class BooleanItemNormalizer

class BooleanItemNormalizer extends FieldItemNormalizer implements DenormalizerInterface {
  
  /**
   * {@inheritdoc}
   */
  public function normalize($object, $format = NULL, array $context = []) : array|string|int|float|bool|\ArrayObject|null {
    $data = parent::normalize($object, $format, $context);
    $data['value'] = $data['value'] ? '👍' : '👎';
    return $data;
  }
  
  /**
   * {@inheritdoc}
   */
  protected function constructValue($data, $context) {
    // Just like \Drupal\serialization\Normalizer\FieldItemNormalizer's logic
    // for denormalization, which uses TypedDataInterface::setValue(), allow the
    // keying by main property name ("value") to be implied.
    if (!is_array($data)) {
      $data = [
        'value' => $data,
      ];
    }
    if (!in_array($data['value'], [
      '👍',
      '👎',
    ], TRUE)) {
      throw new \UnexpectedValueException('Only 👍 and 👎 are acceptable values.');
    }
    $data['value'] = $data['value'] === '👍';
    return $data;
  }
  
  /**
   * {@inheritdoc}
   */
  public function getSupportedTypes(?string $format) : array {
    return [
      BooleanItem::class => TRUE,
    ];
  }

}