class PagerParameters

class PagerParameters implements PagerParametersInterface {
    
    /**
     * The HTTP request stack.
     *
     * @var \Symfony\Component\HttpFoundation\RequestStack
     */
    protected $requestStack;
    
    /**
     * Construct a PagerManager object.
     *
     * @param \Symfony\Component\HttpFoundation\RequestStack $stack
     *   The current HTTP request stack.
     */
    public function __construct(RequestStack $stack) {
        $this->requestStack = $stack;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getQueryParameters() {
        $request = $this->requestStack
            ->getCurrentRequest();
        if ($request) {
            return UrlHelper::filterQueryParameters($request->query
                ->all(), [
                'page',
            ]);
        }
        return [];
    }
    
    /**
     * {@inheritdoc}
     */
    public function findPage($pager_id = 0) {
        $pages = $this->getPagerQuery();
        return (int) ($pages[$pager_id] ?? 0);
    }
    
    /**
     * {@inheritdoc}
     */
    public function getPagerQuery() {
        $query = $this->getPagerParameter();
        return !empty($query) ? explode(',', $query) : [];
    }
    
    /**
     * {@inheritdoc}
     */
    public function getPagerParameter() {
        $request = $this->requestStack
            ->getCurrentRequest();
        if ($request) {
            return $request->query
                ->get('page', '');
        }
        return '';
    }

}