class BlockContentForm

class BlockContentForm extends ContentEntityForm {
    
    /**
     * The block content entity.
     *
     * @var \Drupal\block_content\BlockContentInterface
     */
    protected $entity;
    
    /**
     * {@inheritdoc}
     */
    public function form(array $form, FormStateInterface $form_state) {
        $block = $this->entity;
        $form = parent::form($form, $form_state);
        if ($this->operation == 'edit') {
            $form['#title'] = $this->t('Edit content block %label', [
                '%label' => $block->label(),
            ]);
        }
        // Override the default CSS class name, since the user-defined content block
        // type name in 'TYPE-block-form' potentially clashes with third-party class
        // names.
        $form['#attributes']['class'][0] = 'block-' . Html::getClass($block->bundle()) . '-form';
        return $form;
    }
    
    /**
     * {@inheritdoc}
     */
    protected function actions(array $form, FormStateInterface $form_state) : array {
        $element = parent::actions($form, $form_state);
        if ($this->getRequest()->query
            ->has('theme')) {
            $element['submit']['#value'] = $this->t('Save and configure');
        }
        if ($this->currentUser()
            ->hasPermission('administer blocks') && !$this->getRequest()->query
            ->has('theme') && $this->entity
            ->isNew()) {
            $element['configure_block'] = [
                '#type' => 'submit',
                '#value' => $this->t('Save and configure'),
                '#weight' => 20,
                '#submit' => array_merge($element['submit']['#submit'], [
                    '::configureBlock',
                ]),
            ];
        }
        return $element;
    }
    
    /**
     * Form submission handler for the 'configureBlock' action.
     *
     * @param array $form
     *   An associative array containing the structure of the form.
     * @param \Drupal\Core\Form\FormStateInterface $form_state
     *   The current state of the form.
     */
    public function configureBlock(array $form, FormStateInterface $form_state) : void {
        $block = $this->entity;
        if (!($theme = $block->getTheme())) {
            $theme = $this->config('system.theme')
                ->get('default');
        }
        $form_state->setRedirect('block.admin_add', [
            'plugin_id' => 'block_content:' . $block->uuid(),
            'theme' => $theme,
        ]);
        $form_state->setIgnoreDestination();
    }
    
    /**
     * {@inheritdoc}
     */
    public function save(array $form, FormStateInterface $form_state) {
        $block = $this->entity;
        $insert = $block->isNew();
        $block->save();
        $context = [
            '@type' => $block->bundle(),
            '%info' => $block->label(),
        ];
        $logger = $this->logger('block_content');
        $block_type = $this->getBundleEntity();
        $t_args = [
            '@type' => $block_type->label(),
            '%info' => $block->label(),
        ];
        if ($insert) {
            $logger->info('@type: added %info.', $context);
            $this->messenger()
                ->addStatus($this->t('@type %info has been created.', $t_args));
        }
        else {
            $logger->info('@type: updated %info.', $context);
            $this->messenger()
                ->addStatus($this->t('@type %info has been updated.', $t_args));
        }
        if ($block->id()) {
            $form_state->setValue('id', $block->id());
            $form_state->set('id', $block->id());
            $theme = $block->getTheme();
            if ($insert && $theme) {
                $form_state->setRedirect('block.admin_add', [
                    'plugin_id' => 'block_content:' . $block->uuid(),
                    'theme' => $theme,
                    'region' => $this->getRequest()->query
                        ->getString('region'),
                ]);
            }
            else {
                $form_state->setRedirectUrl($block->toUrl('collection'));
            }
        }
        else {
            // In the unlikely case something went wrong on save, the block will be
            // rebuilt and block form redisplayed.
            $this->messenger()
                ->addError($this->t('The block could not be saved.'));
            $form_state->setRebuild();
        }
    }

}