class FieldLink

class FieldLink extends ProcessPluginBase {
  
  /**
   * {@inheritdoc}
   */
  public function __construct(array $configuration, $plugin_id, $plugin_definition, MigrationInterface $migration) {
    $configuration += [
      'uri_scheme' => 'http://',
    ];
    parent::__construct($configuration, $plugin_id, $plugin_definition);
  }
  
  /**
   * Turn a Drupal 6/7 URI into a Drupal 8-compatible format.
   *
   * @param string $uri
   *   The 'url' value from Drupal 6/7.
   *
   * @return string
   *   The Drupal 8-compatible URI.
   *
   * @see \Drupal\link\Plugin\Field\FieldWidget\LinkWidget::getUserEnteredStringAsUri()
   */
  protected function canonicalizeUri($uri) {
    // If the path starts with 2 slashes then it is always considered an
    // external URL without an explicit protocol part.
    // @todo Remove this when https://www.drupal.org/node/2744729 lands.
    if (str_starts_with($uri, '//')) {
      return $this->configuration['uri_scheme'] . ltrim($uri, '/');
    }
    // If we already have a scheme, we're fine.
    if (parse_url($uri, PHP_URL_SCHEME)) {
      return $uri;
    }
    // Empty URI and non-links are allowed.
    if (empty($uri) || in_array($uri, [
      '<nolink>',
      '<none>',
    ])) {
      return 'route:<nolink>';
    }
    // Remove the <front> component of the URL.
    if (str_starts_with($uri, '<front>')) {
      $uri = substr($uri, strlen('<front>'));
    }
    else {
      // List of unicode-encoded characters that were allowed in URLs,
      // according to link module in Drupal 7. Every character between &#x00BF;
      // and &#x00FF; (except × &#x00D7; and ÷ &#x00F7;) with the addition of
      // &#x0152;, &#x0153; and &#x0178;.
      // @see https://git.drupalcode.org/project/link/blob/7.x-1.5-beta2/link.module#L1382
      // cSpell:disable-next-line
      $link_i_chars = '¿ÀÁÂÃÄÅÆÇÈÉÊËÌÍÎÏÐÑÒÓÔÕÖØÙÚÛÜÝÞßàáâãäåæçèéêëìíîïðñòóôõöøùúûüýþÿŒœŸ';
      // Pattern specific to internal links.
      $internal_pattern = "/^(?:[a-z0-9" . $link_i_chars . "_\\-+\\[\\] ]+)";
      $directories = "(?:\\/[a-z0-9" . $link_i_chars . "_\\-\\.~+%=&,\$'#!():;*@\\[\\]]*)*";
      // Yes, four backslashes == a single backslash.
      $query = "(?:\\/?\\?([?a-z0-9" . $link_i_chars . "+_|\\-\\.~\\/\\\\%=&,\$'():;*@\\[\\]{} ]*))";
      $anchor = "(?:#[a-z0-9" . $link_i_chars . "_\\-\\.~+%=&,\$'():;*@\\[\\]\\/\\?]*)";
      // The rest of the path for a standard URL.
      $end = $directories . '?' . $query . '?' . $anchor . '?$/i';
      if (!preg_match($internal_pattern . $end, $uri)) {
        $link_domains = '[a-z][a-z0-9-]{1,62}';
        // Starting a parenthesis group with (?: means that it is grouped, but is not captured
        $authentication = "(?:(?:(?:[\\w\\.\\-\\+!\$&'\\(\\)*\\+,;=" . $link_i_chars . "]|%[0-9a-f]{2})+(?::(?:[\\w" . $link_i_chars . "\\.\\-\\+%!\$&'\\(\\)*\\+,;=]|%[0-9a-f]{2})*)?)?@)";
        $domain = '(?:(?:[a-z0-9' . $link_i_chars . ']([a-z0-9' . $link_i_chars . '\\-_\\[\\]])*)(\\.(([a-z0-9' . $link_i_chars . '\\-_\\[\\]])+\\.)*(' . $link_domains . '|[a-z]{2}))?)';
        $ipv4 = '(?:[0-9]{1,3}(\\.[0-9]{1,3}){3})';
        $ipv6 = '(?:[0-9a-fA-F]{1,4}(\\:[0-9a-fA-F]{1,4}){7})';
        $port = '(?::([0-9]{1,5}))';
        // Pattern specific to external links.
        $external_pattern = '/^' . $authentication . '?(' . $domain . '|' . $ipv4 . '|' . $ipv6 . ' |localhost)' . $port . '?';
        if (preg_match($external_pattern . $end, $uri)) {
          return $this->configuration['uri_scheme'] . $uri;
        }
      }
    }
    // Add the internal: scheme and ensure a leading slash.
    return 'internal:/' . ltrim($uri, '/');
  }
  
  /**
   * {@inheritdoc}
   */
  public function transform($value, MigrateExecutableInterface $migrate_executable, Row $row, $destination_property) {
    $attributes = unserialize($value['attributes']);
    // Drupal 6/7 link attributes might be double serialized.
    if (!is_array($attributes)) {
      $attributes = unserialize($attributes);
    }
    // In rare cases Drupal 6/7 link attributes are triple serialized. To avoid
    // further problems with them we set them to an empty array in this case.
    if (!is_array($attributes)) {
      $attributes = [];
    }
    // Massage the values into the correct form for the link.
    $route['uri'] = $this->canonicalizeUri($value['url']);
    $route['options']['attributes'] = $attributes;
    $route['title'] = $value['title'];
    return $route;
  }

}