class BlockContent

class BlockContent extends TabTypeBase {
    use StringTranslationTrait;
    
    /**
     * {@inheritdoc}
     */
    public function optionsForm(array $tab) {
        $plugin_id = $this->getPluginDefinition()['id'];
        $form = [];
        $form['bid'] = [
            '#type' => 'select',
            '#options' => $this->getBlockOptions(),
            '#default_value' => isset($tab['content'][$plugin_id]['options']['bid']) ? $tab['content'][$plugin_id]['options']['bid'] : '',
            '#title' => $this->t('Select a block'),
            '#ajax' => [
                'callback' => [
                    $this,
                    'blockTitleAjaxCallback',
                ],
                'event' => 'change',
                'progress' => [
                    'type' => 'throbber',
                    'message' => 'Please wait...',
                ],
                'effect' => 'fade',
            ],
        ];
        $form['block_title'] = [
            '#type' => 'textfield',
            '#default_value' => isset($tab['content'][$plugin_id]['options']['block_title']) ? $tab['content'][$plugin_id]['options']['block_title'] : '',
            '#title' => $this->t('Block Title'),
            '#prefix' => '<div id="block-title-textfield-' . $tab['delta'] . '">',
            '#suffix' => '</div>',
        ];
        $form['display_title'] = [
            '#type' => 'checkbox',
            '#title' => $this->t('Display block title'),
            '#default_value' => isset($tab['content'][$plugin_id]['options']['display_title']) ? $tab['content'][$plugin_id]['options']['display_title'] : 0,
        ];
        return $form;
    }
    
    /**
     * {@inheritdoc}
     */
    public function render(array $tab) {
        $options = $tab['content'][$tab['type']]['options'];
        if (strpos($options['bid'], 'block_content') !== FALSE) {
            $parts = explode(':', $options['bid']);
            $entity_repository = \Drupal::service('entity.repository');
            $block = $entity_repository->loadEntityByUuid($parts[0], $parts[1]);
            $entityTypeManager = \Drupal::entityTypeManager();
            $block_content = $entityTypeManager->getStorage('block_content')
                ->load($block->id());
            $render = $entityTypeManager->getViewBuilder('block_content')
                ->view($block_content);
        }
        else {
            $block_manager = \Drupal::service('plugin.manager.block');
            // You can hard code configuration or you load from settings.
            $config = [];
            $plugin_block = $block_manager->createInstance($options['bid'], $config);
            // Some blocks might implement access check.
            $access_result = $plugin_block->access(\Drupal::currentUser(), TRUE);
            // Return empty render array if user doesn't have access.
            if ($access_result->isForbidden()) {
                return [];
            }
            $render = $plugin_block->build();
        }
        return $render;
    }
    
    /**
     * Get options for the block.
     */
    private function getBlockOptions() {
        $block_manager = \Drupal::service('plugin.manager.block');
        $context_repository = \Drupal::service('context.repository');
        // Only add blocks which work without any available context.
        $definitions = $block_manager->getDefinitionsForContexts($context_repository->getAvailableContexts());
        // Order by category, and then by admin label.
        $definitions = $block_manager->getSortedDefinitions($definitions);
        $blocks = [];
        foreach ($definitions as $block_id => $definition) {
            $blocks[$block_id] = $definition['admin_label'] . ' (' . $definition['provider'] . ')';
        }
        return $blocks;
    }
    
    /**
     * Ajax callback to change block title when block is selected.
     */
    public function blockTitleAjaxCallback(array &$form, FormStateInterface $form_state) {
        $tab_index = $form_state->getTriggeringElement()['#array_parents'][2];
        $element_id = '#block-title-textfield-' . $tab_index;
        $selected_block = $form_state->getValue('configuration_data')[$tab_index]['content']['block_content']['options']['bid'];
        $block_manager = \Drupal::service('plugin.manager.block');
        $context_repository = \Drupal::service('context.repository');
        $definitions = $block_manager->getDefinitionsForContexts($context_repository->getAvailableContexts());
        $form['block_title'] = [
            '#type' => 'textfield',
            '#value' => $definitions[$selected_block]['admin_label'],
            '#title' => $this->t('Block Title'),
            '#prefix' => '<div id="block-title-textfield-' . $tab_index . '">',
            '#suffix' => '</div>',
        ];
        $form_state->setRebuild(TRUE);
        $ajax_response = new AjaxResponse();
        $ajax_response->addCommand(new ReplaceCommand($element_id, $form['block_title']));
        return $ajax_response;
    }

}