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->info('@type: added %label.', $context);
            $this->messenger()
                ->addStatus($this->t('@type %label has been created.', $t_args));
        }
        else {
            $logger->info('@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;
    }

}