class Entity

class Entity extends ArgumentValidatorPluginBase {
    
    /**
     * The entity type manager.
     *
     * @var \Drupal\Core\Entity\EntityTypeManagerInterface
     */
    protected $entityTypeManager;
    
    /**
     * The entity bundle info.
     *
     * @var \Drupal\Core\Entity\EntityTypeBundleInfoInterface
     */
    protected $entityTypeBundleInfo;
    
    /**
     * If this validator can handle multiple arguments.
     *
     * @var bool
     */
    protected $multipleCapable = TRUE;
    
    /**
     * Constructs a \Drupal\views\Plugin\views\argument_validator\Entity object.
     *
     * @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\EntityTypeBundleInfoInterface $entity_type_bundle_info
     *   The entity type bundle info.
     */
    public function __construct(array $configuration, $plugin_id, $plugin_definition, EntityTypeManagerInterface $entity_type_manager, EntityTypeBundleInfoInterface $entity_type_bundle_info) {
        parent::__construct($configuration, $plugin_id, $plugin_definition);
        $this->entityTypeManager = $entity_type_manager;
        $this->entityTypeBundleInfo = $entity_type_bundle_info;
    }
    
    /**
     * {@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_type.bundle.info'));
    }
    
    /**
     * {@inheritdoc}
     */
    protected function defineOptions() {
        $options = parent::defineOptions();
        $options['bundles'] = [
            'default' => [],
        ];
        $options['access'] = [
            'default' => FALSE,
        ];
        $options['operation'] = [
            'default' => 'view',
        ];
        $options['multiple'] = [
            'default' => FALSE,
        ];
        return $options;
    }
    
    /**
     * {@inheritdoc}
     */
    public function buildOptionsForm(&$form, FormStateInterface $form_state) {
        parent::buildOptionsForm($form, $form_state);
        $entity_type_id = $this->definition['entity_type'];
        // Derivative IDs are all entity:entity_type. Sanitized for js.
        // The ID is converted back on submission.
        $sanitized_id = ArgumentPluginBase::encodeValidatorId($this->definition['id']);
        $entity_type = $this->entityTypeManager
            ->getDefinition($entity_type_id);
        // If the entity has bundles, allow option to restrict to bundle(s).
        if ($entity_type->hasKey('bundle')) {
            $bundle_options = [];
            foreach ($this->entityTypeBundleInfo
                ->getBundleInfo($entity_type_id) as $bundle_id => $bundle_info) {
                $bundle_options[$bundle_id] = $bundle_info['label'];
            }
            $form['bundles'] = [
                '#title' => $entity_type->getBundleLabel() ?: $this->t('Bundles'),
                '#default_value' => $this->options['bundles'],
                '#type' => 'checkboxes',
                '#options' => $bundle_options,
                '#description' => $this->t('If none are selected, all are allowed.'),
            ];
        }
        // Offer the option to filter by access to the entity in the argument.
        $form['access'] = [
            '#type' => 'checkbox',
            '#title' => $this->t('Validate user has access to the %name', [
                '%name' => $entity_type->getLabel(),
            ]),
            '#default_value' => $this->options['access'],
        ];
        $form['operation'] = [
            '#type' => 'radios',
            '#title' => $this->t('Access operation to check'),
            '#options' => [
                'view' => $this->t('View'),
                'update' => $this->t('Edit'),
                'delete' => $this->t('Delete'),
            ],
            '#default_value' => $this->options['operation'],
            '#states' => [
                'visible' => [
                    ':input[name="options[validate][options][' . $sanitized_id . '][access]"]' => [
                        'checked' => TRUE,
                    ],
                ],
            ],
        ];
        // If class is multiple capable give the option to validate single/multiple.
        if ($this->multipleCapable) {
            $form['multiple'] = [
                '#type' => 'radios',
                '#title' => $this->t('Multiple arguments'),
                '#options' => [
                    0 => $this->t('Single ID', [
                        '%type' => $entity_type->getLabel(),
                    ]),
                    1 => $this->t('One or more IDs separated by , or +', [
                        '%type' => $entity_type->getLabel(),
                    ]),
                ],
                '#default_value' => (string) $this->options['multiple'],
            ];
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function submitOptionsForm(&$form, FormStateInterface $form_state, &$options = []) {
        // Filter out unused options so we don't store giant unnecessary arrays.
        // Note that the bundles form option doesn't appear on the form if the
        // entity type doesn't support bundles, so the option may not be set.
        if (!empty($options['bundles'])) {
            $options['bundles'] = array_filter($options['bundles']);
        }
        else {
            // Set bundles back to its default empty value.
            $options['bundles'] = [];
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function validateArgument($argument) {
        $entity_type = $this->definition['entity_type'];
        if ($this->multipleCapable && $this->options['multiple'] && isset($argument)) {
            // At this point only interested in individual IDs no matter what type,
            // just splitting by the allowed delimiters.
            $ids = array_filter(preg_split('/[,+ ]/', $argument));
        }
        elseif ($argument) {
            $ids = [
                $argument,
            ];
        }
        else {
            return FALSE;
        }
        $entities = $this->entityTypeManager
            ->getStorage($entity_type)
            ->loadMultiple($ids);
        // Validate each id => entity. If any fails break out and return false.
        foreach ($ids as $id) {
            // There is no entity for this ID.
            if (!isset($entities[$id])) {
                return FALSE;
            }
            if (!$this->validateEntity($entities[$id])) {
                return FALSE;
            }
        }
        return TRUE;
    }
    
    /**
     * Validates an individual entity against class access settings.
     *
     * @param \Drupal\Core\Entity\EntityInterface $entity
     *   The entity.
     *
     * @return bool
     *   True if validated.
     */
    protected function validateEntity(EntityInterface $entity) {
        // If access restricted by entity operation.
        if ($this->options['access'] && !$entity->access($this->options['operation'])) {
            return FALSE;
        }
        // If restricted by bundle.
        $bundles = $this->options['bundles'];
        if (!empty($bundles) && empty($bundles[$entity->bundle()])) {
            return FALSE;
        }
        return TRUE;
    }
    
    /**
     * {@inheritdoc}
     */
    public function calculateDependencies() {
        $dependencies = parent::calculateDependencies();
        $entity_type_id = $this->definition['entity_type'];
        $bundle_entity_type = $this->entityTypeManager
            ->getDefinition($entity_type_id)
            ->getBundleEntityType();
        // The bundle entity type might not exist. For example, users do not have
        // bundles.
        if ($this->entityTypeManager
            ->hasHandler($bundle_entity_type, 'storage')) {
            $bundle_entity_storage = $this->entityTypeManager
                ->getStorage($bundle_entity_type);
            foreach ($bundle_entity_storage->loadMultiple(array_keys($this->options['bundles'])) as $bundle_entity) {
                $dependencies[$bundle_entity->getConfigDependencyKey()][] = $bundle_entity->getConfigDependencyName();
            }
        }
        return $dependencies;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getContextDefinition() {
        return EntityContextDefinition::fromEntityTypeId($this->definition['entity_type'])
            ->setLabel($this->argument
            ->adminLabel())
            ->setRequired(FALSE);
    }

}