function form_element(element_id)
{
  return document.getElementById(element_id);
}

function check_radio_button(id, num)
{
  var button = form_element(id + '_' + num);

  if (button != null)
    button.checked = true;
}

function remove_quotes(value)
{
  var parts, i, n;

  if (value.indexOf('"') >= 0)
  {
    parts = value.split('"');
    n = parts.length;
    value = parts[0];

    for (i = 1; i < n; i++)
      value += parts[i];
  }

  return value;
}

function update_image_alt(image)
{
  var size, id;

  for (size = 0; size < 4; size++)
  {
    id = image + ':url_' + size;

    if (form_element(id) != null)
      update_image_tag(image, size);
  }
}

function update_image_tag(image, size)
{
  var url, alt, width, height, border, vspace, hspace, other;
  var field, id, tag;

  id = image + ':url_' + size;
  url = form_element(id).value;

  id = image + ':width_' + size;
  width = form_element(id).value;

  id = image + ':height_' + size;
  height = form_element(id).value;

  id = image + ':border_' + size;
  border = form_element(id).value;

  id = image + ':vspace_' + size;
  vspace = form_element(id).value;

  id = image + ':hspace_' + size;
  hspace = form_element(id).value;

  id = image + ':other_' + size;
  other = form_element(id).value;

  id = image + ':alt_0';
  field = form_element(id);
  alt = remove_quotes(field.value);
  field.value = alt;

  tag = '<img src="' + url + '"';

  if (alt.length > 0)
    tag += ' alt="' + alt + '"';

  if (width.length > 0)
    tag += ' width="' + width + '"';

  if (height.length > 0)
    tag += ' height="' + height + '"';

  if (border.length > 0)
    tag += ' border="' + border + '"';

  if (vspace.length > 0)
    tag += ' vspace="' + vspace + '"';

  if (hspace.length > 0)
    tag += ' hspace="' + hspace + '"';

  if (other.length > 0)
    tag += ' ' + other;

  id = image + ':image_tag_' + size;
  form_element(id).value = tag + '>';
}

function check_resize_percent(image)
{
  var id, resize_percent;

  id = image + ':image_resize_percent';
  resize_percent = form_element(id);

  if (!resize_percent.disabled)
  {
    if (resize_percent.value > 100)
    {
      alert(images_cannot_be_made_larger);
      resize_percent.value = 100;
      resize_percent.focus();
      return false;
    }
  }

  return true;
}

function check_resize_dimensions(image)
{
  var image_width, image_height;
  var image_resize_width, image_resize_height;
  var id;

  id = image + ':image_width';
  image_width = form_element(id);

  id = image + ':image_height';
  image_height = form_element(id);

  id = image + ':image_resize_width';
  image_resize_width = form_element(id);

  id = image + ':image_resize_height';
  image_resize_height = form_element(id);

  if (!image_resize_width.disabled)
  {
    if (Number(image_resize_width.value) > Math.max(Number(image_width.value), 0))
    {
      alert(images_cannot_be_made_larger);
      image_resize_width.value = image_width.value;
      image_resize_width.focus();
      return false;
    }

    if (Number(image_resize_height.value) > Math.max(Number(image_height.value), 0))
    {
      alert(images_cannot_be_made_larger);
      image_resize_height.value = image_height.value;
      image_resize_height.focus();
      return false;
    }
  }

  return true;
}

function validate(nimages)
{
  var image, image_name, rename_to, alt;
  var renaming = false;
  var id;

  for (image = 0; image < nimages; image++)
  {
    id = image + ':alt_0';
    alt = form_element(id);
    alt.value = remove_quotes(alt.value);
  }

  for (image = 0; image < nimages; image++)
  {
    if (check_resize_percent(image) == false)
      return false;

    if (check_resize_dimensions(image) == false)
      return false;
  }

  for (image = 0; image < nimages; image++)
  {
    id = image + ':image_rename_to';
    rename_to = form_element(id);

    if (check_filename(rename_to) == false)
    {
      rename_to.focus();
      return false;
    }

    id = image + ':image_name';
    image_name = form_element(id).value;
    if ((i = image_name.lastIndexOf('.')) > 0)
      image_name = image_name.slice(0, i);

    if (image_name != rename_to.value)
      renaming = true;
  }

  if (renaming)
    return confirm_rename();
  else
    return true;
}

function check_filename(filename)
{
  if (filename.value.match(/[^a-zA-Z0-9\-._]/g) != null)
  {
    alert(enter_valid_file_name + '  ' + valid_file_name_chars);
    filename.focus();
    return false;
  }

  if (filename.value.charAt(0) == '.')
  {
    alert(cannot_begin_with_dot);
    filename.focus();
    return false;
  }

  return true;
}

function confirm_rename()
{
  return confirm(confirm_rename_msg);
}