onmouseout = function(){that.arrowDownMouseOut()};
	}
}
/*duma.bind(window,"load",function(){
	var myDiv = new duma.BeautifyScrollBar("myDiv","dumascroll_arrow_up","dumascroll_arrow_up_a","dumascroll_handle","dumascroll_handle_a","dumascroll_arrow_down","dumascroll_arrow_down_a").run();
});*/