class AddEventForm

class AddEventForm extends FormBase {
    use AddEventFormTrait;
    
    /**
     * The Reaction Rule being modified.
     *
     * @var \Drupal\rules\Entity\ReactionRuleConfig
     */
    protected $reactionRule;
    
    /**
     * Constructs a new event add form.
     *
     * @param \Drupal\rules\Core\RulesEventManager $event_manager
     *   The Rules event manager.
     * @param \Drupal\Core\Entity\EntityTypeBundleInfoInterface $entity_bundle_info
     *   The entity type bundle information manager.
     */
    public function __construct(RulesEventManager $event_manager, EntityTypeBundleInfoInterface $entity_bundle_info) {
        $this->eventManager = $event_manager;
        $this->entityBundleInfo = $entity_bundle_info;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function create(ContainerInterface $container) {
        return new static($container->get('plugin.manager.rules_event'), $container->get('entity_type.bundle.info'));
    }
    
    /**
     * {@inheritdoc}
     */
    public function getFormId() {
        return 'rules_add_event';
    }
    
    /**
     * Provides the page title on the form.
     */
    public function getTitle(RulesUiHandlerInterface $rules_ui_handler) {
        return $this->t('Add event to %rule', [
            '%rule' => $rules_ui_handler->getComponentLabel(),
        ]);
    }
    
    /**
     * {@inheritdoc}
     */
    protected function actions(array $form, FormStateInterface $form_state) {
        $actions = parent::actions($form, $form_state);
        $actions['submit']['#value'] = $this->t('Save');
        return $actions;
    }
    
    /**
     * {@inheritdoc}
     */
    public function buildForm(array $form, FormStateInterface $form_state, ReactionRuleConfig $rules_reaction_rule = NULL) {
        $this->reactionRule = $rules_reaction_rule;
        $form = $this->buildEventForm($form, $form_state);
        $form['actions'] = [
            '#type' => 'actions',
        ];
        $form['actions']['submit'] = [
            '#type' => 'submit',
            '#value' => $this->t('Add'),
            '#button_type' => 'primary',
        ];
        return $form;
    }
    
    /**
     * {@inheritdoc}
     */
    public function submitForm(array &$form, FormStateInterface $form_state) {
        $event_name = $form_state->getValue([
            'events',
            0,
            'event_name',
        ]);
        // Check if the selected event is an entity event.
        $event_definition = $this->eventManager
            ->getDefinition($event_name);
        $handler_class = $event_definition['class'];
        if (is_subclass_of($handler_class, RulesConfigurableEventHandlerInterface::class)) {
            // Support non-javascript browsers.
            if (!array_key_exists('bundle', $form_state->getValues())) {
                // The form field for "bundle" was not displayed yet, so rebuild the
                // form so that the user gets a chance to fill it in.
                $form_state->setRebuild();
                return;
            }
            // Add the bundle name to the event name if a bundle was selected.
            $this->entityBundleBuilder('rules_reaction_rule', $this->reactionRule, $form, $form_state);
            $event_name = $form_state->getValue([
                'events',
                0,
                'event_name',
            ]);
        }
        $this->reactionRule
            ->addEvent($event_name);
        $this->reactionRule
            ->save();
        $this->messenger()
            ->addMessage($this->t('Added event %label to %rule.', [
            '%label' => $this->eventManager
                ->getDefinition($event_name)['label'],
            '%rule' => $this->reactionRule
                ->label(),
        ]));
        $form_state->setRedirect('entity.rules_reaction_rule.edit_form', [
            'rules_reaction_rule' => $this->reactionRule
                ->id(),
        ]);
    }

}