class FieldConfig

class FieldConfig extends FieldConfigBase implements FieldConfigInterface {
    
    /**
     * Flag indicating whether the field is deleted.
     *
     * The delete() method marks the field as "deleted" and removes the
     * corresponding entry from the config storage, but keeps its definition in
     * the state storage while field data is purged by a separate
     * garbage-collection process.
     *
     * Deleted fields stay out of the regular entity lifecycle (notably, their
     * values are not populated in loaded entities, and are not saved back).
     *
     * @var bool
     */
    protected $deleted = FALSE;
    
    /**
     * The associated FieldStorageConfig entity.
     *
     * @var \Drupal\field\Entity\FieldStorageConfig
     */
    protected $fieldStorage;
    
    /**
     * Constructs a FieldConfig object.
     *
     * In most cases, Field entities are created via
     * FieldConfig::create($values), where $values is the same
     * parameter as in this constructor.
     *
     * @param array $values
     *   An array of field properties, keyed by property name. The
     *   storage associated with the field can be specified either with:
     *   - field_storage: the FieldStorageConfigInterface object,
     *   or by referring to an existing field storage in the current configuration
     *   with:
     *   - field_name: The field name.
     *   - entity_type: The entity type.
     *   Additionally, a 'bundle' property is required to indicate the entity
     *   bundle to which the field is attached to. Other array elements will be
     *   used to set the corresponding properties on the class; see the class
     *   property documentation for details.
     */
    public function __construct(array $values, $entity_type = 'field_config') {
        // Allow either an injected FieldStorageConfig object, or a field_name and
        // entity_type.
        if (isset($values['field_storage'])) {
            if (!$values['field_storage'] instanceof FieldStorageConfigInterface) {
                throw new FieldException('Attempt to create a configurable field for a non-configurable field storage.');
            }
            $field_storage = $values['field_storage'];
            $values['field_name'] = $field_storage->getName();
            $values['entity_type'] = $field_storage->getTargetEntityTypeId();
            // The internal property is fieldStorage, not field_storage.
            unset($values['field_storage']);
            $values['fieldStorage'] = $field_storage;
        }
        else {
            if (empty($values['field_name'])) {
                throw new FieldException('Attempt to create a field without a field_name.');
            }
            if (empty($values['entity_type'])) {
                throw new FieldException("Attempt to create a field '{$values['field_name']}' without an entity_type.");
            }
        }
        // 'bundle' is required in either case.
        if (empty($values['bundle'])) {
            throw new FieldException("Attempt to create a field '{$values['field_name']}' without a bundle.");
        }
        parent::__construct($values, $entity_type);
    }
    
    /**
     * {@inheritdoc}
     */
    public function postCreate(EntityStorageInterface $storage) {
        parent::postCreate($storage);
        // Validate that we have a valid storage for this field. This throws an
        // exception if the storage is invalid.
        $this->getFieldStorageDefinition();
        // 'Label' defaults to the field name (mostly useful for fields created in
        // tests).
        if (empty($this->label)) {
            $this->label = $this->getName();
        }
    }
    
    /**
     * Overrides \Drupal\Core\Entity\Entity::preSave().
     *
     * @throws \Drupal\Core\Field\FieldException
     *   If the field definition is invalid.
     * @throws \Drupal\Core\Entity\EntityStorageException
     *   In case of failures at the configuration storage level.
     */
    public function preSave(EntityStorageInterface $storage) {
        $field_type_manager = \Drupal::service('plugin.manager.field.field_type');
        $storage_definition = $this->getFieldStorageDefinition();
        // Filter out unknown settings and make sure all settings are present, so
        // that a complete field definition is passed to the various hooks and
        // written to config.
        $default_settings = $field_type_manager->getDefaultFieldSettings($storage_definition->getType());
        $this->settings = array_intersect_key($this->settings, $default_settings) + $default_settings;
        if ($this->isNew()) {
            // Notify the entity storage.
            \Drupal::service('field_definition.listener')->onFieldDefinitionCreate($this);
        }
        else {
            // Some updates are always disallowed.
            if ($this->entity_type != $this->original->entity_type) {
                throw new FieldException("Cannot change an existing field's entity_type.");
            }
            if ($this->bundle != $this->original->bundle) {
                throw new FieldException("Cannot change an existing field's bundle.");
            }
            if ($storage_definition->uuid() != $this->original
                ->getFieldStorageDefinition()
                ->uuid()) {
                throw new FieldException("Cannot change an existing field's storage.");
            }
            // Notify the entity storage.
            \Drupal::service('field_definition.listener')->onFieldDefinitionUpdate($this, $this->original);
        }
        parent::preSave($storage);
    }
    
    /**
     * {@inheritdoc}
     */
    public function calculateDependencies() {
        parent::calculateDependencies();
        // Mark the field_storage_config as a dependency.
        $this->addDependency('config', $this->getFieldStorageDefinition()
            ->getConfigDependencyName());
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function preDelete(EntityStorageInterface $storage, array $fields) {
        
        /** @var \Drupal\Core\Field\DeletedFieldsRepositoryInterface $deleted_fields_repository */
        $deleted_fields_repository = \Drupal::service('entity_field.deleted_fields_repository');
        $entity_type_manager = \Drupal::entityTypeManager();
        parent::preDelete($storage, $fields);
        // Keep the field definitions in the deleted fields repository so we can use
        // them later during field_purge_batch().
        
        /** @var \Drupal\field\FieldConfigInterface $field */
        foreach ($fields as $field) {
            // Only mark a field for purging if there is data. Otherwise, just remove
            // it.
            $target_entity_storage = $entity_type_manager->getStorage($field->getTargetEntityTypeId());
            if (!$field->deleted && $target_entity_storage instanceof FieldableEntityStorageInterface && $target_entity_storage->countFieldData($field->getFieldStorageDefinition(), TRUE)) {
                $field = clone $field;
                $field->deleted = TRUE;
                $field->fieldStorage = NULL;
                $deleted_fields_repository->addFieldDefinition($field);
            }
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public static function postDelete(EntityStorageInterface $storage, array $fields) {
        // Clear the cache upfront, to refresh the results of getBundles().
        \Drupal::service('entity_field.manager')->clearCachedFieldDefinitions();
        // Notify the entity storage.
        foreach ($fields as $field) {
            if (!$field->deleted) {
                \Drupal::service('field_definition.listener')->onFieldDefinitionDelete($field);
            }
        }
        // If this is part of a configuration synchronization then the following
        // configuration updates are not necessary.
        $entity = reset($fields);
        if ($entity->isSyncing()) {
            return;
        }
        // Delete the associated field storages if they are not used anymore and are
        // not persistent.
        $storages_to_delete = [];
        foreach ($fields as $field) {
            $storage_definition = $field->getFieldStorageDefinition();
            if (!$field->deleted && !$field->isUninstalling() && $storage_definition->isDeletable()) {
                // Key by field UUID to avoid deleting the same storage twice.
                $storages_to_delete[$storage_definition->uuid()] = $storage_definition;
            }
        }
        if ($storages_to_delete) {
            \Drupal::entityTypeManager()->getStorage('field_storage_config')
                ->delete($storages_to_delete);
        }
    }
    
    /**
     * {@inheritdoc}
     */
    protected function linkTemplates() {
        $link_templates = parent::linkTemplates();
        if (\Drupal::moduleHandler()->moduleExists('field_ui')) {
            $link_templates["{$this->entity_type}-field-edit-form"] = 'entity.field_config.' . $this->entity_type . '_field_edit_form';
            $link_templates["{$this->entity_type}-storage-edit-form"] = 'entity.field_config.' . $this->entity_type . '_storage_edit_form';
            $link_templates["{$this->entity_type}-field-delete-form"] = 'entity.field_config.' . $this->entity_type . '_field_delete_form';
            if (isset($link_templates['config-translation-overview'])) {
                $link_templates["config-translation-overview.{$this->entity_type}"] = "entity.field_config.config_translation_overview.{$this->entity_type}";
            }
        }
        return $link_templates;
    }
    
    /**
     * {@inheritdoc}
     */
    protected function urlRouteParameters($rel) {
        $parameters = parent::urlRouteParameters($rel);
        $entity_type = \Drupal::entityTypeManager()->getDefinition($this->entity_type);
        $bundle_parameter_key = $entity_type->getBundleEntityType() ?: 'bundle';
        $parameters[$bundle_parameter_key] = $this->bundle;
        return $parameters;
    }
    
    /**
     * {@inheritdoc}
     */
    public function isDeleted() {
        return $this->deleted;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getFieldStorageDefinition() {
        if (!$this->fieldStorage) {
            $field_storage_definition = NULL;
            $field_storage_definitions = \Drupal::service('entity_field.manager')->getFieldStorageDefinitions($this->entity_type);
            if (isset($field_storage_definitions[$this->field_name])) {
                $field_storage_definition = $field_storage_definitions[$this->field_name];
            }
            elseif ($this->deleted) {
                $deleted_storage_definitions = \Drupal::service('entity_field.deleted_fields_repository')->getFieldStorageDefinitions();
                foreach ($deleted_storage_definitions as $deleted_storage_definition) {
                    if ($deleted_storage_definition->getName() === $this->field_name) {
                        $field_storage_definition = $deleted_storage_definition;
                    }
                }
            }
            if (!$field_storage_definition) {
                throw new FieldException("Attempt to create a field {$this->field_name} that does not exist on entity type {$this->entity_type}.");
            }
            if (!$field_storage_definition instanceof FieldStorageConfigInterface) {
                throw new FieldException("Attempt to create a configurable field of non-configurable field storage {$this->field_name}.");
            }
            $this->fieldStorage = $field_storage_definition;
        }
        return $this->fieldStorage;
    }
    
    /**
     * {@inheritdoc}
     */
    public function isDisplayConfigurable($context) {
        return TRUE;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getDisplayOptions($display_context) {
        // Hide configurable fields by default.
        return [
            'region' => 'hidden',
        ];
    }
    
    /**
     * {@inheritdoc}
     */
    public function isReadOnly() {
        return FALSE;
    }
    
    /**
     * {@inheritdoc}
     */
    public function isComputed() {
        return FALSE;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getUniqueIdentifier() {
        return $this->uuid();
    }
    
    /**
     * Loads a field config entity based on the entity type and field name.
     *
     * @param string $entity_type_id
     *   ID of the entity type.
     * @param string $bundle
     *   Bundle name.
     * @param string $field_name
     *   Name of the field.
     *
     * @return static
     *   The field config entity if one exists for the provided field
     *   name, otherwise NULL.
     */
    public static function loadByName($entity_type_id, $bundle, $field_name) {
        return \Drupal::entityTypeManager()->getStorage('field_config')
            ->load($entity_type_id . '.' . $bundle . '.' . $field_name);
    }

}