/**
 * Provide the Publisher ID of the the specified user
 *
 * @param $uid
 *   User ID
 * @return
 *   Publisher ID of the specified user in case it applies, otherwise NULL
 */
function revenue_sharing_basic_get_profile_client_id($uid) {
  $client_id = NULL;

  // Get the profile field for a certain user
  $profile_field = explode(':', variable_get('revenue_sharing_basic_client_id_profile_field', REVENUE_SHARING_BASIC_CLIENT_ID_PROFILE_FIELD_DEFAULT));
  if ($uid && (count($profile_field) > 1) && module_exists($profile_field[0])) {
    $user = user_load($uid);

    switch ($profile_field[0]) {
      case 'field':
        $fields = field_get_items('user', $user, $profile_field[1]);
        $client_id = render(field_view_value('user', $user, $profile_field[1], $fields[0]));
        break;
      case 'profile':
        $client_id = isset($user->{$profile_field[1]}) ? $user->{$profile_field[1]} : NULL;
        break;
      case 'profile2':
        $profile = profile2_load_by_user($user);
        $items = field_get_items('profile2', $profile[$profile_field[1]], $profile_field[2]);
        $client_id = drupal_render(field_view_value('profile2', $profile[$profile_field[1]], $profile_field[2], $items[0]));
        break;
    }
  }