class FieldUI

class FieldUI {
    
    /**
     * Returns the route info for the field overview of a given entity bundle.
     *
     * @param string $entity_type_id
     *   An entity type.
     * @param string $bundle
     *   The entity bundle.
     *
     * @return \Drupal\Core\Url
     *   A URL object.
     */
    public static function getOverviewRouteInfo($entity_type_id, $bundle) {
        $entity_type = \Drupal::entityTypeManager()->getDefinition($entity_type_id);
        if ($entity_type->get('field_ui_base_route')) {
            return new Url("entity.{$entity_type_id}.field_ui_fields", static::getRouteBundleParameter($entity_type, $bundle));
        }
    }
    
    /**
     * Returns the next redirect path in a multipage sequence.
     *
     * @param array $destinations
     *   An array of destinations to redirect to.
     *
     * @return \Drupal\Core\Url|null
     *   The next destination to redirect to.
     */
    public static function getNextDestination(array $destinations) {
        // If there are no valid destinations left, return here.
        if (empty($destinations)) {
            return NULL;
        }
        $next_destination = array_shift($destinations);
        if (is_array($next_destination)) {
            $next_destination['options']['query']['destinations'] = $destinations;
            $next_destination += [
                'route_parameters' => [],
            ];
            $next_destination = Url::fromRoute($next_destination['route_name'], $next_destination['route_parameters'], $next_destination['options']);
        }
        else {
            $options = UrlHelper::parse($next_destination);
            if ($destinations) {
                $options['query']['destinations'] = $destinations;
            }
            // Redirect to any given path within the same domain.
            // @todo Revisit this in https://www.drupal.org/node/2418219.
            $next_destination = Url::fromUserInput('/' . $options['path'], $options);
        }
        return $next_destination;
    }
    
    /**
     * Gets the route parameter that should be used for Field UI routes.
     *
     * @param \Drupal\Core\Entity\EntityTypeInterface $entity_type
     *   The actual entity type, not the bundle (e.g. the content entity type).
     * @param string $bundle
     *   The bundle name.
     *
     * @return array
     *   An array that can be used a route parameter.
     */
    public static function getRouteBundleParameter(EntityTypeInterface $entity_type, $bundle) {
        $bundle_parameter_key = $entity_type->getBundleEntityType() ?: 'bundle';
        return [
            $bundle_parameter_key => $bundle,
        ];
    }

}