var hidden_images=[];
var gallery_images=[]
var dir='i/';

function initialize() {
  var r=new XMLHttpRequest();
  r.onreadystatechange=function(){
    if(r.readyState==4&&r.status==200){
      var x=r.responseText.replace(/\n|\r/g,'');
      x=x.split('<a ');
      for(var i=1;i<x.length;++i){
        var im=x[i].replace(/.*?href="/i,'');
        im=im.replace(/".*/,'');
        if(/\.jpg$/.test(im))gallery_images[gallery_images.length]=dir+im;
      }
    }
  }
  r.open('GET',dir);
  r.send(null);
  return;
}

function showimage(id) {
  initialize();
  // delete current image
  div = document.getElementById("image")
  clean_div(div);
  // get random image
  // var id = Math.floor(gallery_images.length*Math.random());
  var img=document.createElement('img');
  img.src=gallery_images[id];
  // document.writeln("img: "+img.src);
  // document.close();
  var im2=img.src.replace(/^.*?\-/,'');
  var a=document.createElement('a');
  a.href='http://gallery.reisavonturen.net/Alle%20fotos%20op%20reisavonturen.net/'+im2;
  div.appendChild(a);     
  a.appendChild(img);
  // show image
  div.style.display='block'
  // show arrows
  divleft = document.getElementById("arrow_left")
  divright = document.getElementById("arrow_right")
  a_left = document.getElementById("left")
  a_left.setAttribute('href','#');
  a_left.setAttribute('onclick',"showimage("  + (id-1) + ")");
  a_right = document.getElementById("right")
  a_right.setAttribute('href','#');
  a_right.setAttribute('onclick',"showimage("  + (id+1) + ")");
  if (id == 0) {
    // no left arrow, set right arrow properties
    a_left.setAttribute('onclick',"showimage("  + (gallery_images.length -1) + ")");
    divright.appendChild(a_right);
    divleft.style.display='block';
    divright.style.display='block';
  } else if (id == (gallery_images.length -1)) {
    // no right arrow, set left arrow properties
    divleft.appendChild(a_left);
    divright.style.display='block';
    divleft.style.display='block';
  } else {
    // show both arrow with properties
    divleft.appendChild(a_left);
    divright.appendChild(a_right);
    divleft.style.display='block';
    divright.style.display='block';
  }
}

function clean_div(div) {
  if(div.hasChildNodes()) {
    var children = div.childNodes;
    var n = children.length - 1;
    var lastChild = children.item(n);
    div.removeChild(lastChild);
  }
}