// Plugin: jQuery.dragmove
// Source: github.com/nathco/jQuery.dragmove
// Author: Nathan Rutzky
// Update: 1.0

(function($) {

    $.fn.dragmove = function(divParent) {
    
        return this.each(function() {
    
            var $document = $(document),
                $this = $(this),
                active,
                startX,
                startY;
            
            $this.on('mousedown touchstart', function(e) {
            
                active = true;
                startX = e.originalEvent.pageX - $this.offset().left;
                startY = e.originalEvent.pageY - $this.offset().top;	
                
                if ('mousedown' == e.type)
                    if(divParent){
                        click = divParent;
                    }else {
                        click = $this;
                    }
                                    
                if ('touchstart' == e.type)
                    if(divParent){
                        click = divParent;
                    }else {
                        touch = $this;
                    }
                                    
                if (window.mozInnerScreenX == null)
                
                    return false;	
            });
            
            $document.on('mousemove touchmove', function(e) {

                var topZhi = e.originalEvent.pageY - startY;
                var screenHeight = document.body.clientHeight || document.documentElement.clientHeight;
                if((e.originalEvent.pageY - startY)<0){
                    topZhi = 0;
                }
                if(e.originalEvent.pageY>screenHeight){
                    topZhi = screenHeight-48;   //弹窗高度不固定，保留弹窗头部高度
                }
                if ('mousemove' == e.type && active)
                
                    click.offset({ 
                    
                        left: e.originalEvent.pageX - startX,
                        top: topZhi
                    
                    });
                
                if ('touchmove' == e.type && active)
                
                    touch.offset({
                    
                        left: e.originalEvent.pageX - startX,
                        top: e.originalEvent.pageY - startY
                        
                    });
                
            }).on('mouseup touchend', function() {
                
                active = false;
                
            });
                                
        });
            
    };

})(jQuery);