trait HtmlFormatterTrait in HTML Formatter 8

trait HtmlFormatterTrait {

  /**
   * Gets the default settings for the html formatter.
   *
   * @return array
   */
  public static function getHtmlFormatterDefaultSettings() {
    return [
      'tag' => '',
      'class' => '',
      'link' => FALSE,
    ];
  }

  /**
   * Get form elements for the html formatter.
   *
   * @return array $elements
   */
  public function getHtmlFormatterSettingsForm() {
    $elements = [];
    $elements['tag'] = [
      '#type' => 'textfield',
      '#title' => $this
        ->t('HTML Tag'),
      '#default_value' => $this
        ->getSetting('tag'),
      '#min' => 1,
      '#description' => t('HTML tags like: h2, div, article, etc..'),
    ];
    $elements['class'] = [
      '#type' => 'textfield',
      '#title' => $this
        ->t('Class Name'),
      '#default_value' => $this
        ->getSetting('class'),
      '#min' => 1,
      '#description' => $this
        ->t('If left blank no class will be added.'),
    ];
    $elements['link'] = [
      '#type' => 'checkbox',
      '#title' => $this
        ->t('Link to Content'),
      '#default_value' => $this
        ->getSetting('link'),
    ];
    return $elements;
  }

  /**
   * Get summary for html formatter.
   *
   * @return array
   */
  public function getHtmlFormatterSettingsSummary($settings) {
    $summary = [];
    if (!empty($settings['tag'])) {
      $summary[] = $this
        ->t('Rendered with HTML tag: @tag', [
        '@tag' => $settings['tag'],
      ]);
    }
    if (!empty($settings['class'])) {
      $summary[] = $this
        ->t('With class: @class', [
        '@class' => $settings['class'],
      ]);
    }
    if (!empty($settings['link'])) {
      $summary[] = $this
        ->t('Linked to Content');
    }
    return $summary;
  }

  /**
   * Get url from entity.
   *
   * @param FieldItemListInterface $items
   *   FieldItemListInterface items.
   *
   * @return string $url
   *   Entity url or blank if none.
   */
  public function getEntityUrl(FieldItemListInterface $items) {
    $url = '';
    $entity = $items
      ->getEntity();
    if (!$entity
      ->isNew()) {
      if ($entity
        ->hasLinkTemplate('canonical')) {
        $url = $entity
          ->toUrl('canonical', [
          'language' => $entity
            ->language(),
        ]);
      }
    }
    return $url;
  }

  /**
   * If the field formatter is set to link to content, add a link.
   *
   * @param array $settings
   *   Settings array.
   * @param string $value
   *   The value that will be printed.
   * @param string $url
   *   The url to the content.
   *
   * @return string $value
   *   The value that will be printed.
   */
  public function getLinkedValue($settings, $value, $url = '') {
    if ($settings['link'] && $url) {
      $value = [
        '#theme' => 'link_formatter_link_separate',
        '#url_title' => $value,
        '#url' => $url,
      ];
    }
    return $value;
  }

}