class MediaForm

class MediaForm extends ContentEntityForm {
  
  /**
   * {@inheritdoc}
   */
  public function form(array $form, FormStateInterface $form_state) {
    $form = parent::form($form, $form_state);
    /** @var \Drupal\media\MediaTypeInterface $media_type */
    $media_type = $this->entity->bundle->entity;
    if ($this->operation === 'edit') {
      $form['#title'] = $this->t('Edit %type_label @label', [
        '%type_label' => $media_type->label(),
        '@label' => $this->entity
          ->label(),
      ]);
    }
    // Media author information for administrators.
    if (isset($form['uid']) || isset($form['created'])) {
      $form['author'] = [
        '#type' => 'details',
        '#title' => $this->t('Authoring information'),
        '#group' => 'advanced',
        '#attributes' => [
          'class' => [
            'media-form-author',
          ],
        ],
        '#weight' => 90,
        '#optional' => TRUE,
      ];
    }
    if (isset($form['uid'])) {
      $form['uid']['#group'] = 'author';
    }
    if (isset($form['created'])) {
      $form['created']['#group'] = 'author';
    }
    $form['#attached']['library'][] = 'media/form';
    return $form;
  }
  
  /**
   * {@inheritdoc}
   */
  public function save(array $form, FormStateInterface $form_state) {
    $saved = parent::save($form, $form_state);
    $context = [
      '@type' => $this->entity
        ->bundle(),
      '%label' => $this->entity
        ->label(),
      'link' => $this->entity
        ->toLink($this->t('View'))
        ->toString(),
    ];
    $logger = $this->logger('media');
    $t_args = [
      '@type' => $this->entity->bundle->entity
        ->label(),
      '%label' => $this->entity
        ->toLink($this->entity
        ->label())
        ->toString(),
    ];
    if ($saved === SAVED_NEW) {
      $logger->notice('@type: added %label.', $context);
      $this->messenger()
        ->addStatus($this->t('@type %label has been created.', $t_args));
    }
    else {
      $logger->notice('@type: updated %label.', $context);
      $this->messenger()
        ->addStatus($this->t('@type %label has been updated.', $t_args));
    }
    // Redirect the user to the media overview if the user has the 'access media
    // overview' permission. If not, redirect to the canonical URL of the media
    // item.
    if ($this->currentUser()
      ->hasPermission('access media overview')) {
      $form_state->setRedirectUrl($this->entity
        ->toUrl('collection'));
    }
    else {
      $form_state->setRedirectUrl($this->entity
        ->toUrl());
    }
    return $saved;
  }

}