Future<AuthToken> exchange(String authCodeString, String clientID, String clientSecret, { int expirationInSeconds: 3600 })

Exchanges a valid authorization code for an AuthToken.

If the authorization code has not expired, has not been used, matches the client ID, and the client secret is correct, it will return a valid AuthToken. Otherwise, it will throw an appropriate AuthRequestError.

Source 

Future<AuthToken> exchange(
    String authCodeString, String clientID, String clientSecret,
    {int expirationInSeconds: 3600}) async {
  if (clientID == null) {
    throw new AuthServerException(AuthRequestError.invalidClient, null);
  }

  AuthClient client = await clientForID(clientID);
  if (client == null) {
    throw new AuthServerException(AuthRequestError.invalidClient, null);
  }

  if (authCodeString == null) {
    throw new AuthServerException(AuthRequestError.invalidRequest, null);
  }

  if (clientSecret == null) {
    throw new AuthServerException(AuthRequestError.invalidClient, client);
  }

  if (client.hashedSecret != hashPassword(clientSecret, client.salt)) {
    throw new AuthServerException(AuthRequestError.invalidClient, client);
  }

  AuthCode authCode = await storage.fetchAuthCodeByCode(this, authCodeString);
  if (authCode == null) {
    throw new AuthServerException(AuthRequestError.invalidGrant, client);
  }

  // check if valid still
  if (authCode.isExpired) {
    await storage.revokeAuthCodeWithCode(this, authCode.code);
    throw new AuthServerException(AuthRequestError.invalidGrant, client);
  }

  // check that client ids match
  if (authCode.clientID != client.id) {
    throw new AuthServerException(AuthRequestError.invalidGrant, client);
  }

  // check to see if has already been used
  if (authCode.hasBeenExchanged) {
    await storage.revokeTokenIssuedFromCode(this, authCode);

    throw new AuthServerException(AuthRequestError.invalidGrant, client);
  }
  AuthToken token = _generateToken(
      authCode.resourceOwnerIdentifier, client.id, expirationInSeconds, scopes: authCode.requestedScopes);
  await storage.storeToken(this, token, issuedFrom: authCode);

  return token;
}