Credentials handleAccessTokenResponse()

in lib/src/handle_access_token_response.dart [33:110]
66 lines of code
16 McCabe index (conditional complexity)

Credentials handleAccessTokenResponse(http.Response response, Uri tokenEndpoint,
    DateTime startTime, List<String>? scopes, String delimiter,
    {Map<String, dynamic> Function(MediaType? contentType, String body)?
        getParameters}) {
  getParameters ??= parseJsonParameters;

  try {
    if (response.statusCode != 200) {
      _handleErrorResponse(response, tokenEndpoint, getParameters);
    }

    var contentTypeString = response.headers['content-type'];
    if (contentTypeString == null) {
      throw FormatException('Missing Content-Type string.');
    }

    var parameters =
        getParameters(MediaType.parse(contentTypeString), response.body);

    for (var requiredParameter in ['access_token', 'token_type']) {
      if (!parameters.containsKey(requiredParameter)) {
        throw FormatException(
            'did not contain required parameter "$requiredParameter"');
      } else if (parameters[requiredParameter] is! String) {
        throw FormatException(
            'required parameter "$requiredParameter" was not a string, was '
            '"${parameters[requiredParameter]}"');
      }
    }

    // TODO(nweiz): support the "mac" token type
    // (http://tools.ietf.org/html/draft-ietf-oauth-v2-http-mac-01)
    if (parameters['token_type'].toLowerCase() != 'bearer') {
      throw FormatException(
          '"$tokenEndpoint": unknown token type "${parameters['token_type']}"');
    }

    var expiresIn = parameters['expires_in'];
    if (expiresIn != null) {
      if (expiresIn is String) {
        try {
          expiresIn = double.parse(expiresIn).toInt();
        } on FormatException {
          throw FormatException(
              'parameter "expires_in" could not be parsed as in, was: "$expiresIn"');
        }
      } else if (expiresIn is! int) {
        throw FormatException(
            'parameter "expires_in" was not an int, was: "$expiresIn"');
      }
    }

    for (var name in ['refresh_token', 'id_token', 'scope']) {
      var value = parameters[name];
      if (value != null && value is! String) {
        throw FormatException(
            'parameter "$name" was not a string, was "$value"');
      }
    }

    var scope = parameters['scope'] as String?;
    if (scope != null) scopes = scope.split(delimiter);

    var expiration = expiresIn == null
        ? null
        : startTime.add(Duration(seconds: expiresIn) - _expirationGrace);

    return Credentials(parameters['access_token'],
        refreshToken: parameters['refresh_token'],
        idToken: parameters['id_token'],
        tokenEndpoint: tokenEndpoint,
        scopes: scopes,
        expiration: expiration);
  } on FormatException catch (e) {
    throw FormatException('Invalid OAuth response for "$tokenEndpoint": '
        '${e.message}.\n\n${response.body}');
  }
}