/*!
jquery.higo_plugins_ad.js(v0.1)
http://www.higosoft.cn
mailto:wdong0472@gmail.com

Copyright (c) 2011 wdong
Dual licensed under the MIT and GPL licenses.
*/

/*
 * 创建浮动图片广告（Generate a dock AD image）
 *
 * USAGE: 
 *	$(selector).higo_plugins_ad({
 *		src:null,                    // 广告图片路径
 *		closeSrc:null,               // 关闭图片路径
 *		href:"#",                    // 广告图片链接地址
 *		autoHide:true,               // 是否自动隐藏
 *		hideSecond:10,               // 延迟隐藏秒数
 *		top:20,                      // 距离顶部偏移高度
 *		layout:"left",               // 图片位置：left 居左 ,right 居右, center 居中, 
 *		width:100,                   // 宽度
 *		height:100,                  // 高度
 *		opacity:0.5					 // 透明度opacity:0.5(firefox), filter:alpha(opacity=50)(IE)
 *		setPosition:function(left, top){ // 预留自定义显示位置的方法（尚未实现）
 *			return;
 *		}	
 *	})
 */
 
(function($){
	$.fn.lastScrollY= 0;
	$.fn.higo_plugins_ad = function(options){
	    $(this).addClass("higo_plugins_ad");
		var settings = $.extend({
			src:null,                    
			closeSrc:null,               
			href:"#",
			autoHide:true,               
			hideSecond:12,               
			top:20,                      
			layout:"left",               
			width:100,                   
			height:100,                  
			opacity:0.5,
			setPosition:function(left, top){
				return;
			}
		},options || {});
		
		if(settings.src && settings.closeSrc){		
			var imgEl = "<a title=\"点击关闭\" href='" + settings.href + "'; onclick=\"this.parentElement.style.visibility='hidden'\"><img border=0 width='" + settings.width + "px' height='" + settings.height + "px' src='" + settings.src + "'/> <br></a>";
			var closeImgEl = "<a href=\"#\"; onclick=\"this.parentElement.style.visibility='hidden'\"><img border=0 src='" + settings.closeSrc +"'/></a>";
			
			$(this).append(imgEl + closeImgEl);
			
			$(this).css("position","absolute");
			$(this).css("top",settings.top + "px");
			$(this).css("opacity",settings.opacity);
			$(this).css("filter","alpha(opacity=" + parseInt(settings.opacity * 100)  + ")");
			
			switch(settings.layout) {
				case "left":
					$(this).css("left","22px");
					break;
				case "right":
					$(this).css("right","22px");
					break;
				case "center":
					var left = (parseInt(window.screen.availWidth) - parseInt(settings.width))/2 + "px";
					$(this).css("left",left);
					break;
				default:
					$(this).css("left","22px");
					break;
			}
		} else {
			return;
		}
		
		if(settings.autoHide) {
			setTimeout("(function(){$('" + $(this).selector +  "').hide();})();",parseInt(settings.hideSecond) * 1000);
		}
		
		window.onscroll = function(){
			var diffY;
			if (document.documentElement && document.documentElement.scrollTop)
				diffY = document.documentElement.scrollTop;
			else if (document.body)
				diffY = document.body.scrollTop
			else {
				/*Netscape stuff*/
			}
			
			percent= 1 * (diffY - $.fn.lastScrollY);
			if(percent>0)
				percent=Math.ceil(percent);
			else 
				percent=Math.floor(percent);
			
			var top = $('.higo_plugins_ad').css("top");
			
			$('.higo_plugins_ad').css("top", parseInt(top) + percent + "px");
			$.fn.lastScrollY += percent;
		}
	}
})(jQuery);