class PlaceBlockPageVariant

class PlaceBlockPageVariant extends BlockPageVariant {
    
    /**
     * The theme manager.
     *
     * @var \Drupal\Core\Theme\ThemeManagerInterface
     */
    protected $themeManager;
    
    /**
     * The redirect destination.
     *
     * @var \Drupal\Core\Routing\RedirectDestinationInterface
     */
    protected $redirectDestination;
    
    /**
     * Constructs a new PlaceBlockPageVariant.
     *
     * @param array $configuration
     *   A configuration array containing information about the plugin instance.
     * @param string $plugin_id
     *   The plugin ID for the plugin instance.
     * @param mixed $plugin_definition
     *   The plugin implementation definition.
     * @param \Drupal\block\BlockRepositoryInterface $block_repository
     *   The block repository.
     * @param \Drupal\Core\Entity\EntityViewBuilderInterface $block_view_builder
     *   The block view builder.
     * @param string[] $block_list_cache_tags
     *   The Block entity type list cache tags.
     * @param \Drupal\Core\Theme\ThemeManagerInterface $theme_manager
     *   The theme manager.
     * @param \Drupal\Core\Routing\RedirectDestinationInterface $redirect_destination
     *   The redirect destination.
     */
    public function __construct(array $configuration, $plugin_id, $plugin_definition, BlockRepositoryInterface $block_repository, EntityViewBuilderInterface $block_view_builder, array $block_list_cache_tags, ThemeManagerInterface $theme_manager, RedirectDestinationInterface $redirect_destination) {
        @trigger_error('The ' . __NAMESPACE__ . '\\PlaceBlockPageVariant is deprecated in drupal:8.8.0 and will be removed from drupal:9.0.0. See the change record for a list of alternatives. See https://www.drupal.org/node/3081957.', E_USER_DEPRECATED);
        parent::__construct($configuration, $plugin_id, $plugin_definition, $block_repository, $block_view_builder, $block_list_cache_tags);
        $this->themeManager = $theme_manager;
        $this->redirectDestination = $redirect_destination;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
        return new static($configuration, $plugin_id, $plugin_definition, $container->get('block.repository'), $container->get('entity_type.manager')
            ->getViewBuilder('block'), $container->get('entity_type.manager')
            ->getDefinition('block')
            ->getListCacheTags(), $container->get('theme.manager'), $container->get('redirect.destination'));
    }
    
    /**
     * {@inheritdoc}
     */
    public function build() {
        $build = parent::build();
        $active_theme = $this->themeManager
            ->getActiveTheme();
        $theme_name = $active_theme->getName();
        $destination = $this->redirectDestination
            ->get();
        $visible_regions = $this->getVisibleRegionNames($theme_name);
        // Build an array of the region names in the right order.
        $build += array_fill_keys(array_keys($visible_regions), []);
        foreach ($visible_regions as $region => $region_name) {
            $query = [
                'region' => $region,
            ];
            if ($destination) {
                $query['destination'] = $destination;
            }
            $title = $this->t('<span class="visually-hidden">Place block in the %region region</span>', [
                '%region' => $region_name,
            ]);
            $operations['block_description'] = [
                '#type' => 'inline_template',
                '#template' => '<div class="block-place-region">{{ link }}</div>',
                '#context' => [
                    'link' => Link::createFromRoute($title, 'block.admin_library', [
                        'theme' => $theme_name,
                    ], [
                        'query' => $query,
                        'attributes' => [
                            'title' => $title,
                            'class' => [
                                'use-ajax',
                                'button',
                                'button--small',
                            ],
                            'data-dialog-type' => 'modal',
                            'data-dialog-options' => Json::encode([
                                'width' => 700,
                            ]),
                        ],
                    ]),
                ],
            ];
            $build[$region] = [
                'block_place_operations' => $operations,
            ] + $build[$region];
        }
        $build['#attached']['library'][] = 'block_place/drupal.block_place';
        return $build;
    }
    
    /**
     * Returns the human-readable list of regions keyed by machine name.
     *
     * @param string $theme
     *   The name of the theme.
     *
     * @return array
     *   An array of human-readable region names keyed by machine name.
     */
    protected function getVisibleRegionNames($theme) {
        return system_region_list($theme, REGIONS_VISIBLE);
    }

}