class FileTestForm

class FileTestForm extends FormBase {
  use FileTestFormTrait;
  use StringTranslationTrait;
  
  /**
   * {@inheritdoc}
   */
  public function getFormId() : string {
    return '_file_test_form';
  }
  
  /**
   * {@inheritdoc}
   */
  public function buildForm(array $form, FormStateInterface $form_state) : array {
    $form = $this->baseForm($form, $form_state);
    $form['file_test_upload'] = [
      '#type' => 'file',
      '#title' => $this->t('Upload a file'),
    ];
    return $form;
  }
  
  /**
   * {@inheritdoc}
   */
  public function submitForm(array &$form, FormStateInterface $form_state) : void {
    // Process the upload and perform validation. Note: we're using the
    // form value for the $replace parameter.
    if (!$form_state->isValueEmpty('file_subdir')) {
      $destination = 'temporary://' . $form_state->getValue('file_subdir');
      \Drupal::service('file_system')->prepareDirectory($destination, FileSystemInterface::CREATE_DIRECTORY);
    }
    else {
      $destination = FALSE;
    }
    // Setup validators.
    $validators = [];
    if ($form_state->getValue('is_image_file')) {
      $validators['FileIsImage'] = [];
    }
    $allow = $form_state->getValue('allow_all_extensions');
    if ($allow === 'empty_array') {
      $validators['FileExtension'] = [];
    }
    elseif ($allow === 'empty_string') {
      $validators['FileExtension'] = [
        'extensions' => '',
      ];
    }
    elseif (!$form_state->isValueEmpty('extensions')) {
      $validators['FileExtension'] = [
        'extensions' => $form_state->getValue('extensions'),
      ];
    }
    // The test for \Drupal::service('file_system')->moveUploadedFile()
    // triggering a warning is unavoidable. We're interested in what happens
    // afterwards in file_save_upload().
    if (\Drupal::state()->get('file_test.disable_error_collection')) {
      define('SIMPLETEST_COLLECT_ERRORS', FALSE);
    }
    $file = file_save_upload('file_test_upload', $validators, $destination, 0, static::fileExistsFromName($form_state->getValue('file_test_replace')));
    if ($file) {
      $form_state->setValue('file_test_upload', $file);
      \Drupal::messenger()->addStatus($this->t('File @filepath was uploaded.', [
        '@filepath' => $file->getFileUri(),
      ]));
      \Drupal::messenger()->addStatus($this->t('File name is @filename.', [
        '@filename' => $file->getFilename(),
      ]));
      \Drupal::messenger()->addStatus($this->t('File MIME type is @mimetype.', [
        '@mimetype' => $file->getMimeType(),
      ]));
      \Drupal::messenger()->addStatus($this->t('You WIN!'));
    }
    elseif ($file === FALSE) {
      \Drupal::messenger()->addError($this->t('Epic upload FAIL!'));
    }
  }
  
  /**
   * Get a FileExists enum from its name.
   */
  protected static function fileExistsFromName(string $name) : FileExists {
    return match ($name) {  FileExists::Replace->name => FileExists::Replace,
      FileExists::Error->name => FileExists::Error,
      default => FileExists::Rename,
    
    };
  }

}