function _file_name(s)
{return (s.lastIndexOf("/") == -1) ? s : s.substr(s.lastIndexOf("/")+1);}

function _file_path(s)
{return (s.lastIndexOf("/") == -1) ? '' : s.substr(0, s.lastIndexOf("/")+1);}

function swap_images(ilarge, ismall)
{
    d=document;
    var s1=d[ismall].src, s2=d[ilarge].src;
    d[ismall].src = _file_path(s1) + _file_name(s2);
    d[ilarge].src = _file_path(s2) + _file_name(s1);
}

function $(i)
{
    return document.getElementById(i);
}

function set_image(ismall, ilarge)
{
    if (!ilarge) ilarge = "mainPhoto";

    
    if ($(ismall) && $(ilarge))
    {
       var s1=$(ismall).src;
       var s2=$(ilarge).src;
       $(ilarge).src = _file_path(s2) + _file_name(s1);
    }
}

function nextImage(d)
{
    if (!d) d = 1;

    if($('mainPhoto'))
    {

    var prev, uselast, prevImg, nextSet, first;
    var curImg = _file_name($('mainPhoto').src)
    //console.log(curImg)
    //return
    var el = document.getElementsByTagName("img");
    for (i=0; i<el.length; i++)
    {
        re = /listing_(2_)?photo\d?/
        if (re.test(el[i].id))
        {
            //console.log(el[i].id)
            if(!first) first=el[i].id
            if (d == -1 && curImg == _file_name(el[i].src))
            {
                if(!prev) uselast = 1;
                else
                set_image(prev)
            }
            if (d == 1 && prevImg == curImg)
            {
                set_image(el[i].id)
                nextSet = 1
            }

            prev = el[i].id
            prevImg = _file_name(el[i].src)
            //console.log(prev)
        }
    }
    if(d == -1 && uselast)
    {
        set_image(prev)
    }
    if(d == 1 && !nextSet)
    {
        set_image(first)
    }
    }
}