/**
 * Implementation of the pathauto_node hook
 *
 * @arg $op
 *    the operation to perform -- currently 'placeholders' or 'values'
 * @arg $node
 *    if called with $op='value', generate the placeholder values for $node
 * @return
 *    returns the placeholder names or values for the given node
 */
function audio_pathauto_node($op, $node=null) {
  switch ($op) {
  case 'placeholders':
    $placeholders = array();
    foreach (audio_get_tags_allowed() as $tag) {
      $placeholders[t('[audio' . $tag . ']')] = t('The ' . $tag . ' tag of the audio file.');
    }
    return $placeholders;
  case 'values':
    $values = array();
    foreach (audio_get_tags_allowed() as $tag) {
      $values[t('[audio' . $tag . ']')] = '';
    }
    if ($node->type != 'audio')
      return $values;
    if (!$node->audio_tags)
      $node = node_load(array('nid' => $node->nid));
    if (empty($node->audio_tags))
      return $values;
    foreach (audio_get_tags_allowed() as $tag) {
      $values[t('[audio' . $tag . ']')] = pathauto_cleanstring($node->audio_tags[$tag]);
    }
    return $values;
  }
}