class BlockListBuilder

class BlockListBuilder extends ConfigEntityListBuilder implements FormInterface {
    
    /**
     * The theme containing the blocks.
     *
     * @var string
     */
    protected $theme;
    
    /**
     * The current request.
     *
     * @var \Symfony\Component\HttpFoundation\Request
     */
    protected $request;
    
    /**
     * The theme manager.
     *
     * @var \Drupal\Core\Theme\ThemeManagerInterface
     */
    protected $themeManager;
    
    /**
     * The form builder.
     *
     * @var \Drupal\Core\Form\FormBuilderInterface
     */
    protected $formBuilder;
    
    /**
     * {@inheritdoc}
     */
    protected $limit = FALSE;
    
    /**
     * The messenger.
     *
     * @var \Drupal\Core\Messenger\MessengerInterface
     */
    protected $messenger;
    
    /**
     * Constructs a new BlockListBuilder object.
     *
     * @param \Drupal\Core\Entity\EntityTypeInterface $entity_type
     *   The entity type definition.
     * @param \Drupal\Core\Entity\EntityStorageInterface $storage
     *   The entity storage class.
     * @param \Drupal\Core\Theme\ThemeManagerInterface $theme_manager
     *   The theme manager.
     * @param \Drupal\Core\Form\FormBuilderInterface $form_builder
     *   The form builder.
     */
    public function __construct(EntityTypeInterface $entity_type, EntityStorageInterface $storage, ThemeManagerInterface $theme_manager, FormBuilderInterface $form_builder, MessengerInterface $messenger) {
        parent::__construct($entity_type, $storage);
        $this->themeManager = $theme_manager;
        $this->formBuilder = $form_builder;
        $this->messenger = $messenger;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function createInstance(ContainerInterface $container, EntityTypeInterface $entity_type) {
        return new static($entity_type, $container->get('entity_type.manager')
            ->getStorage($entity_type->id()), $container->get('theme.manager'), $container->get('form_builder'), $container->get('messenger'));
    }
    
    /**
     * {@inheritdoc}
     *
     * @param string|null $theme
     *   (optional) The theme to display the blocks for. If NULL, the current
     *   theme will be used.
     * @param \Symfony\Component\HttpFoundation\Request $request
     *   The current request.
     *
     * @return array
     *   The block list as a renderable array.
     */
    public function render($theme = NULL, Request $request = NULL) {
        $this->request = $request;
        $this->theme = $theme;
        return $this->formBuilder
            ->getForm($this);
    }
    
    /**
     * {@inheritdoc}
     */
    public function getFormId() {
        return 'block_admin_display_form';
    }
    
    /**
     * {@inheritdoc}
     */
    public function buildForm(array $form, FormStateInterface $form_state) {
        $form['#attached']['library'][] = 'core/drupal.tableheader';
        $form['#attached']['library'][] = 'block/drupal.block';
        $form['#attached']['library'][] = 'block/drupal.block.admin';
        $form['#attributes']['class'][] = 'clearfix';
        // Build the form tree.
        $form['blocks'] = $this->buildBlocksForm();
        $form['actions'] = [
            '#tree' => FALSE,
            '#type' => 'actions',
        ];
        $form['actions']['submit'] = [
            '#type' => 'submit',
            '#value' => $this->t('Save blocks'),
            '#button_type' => 'primary',
        ];
        return $form;
    }
    
    /**
     * Builds the main "Blocks" portion of the form.
     *
     * @return array
     */
    protected function buildBlocksForm() {
        // Build blocks first for each region.
        $blocks = [];
        $entities = $this->load();
        
        /** @var \Drupal\block\BlockInterface[] $entities */
        foreach ($entities as $entity_id => $entity) {
            $definition = $entity->getPlugin()
                ->getPluginDefinition();
            $blocks[$entity->getRegion()][$entity_id] = [
                'label' => $entity->label(),
                'entity_id' => $entity_id,
                'weight' => $entity->getWeight(),
                'entity' => $entity,
                'category' => $definition['category'],
                'status' => $entity->status(),
            ];
        }
        $form = [
            '#type' => 'table',
            '#header' => [
                $this->t('Block'),
                $this->t('Category'),
                $this->t('Region'),
                $this->t('Weight'),
                $this->t('Operations'),
            ],
            '#attributes' => [
                'id' => 'blocks',
            ],
        ];
        // Weights range from -delta to +delta, so delta should be at least half
        // of the amount of blocks present. This makes sure all blocks in the same
        // region get an unique weight.
        $weight_delta = round(count($entities) / 2);
        $placement = FALSE;
        if ($this->request->query
            ->has('block-placement')) {
            $placement = $this->request->query
                ->get('block-placement');
            $form['#attached']['drupalSettings']['blockPlacement'] = $placement;
            // Remove the block placement from the current request so that it is not
            // passed on to any redirect destinations.
            $this->request->query
                ->remove('block-placement');
        }
        // Loop over each region and build blocks.
        $regions = $this->systemRegionList($this->getThemeName(), REGIONS_VISIBLE);
        foreach ($regions as $region => $title) {
            $form['#tabledrag'][] = [
                'action' => 'match',
                'relationship' => 'sibling',
                'group' => 'block-region-select',
                'subgroup' => 'block-region-' . $region,
                'hidden' => FALSE,
            ];
            $form['#tabledrag'][] = [
                'action' => 'order',
                'relationship' => 'sibling',
                'group' => 'block-weight',
                'subgroup' => 'block-weight-' . $region,
            ];
            $form['region-' . $region] = [
                '#attributes' => [
                    'class' => [
                        'region-title',
                        'region-title-' . $region,
                    ],
                    'no_striping' => TRUE,
                ],
            ];
            $form['region-' . $region]['title'] = [
                '#theme_wrappers' => [
                    'container' => [
                        '#attributes' => [
                            'class' => 'region-title__action',
                        ],
                    ],
                ],
                '#prefix' => $title,
                '#type' => 'link',
                '#title' => $this->t('Place block <span class="visually-hidden">in the %region region</span>', [
                    '%region' => $title,
                ]),
                '#url' => Url::fromRoute('block.admin_library', [
                    'theme' => $this->getThemeName(),
                ], [
                    'query' => [
                        'region' => $region,
                    ],
                ]),
                '#wrapper_attributes' => [
                    'colspan' => 5,
                ],
                '#attributes' => [
                    'class' => [
                        'use-ajax',
                        'button',
                        'button--small',
                    ],
                    'data-dialog-type' => 'modal',
                    'data-dialog-options' => Json::encode([
                        'width' => 700,
                    ]),
                ],
            ];
            $form['region-' . $region . '-message'] = [
                '#attributes' => [
                    'class' => [
                        'region-message',
                        'region-' . $region . '-message',
                        empty($blocks[$region]) ? 'region-empty' : 'region-populated',
                    ],
                ],
            ];
            $form['region-' . $region . '-message']['message'] = [
                '#markup' => '<em>' . $this->t('No blocks in this region') . '</em>',
                '#wrapper_attributes' => [
                    'colspan' => 5,
                ],
            ];
            if (isset($blocks[$region])) {
                foreach ($blocks[$region] as $info) {
                    $entity_id = $info['entity_id'];
                    $form[$entity_id] = [
                        '#attributes' => [
                            'class' => [
                                'draggable',
                            ],
                        ],
                    ];
                    $form[$entity_id]['#attributes']['class'][] = $info['status'] ? 'block-enabled' : 'block-disabled';
                    if ($placement && $placement == Html::getClass($entity_id)) {
                        $form[$entity_id]['#attributes']['class'][] = 'color-success';
                        $form[$entity_id]['#attributes']['class'][] = 'js-block-placed';
                    }
                    $form[$entity_id]['info'] = [
                        '#plain_text' => $info['status'] ? $info['label'] : $this->t('@label (disabled)', [
                            '@label' => $info['label'],
                        ]),
                        '#wrapper_attributes' => [
                            'class' => [
                                'block',
                            ],
                        ],
                    ];
                    $form[$entity_id]['type'] = [
                        '#markup' => $info['category'],
                    ];
                    $form[$entity_id]['region-theme']['region'] = [
                        '#type' => 'select',
                        '#default_value' => $region,
                        '#required' => TRUE,
                        '#title' => $this->t('Region for @block block', [
                            '@block' => $info['label'],
                        ]),
                        '#title_display' => 'invisible',
                        '#options' => $regions,
                        '#attributes' => [
                            'class' => [
                                'block-region-select',
                                'block-region-' . $region,
                            ],
                        ],
                        '#parents' => [
                            'blocks',
                            $entity_id,
                            'region',
                        ],
                    ];
                    $form[$entity_id]['region-theme']['theme'] = [
                        '#type' => 'hidden',
                        '#value' => $this->getThemeName(),
                        '#parents' => [
                            'blocks',
                            $entity_id,
                            'theme',
                        ],
                    ];
                    $form[$entity_id]['weight'] = [
                        '#type' => 'weight',
                        '#default_value' => $info['weight'],
                        '#delta' => $weight_delta,
                        '#title' => $this->t('Weight for @block block', [
                            '@block' => $info['label'],
                        ]),
                        '#title_display' => 'invisible',
                        '#attributes' => [
                            'class' => [
                                'block-weight',
                                'block-weight-' . $region,
                            ],
                        ],
                    ];
                    $form[$entity_id]['operations'] = $this->buildOperations($info['entity']);
                }
            }
        }
        // Do not allow disabling the main system content block when it is present.
        if (isset($form['system_main']['region'])) {
            $form['system_main']['region']['#required'] = TRUE;
        }
        return $form;
    }
    
    /**
     * Gets the name of the theme used for this block listing.
     *
     * @return string
     *   The name of the theme.
     */
    protected function getThemeName() {
        // If no theme was specified, use the current theme.
        if (!$this->theme) {
            $this->theme = $this->themeManager
                ->getActiveTheme()
                ->getName();
        }
        return $this->theme;
    }
    
    /**
     * {@inheritdoc}
     */
    protected function getEntityIds() {
        return $this->getStorage()
            ->getQuery()
            ->condition('theme', $this->getThemeName())
            ->sort($this->entityType
            ->getKey('id'))
            ->execute();
    }
    
    /**
     * {@inheritdoc}
     */
    public function getDefaultOperations(EntityInterface $entity) {
        $operations = parent::getDefaultOperations($entity);
        if (isset($operations['edit'])) {
            $operations['edit']['title'] = $this->t('Configure');
        }
        if (isset($operations['delete'])) {
            $operations['delete']['title'] = $this->t('Remove');
        }
        return $operations;
    }
    
    /**
     * {@inheritdoc}
     */
    public function validateForm(array &$form, FormStateInterface $form_state) {
        // No validation.
    }
    
    /**
     * {@inheritdoc}
     */
    public function submitForm(array &$form, FormStateInterface $form_state) {
        $entities = $this->storage
            ->loadMultiple(array_keys($form_state->getValue('blocks')));
        
        /** @var \Drupal\block\BlockInterface[] $entities */
        foreach ($entities as $entity_id => $entity) {
            $entity_values = $form_state->getValue([
                'blocks',
                $entity_id,
            ]);
            $entity->setWeight($entity_values['weight']);
            $entity->setRegion($entity_values['region']);
            $entity->save();
        }
        $this->messenger
            ->addStatus($this->t('The block settings have been updated.'));
    }
    
    /**
     * Wraps system_region_list().
     */
    protected function systemRegionList($theme, $show = REGIONS_ALL) {
        return system_region_list($theme, $show);
    }

}