class Html

class Html implements FormatInterface {
  use MessengerTrait;

  /**
   * Returns base64 encoded data that is safe for use in xml ids.
   */
  protected function encodeIdSafeBase64($data) {

    // Prefix with a b to enforce that the first character is a letter.
    return 'b' . rtrim(strtr(base64_encode($data), '+/', '-_'), '=');
  }

  /**
   * Returns decoded id safe base64 data.
   */
  protected function decodeIdSafeBase64($data) {

    // Remove prefixed b.
    $data = substr($data, 1);
    return base64_decode(str_pad(strtr($data, '-_', '+/'), strlen($data) % 4, '=', STR_PAD_RIGHT));
  }

  /**
   * Implements TMGMTFileExportInterface::export().
   */
  public function export(JobInterface $job, $conditions = array()) {
    $items = array();
    foreach ($job
      ->getItems($conditions) as $item) {
      $data = \Drupal::service('tmgmt.data')
        ->filterTranslatable($item
        ->getData());
      foreach ($data as $key => $value) {
        $items[$item
          ->id()][$this
          ->encodeIdSafeBase64($item
          ->id() . '][' . $key)] = $value;
      }
    }
    $elements = array(
      '#theme' => 'tmgmt_file_html_template',
      '#tjid' => $job
        ->id(),
      '#source_language' => $job
        ->getRemoteSourceLanguage(),
      '#target_language' => $job
        ->getRemoteTargetLanguage(),
      '#items' => $items,
    );
    return \Drupal::service('renderer')
      ->renderPlain($elements);
  }

  /**
   * Implements TMGMTFileExportInterface::import().
   */
  public function import($imported_file, $is_file = TRUE) {
    $dom = new \DOMDocument();
    $is_file ? $dom
      ->loadHTMLFile($imported_file) : $dom
      ->loadHTML($imported_file);
    $xml = simplexml_import_dom($dom);
    $data = array();
    foreach ($xml
      ->xpath("//div[@class='atom']") as $atom) {

      // Assets are our strings (eq fields in nodes).
      $key = $this
        ->decodeIdSafeBase64((string) $atom['id']);
      $data[$key]['#text'] = (string) $atom;
    }
    return \Drupal::service('tmgmt.data')
      ->unflatten($data);
  }

  /**
   * {@inheritdoc}
   */
  public function validateImport($imported_file, $is_file = TRUE) {
    $dom = new \DOMDocument();
    if (!$dom
      ->loadHTMLFile($imported_file)) {
      return FALSE;
    }
    $xml = simplexml_import_dom($dom);

    // Collect meta information.
    $meta_tags = $xml
      ->xpath('//meta');
    $meta = array();
    foreach ($meta_tags as $meta_tag) {
      $meta[(string) $meta_tag['name']] = (string) $meta_tag['content'];
    }

    // Check required meta tags.
    foreach (array(
      'JobID',
      'languageSource',
      'languageTarget',
    ) as $name) {
      if (!isset($meta[$name])) {
        return FALSE;
      }
    }

    // Attempt to load the job.
    if (!($job = Job::load($meta['JobID']))) {
      \Drupal::messenger()
        ->addError(t('The imported file job id @file_id is not available.', array(
        '@file_id' => $meta['JobID'],
      )));
      return FALSE;
    }

    // Check language.
    if ($meta['languageSource'] != $job
      ->getRemoteSourceLanguage() || $meta['languageTarget'] != $job
      ->getRemoteTargetLanguage()) {
      return FALSE;
    }

    // Validation successful.
    return $job;
  }

}