class ActionFormBase

abstract class ActionFormBase extends EntityForm {
    
    /**
     * The action storage.
     *
     * @var \Drupal\Core\Entity\EntityStorageInterface
     */
    protected $storage;
    
    /**
     * The action entity.
     *
     * @var \Drupal\system\ActionConfigEntityInterface
     */
    protected $entity;
    
    /**
     * Constructs a new action form.
     *
     * @param \Drupal\Core\Entity\EntityStorageInterface $storage
     *   The action storage.
     */
    public function __construct(EntityStorageInterface $storage) {
        $this->storage = $storage;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function create(ContainerInterface $container) {
        return new static($container->get('entity_type.manager')
            ->getStorage('action'));
    }
    
    /**
     * {@inheritdoc}
     */
    public function form(array $form, FormStateInterface $form_state) {
        $form['label'] = [
            '#type' => 'textfield',
            '#title' => $this->t('Label'),
            '#default_value' => $this->entity
                ->label(),
            '#maxlength' => '255',
            '#description' => $this->t('A unique label for this advanced action. This label will be displayed in the interface of modules that integrate with actions.'),
        ];
        $form['id'] = [
            '#type' => 'machine_name',
            '#default_value' => $this->entity
                ->id(),
            '#disabled' => !$this->entity
                ->isNew(),
            '#maxlength' => 64,
            '#description' => $this->t('A unique name for this action. It must only contain lowercase letters, numbers and underscores.'),
            '#machine_name' => [
                'exists' => [
                    $this,
                    'exists',
                ],
            ],
        ];
        $form['plugin'] = [
            '#type' => 'value',
            '#value' => $this->entity
                ->get('plugin'),
        ];
        $form['type'] = [
            '#type' => 'value',
            '#value' => $this->entity
                ->getType(),
        ];
        if ($plugin = $this->getPlugin()) {
            $form += $plugin->buildConfigurationForm($form, $form_state);
        }
        return parent::form($form, $form_state);
    }
    
    /**
     * Determines if the action already exists.
     *
     * @param string $id
     *   The action ID.
     *
     * @return bool
     *   TRUE if the action exists, FALSE otherwise.
     */
    public function exists($id) {
        $action = $this->storage
            ->load($id);
        return !empty($action);
    }
    
    /**
     * {@inheritdoc}
     */
    protected function actions(array $form, FormStateInterface $form_state) {
        $actions = parent::actions($form, $form_state);
        unset($actions['delete']);
        return $actions;
    }
    
    /**
     * {@inheritdoc}
     */
    public function validateForm(array &$form, FormStateInterface $form_state) {
        parent::validateForm($form, $form_state);
        if ($plugin = $this->getPlugin()) {
            $plugin->validateConfigurationForm($form, $form_state);
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function submitForm(array &$form, FormStateInterface $form_state) {
        parent::submitForm($form, $form_state);
        if ($plugin = $this->getPlugin()) {
            $plugin->submitConfigurationForm($form, $form_state);
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function save(array $form, FormStateInterface $form_state) {
        $this->entity
            ->save();
        $this->messenger()
            ->addStatus($this->t('The action has been successfully saved.'));
        $form_state->setRedirect('entity.action.collection');
    }
    
    /**
     * Gets the action plugin while ensuring it implements configuration form.
     *
     * @return \Drupal\Core\Action\ActionInterface|\Drupal\Core\Plugin\PluginFormInterface|null
     *   The action plugin, or NULL if it does not implement configuration forms.
     */
    protected function getPlugin() {
        if ($this->entity
            ->getPlugin() instanceof PluginFormInterface) {
            return $this->entity
                ->getPlugin();
        }
        return NULL;
    }

}