class PathProcessorManager

class PathProcessorManager implements InboundPathProcessorInterface, OutboundPathProcessorInterface {
    
    /**
     * Holds the array of inbound processors to cycle through.
     *
     * @var array
     *   An array whose keys are priorities and whose values are arrays of path
     *   processor objects.
     */
    protected $inboundProcessors = [];
    
    /**
     * Holds the array of inbound processors, sorted by priority.
     *
     * @var array
     *   An array of path processor objects.
     */
    protected $sortedInbound = [];
    
    /**
     * 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 inbound processor object to the $inboundProcessors property.
     *
     * @param \Drupal\Core\PathProcessor\InboundPathProcessorInterface $processor
     *   The processor object to add.
     * @param int $priority
     *   The priority of the processor being added.
     */
    public function addInbound(InboundPathProcessorInterface $processor, $priority = 0) {
        $this->inboundProcessors[$priority][] = $processor;
        $this->sortedInbound = [];
    }
    
    /**
     * {@inheritdoc}
     */
    public function processInbound($path, Request $request) {
        $processors = $this->getInbound();
        foreach ($processors as $processor) {
            $path = $processor->processInbound($path, $request);
        }
        return $path;
    }
    
    /**
     * Returns the sorted array of inbound processors.
     *
     * @return array
     *   An array of processor objects.
     */
    protected function getInbound() {
        if (empty($this->sortedInbound)) {
            $this->sortedInbound = $this->sortProcessors('inboundProcessors');
        }
        return $this->sortedInbound;
    }
    
    /**
     * Adds an outbound processor object to the $outboundProcessors property.
     *
     * @param \Drupal\Core\PathProcessor\OutboundPathProcessorInterface $processor
     *   The processor object to add.
     * @param int $priority
     *   The priority of the processor being added.
     */
    public function addOutbound(OutboundPathProcessorInterface $processor, $priority = 0) {
        $this->outboundProcessors[$priority][] = $processor;
        $this->sortedOutbound = [];
    }
    
    /**
     * {@inheritdoc}
     */
    public function processOutbound($path, &$options = [], Request $request = NULL, BubbleableMetadata $bubbleable_metadata = NULL) {
        $processors = $this->getOutbound();
        foreach ($processors as $processor) {
            $path = $processor->processOutbound($path, $options, $request, $bubbleable_metadata);
        }
        return $path;
    }
    
    /**
     * 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('outboundProcessors');
        }
        return $this->sortedOutbound;
    }
    
    /**
     * Sorts the processors according to priority.
     *
     * @param string $type
     *   The processor type to sort, e.g. 'inboundProcessors'.
     */
    protected function sortProcessors($type) {
        $sorted = [];
        krsort($this->{$type});
        foreach ($this->{$type} as $processors) {
            $sorted = array_merge($sorted, $processors);
        }
        return $sorted;
    }

}