authenticate method

@override Future<void> authenticate(Map<String, String> metadata, String uri)

Implementation

@override
Future<void> authenticate(Map<String, String> metadata, String uri) async {
  _accessToken = await token;
  if (_accessToken == null || uri != _lastUri) {
    try {
      await obtainAccessCredentials(uri);
      _lastUri = uri;
      _accessToken = await token;
    } catch (e) {
      throw $grpc.GrpcError.unauthenticated('Require Authentication.');
    }
  }

  if (_accessToken == null) {
    throw $grpc.GrpcError.unauthenticated('Require Authentication.');
  }
  final tokenHeaders = _tokenHeader != null
      ? _tokenHeader!(_accessToken!)
      : const <String, String>{};

  metadata.addAll(tokenHeaders);

  if (_shouldRefresh(null, _accessToken!)) {
    // Token is about to expire. Extend it prematurely.
    final authClient = http.Client();
    unawaited(_refreshToken(_accessToken, _lastUri, authClient)
        .catchError((_) {})
        .then((refreshedToken) async {
      unawaited(setToken(refreshedToken));
    }).whenComplete(() => authClient.close()));
  }
}