class ContentEntityConfirmFormBase

abstract class ContentEntityConfirmFormBase extends ContentEntityForm implements ConfirmFormInterface {
    
    /**
     * {@inheritdoc}
     */
    public function getBaseFormId() {
        return $this->entity
            ->getEntityTypeId() . '_confirm_form';
    }
    
    /**
     * {@inheritdoc}
     */
    public function getDescription() {
        return $this->t('This action cannot be undone.');
    }
    
    /**
     * {@inheritdoc}
     */
    public function getConfirmText() {
        return $this->t('Confirm');
    }
    
    /**
     * {@inheritdoc}
     */
    public function getCancelText() {
        return $this->t('Cancel');
    }
    
    /**
     * {@inheritdoc}
     */
    public function getFormName() {
        return 'confirm';
    }
    
    /**
     * {@inheritdoc}
     */
    public function buildForm(array $form, FormStateInterface $form_state) {
        $form = parent::buildForm($form, $form_state);
        $form['#title'] = $this->getQuestion();
        $form['#attributes']['class'][] = 'confirmation';
        $form['description'] = [
            '#markup' => $this->getDescription(),
        ];
        $form[$this->getFormName()] = [
            '#type' => 'hidden',
            '#value' => 1,
        ];
        // By default, render the form using theme_confirm_form().
        if (!isset($form['#theme'])) {
            $form['#theme'] = 'confirm_form';
        }
        return $form;
    }
    
    /**
     * {@inheritdoc}
     */
    public function form(array $form, FormStateInterface $form_state) {
        // Do not attach fields to the confirm form.
        return $form;
    }
    
    /**
     * {@inheritdoc}
     */
    protected function actions(array $form, FormStateInterface $form_state) {
        return [
            'submit' => [
                '#type' => 'submit',
                '#value' => $this->getConfirmText(),
                '#submit' => [
                    [
                        $this,
                        'submitForm',
                    ],
                ],
            ],
            'cancel' => ConfirmFormHelper::buildCancelLink($this, $this->getRequest()),
        ];
    }
    
    /**
     * {@inheritdoc}
     *
     * The save() method is not used in ContentEntityConfirmFormBase. This
     * overrides the default implementation that saves the entity.
     *
     * Confirmation forms should override submitForm() instead for their logic.
     */
    public function save(array $form, FormStateInterface $form_state) {
    }
    
    /**
     * {@inheritdoc}
     *
     * The delete() method is not used in ContentEntityConfirmFormBase. This
     * overrides the default implementation that redirects to the delete-form
     * confirmation form.
     *
     * Confirmation forms should override submitForm() instead for their logic.
     */
    public function delete(array $form, FormStateInterface $form_state) {
    }
    
    /**
     * {@inheritdoc}
     */
    public function validateForm(array &$form, FormStateInterface $form_state) {
        // Override the default validation implementation as it is not necessary
        // nor possible to validate an entity in a confirmation form.
        return $this->entity;
    }

}