class SessionWorkspaceNegotiator

class SessionWorkspaceNegotiator implements WorkspaceNegotiatorInterface {
    
    /**
     * The current user.
     *
     * @var \Drupal\Core\Session\AccountInterface
     */
    protected $currentUser;
    
    /**
     * The session.
     *
     * @var \Symfony\Component\HttpFoundation\Session\Session
     */
    protected $session;
    
    /**
     * The workspace storage handler.
     *
     * @var \Drupal\Core\Entity\EntityStorageInterface
     */
    protected $workspaceStorage;
    
    /**
     * Constructor.
     *
     * @param \Drupal\Core\Session\AccountInterface $current_user
     *   The current user.
     * @param \Symfony\Component\HttpFoundation\Session\Session $session
     *   The session.
     * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
     *   The entity type manager.
     */
    public function __construct(AccountInterface $current_user, Session $session, EntityTypeManagerInterface $entity_type_manager) {
        $this->currentUser = $current_user;
        $this->session = $session;
        $this->workspaceStorage = $entity_type_manager->getStorage('workspace');
    }
    
    /**
     * {@inheritdoc}
     */
    public function applies(Request $request) {
        // This negotiator only applies if the current user is authenticated.
        return $this->currentUser
            ->isAuthenticated();
    }
    
    /**
     * {@inheritdoc}
     */
    public function getActiveWorkspace(Request $request) {
        $workspace_id = $this->session
            ->get('active_workspace_id');
        if ($workspace_id && ($workspace = $this->workspaceStorage
            ->load($workspace_id))) {
            return $workspace;
        }
        return NULL;
    }
    
    /**
     * {@inheritdoc}
     */
    public function setActiveWorkspace(WorkspaceInterface $workspace) {
        $this->session
            ->set('active_workspace_id', $workspace->id());
    }
    
    /**
     * {@inheritdoc}
     */
    public function unsetActiveWorkspace() {
        $this->session
            ->remove('active_workspace_id');
    }

}