function addClass (elementName, newClass) {
  elementName.className = newClass + (elementName.className ? ' ' : '') + elementName.className;
}

function removeClass(elementName, oldClass) {
  var classesOld = elementName.className.split(' ');
  var classesNew = new Array();
  var i;

  for (i in classesOld) {
    if (classesOld[i] != oldClass) {
      classesNew.push(classesOld[i]);
    }
  }
  elementName.className = classesNew.join(' ');
}

function mySubmit(button, nextActionVar, nextActionValue) {
  na = document.getElementById(nextActionVar);
  na.value = nextActionValue;
  b = document.getElementById(button);
  b.click();
  return false;
}

function positionMessageWindow() {
  middle = document.getElementById('page');
  message = document.getElementById('messages');

  if (message) {
    message.style.top = middle.offsetTop+200 + "px";
    message.style.left = middle.offsetLeft+300 + "px";
  }
}

function displayVideoNewSource() {
  oldSource = document.getElementById('oldSource');
  newSource = document.getElementById('newSource');

  oldSource.style.display = 'none';
  newSource.style.display = 'block';
}

function showDiscussionPost(id) {
  form = document.getElementById('post_'+id);
  form.style.display = 'block';
  
  input = document.getElementById('input_'+id);
  input.focus();
  
  reply = document.getElementById('reply_'+id);
  reply.style.display = 'none';
}

function showFriendGroupForm(id) {
  form = document.getElementById('form_'+id);
  form.style.display = 'block';

  input = document.getElementById('input_'+id);
  input.focus();
  
  reply = document.getElementById('url_'+id);
  reply.style.display = 'none';
}

function evaluatePublicCheck() {
  public = document.getElementById('publicCheckBox');
  group = document.getElementsByName('friendGroupId[]');

  for (i=0;i<group.length;i++) {
    if (group[i].checked) {
      public.checked = false;
      break;
    }
  }
}

function evaluateGroupChecks() {
  public = document.getElementById('publicCheckBox');
  group = document.getElementsByName('friendGroupId[]');

  if (public.checked) {
    for (i=0;i<group.length;i++) {
      group[i].checked = false;
    }
  }
}

function showHideEmbedding() {
  input = document.getElementById('embedding');

  if (input.style.display == 'none') input.style.display = 'block';
  else if (input.style.display == 'block') input.style.display = 'none';
}