class Entity

class Entity extends TokenizeAreaPluginBase {
    
    /**
     * Stores the entity type of the result entities.
     *
     * @var string
     */
    protected $entityType;
    
    /**
     * The entity type manager.
     *
     * @var \Drupal\Core\Entity\EntityTypeManagerInterface
     */
    protected $entityTypeManager;
    
    /**
     * The entity repository service.
     *
     * @var \Drupal\Core\Entity\EntityRepositoryInterface
     */
    protected $entityRepository;
    
    /**
     * The entity display repository.
     *
     * @var \Drupal\Core\Entity\EntityDisplayRepositoryInterface
     */
    protected $entityDisplayRepository;
    
    /**
     * Constructs a new Entity instance.
     *
     * @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\EntityRepositoryInterface $entity_repository
     *   The entity repository.
     * @param \Drupal\Core\Entity\EntityDisplayRepositoryInterface $entity_display_repository
     *   The entity display repository.
     */
    public function __construct(array $configuration, $plugin_id, $plugin_definition, EntityTypeManagerInterface $entity_type_manager, EntityRepositoryInterface $entity_repository, EntityDisplayRepositoryInterface $entity_display_repository) {
        parent::__construct($configuration, $plugin_id, $plugin_definition);
        $this->entityTypeManager = $entity_type_manager;
        $this->entityRepository = $entity_repository;
        $this->entityDisplayRepository = $entity_display_repository;
    }
    
    /**
     * {@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.repository'), $container->get('entity_display.repository'));
    }
    
    /**
     * {@inheritdoc}
     */
    public function init(ViewExecutable $view, DisplayPluginBase $display, array &$options = NULL) {
        parent::init($view, $display, $options);
        $this->entityType = $this->definition['entity_type'];
    }
    
    /**
     * {@inheritdoc}
     */
    protected function defineOptions() {
        $options = parent::defineOptions();
        // Per default we enable tokenize, as this is the most common use case for
        // this handler.
        $options['tokenize']['default'] = TRUE;
        // Contains the config target identifier for the entity.
        $options['target'] = [
            'default' => '',
        ];
        $options['view_mode'] = [
            'default' => 'default',
        ];
        $options['bypass_access'] = [
            'default' => FALSE,
        ];
        return $options;
    }
    
    /**
     * {@inheritdoc}
     */
    public function buildOptionsForm(&$form, FormStateInterface $form_state) {
        parent::buildOptionsForm($form, $form_state);
        $form['view_mode'] = [
            '#type' => 'select',
            '#options' => $this->entityDisplayRepository
                ->getViewModeOptions($this->entityType),
            '#title' => $this->t('View mode'),
            '#default_value' => $this->options['view_mode'],
        ];
        $label = $this->entityTypeManager
            ->getDefinition($this->entityType)
            ->getLabel();
        $target = $this->options['target'];
        // If the target does not contain tokens, try to load the entity and
        // display the entity ID to the admin form user.
        // @todo Use a method to check for tokens in
        //   https://www.drupal.org/node/2396607.
        if (strpos($this->options['target'], '{{') === FALSE) {
            // @todo If the entity does not exist, this will show the config target
            //   identifier. Decide if this is the correct behavior in
            //   https://www.drupal.org/node/2415391.
            if ($target_entity = $this->entityRepository
                ->loadEntityByConfigTarget($this->entityType, $this->options['target'])) {
                $target = $target_entity->id();
            }
        }
        $form['target'] = [
            '#title' => $this->t('@entity_type_label ID', [
                '@entity_type_label' => $label,
            ]),
            '#type' => 'textfield',
            '#default_value' => $target,
        ];
        $form['bypass_access'] = [
            '#type' => 'checkbox',
            '#title' => $this->t('Bypass access checks'),
            '#description' => $this->t('If enabled, access permissions for rendering the entity are not checked.'),
            '#default_value' => !empty($this->options['bypass_access']),
        ];
    }
    
    /**
     * {@inheritdoc}
     */
    public function submitOptionsForm(&$form, FormStateInterface $form_state) {
        parent::submitOptionsForm($form, $form_state);
        // Load the referenced entity and store its config target identifier if
        // the target does not contains tokens.
        // @todo Use a method to check for tokens in
        //   https://www.drupal.org/node/2396607.
        $options = $form_state->getValue('options');
        if (strpos($options['target'], '{{') === FALSE) {
            if ($entity = $this->entityTypeManager
                ->getStorage($this->entityType)
                ->load($options['target'])) {
                $options['target'] = $entity->getConfigTarget();
            }
            $form_state->setValue('options', $options);
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function render($empty = FALSE) {
        if (!$empty || !empty($this->options['empty'])) {
            // @todo Use a method to check for tokens in
            //   https://www.drupal.org/node/2396607.
            if (strpos($this->options['target'], '{{') !== FALSE) {
                // We cast as we need the integer/string value provided by the
                // ::tokenizeValue() call.
                $target_id = (string) $this->tokenizeValue($this->options['target']);
                if ($entity = $this->entityTypeManager
                    ->getStorage($this->entityType)
                    ->load($target_id)) {
                    $target_entity = $entity;
                }
            }
            else {
                if ($entity = $this->entityRepository
                    ->loadEntityByConfigTarget($this->entityType, $this->options['target'])) {
                    $target_entity = $entity;
                }
            }
            if (isset($target_entity) && (!empty($this->options['bypass_access']) || $target_entity->access('view'))) {
                $view_builder = $this->entityTypeManager
                    ->getViewBuilder($this->entityType);
                return $view_builder->view($target_entity, $this->options['view_mode']);
            }
        }
        return [];
    }
    
    /**
     * {@inheritdoc}
     */
    public function calculateDependencies() {
        $dependencies = parent::calculateDependencies();
        // Ensure that we don't add dependencies for placeholders.
        // @todo Use a method to check for tokens in
        //   https://www.drupal.org/node/2396607.
        if (strpos($this->options['target'], '{{') === FALSE) {
            if ($entity = $this->entityRepository
                ->loadEntityByConfigTarget($this->entityType, $this->options['target'])) {
                $dependencies[$this->entityTypeManager
                    ->getDefinition($this->entityType)
                    ->getConfigDependencyKey()][] = $entity->getConfigDependencyName();
            }
        }
        return $dependencies;
    }

}