class WorkspaceSwitcherForm

class WorkspaceSwitcherForm extends FormBase implements WorkspaceFormInterface {
    
    /**
     * The workspace manager.
     *
     * @var \Drupal\workspaces\WorkspaceManagerInterface
     */
    protected $workspaceManager;
    
    /**
     * The workspace entity storage handler.
     *
     * @var \Drupal\Core\Entity\EntityStorageInterface
     */
    protected $workspaceStorage;
    
    /**
     * The messenger service.
     *
     * @var \Drupal\Core\Messenger\MessengerInterface
     */
    protected $messenger;
    
    /**
     * Constructs a new WorkspaceSwitcherForm.
     *
     * @param \Drupal\workspaces\WorkspaceManagerInterface $workspace_manager
     *   The workspace manager.
     * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
     *   The entity type manager.
     * @param \Drupal\Core\Messenger\MessengerInterface $messenger
     *   The messenger service.
     */
    public function __construct(WorkspaceManagerInterface $workspace_manager, EntityTypeManagerInterface $entity_type_manager, MessengerInterface $messenger) {
        $this->workspaceManager = $workspace_manager;
        $this->workspaceStorage = $entity_type_manager->getStorage('workspace');
        $this->messenger = $messenger;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function create(ContainerInterface $container) {
        return new static($container->get('workspaces.manager'), $container->get('entity_type.manager'), $container->get('messenger'));
    }
    
    /**
     * {@inheritdoc}
     */
    public function getFormId() {
        return 'workspace_switcher_form';
    }
    
    /**
     * {@inheritdoc}
     */
    public function buildForm(array $form, FormStateInterface $form_state) {
        $workspaces = $this->workspaceStorage
            ->loadMultiple();
        $workspace_labels = [];
        foreach ($workspaces as $workspace) {
            $workspace_labels[$workspace->id()] = $workspace->label();
        }
        $active_workspace = $this->workspaceManager
            ->getActiveWorkspace();
        if ($active_workspace) {
            unset($workspace_labels[$active_workspace->id()]);
        }
        $form['current'] = [
            '#type' => 'item',
            '#title' => $this->t('Current workspace'),
            '#markup' => $active_workspace ? $active_workspace->label() : $this->t('None'),
            '#wrapper_attributes' => [
                'class' => [
                    'container-inline',
                ],
            ],
        ];
        $form['workspace_id'] = [
            '#type' => 'select',
            '#title' => $this->t('Select workspace'),
            '#required' => TRUE,
            '#options' => $workspace_labels,
            '#wrapper_attributes' => [
                'class' => [
                    'container-inline',
                ],
            ],
            '#access' => !empty($workspace_labels),
        ];
        $form['actions']['#type'] = 'actions';
        $form['actions']['submit'] = [
            '#type' => 'submit',
            '#value' => $this->t('Activate'),
            '#button_type' => 'primary',
            '#access' => !empty($workspace_labels),
        ];
        if ($active_workspace) {
            $form['actions']['switch_to_live'] = [
                '#type' => 'submit',
                '#submit' => [
                    '::submitSwitchToLive',
                ],
                '#value' => $this->t('Switch to Live'),
                '#limit_validation_errors' => [],
                '#button_type' => 'primary',
            ];
        }
        return $form;
    }
    
    /**
     * {@inheritdoc}
     */
    public function submitForm(array &$form, FormStateInterface $form_state) {
        $id = $form_state->getValue('workspace_id');
        
        /** @var \Drupal\workspaces\WorkspaceInterface $workspace */
        $workspace = $this->workspaceStorage
            ->load($id);
        try {
            $this->workspaceManager
                ->setActiveWorkspace($workspace);
            $this->messenger
                ->addMessage($this->t('%workspace_label is now the active workspace.', [
                '%workspace_label' => $workspace->label(),
            ]));
        } catch (WorkspaceAccessException $e) {
            $this->messenger
                ->addError($this->t('You do not have access to activate the %workspace_label workspace.', [
                '%workspace_label' => $workspace->label(),
            ]));
        }
    }
    
    /**
     * Submit handler for switching to the live version of the site.
     */
    public function submitSwitchToLive(array &$form, FormStateInterface $form_state) {
        $this->workspaceManager
            ->switchToLive();
        $this->messenger
            ->addMessage($this->t('You are now viewing the live version of the site.'));
    }

}