AjaxPageState.php

<?php

namespace Drupal\Core\StackMiddleware;

use Drupal\Component\Utility\UrlHelper;
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\HttpKernel\HttpKernelInterface;

/**
 * Expands the compressed ajax_page_state query parameter into an array.
 */
class AjaxPageState implements HttpKernelInterface {
    
    /**
     * Constructs a new AjaxPageState instance.
     *
     * @param \Symfony\Component\HttpKernel\HttpKernelInterface $httpKernel
     *   The wrapped HTTP kernel.
     */
    public function __construct(HttpKernelInterface $httpKernel) {
    }
    
    /**
     * {@inheritdoc}
     */
    public function handle(Request $request, $type = self::MAIN_REQUEST, $catch = TRUE) : Response {
        if ($type === static::MAIN_REQUEST) {
            if ($request->request
                ->has('ajax_page_state')) {
                $request->request
                    ->set('ajax_page_state', $this->parseAjaxPageState($request->request
                    ->all('ajax_page_state')));
            }
            elseif ($request->query
                ->has('ajax_page_state')) {
                $request->query
                    ->set('ajax_page_state', $this->parseAjaxPageState($request->query
                    ->all('ajax_page_state')));
            }
        }
        return $this->httpKernel
            ->handle($request, $type, $catch);
    }
    
    /**
     * Parse the ajax_page_state variable in the request.
     *
     * Decompresses the libraries array key.
     *
     * @param array $ajax_page_state
     *   An array of query parameters, where the libraries parameter is compressed.
     *
     * @return array
     */
    private function parseAjaxPageState(array $ajax_page_state) : array {
        $ajax_page_state['libraries'] = UrlHelper::uncompressQueryParameter($ajax_page_state['libraries']);
        return $ajax_page_state;
    }

}