class EntityField

class EntityField extends BlockBase implements ContextAwarePluginInterface, ContainerFactoryPluginInterface {
    
    /**
     * The entity type manager.
     *
     * @var \Drupal\Core\Entity\EntityTypeManagerInterface
     */
    protected $entityTypeManager;
    
    /**
     * The entity field manager.
     *
     * @var \Drupal\Core\Entity\EntityFieldManagerInterface
     */
    protected $entityFieldManager;
    
    /**
     * The field type manager.
     *
     * @var \Drupal\Core\Field\FieldTypePluginManagerInterface
     */
    protected $fieldTypeManager;
    
    /**
     * The formatter manager.
     *
     * @var \Drupal\Core\Field\FormatterPluginManager
     */
    protected $formatterManager;
    
    /**
     * The entity type id.
     *
     * @var string
     */
    protected $entityTypeId;
    
    /**
     * The field name.
     *
     * @var string
     */
    protected $fieldName;
    
    /**
     * The field definition.
     *
     * @var \Drupal\Core\Field\FieldDefinitionInterface
     */
    protected $fieldDefinition;
    
    /**
     * The field storage definition.
     *
     * @var \Drupal\Core\Field\FieldStorageDefinitionInterface
     */
    protected $fieldStorageDefinition;
    
    /**
     * Constructs a new EntityField.
     *
     * @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\EntityTypeManagerInterface $entity_type_manager
     *   The entity type manager.
     * @param \Drupal\Core\Entity\EntityFieldManagerInterface $entity_field_manager
     *   The entity field manager.
     * @param \Drupal\Core\Field\FieldTypePluginManagerInterface $field_type_manager
     *   The field type manager.
     * @param \Drupal\Core\Field\FormatterPluginManager $formatter_manager
     *   The formatter manager.
     */
    public function __construct(array $configuration, $plugin_id, $plugin_definition, EntityTypeManagerInterface $entity_type_manager, EntityFieldManagerInterface $entity_field_manager, FieldTypePluginManagerInterface $field_type_manager, FormatterPluginManager $formatter_manager) {
        $this->entityTypeManager = $entity_type_manager;
        $this->entityFieldManager = $entity_field_manager;
        $this->fieldTypeManager = $field_type_manager;
        $this->formatterManager = $formatter_manager;
        // Get the entity type and field name from the plugin id.
        [
            ,
            $entity_type_id,
            $field_name,
        ] = explode(':', $plugin_id);
        $this->entityTypeId = $entity_type_id;
        $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_type.manager'), $container->get('entity_field.manager'), $container->get('plugin.manager.field.field_type'), $container->get('plugin.manager.field.formatter'));
    }
    
    /**
     * {@inheritdoc}
     */
    public function build() {
        
        /** @var \Drupal\Core\Entity\FieldableEntityInterface $entity */
        $entity = $this->getContextValue('entity');
        $build = [];
        
        /** @var \Drupal\Core\Field\FieldItemListInterface $field */
        $field = $entity->{$this->fieldName};
        $display_settings = $this->getConfiguration()['formatter'];
        $build['field'] = $field->view($display_settings);
        // Set the cache data appropriately.
        $build['#cache']['contexts'] = $this->getCacheContexts();
        $build['#cache']['tags'] = $this->getCacheTags();
        $build['#cache']['max-age'] = $this->getCacheMaxAge();
        return $build;
    }
    
    /**
     * {@inheritdoc}
     */
    protected function blockAccess(AccountInterface $account) {
        
        /** @var \Drupal\Core\Entity\EntityInterface $entity */
        $entity = $this->getContextValue('entity');
        // Make sure we have access to the entity.
        $access = $entity->access('view', $account, TRUE);
        if ($access->isAllowed()) {
            // Check that the entity in question has this field.
            if ($entity instanceof FieldableEntityInterface && $entity->hasField($this->fieldName)) {
                // Check field access.
                $field_access = $this->entityTypeManager
                    ->getAccessControlHandler($this->entityTypeId)
                    ->fieldAccess('view', $this->getFieldDefinition(), $account);
                if ($field_access) {
                    // Build a renderable array for the field.
                    $build = $entity->get($this->fieldName)
                        ->view($this->configuration['formatter']);
                    // If there are actual renderable children, grant access.
                    if (Element::children($build)) {
                        return AccessResult::allowed();
                    }
                }
            }
            // Entity doesn't have this field, so access is denied.
            return AccessResult::forbidden();
        }
        // If we don't have access to the entity, return the forbidden result.
        return $access;
    }
    
    /**
     * {@inheritdoc}
     */
    public function defaultConfiguration() {
        $field_type_definition = $this->getFieldTypeDefinition();
        return [
            'formatter' => [
                'label' => 'above',
                'type' => $field_type_definition['default_formatter'] ?? '',
                'settings' => [],
                'third_party_settings' => [],
                'weight' => 0,
            ],
        ];
    }
    
    /**
     * {@inheritdoc}
     */
    public function blockForm($form, FormStateInterface $form_state) {
        $config = $this->getConfiguration();
        $form['formatter_label'] = [
            '#type' => 'select',
            '#title' => $this->t('Label'),
            '#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->getFormatterOptions(),
            '#default_value' => $config['formatter']['type'],
            '#ajax' => [
                'callback' => [
                    static::class,
                    'formatterSettingsAjaxCallback',
                ],
                'wrapper' => 'formatter-settings-wrapper',
                'effect' => 'fade',
            ],
        ];
        // Add the formatter settings to the form via AJAX.
        $form['#process'][] = [
            $this,
            'formatterSettingsProcessCallback',
        ];
        $form['formatter_settings_wrapper'] = [
            '#prefix' => '<div id="formatter-settings-wrapper">',
            '#suffix' => '</div>',
        ];
        $form['formatter_settings_wrapper']['formatter_settings'] = [
            '#tree' => TRUE,
        ];
        return $form;
    }
    
    /**
     * Render API callback: builds the formatter settings elements.
     */
    public function formatterSettingsProcessCallback(array &$element, FormStateInterface $form_state, array &$complete_form) {
        $config = $this->getConfiguration();
        $parents_base = $element['#parents'];
        $formatter_parent = array_merge($parents_base, [
            'formatter_type',
        ]);
        $formatter_settings_parent = array_merge($parents_base, [
            'formatter_settings',
        ]);
        $settings_element =& $element['formatter_settings_wrapper']['formatter_settings'];
        // Set the #parents on the formatter_settings so they end up as a peer to
        // formatter_type.
        $settings_element['#parents'] = $formatter_settings_parent;
        // Get the formatter name in a way that works regardless of whether we're
        // getting the value via AJAX or not.
        $formatter_name = NestedArray::getValue($form_state->getUserInput(), $formatter_parent) ?: $element['formatter_type']['#default_value'];
        // Place the formatter settings on the form if a formatter is selected.
        $formatter = $this->getFormatter($formatter_name, $form_state->getValue('formatter_label'), $form_state->getValue($formatter_settings_parent, $config['formatter']['settings']), $config['formatter']['third_party_settings']);
        $settings_element = array_merge($formatter->settingsForm($settings_element, $form_state), $settings_element);
        // Store the array parents for our element so that we can use it to pull out
        // the formatter settings in our AJAX callback.
        $complete_form['#formatter_array_parents'] = $element['#array_parents'];
        return $element;
    }
    
    /**
     * Render API callback: gets the layout settings elements.
     */
    public static function formatterSettingsAjaxCallback(array $form, FormStateInterface $form_state) {
        $formatter_array_parents = $form['#formatter_array_parents'];
        return NestedArray::getValue($form, array_merge($formatter_array_parents, [
            'formatter_settings_wrapper',
        ]));
    }
    
    /**
     * {@inheritdoc}
     */
    public function blockSubmit($form, FormStateInterface $form_state) {
        $this->configuration['formatter']['label'] = $form_state->getValue('formatter_label');
        $this->configuration['formatter']['type'] = $form_state->getValue('formatter_type');
        // @todo Remove this manual cast after https://www.drupal.org/node/2635236
        //   is resolved.
        $this->configuration['formatter']['settings'] = (array) $form_state->getValue('formatter_settings');
    }
    
    /**
     * Gets the field definition.
     *
     * @return \Drupal\Core\Field\FieldDefinitionInterface
     *   The field definition.
     */
    protected function getFieldDefinition() {
        if (empty($this->fieldDefinition)) {
            $field_map = $this->entityFieldManager
                ->getFieldMap();
            $bundle = reset($field_map[$this->entityTypeId][$this->fieldName]['bundles']);
            $field_definitions = $this->entityFieldManager
                ->getFieldDefinitions($this->entityTypeId, $bundle);
            $this->fieldDefinition = $field_definitions[$this->fieldName];
        }
        return $this->fieldDefinition;
    }
    
    /**
     * Gets the field storage definition.
     *
     * @return \Drupal\Core\Field\FieldStorageDefinitionInterface
     *   The field storage definition.
     */
    protected function getFieldStorageDefinition() {
        if (empty($this->fieldStorageDefinition)) {
            // Some base fields have no storage.
            $field_definitions = array_merge($this->entityFieldManager
                ->getBaseFieldDefinitions($this->entityTypeId), $this->entityFieldManager
                ->getFieldStorageDefinitions($this->entityTypeId));
            $this->fieldStorageDefinition = $field_definitions[$this->fieldName];
        }
        return $this->fieldStorageDefinition;
    }
    
    /**
     * Gets field type definition.
     *
     * @return array
     *   The field type definition.
     */
    protected function getFieldTypeDefinition() {
        return $this->fieldTypeManager
            ->getDefinition($this->getFieldStorageDefinition()
            ->getType());
    }
    
    /**
     * Gets the formatter options for this field type.
     *
     * @return array
     *   The formatter options.
     */
    protected function getFormatterOptions() {
        return $this->formatterManager
            ->getOptions($this->getFieldStorageDefinition()
            ->getType());
    }
    
    /**
     * Gets the formatter object.
     *
     * @param string $type
     *   The formatter name.
     * @param string $label
     *   The label option for the formatter.
     * @param array $settings
     *   The formatter settings.
     * @param array $third_party_settings
     *   The formatter third party settings.
     *
     * @return \Drupal\Core\Field\FormatterInterface
     *   The formatter object.
     */
    protected function getFormatter($type, $label, array $settings, array $third_party_settings) {
        return $this->formatterManager
            ->createInstance($type, [
            'field_definition' => $this->getFieldDefinition(),
            'view_mode' => 'default',
            'prepare' => TRUE,
            'label' => $label,
            'settings' => $settings,
            'third_party_settings' => $third_party_settings,
        ]);
    }
    
    /**
     * {@inheritdoc}
     */
    public function __wakeup() {
        parent::__wakeup();
        // @todo figure out why this happens.
        // prevent $fieldStorageDefinition being erroneously set to $this.
        $this->fieldStorageDefinition = NULL;
    }

}