getMediaImageSourceFieldName example

  public function mediaEntityMetadata(Request $request) {
    $uuid = $request->query->get('uuid');
    if (!$uuid || !Uuid::isValid($uuid)) {
      throw new BadRequestHttpException();
    }
    // Access is enforced on route level.     // @see \Drupal\ckeditor5\Controller\CKEditor5MediaController::access().     if (!$media = $this->entityRepository->loadEntityByUuid('media', $uuid)) {
      throw new NotFoundHttpException();
    }
    $image_field = $this->getMediaImageSourceFieldName($media);
    $response = [];
    $response['type'] = $media->bundle();
    // If this uses the image media source and the "alt" field is enabled,     // expose additional metadata.     // @see \Drupal\media\Plugin\media\Source\Image     // @see core/modules/ckeditor5/js/ckeditor5_plugins/drupalMedia/src/mediaimagetextalternative/mediaimagetextalternativeui.js     if ($image_field) {
      $settings = $media->{$image_field}->getItemDefinition()->getSettings();
      if (!empty($settings['alt_field'])) {
        $response['imageSourceMetadata'] = [
          'alt' => $this->entityRepository->getTranslationFromContext($media)->{$image_field}->alt,
        ];

$filter_caption = $filters->get('filter_caption');
    $media_embed_filter = $filters->get('media_embed');

    $allowed_attributes = [];
    if ($filter_html->status) {
      $restrictions = $filter_html->getHTMLRestrictions();
      $allowed_attributes = $restrictions['allowed']['drupal-media'];
    }

    $media = $this->entityRepository->loadEntityByUuid('media', $media_embed_element['data-entity-uuid']);

    if ($image_field_name = $this->getMediaImageSourceFieldName($media)) {
      // We'll want the alt text from the same language as the host.       if (!empty($editor_object['hostEntityLangcode']) && $media->hasTranslation($editor_object['hostEntityLangcode'])) {
        $media = $media->getTranslation($editor_object['hostEntityLangcode']);
      }
      $settings = $media->{$image_field_name}->getItemDefinition()->getSettings();
      $alt = $media_embed_element['alt'] ?? NULL;
      $form['alt'] = [
        '#type' => 'textfield',
        '#title' => $this->t('Alternate text'),
        '#default_value' => $alt,
        '#description' => $this->t('Short description of the image used by screen readers and displayed when the image is not loaded. This is important for accessibility.'),