public virtual async Task StartWithSrpAuthAsync()

in src/Amazon.Extensions.CognitoAuthentication/CognitoUserAuthentication.cs [42:98]
46 lines of code
12 McCabe index (conditional complexity)

        public virtual async Task<AuthFlowResponse> StartWithSrpAuthAsync(InitiateSrpAuthRequest srpRequest)
        {
            if (srpRequest == null || string.IsNullOrEmpty(srpRequest.Password))
            {
                throw new ArgumentNullException("Password required for authentication.", "srpRequest");
            }

            Tuple<BigInteger, BigInteger> tupleAa = AuthenticationHelper.CreateAaTuple();
            InitiateAuthRequest initiateRequest = CreateSrpAuthRequest(tupleAa);

            InitiateAuthResponse initiateResponse = await Provider.InitiateAuthAsync(initiateRequest).ConfigureAwait(false);
            UpdateUsernameAndSecretHash(initiateResponse.ChallengeParameters);

            RespondToAuthChallengeRequest challengeRequest =
                CreateSrpPasswordVerifierAuthRequest(initiateResponse, srpRequest.Password, tupleAa);

            bool challengeResponsesValid = challengeRequest != null && challengeRequest.ChallengeResponses != null;
            bool deviceKeyValid = Device != null && !string.IsNullOrEmpty(Device.DeviceKey);

            if (challengeResponsesValid && deviceKeyValid)
            {
                challengeRequest.ChallengeResponses[CognitoConstants.ChlgParamDeviceKey] = Device.DeviceKey;
            }

            RespondToAuthChallengeResponse verifierResponse =
                await Provider.RespondToAuthChallengeAsync(challengeRequest).ConfigureAwait(false);
            var isDeviceAuthRequest = verifierResponse.AuthenticationResult == null && (!string.IsNullOrEmpty(srpRequest.DeviceGroupKey)
                || !string.IsNullOrEmpty(srpRequest.DevicePass));
            #region Device-level authentication
            if (isDeviceAuthRequest)
            {
                if (string.IsNullOrEmpty(srpRequest.DeviceGroupKey) || string.IsNullOrEmpty(srpRequest.DevicePass))
                {
                    throw new ArgumentNullException("Device Group Key and Device Pass required for authentication.", "srpRequest");
                }

                #region Device SRP Auth
                var deviceAuthRequest = CreateDeviceSrpAuthRequest(verifierResponse, tupleAa);
                var deviceAuthResponse = await Provider.RespondToAuthChallengeAsync(deviceAuthRequest).ConfigureAwait(false); 
                #endregion

                #region Device Password Verifier
                var devicePasswordChallengeRequest = CreateDevicePasswordVerifierAuthRequest(deviceAuthResponse, srpRequest.DeviceGroupKey, srpRequest.DevicePass, tupleAa);
                verifierResponse = await Provider.RespondToAuthChallengeAsync(devicePasswordChallengeRequest).ConfigureAwait(false);
                #endregion

            }
            #endregion

            UpdateSessionIfAuthenticationComplete(verifierResponse.ChallengeName, verifierResponse.AuthenticationResult);

            return new AuthFlowResponse(verifierResponse.Session,
                verifierResponse.AuthenticationResult,
                verifierResponse.ChallengeName,
                verifierResponse.ChallengeParameters,
                new Dictionary<string, string>(verifierResponse.ResponseMetadata.Metadata));
        }