class Overview

class Overview extends OverviewTerms {
    
    /**
     * {@inheritdoc}
     */
    public function getFormId() {
        return 'forum_overview';
    }
    
    /**
     * {@inheritdoc}
     */
    public function buildForm(array $form, FormStateInterface $form_state, VocabularyInterface $taxonomy_vocabulary = NULL) {
        $forum_config = $this->config('forum.settings');
        $vid = $forum_config->get('vocabulary');
        $vocabulary = $this->entityTypeManager
            ->getStorage('taxonomy_vocabulary')
            ->load($vid);
        if (!$vocabulary) {
            throw new NotFoundHttpException();
        }
        // Build base taxonomy term overview.
        $form = parent::buildForm($form, $form_state, $vocabulary);
        foreach (Element::children($form['terms']) as $key) {
            if (isset($form['terms'][$key]['#term'])) {
                
                /** @var \Drupal\taxonomy\TermInterface $term */
                $term = $form['terms'][$key]['#term'];
                $form['terms'][$key]['term']['#url'] = Url::fromRoute('forum.page', [
                    'taxonomy_term' => $term->id(),
                ]);
                if (!empty($term->forum_container->value)) {
                    $title = $this->t('edit container');
                    $url = Url::fromRoute('entity.taxonomy_term.forum_edit_container_form', [
                        'taxonomy_term' => $term->id(),
                    ]);
                }
                else {
                    $title = $this->t('edit forum');
                    $url = Url::fromRoute('entity.taxonomy_term.forum_edit_form', [
                        'taxonomy_term' => $term->id(),
                    ]);
                }
                // Re-create the operations column and add only the edit link.
                $form['terms'][$key]['operations'] = [
                    '#type' => 'operations',
                    '#links' => [
                        'edit' => [
                            'title' => $title,
                            'url' => $url,
                        ],
                    ],
                ];
            }
        }
        // Remove the alphabetical reset.
        unset($form['actions']['reset_alphabetical']);
        // Use the existing taxonomy overview submit handler.
        $form['terms']['#empty'] = $this->t('No containers or forums available. <a href=":container">Add container</a> or <a href=":forum">Add forum</a>.', [
            ':container' => Url::fromRoute('forum.add_container')->toString(),
            ':forum' => Url::fromRoute('forum.add_forum')->toString(),
        ]);
        return $form;
    }

}