class CommentManager

class CommentManager implements CommentManagerInterface {
    use StringTranslationTrait;
    
    /**
     * The entity field manager.
     *
     * @var \Drupal\Core\Entity\EntityFieldManagerInterface
     */
    protected $entityFieldManager;
    
    /**
     * The entity display repository.
     *
     * @var \Drupal\Core\Entity\EntityDisplayRepositoryInterface
     */
    protected $entityDisplayRepository;
    
    /**
     * The entity type manager.
     *
     * @var \Drupal\Core\Entity\EntityTypeManagerInterface
     */
    protected $entityTypeManager;
    
    /**
     * Whether the \Drupal\user\RoleInterface::AUTHENTICATED_ID can post comments.
     *
     * @var bool
     */
    protected $authenticatedCanPostComments;
    
    /**
     * The user settings config object.
     *
     * @var \Drupal\Core\Config\Config
     */
    protected $userConfig;
    
    /**
     * The module handler service.
     *
     * @var \Drupal\Core\Extension\ModuleHandlerInterface
     */
    protected $moduleHandler;
    
    /**
     * The current user.
     *
     * @var \Drupal\Core\Session\AccountInterface
     */
    protected $currentUser;
    
    /**
     * Construct the CommentManager object.
     *
     * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
     *   The entity type manager service.
     * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory
     *   The config factory.
     * @param \Drupal\Core\StringTranslation\TranslationInterface $string_translation
     *   The string translation service.
     * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
     *   The module handler service.
     * @param \Drupal\Core\Session\AccountInterface $current_user
     *   The current user.
     * @param \Drupal\Core\Entity\EntityFieldManagerInterface $entity_field_manager
     *   The entity field manager service.
     * @param \Drupal\Core\Entity\EntityDisplayRepositoryInterface $entity_display_repository
     *   The entity display repository service.
     */
    public function __construct(EntityTypeManagerInterface $entity_type_manager, ConfigFactoryInterface $config_factory, TranslationInterface $string_translation, ModuleHandlerInterface $module_handler, AccountInterface $current_user, EntityFieldManagerInterface $entity_field_manager, EntityDisplayRepositoryInterface $entity_display_repository) {
        $this->entityTypeManager = $entity_type_manager;
        $this->userConfig = $config_factory->get('user.settings');
        $this->stringTranslation = $string_translation;
        $this->moduleHandler = $module_handler;
        $this->currentUser = $current_user;
        $this->entityFieldManager = $entity_field_manager;
        $this->entityDisplayRepository = $entity_display_repository;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getFields($entity_type_id) {
        $entity_type = $this->entityTypeManager
            ->getDefinition($entity_type_id);
        if (!$entity_type->entityClassImplements(FieldableEntityInterface::class)) {
            return [];
        }
        $map = $this->entityFieldManager
            ->getFieldMapByFieldType('comment');
        return $map[$entity_type_id] ?? [];
    }
    
    /**
     * {@inheritdoc}
     */
    public function addBodyField($comment_type_id) {
        if (!FieldConfig::loadByName('comment', $comment_type_id, 'comment_body')) {
            // Attaches the body field by default.
            $field = $this->entityTypeManager
                ->getStorage('field_config')
                ->create([
                'label' => 'Comment',
                'bundle' => $comment_type_id,
                'required' => TRUE,
                'field_storage' => FieldStorageConfig::loadByName('comment', 'comment_body'),
            ]);
            $field->save();
            // Assign widget settings for the default form mode.
            $this->entityDisplayRepository
                ->getFormDisplay('comment', $comment_type_id)
                ->setComponent('comment_body', [
                'type' => 'text_textarea',
            ])
                ->save();
            // Assign display settings for the default view mode.
            $this->entityDisplayRepository
                ->getViewDisplay('comment', $comment_type_id)
                ->setComponent('comment_body', [
                'label' => 'hidden',
                'type' => 'text_default',
                'weight' => 0,
            ])
                ->save();
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function forbiddenMessage(EntityInterface $entity, $field_name) {
        if (!isset($this->authenticatedCanPostComments)) {
            // We only output a link if we are certain that users will get the
            // permission to post comments by logging in.
            $this->authenticatedCanPostComments = $this->entityTypeManager
                ->getStorage('user_role')
                ->load(RoleInterface::AUTHENTICATED_ID)
                ->hasPermission('post comments');
        }
        if ($this->authenticatedCanPostComments) {
            // We cannot use the redirect.destination service here because these links
            // sometimes appear on /node and taxonomy listing pages.
            if ($entity->get($field_name)
                ->getFieldDefinition()
                ->getSetting('form_location') == CommentItemInterface::FORM_SEPARATE_PAGE) {
                $comment_reply_parameters = [
                    'entity_type' => $entity->getEntityTypeId(),
                    'entity' => $entity->id(),
                    'field_name' => $field_name,
                ];
                $destination = [
                    'destination' => Url::fromRoute('comment.reply', $comment_reply_parameters, [
                        'fragment' => 'comment-form',
                    ])->toString(),
                ];
            }
            else {
                $destination = [
                    'destination' => $entity->toUrl('canonical', [
                        'fragment' => 'comment-form',
                    ])
                        ->toString(),
                ];
            }
            if ($this->userConfig
                ->get('register') != UserInterface::REGISTER_ADMINISTRATORS_ONLY) {
                // Users can register themselves.
                return $this->t('<a href=":login">Log in</a> or <a href=":register">register</a> to post comments', [
                    ':login' => Url::fromRoute('user.login', [], [
                        'query' => $destination,
                    ])->toString(),
                    ':register' => Url::fromRoute('user.register', [], [
                        'query' => $destination,
                    ])->toString(),
                ]);
            }
            else {
                // Only admins can add new users, no public registration.
                return $this->t('<a href=":login">Log in</a> to post comments', [
                    ':login' => Url::fromRoute('user.login', [], [
                        'query' => $destination,
                    ])->toString(),
                ]);
            }
        }
        return '';
    }
    
    /**
     * {@inheritdoc}
     */
    public function getCountNewComments(EntityInterface $entity, $field_name = NULL, $timestamp = 0) {
        // @todo Replace module handler with optional history service injection
        //   after https://www.drupal.org/node/2081585.
        if ($this->currentUser
            ->isAuthenticated() && $this->moduleHandler
            ->moduleExists('history')) {
            // Retrieve the timestamp at which the current user last viewed this entity.
            if (!$timestamp) {
                if ($entity->getEntityTypeId() == 'node') {
                    $timestamp = history_read($entity->id());
                }
                else {
                    $function = $entity->getEntityTypeId() . '_last_viewed';
                    if (function_exists($function)) {
                        $timestamp = $function($entity->id());
                    }
                    else {
                        // Default to 30 days ago.
                        // @todo Remove once https://www.drupal.org/node/1029708 lands.
                        $timestamp = COMMENT_NEW_LIMIT;
                    }
                }
            }
            $timestamp = $timestamp > HISTORY_READ_LIMIT ? $timestamp : HISTORY_READ_LIMIT;
            // Use the timestamp to retrieve the number of new comments.
            $query = $this->entityTypeManager
                ->getStorage('comment')
                ->getQuery()
                ->accessCheck(TRUE)
                ->condition('entity_type', $entity->getEntityTypeId())
                ->condition('entity_id', $entity->id())
                ->condition('created', $timestamp, '>')
                ->condition('status', CommentInterface::PUBLISHED);
            if ($field_name) {
                // Limit to a particular field.
                $query->condition('field_name', $field_name);
            }
            return $query->count()
                ->execute();
        }
        return FALSE;
    }

}