class CommentViewBuilder

class CommentViewBuilder extends EntityViewBuilder {
    
    /**
     * The current user.
     *
     * @var \Drupal\Core\Session\AccountInterface
     */
    protected $currentUser;
    
    /**
     * The entity type manager.
     *
     * @var \Drupal\Core\Entity\EntityTypeManagerInterface
     */
    protected $entityTypeManager;
    
    /**
     * Constructs a new CommentViewBuilder.
     *
     * @param \Drupal\Core\Entity\EntityTypeInterface $entity_type
     *   The entity type definition.
     * @param \Drupal\Core\Entity\EntityRepositoryInterface $entity_repository
     *   The entity repository service.
     * @param \Drupal\Core\Language\LanguageManagerInterface $language_manager
     *   The language manager.
     * @param \Drupal\Core\Session\AccountInterface $current_user
     *   The current user.
     * @param \Drupal\Core\Theme\Registry $theme_registry
     *   The theme registry.
     * @param \Drupal\Core\Entity\EntityDisplayRepositoryInterface $entity_display_repository
     *   The entity display repository.
     * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
     *   The entity type manager.
     */
    public function __construct(EntityTypeInterface $entity_type, EntityRepositoryInterface $entity_repository, LanguageManagerInterface $language_manager, AccountInterface $current_user, Registry $theme_registry, EntityDisplayRepositoryInterface $entity_display_repository, EntityTypeManagerInterface $entity_type_manager) {
        parent::__construct($entity_type, $entity_repository, $language_manager, $theme_registry, $entity_display_repository);
        $this->currentUser = $current_user;
        $this->entityTypeManager = $entity_type_manager;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function createInstance(ContainerInterface $container, EntityTypeInterface $entity_type) {
        return new static($entity_type, $container->get('entity.repository'), $container->get('language_manager'), $container->get('current_user'), $container->get('theme.registry'), $container->get('entity_display.repository'), $container->get('entity_type.manager'));
    }
    
    /**
     * {@inheritdoc}
     */
    protected function getBuildDefaults(EntityInterface $entity, $view_mode) {
        $build = parent::getBuildDefaults($entity, $view_mode);
        
        /** @var \Drupal\comment\CommentInterface $entity */
        // Store a threading field setting to use later in self::buildComponents().
        $commented_entity = $entity->getCommentedEntity();
        $build['#comment_threaded'] = is_null($commented_entity) || $commented_entity->getFieldDefinition($entity->getFieldName())
            ->getSetting('default_mode') === CommentManagerInterface::COMMENT_MODE_THREADED;
        // If threading is enabled, don't render cache individual comments, but do
        // keep the cacheability metadata, so it can bubble up.
        if ($build['#comment_threaded']) {
            unset($build['#cache']['keys']);
        }
        return $build;
    }
    
    /**
     * {@inheritdoc}
     *
     * In addition to modifying the content key on entities, this implementation
     * will also set the comment entity key which all comments carry.
     *
     * @throws \InvalidArgumentException
     *   Thrown when a comment is attached to an entity that no longer exists.
     */
    public function buildComponents(array &$build, array $entities, array $displays, $view_mode) {
        
        /** @var \Drupal\comment\CommentInterface[] $entities */
        if (empty($entities)) {
            return;
        }
        // Pre-load associated users into cache to leverage multiple loading.
        $uids = [];
        foreach ($entities as $entity) {
            $uids[] = $entity->getOwnerId();
        }
        $this->entityTypeManager
            ->getStorage('user')
            ->loadMultiple(array_unique($uids));
        parent::buildComponents($build, $entities, $displays, $view_mode);
        // A counter to track the indentation level.
        $current_indent = 0;
        $attach_history = $this->moduleHandler
            ->moduleExists('history') && $this->currentUser
            ->isAuthenticated();
        foreach ($entities as $id => $entity) {
            if ($build[$id]['#comment_threaded']) {
                $comment_indent = count(explode('.', (string) $entity->getThread())) - 1;
                if ($comment_indent > $current_indent) {
                    // Set 1 to indent this comment from the previous one (its parent).
                    // Set only one extra level of indenting even if the difference in
                    // depth is higher.
                    $build[$id]['#comment_indent'] = 1;
                    $current_indent++;
                }
                else {
                    // Set zero if this comment is on the same level as the previous one
                    // or negative value to point an amount indents to close.
                    $build[$id]['#comment_indent'] = $comment_indent - $current_indent;
                    $current_indent = $comment_indent;
                }
            }
            // Commented entities already loaded after self::getBuildDefaults().
            $commented_entity = $entity->getCommentedEntity();
            // Set defaults if the commented_entity does not exist.
            $bundle = $commented_entity ? $commented_entity->bundle() : '';
            $is_node = $commented_entity ? $commented_entity->getEntityTypeId() === 'node' : NULL;
            $build[$id]['#entity'] = $entity;
            $build[$id]['#theme'] = 'comment__' . $entity->getFieldName() . '__' . $bundle;
            $display = $displays[$entity->bundle()];
            if ($display->getComponent('links')) {
                $build[$id]['links'] = [
                    '#lazy_builder' => [
                        'comment.lazy_builders:renderLinks',
                        [
                            $entity->id(),
                            $view_mode,
                            $entity->language()
                                ->getId(),
                            !empty($entity->in_preview),
                        ],
                    ],
                    '#create_placeholder' => TRUE,
                ];
            }
            if (!isset($build[$id]['#attached'])) {
                $build[$id]['#attached'] = [];
            }
            $build[$id]['#attached']['library'][] = 'comment/drupal.comment-by-viewer';
            if ($attach_history && $is_node) {
                $build[$id]['#attached']['library'][] = 'comment/drupal.comment-new-indicator';
                // Embed the metadata for the comment "new" indicators on this node.
                $build[$id]['history'] = [
                    '#lazy_builder' => [
                        '\\Drupal\\history\\HistoryRenderCallback::lazyBuilder',
                        [
                            $commented_entity->id(),
                        ],
                    ],
                    '#create_placeholder' => TRUE,
                ];
            }
        }
        if ($build[$id]['#comment_threaded']) {
            // The final comment must close up some hanging divs.
            $build[$id]['#comment_indent_final'] = $current_indent;
        }
    }
    
    /**
     * {@inheritdoc}
     */
    protected function alterBuild(array &$build, EntityInterface $comment, EntityViewDisplayInterface $display, $view_mode) {
        parent::alterBuild($build, $comment, $display, $view_mode);
        if (empty($comment->in_preview)) {
            $prefix = '';
            // Add indentation div or close open divs as needed.
            if ($build['#comment_threaded']) {
                $prefix .= $build['#comment_indent'] <= 0 ? str_repeat('</div>', abs($build['#comment_indent'])) : "\n" . '<div class="indented">';
            }
            $build['#prefix'] = $prefix;
            // Close all open divs.
            if (!empty($build['#comment_indent_final'])) {
                $build['#suffix'] = str_repeat('</div>', $build['#comment_indent_final']);
            }
        }
    }

}