class ContentTranslationManageAccessCheck

class ContentTranslationManageAccessCheck implements AccessInterface {
    
    /**
     * The entity type manager.
     *
     * @var \Drupal\Core\Entity\EntityTypeManagerInterface
     */
    protected $entityTypeManager;
    
    /**
     * The language manager.
     *
     * @var \Drupal\Core\Language\LanguageManagerInterface
     */
    protected $languageManager;
    
    /**
     * Constructs a ContentTranslationManageAccessCheck object.
     *
     * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
     *   The entity type manager.
     * @param \Drupal\Core\Language\LanguageManagerInterface $language_manager
     *   The language manager.
     */
    public function __construct(EntityTypeManagerInterface $entity_type_manager, LanguageManagerInterface $language_manager) {
        $this->entityTypeManager = $entity_type_manager;
        $this->languageManager = $language_manager;
    }
    
    /**
     * Checks translation access for the entity and operation on the given route.
     *
     * @param \Symfony\Component\Routing\Route $route
     *   The route to check against.
     * @param \Drupal\Core\Routing\RouteMatchInterface $route_match
     *   The parametrized route.
     * @param \Drupal\Core\Session\AccountInterface $account
     *   The currently logged in account.
     * @param string $source
     *   (optional) For a create operation, the language code of the source.
     * @param string $target
     *   (optional) For a create operation, the language code of the translation.
     * @param string $language
     *   (optional) For an update or delete operation, the language code of the
     *   translation being updated or deleted.
     * @param string $entity_type_id
     *   (optional) The entity type ID.
     *
     * @return \Drupal\Core\Access\AccessResultInterface
     *   The access result.
     */
    public function access(Route $route, RouteMatchInterface $route_match, AccountInterface $account, $source = NULL, $target = NULL, $language = NULL, $entity_type_id = NULL) {
        
        /** @var \Drupal\Core\Entity\ContentEntityInterface $entity */
        if ($entity = $route_match->getParameter($entity_type_id)) {
            $operation = $route->getRequirement('_access_content_translation_manage');
            $language = $this->languageManager
                ->getLanguage($language) ?: $this->languageManager
                ->getCurrentLanguage(LanguageInterface::TYPE_CONTENT);
            $entity_type = $this->entityTypeManager
                ->getDefinition($entity_type_id);
            if (in_array($operation, [
                'update',
                'delete',
            ])) {
                // Translation operations cannot be performed on the default
                // translation.
                if ($language->getId() == $entity->getUntranslated()
                    ->language()
                    ->getId()) {
                    return AccessResult::forbidden()->addCacheableDependency($entity);
                }
                // Editors have no access to the translation operations, as entity
                // access already grants them an equal or greater access level.
                $templates = [
                    'update' => 'edit-form',
                    'delete' => 'delete-form',
                ];
                if ($entity->access($operation) && $entity_type->hasLinkTemplate($templates[$operation])) {
                    return AccessResult::forbidden()->cachePerPermissions();
                }
            }
            if ($account->hasPermission('translate any entity')) {
                return AccessResult::allowed()->cachePerPermissions();
            }
            switch ($operation) {
                case 'create':
                    
                    /** @var \Drupal\content_translation\ContentTranslationHandlerInterface $handler */
                    $handler = $this->entityTypeManager
                        ->getHandler($entity->getEntityTypeId(), 'translation');
                    $translations = $entity->getTranslationLanguages();
                    $languages = $this->languageManager
                        ->getLanguages();
                    $source_language = $this->languageManager
                        ->getLanguage($source) ?: $entity->language();
                    $target_language = $this->languageManager
                        ->getLanguage($target) ?: $this->languageManager
                        ->getCurrentLanguage(LanguageInterface::TYPE_CONTENT);
                    $is_new_translation = $source_language->getId() != $target_language->getId() && isset($languages[$source_language->getId()]) && isset($languages[$target_language->getId()]) && !isset($translations[$target_language->getId()]);
                    return AccessResult::allowedIf($is_new_translation)->cachePerPermissions()
                        ->addCacheableDependency($entity)
                        ->andIf($handler->getTranslationAccess($entity, $operation));
                case 'delete':
                    // @todo Remove this in https://www.drupal.org/node/2945956.
                    
                    /** @var \Drupal\Core\Access\AccessResultInterface $delete_access */
                    $delete_access = \Drupal::service('content_translation.delete_access')->checkAccess($entity);
                    $access = $this->checkAccess($entity, $language, $operation);
                    return $delete_access->andIf($access);
                case 'update':
                    return $this->checkAccess($entity, $language, $operation);
            }
        }
        // No opinion.
        return AccessResult::neutral();
    }
    
    /**
     * Performs access checks for the specified operation.
     *
     * @param \Drupal\Core\Entity\ContentEntityInterface $entity
     *   The entity being checked.
     * @param \Drupal\Core\Language\LanguageInterface $language
     *   For an update or delete operation, the language code of the translation
     *   being updated or deleted.
     * @param string $operation
     *   The operation to be checked.
     *
     * @return \Drupal\Core\Access\AccessResultInterface
     *   An access result object.
     */
    protected function checkAccess(ContentEntityInterface $entity, LanguageInterface $language, $operation) {
        
        /** @var \Drupal\content_translation\ContentTranslationHandlerInterface $handler */
        $handler = $this->entityTypeManager
            ->getHandler($entity->getEntityTypeId(), 'translation');
        $translations = $entity->getTranslationLanguages();
        $languages = $this->languageManager
            ->getLanguages();
        $has_translation = isset($languages[$language->getId()]) && $language->getId() != $entity->getUntranslated()
            ->language()
            ->getId() && isset($translations[$language->getId()]);
        return AccessResult::allowedIf($has_translation)->cachePerPermissions()
            ->addCacheableDependency($entity)
            ->andIf($handler->getTranslationAccess($entity, $operation));
    }

}