var active_slide = 1;

function change_slide (target_slide){
  if (target_slide == 4){
    active_slide = 1;
  }else if (target_slide == 0){
    active_slide = 3;
  }else{
    active_slide = target_slide;
  }

  document.getElementById('slide1').style.display = "none";
  document.getElementById('slide2').style.display = "none";
  document.getElementById('slide3').style.display = "none";

  document.getElementById('slide'+active_slide).style.display = "block";

  document.getElementById('num1').src = "../images/num1.png";
  document.getElementById('num2').src = "../images/num2.png";
  document.getElementById('num3').src = "../images/num3.png";

  document.getElementById('num'+active_slide).src = "../images/num"+active_slide+"-active.png";
}

function rotate_display_handler (action_wanted){
  if (action_wanted == "start"){
    rotate_display_id = setInterval('change_slide((active_slide+1))',6000);
  }else if (action_wanted == "change"){
    if (rotate_display_id){
      rotate_display_handler('stop');
    }else{
      rotate_display();
      rotate_display_handler('start');
    }
  }else{
    clearInterval(rotate_display_id);
    rotate_display_id = "";
  }

}