(Drupal 8) Convert file entities to media entities with batch update script

convert_file_to_media.install

<?php

use Drupal\media\Entity\Media;

/**
 * @file
 */

/**
 * Convert transient file entities that weren't processed during migration.
 */
function convert_file_to_media_update_8101(&$sandbox) {

  $mime_types = [
    'image/jpeg',
    'image/png',
    'image/gif',
    'application/pdf',
  ];

  if (!isset($sandbox['progress'])) {

    $fids = \Drupal::entityQuery('file')
      ->condition('uri', 'public://%', 'LIKE')
      ->condition('filemime', $mime_types, 'IN')
      ->execute();

    $sandbox['progress'] = 0;
    $sandbox['total'] = count($fids);
    $sandbox['created'] = 0;
    $sandbox['current'] = 0;
  }

  $entities_per_batch = 25;

  $fids = \Drupal::entityQuery('file')
    ->condition('uri', 'public://%', 'LIKE')
    ->condition('filemime', $mime_types, 'IN')
    ->range($sandbox['current'], $sandbox['current'] + $entities_per_batch)
    ->execute();

  foreach ($fids as $id) {
    $file = \Drupal\file\Entity\File::load($id);

    $fid = $file->id();
    $file_created = $file->getCreatedTime();
    $file_changed = $file->getChangedTime();
    $filename = $file->getFilename();
    $mimetype = $file->getMimeType();

    $bundles = ['image', 'file'];

    $query = \Drupal::entityQuery('media')
      ->condition('bundle', $bundles, 'IN');

    $orGroup = $query->orConditionGroup()
      ->condition('field_media_image', $fid)
      ->condition('field_media_file', $fid);

    $entity_ids = $query->condition($orGroup)->execute();

    if (empty($entity_ids)) {
      switch ($mimetype) {
        case 'image/jpeg':
        case 'image/png':
        case 'image/gif':

          // Create 'Image' media entity.
          $media = Media::create([
            'bundle' => 'image',
            'uid' => 1,
            'name' => $filename,
            'field_media_image' => $file,
          ]);
          $media->setCreatedTime($file_created);
          $media->setChangedTime($file_changed);
          $media->save();
          $sandbox['created']++;

          break;
        case 'application/pdf':

          // Create 'Document' media entity.
          $media = Media::create([
            'bundle' => 'file',
            'uid' => 1,
            'name' => $filename,
            'field_media_title' => $filename,
            'field_media_file' => $file,
          ]);
          $media->setCreatedTime($file_created);
          $media->setChangedTime($file_changed);
          $media->save();
          $sandbox['created']++;

          break;
      }
    }
    $sandbox['current']++;
  }

  \Drupal::logger('convert_file_to_media')->notice($sandbox['current'] . ' file entities processed. ' . $sandbox['created'] . ' media entities created.');

  if ($sandbox['total'] == 0) {
    $sandbox['#finished'] = 1;
  } else {
    $sandbox['#finished'] = ($sandbox['current'] / $sandbox['total']);
  }
}