class FieldBlock

class FieldBlock extends BlockBase implements ContextAwarePluginInterface, ContainerFactoryPluginInterface {
    
    /**
     * The entity field manager.
     *
     * @var \Drupal\Core\Entity\EntityFieldManagerInterface
     */
    protected $entityFieldManager;
    
    /**
     * The formatter manager.
     *
     * @var \Drupal\Core\Field\FormatterPluginManager
     */
    protected $formatterManager;
    
    /**
     * The entity type ID.
     *
     * @var string
     */
    protected $entityTypeId;
    
    /**
     * The bundle ID.
     *
     * @var string
     */
    protected $bundle;
    
    /**
     * The field name.
     *
     * @var string
     */
    protected $fieldName;
    
    /**
     * The field definition.
     *
     * @var \Drupal\Core\Field\FieldDefinitionInterface
     */
    protected $fieldDefinition;
    
    /**
     * The module handler.
     *
     * @var \Drupal\Core\Extension\ModuleHandlerInterface
     */
    protected $moduleHandler;
    
    /**
     * The logger.
     *
     * @var \Psr\Log\LoggerInterface
     */
    protected $logger;
    
    /**
     * Constructs a new FieldBlock.
     *
     * @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\Core\Entity\EntityFieldManagerInterface $entity_field_manager
     *   The entity field manager.
     * @param \Drupal\Core\Field\FormatterPluginManager $formatter_manager
     *   The formatter manager.
     * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
     *   The module handler.
     * @param \Psr\Log\LoggerInterface $logger
     *   The logger.
     */
    public function __construct(array $configuration, $plugin_id, $plugin_definition, EntityFieldManagerInterface $entity_field_manager, FormatterPluginManager $formatter_manager, ModuleHandlerInterface $module_handler, LoggerInterface $logger) {
        $this->entityFieldManager = $entity_field_manager;
        $this->formatterManager = $formatter_manager;
        $this->moduleHandler = $module_handler;
        $this->logger = $logger;
        // Get the entity type and field name from the plugin ID.
        list(, $entity_type_id, $bundle, $field_name) = explode(static::DERIVATIVE_SEPARATOR, $plugin_id, 4);
        $this->entityTypeId = $entity_type_id;
        $this->bundle = $bundle;
        $this->fieldName = $field_name;
        parent::__construct($configuration, $plugin_id, $plugin_definition);
    }
    
    /**
     * {@inheritdoc}
     */
    public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
        return new static($configuration, $plugin_id, $plugin_definition, $container->get('entity_field.manager'), $container->get('plugin.manager.field.formatter'), $container->get('module_handler'), $container->get('logger.channel.layout_builder'));
    }
    
    /**
     * Gets the entity that has the field.
     *
     * @return \Drupal\Core\Entity\FieldableEntityInterface
     *   The entity.
     */
    protected function getEntity() {
        return $this->getContextValue('entity');
    }
    
    /**
     * {@inheritdoc}
     */
    public function build() {
        $display_settings = $this->getConfiguration()['formatter'];
        $display_settings['third_party_settings']['layout_builder']['view_mode'] = $this->getContextValue('view_mode');
        $entity = $this->getEntity();
        try {
            $build = $entity->get($this->fieldName)
                ->view($display_settings);
        } catch (EnforcedResponseException $e) {
            throw $e;
        } catch (\Exception $e) {
            $build = [];
            $this->logger
                ->warning('The field "%field" failed to render with the error of "%error".', [
                '%field' => $this->fieldName,
                '%error' => $e->getMessage(),
            ]);
        }
        CacheableMetadata::createFromRenderArray($build)->addCacheableDependency($this)
            ->applyTo($build);
        return $build;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getPreviewFallbackString() {
        return new TranslatableMarkup('"@field" field', [
            '@field' => $this->getFieldDefinition()
                ->getLabel(),
        ]);
    }
    
    /**
     * {@inheritdoc}
     */
    protected function blockAccess(AccountInterface $account) {
        $entity = $this->getEntity();
        // First consult the entity.
        $access = $entity->access('view', $account, TRUE);
        if (!$access->isAllowed()) {
            return $access;
        }
        // Check that the entity in question has this field.
        if (!$entity instanceof FieldableEntityInterface || !$entity->hasField($this->fieldName)) {
            return $access->andIf(AccessResult::forbidden());
        }
        // Check field access.
        $field = $entity->get($this->fieldName);
        $access = $access->andIf($field->access('view', $account, TRUE));
        if (!$access->isAllowed()) {
            return $access;
        }
        // Check to see if the field has any values.
        if ($field->isEmpty()) {
            return $access->andIf(AccessResult::forbidden());
        }
        return $access;
    }
    
    /**
     * {@inheritdoc}
     */
    public function defaultConfiguration() {
        return [
            'label_display' => FALSE,
            'formatter' => [
                'label' => 'above',
                'type' => $this->pluginDefinition['default_formatter'],
                'settings' => [],
                'third_party_settings' => [],
            ],
        ];
    }
    
    /**
     * {@inheritdoc}
     */
    public function blockForm($form, FormStateInterface $form_state) {
        $config = $this->getConfiguration();
        $form['formatter'] = [
            '#tree' => TRUE,
            '#process' => [
                [
                    $this,
                    'formatterSettingsProcessCallback',
                ],
            ],
        ];
        $form['formatter']['label'] = [
            '#type' => 'select',
            '#title' => $this->t('Label'),
            // @todo This is directly copied from
            //   \Drupal\field_ui\Form\EntityViewDisplayEditForm::getFieldLabelOptions(),
            //   resolve this in https://www.drupal.org/project/drupal/issues/2933924.
'#options' => [
                'above' => $this->t('Above'),
                'inline' => $this->t('Inline'),
                'hidden' => '- ' . $this->t('Hidden') . ' -',
                'visually_hidden' => '- ' . $this->t('Visually Hidden') . ' -',
            ],
            '#default_value' => $config['formatter']['label'],
        ];
        $form['formatter']['type'] = [
            '#type' => 'select',
            '#title' => $this->t('Formatter'),
            '#options' => $this->getApplicablePluginOptions($this->getFieldDefinition()),
            '#required' => TRUE,
            '#default_value' => $config['formatter']['type'],
            '#ajax' => [
                'callback' => [
                    static::class,
                    'formatterSettingsAjaxCallback',
                ],
                'wrapper' => 'formatter-settings-wrapper',
            ],
        ];
        // Add the formatter settings to the form via AJAX.
        $form['formatter']['settings_wrapper'] = [
            '#prefix' => '<div id="formatter-settings-wrapper">',
            '#suffix' => '</div>',
        ];
        return $form;
    }
    
    /**
     * Render API callback: builds the formatter settings elements.
     */
    public function formatterSettingsProcessCallback(array &$element, FormStateInterface $form_state, array &$complete_form) {
        if ($formatter = $this->getFormatter($element['#parents'], $form_state)) {
            $element['settings_wrapper']['settings'] = $formatter->settingsForm($complete_form, $form_state);
            $element['settings_wrapper']['settings']['#parents'] = array_merge($element['#parents'], [
                'settings',
            ]);
            $element['settings_wrapper']['third_party_settings'] = $this->thirdPartySettingsForm($formatter, $this->getFieldDefinition(), $complete_form, $form_state);
            $element['settings_wrapper']['third_party_settings']['#parents'] = array_merge($element['#parents'], [
                'third_party_settings',
            ]);
            FormHelper::rewriteStatesSelector($element['settings_wrapper'], "fields[{$this->fieldName}][settings_edit_form]", 'settings[formatter]');
            // Store the array parents for our element so that we can retrieve the
            // formatter settings in our AJAX callback.
            $form_state->set('field_block_array_parents', $element['#array_parents']);
        }
        return $element;
    }
    
    /**
     * Adds the formatter third party settings forms.
     *
     * @param \Drupal\Core\Field\FormatterInterface $plugin
     *   The formatter.
     * @param \Drupal\Core\Field\FieldDefinitionInterface $field_definition
     *   The field definition.
     * @param array $form
     *   The (entire) configuration form array.
     * @param \Drupal\Core\Form\FormStateInterface $form_state
     *   The form state.
     *
     * @return array
     *   The formatter third party settings form.
     */
    protected function thirdPartySettingsForm(FormatterInterface $plugin, FieldDefinitionInterface $field_definition, array $form, FormStateInterface $form_state) {
        $settings_form = [];
        // Invoke hook_field_formatter_third_party_settings_form(), keying resulting
        // subforms by module name.
        foreach ($this->moduleHandler
            ->getImplementations('field_formatter_third_party_settings_form') as $module) {
            $settings_form[$module] = $this->moduleHandler
                ->invoke($module, 'field_formatter_third_party_settings_form', [
                $plugin,
                $field_definition,
                EntityDisplayBase::CUSTOM_MODE,
                $form,
                $form_state,
            ]);
        }
        return $settings_form;
    }
    
    /**
     * Render API callback: gets the layout settings elements.
     */
    public static function formatterSettingsAjaxCallback(array $form, FormStateInterface $form_state) {
        $formatter_array_parents = $form_state->get('field_block_array_parents');
        return NestedArray::getValue($form, array_merge($formatter_array_parents, [
            'settings_wrapper',
        ]));
    }
    
    /**
     * {@inheritdoc}
     */
    public function blockSubmit($form, FormStateInterface $form_state) {
        $this->configuration['formatter'] = $form_state->getValue('formatter');
    }
    
    /**
     * Gets the field definition.
     *
     * @return \Drupal\Core\Field\FieldDefinitionInterface
     *   The field definition.
     */
    protected function getFieldDefinition() {
        if (empty($this->fieldDefinition)) {
            $field_definitions = $this->entityFieldManager
                ->getFieldDefinitions($this->entityTypeId, $this->bundle);
            $this->fieldDefinition = $field_definitions[$this->fieldName];
        }
        return $this->fieldDefinition;
    }
    
    /**
     * Returns an array of applicable formatter options for a field.
     *
     * @param \Drupal\Core\Field\FieldDefinitionInterface $field_definition
     *   The field definition.
     *
     * @return array
     *   An array of applicable formatter options.
     *
     * @see \Drupal\field_ui\Form\EntityDisplayFormBase::getApplicablePluginOptions()
     */
    protected function getApplicablePluginOptions(FieldDefinitionInterface $field_definition) {
        $options = $this->formatterManager
            ->getOptions($field_definition->getType());
        $applicable_options = [];
        foreach ($options as $option => $label) {
            $plugin_class = DefaultFactory::getPluginClass($option, $this->formatterManager
                ->getDefinition($option));
            if ($plugin_class::isApplicable($field_definition)) {
                $applicable_options[$option] = $label;
            }
        }
        return $applicable_options;
    }
    
    /**
     * Gets the formatter object.
     *
     * @param array $parents
     *   The #parents of the element representing the formatter.
     * @param \Drupal\Core\Form\FormStateInterface $form_state
     *   The current state of the form.
     *
     * @return \Drupal\Core\Field\FormatterInterface
     *   The formatter object.
     */
    protected function getFormatter(array $parents, FormStateInterface $form_state) {
        // Use the processed values, if available.
        $configuration = NestedArray::getValue($form_state->getValues(), $parents);
        if (!$configuration) {
            // Next check the raw user input.
            $configuration = NestedArray::getValue($form_state->getUserInput(), $parents);
            if (!$configuration) {
                // If no user input exists, use the default values.
                $configuration = $this->getConfiguration()['formatter'];
            }
        }
        return $this->formatterManager
            ->getInstance([
            'configuration' => $configuration,
            'field_definition' => $this->getFieldDefinition(),
            'view_mode' => EntityDisplayBase::CUSTOM_MODE,
            'prepare' => TRUE,
        ]);
    }

}