/**
 * 基于somesayss.js的模拟滚动条;
 * 只有滚动块和鼠标滚轮的功能;
 */
;(function($){

var scrollbar = function(block, content){
	return this instanceof scrollbar ? this.init(block, content) : new scrollbar(block, content);
}
scrollbar.prototype = {
	init: function(block, content){
		this.bind(block, content);
	},
	bind: function(block, content){
		var self =this, block = self.block = $(block), content = $(content);
		//代码防御;
		if(!content.length || !block.length)
			return this;
		var contentbox = self.contentbox = content.parent(), blockbox = block.parent(),
			heightcont = content.height(), heightcontbox = contentbox.height(), heightblock = block.height(), heightblockbox = blockbox.height(),
			maxtopblock = heightblockbox - heightblock, maxtopcontent = heightcontbox - heightcont;
		//如果
		if(maxtopcontent >= 0){
			blockbox.hide();
			return this;
		}
		self.bindblock(block, content, maxtopblock, maxtopcontent);
		self.bindmousewheel(contentbox, block, content, maxtopblock, maxtopcontent);
		return this;
	},
	bindblock: function(block, content, maxtopblock, maxtopcontent){
		var self = this, event = $.event, data = $.data, pointerynew = block.offset().top;
		var docmu = self.docmu = function(e){
			event.unbind(document, 'mousemove');
			document.onselectstart = function(){
				return true;
			}
		}
		data(document, 'docmu', docmu);
		//绑定滑块鼠标按下事件
		event(block[0], 'mousedown', function(e){
			//阻止鼠标按下的时候会全选文字
			document.onselectstart = function(){
				return false;
			}
			e.stop();
			//让滑块动起来!!!
			event(document, 'mousemove', function(e){
				var pointeryold = e.pointery, guid = self.guid = pointeryold - pointerynew;
				//确立阀值最大,最小
				guid < 0 && (guid = 0);
				guid > maxtopblock && (guid = maxtopblock);
				self.mainrun(block, content, guid, maxtopblock, maxtopcontent);
			});
		});
		//绑定滑块鼠标弹起事件
		event(document, 'mouseup', docmu);
	},
	bindmousewheel: function(contentbox, block, content, maxtopblock, maxtopcontent){
		var self = this, event = $.event,  guid = self.guid = 0;
		event(contentbox[0], 'mousewheel', function(e){
			e.stop();
			if(e.wheeldelta){
				guid = self.guid += 30;
				guid > maxtopblock && (guid = self.guid = maxtopblock);
				self.mainrun(block, content, guid, maxtopblock, maxtopcontent);
			}else{
				guid = self.guid -= 30;
				guid < 0 && (guid = self.guid = 0);
				self.mainrun(block, content, guid, maxtopblock, maxtopcontent);
			}
		});
	},
	mainrun: function(block, content, guid, maxtopblock, maxtopcontent){
		block.css('top', guid+'px');
		//通过滑块的百分比去设置内容层的top;
		var percent = guid/maxtopblock, needtop = maxtopcontent*percent;
		content.css('top', needtop+'px');
	},
	unbind: function(){
		var self = this, event = $.event, data = $.data;
		event.unbind(self.block[0], 'mousedown');
		event.unbind(self.contentbox[0], 'mousewheel');
		event.unbind(document, 'mouseup', self.docmu);
	}
}
'bind bindblock unbind bindmousewheel mainrun'.replace(/\w+/g,function(n){
	scrollbar[n] = scrollbar.prototype[n]
})
//全局调用
window.scrollbar = scrollbar;
scrollbar('#scrollblock', '#scrollcontent');

})(somesayss);