class RouteProcessorManager

class RouteProcessorManager implements OutboundRouteProcessorInterface {

  /**
   * Holds the array of outbound processors to cycle through.
   *
   * @var array
   *   An array whose keys are priorities and whose values are arrays of path
   *   processor objects.
   */
  protected $outboundProcessors = [];

  /**
   * Holds the array of outbound processors, sorted by priority.
   *
   * @var array
   *   An array of path processor objects.
   */
  protected $sortedOutbound = [];

  /**
   * Adds an outbound processor object to the $outboundProcessors property.
   *
   * @param \Drupal\Core\RouteProcessor\OutboundRouteProcessorInterface $processor
   *   The processor object to add.
   * @param int $priority
   *   The priority of the processor being added.
   */
  public function addOutbound(OutboundRouteProcessorInterface $processor, $priority = 0) {
    $this->outboundProcessors[$priority][] = $processor;
    $this->sortedOutbound = [];
  }

  /**
   * {@inheritdoc}
   */
  public function processOutbound($route_name, Route $route, array &$parameters, BubbleableMetadata $bubbleable_metadata = NULL) {
    $processors = $this
      ->getOutbound();
    foreach ($processors as $processor) {
      $processor
        ->processOutbound($route_name, $route, $parameters, $bubbleable_metadata);
    }
  }

  /**
   * Returns the sorted array of outbound processors.
   *
   * @return array
   *   An array of processor objects.
   */
  protected function getOutbound() {
    if (empty($this->sortedOutbound)) {
      $this->sortedOutbound = $this
        ->sortProcessors();
    }
    return $this->sortedOutbound;
  }

  /**
   * Sorts the processors according to priority.
   */
  protected function sortProcessors() {
    krsort($this->outboundProcessors);
    return array_merge(...$this->outboundProcessors);
  }

}