EmaDocumentFile.php

<?php

namespace Drupal\ema_document\Plugin\media\Source;

use Drupal\media\MediaInterface;
use Drupal\media\MediaSourceBase;

/**
 * EMA file entity media source.
 *
 * @see \Drupal\file\FileInterface
 *
 * @MediaSource(
 *   id = "ema_document_file",
 *   label = @Translation("EMA Document File"),
 *   description = @Translation("Embed EMA document files."),
 *   allowed_field_types = {"string_long"}
 * )
 */
class EmaDocumentFile extends MediaSourceBase {

  /**
   * {@inheritdoc}
   */
  public function getMetadataAttributes() {
    return [
      'title' => $this->t('Resource Title'),
      'published' => $this->t('Published date'),
      'updated' => $this->t('Updated date'),
    ];
  }

  /**
   * {@inheritdoc}
   */
  public function getMetadata(MediaInterface $media, $attribute_name) {
    // Get the text_long field where the JSON object is stored.
    $remote_field = $media->get($this->configuration['source_field']);
    $json_arr = json_decode($remote_field->value);
    // If the source field is not required, it may be empty.
    if (!$remote_field) {
      return parent::getMetadata($media, $attribute_name);
    }
    return $json_arr->$attribute_name ?? parent::getMetadata($media, $attribute_name);
  }

}