class EntityAdapter

class EntityAdapter extends TypedData implements \IteratorAggregate, ComplexDataInterface {
    
    /**
     * The wrapped entity object.
     *
     * @var \Drupal\Core\Entity\EntityInterface|null
     */
    protected $entity;
    
    /**
     * Creates an instance wrapping the given entity.
     *
     * @param \Drupal\Core\Entity\EntityInterface|null $entity
     *   The entity object to wrap.
     *
     * @return static
     */
    public static function createFromEntity(EntityInterface $entity) {
        $definition = EntityDataDefinition::create()->setEntityTypeId($entity->getEntityTypeId())
            ->setBundles([
            $entity->bundle(),
        ]);
        $instance = new static($definition);
        $instance->setValue($entity);
        return $instance;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getValue() {
        return $this->entity;
    }
    
    /**
     * {@inheritdoc}
     */
    public function setValue($entity, $notify = TRUE) {
        $this->entity = $entity;
        // Notify the parent of any changes.
        if ($notify && isset($this->parent)) {
            $this->parent
                ->onChange($this->name);
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function get($property_name) {
        if (!isset($this->entity)) {
            throw new MissingDataException("Unable to get property {$property_name} as no entity has been provided.");
        }
        if (!$this->entity instanceof FieldableEntityInterface) {
            throw new \InvalidArgumentException("Unable to get unknown property {$property_name}.");
        }
        // This will throw an exception for unknown fields.
        return $this->entity
            ->get($property_name);
    }
    
    /**
     * {@inheritdoc}
     */
    public function set($property_name, $value, $notify = TRUE) {
        if (!isset($this->entity)) {
            throw new MissingDataException("Unable to set property {$property_name} as no entity has been provided.");
        }
        if (!$this->entity instanceof FieldableEntityInterface) {
            throw new \InvalidArgumentException("Unable to set unknown property {$property_name}.");
        }
        // This will throw an exception for unknown fields.
        $this->entity
            ->set($property_name, $value, $notify);
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getProperties($include_computed = FALSE) {
        if (!isset($this->entity)) {
            throw new MissingDataException('Unable to get properties as no entity has been provided.');
        }
        if (!$this->entity instanceof FieldableEntityInterface) {
            return [];
        }
        return $this->entity
            ->getFields($include_computed);
    }
    
    /**
     * {@inheritdoc}
     */
    public function toArray() {
        if (!isset($this->entity)) {
            throw new MissingDataException('Unable to get property values as no entity has been provided.');
        }
        return $this->entity
            ->toArray();
    }
    
    /**
     * {@inheritdoc}
     */
    public function isEmpty() {
        return !isset($this->entity);
    }
    
    /**
     * {@inheritdoc}
     */
    public function onChange($property_name) {
        if (isset($this->entity) && $this->entity instanceof FieldableEntityInterface) {
            // Let the entity know of any changes.
            $this->entity
                ->onChange($property_name);
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function getString() {
        return isset($this->entity) ? $this->entity
            ->label() : '';
    }
    
    /**
     * {@inheritdoc}
     */
    public function applyDefaultValue($notify = TRUE) {
        // Apply the default value of all properties.
        foreach ($this->getProperties() as $property) {
            $property->applyDefaultValue(FALSE);
        }
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getIterator() : \ArrayIterator {
        return $this->entity instanceof \IteratorAggregate ? $this->entity
            ->getIterator() : new \ArrayIterator([]);
    }
    
    /**
     * Returns the wrapped entity object.
     *
     * @return \Drupal\Core\Entity\EntityInterface
     *   The wrapped entity object. If the entity is translatable and a specific
     *   translation is required, always request it by calling ::getTranslation()
     *   or ::getUntranslated() as the language of the returned object is not
     *   defined.
     */
    public function getEntity() {
        return $this->entity;
    }

}