//定义插件
!function($) {
    /**
     * Description: jquery飘窗插件，可自适应浏览器宽高的变化 Author: YZCS CreateTime: 2015-04-25
     * param: args={startL:default, startT:default, angle:-Math.PI/4, speed:
     * 125} 参数说名: startL飘窗初始时距离左边的距离, startT飘窗初始化距离顶部的距离, angle飘窗初始运动方向,
     * speed运动速度(px/s) CopyRight: GPL
     */
    $.fn.autoMove = function(args) {
	// 先定义一些工具函数判断边距
	function isTop(pos, w_w, w_h, d_w, d_h) {// 飘窗到达上边距
	    if (pos.top <= 0) {
		return true;
	    } else {
		return false;
	    }
	}
	function isBottom(pos, w_w, w_h, d_w, d_h) {// 飘窗到达下边距
	    if (pos.top >= (w_h - d_h)) {
		return true;
	    } else {
		return false;
	    }
	}
	function isLeft(pos, w_w, w_h, d_w, d_h) {// 飘窗到达左边距
	    if (pos.left <= 0) {
		return true;
	    } else {
		return false;
	    }
	}
	function isRight(pos, w_w, w_h, d_w, d_h) {// 飘窗到达右边距
	    if (pos.left >= (w_w - d_w)) {
		return true;
	    } else {
		return false;
	    }
	}
//	return this
//		.each(function() {
		    var w_w = parseInt($(window).width()), w_h = parseInt($(
			    window).height()), d_w = parseInt($(this).width()), d_h = parseInt($(
			    this).height()), d_l = (w_w - d_w) / 2, d_t = (w_h - d_h) / 2, max_l = w_w
			    - d_w;
		    max_t = w_h - d_h;
		    // 位置及参数的初始化
		    var setobj = $.extend({
			startL : 0, 
			startT : d_t,  
			angle : Math.PI / 4,
			speed : 100
		    }, args);
		    $(this).css({
			position : 'absolute',
			left : setobj['startL'] + 'px',
			top : setobj['startT'] + 'px'
		    });
		    var position = {
			left : setobj['startL'],
			top : setobj['startT']
		    };// 飘窗位置对象
		    var that = $(this);
		    var angle = setobj.angle;
		    var time = 10;// 控制飘窗运动效果，值越小越细腻
		    var step = setobj.speed * (time / 1000);// 计算运动步长
		    var decoration = {
			x : step * Math.cos(angle),
			y : step * Math.sin(angle)
		    };// 计算二维上的运动增量
		    var mvtid;
		    $(window).on(
			    'resize',
			    function() {// 窗口大小变动时重新设置运动相关参数
				w_w = parseInt($(window).width()),
					w_h = parseInt($(window).height()),
					max_l = w_w - d_w;
				max_t = w_h - d_h;
			    });
		    function move() {
			position.left += decoration.x;
			position.top += decoration.y;
			if (isLeft(position, w_w, w_h, d_w, d_h)
				|| isRight(position, w_w, w_h, d_w, d_h)) {
			    decoration.x = -1 * decoration.x;
			}
			if (isRight(position, w_w, w_h, d_w, d_h)) {
			    position.left = max_l;
			}
			if (isTop(position, w_w, w_h, d_w, d_h)
				|| isBottom(position, w_w, w_h, d_w, d_h)) {
			    decoration.y = -1 * decoration.y;
			}
			if (isBottom(position, w_w, w_h, d_w, d_h)) {
			    position.top = max_t;
			}
			// that.css({left:position.left, top:position.top});
//			that.animate({
//			    left : position.left,
//			    top : position.top
//			}, time);// 改用jquery动画函数使其更加平滑
			that.css({
	                        'top': position.top,
	                        'left': position.left-1  
	                    })  
		    }  
		    mvtid = setInterval(move, time);// 递归调用，使飘窗连续运动
		    that.bind('mouseover', function() {
			clearInterval(mvtid);
		    });// 添加鼠标事件 
		    that.bind('mouseout', function() { 
			clearInterval(mvtid);
			mvtid =setInterval(move, time);
		    });
		}
//    }// end plugin definition
}(jQuery);