class ContactLink

class ContactLink extends LinkBase {
  
  /**
   * {@inheritdoc}
   */
  public function buildOptionsForm(&$form, FormStateInterface $form_state) {
    parent::buildOptionsForm($form, $form_state);
    $form['text']['#title'] = $this->t('Link label');
    $form['text']['#required'] = TRUE;
    $form['text']['#default_value'] = empty($this->options['text']) ? $this->getDefaultLabel() : $this->options['text'];
  }
  
  /**
   * {@inheritdoc}
   */
  protected function getUrlInfo(ResultRow $row) {
    return Url::fromRoute('entity.user.contact_form', [
      'user' => $this->getEntity($row)
        ->id(),
    ]);
  }
  
  /**
   * {@inheritdoc}
   */
  protected function renderLink(ResultRow $row) {
    $entity = $this->getEntity($row);
    $this->options['alter']['make_link'] = TRUE;
    $this->options['alter']['url'] = $this->getUrlInfo($row);
    $title = $this->t('Contact %user', [
      '%user' => $entity->label(),
    ]);
    $this->options['alter']['attributes'] = [
      'title' => $title,
    ];
    if (!empty($this->options['text'])) {
      return $this->options['text'];
    }
    else {
      return $title;
    }
  }
  
  /**
   * {@inheritdoc}
   */
  protected function getDefaultLabel() {
    return $this->t('contact');
  }

}