public void startSignIn()

in auth/src/main/java/com/firebase/ui/auth/viewmodel/idp/SocialProviderResponseHandler.java [47:127]
59 lines of code
12 McCabe index (conditional complexity)

    public void startSignIn(@NonNull final IdpResponse response) {
        if (!response.isSuccessful() && !response.isRecoverableErrorResponse()) {
            setResult(Resource.forFailure(response.getError()));
            return;
        }

        if (isEmailOrPhoneProvider(response.getProviderType())) {
            throw new IllegalStateException(
                    "This handler cannot be used with email or phone providers");
        }

        setResult(Resource.forLoading());

        // Recoverable error flows (linking) for Generic OAuth providers are handled here.
        // For Generic OAuth providers, the credential is set on the IdpResponse, as
        // a credential made from the id token/access token cannot be used to sign-in.
        if (response.hasCredentialForLinking()) {
            handleGenericIdpLinkingFlow(response);
            return;
        }

        final AuthCredential credential = ProviderUtils.getAuthCredential(response);
        AuthOperationManager.getInstance().signInAndLinkWithCredential(
                getAuth(),
                getArguments(),
                credential)
                .continueWithTask(new ProfileMerger(response))
                .addOnSuccessListener(result -> handleSuccess(response, result))
                .addOnFailureListener(e -> {
                    // For some reason disabled users can hit FirebaseAuthUserCollisionException
                    // so we have to handle this special case.
                    boolean isDisabledUser = (e instanceof FirebaseAuthInvalidUserException);
                    if (e instanceof FirebaseAuthException) {
                        FirebaseAuthException authEx = (FirebaseAuthException) e;
                        FirebaseAuthError fae = FirebaseAuthError.fromException(authEx);
                        if (fae == FirebaseAuthError.ERROR_USER_DISABLED) {
                           isDisabledUser = true;
                        }
                    }

                    if (isDisabledUser) {
                        setResult(Resource.forFailure(
                                new FirebaseUiException(ErrorCodes.ERROR_USER_DISABLED)
                        ));
                    } else if (e instanceof FirebaseAuthUserCollisionException) {
                        final String email = response.getEmail();
                        if (email == null) {
                            setResult(Resource.forFailure(e));
                            return;
                        }

                        // There can be a collision due to:
                        // CASE 1: Anon user signing in with a credential that belongs to an
                        // existing user.
                        // CASE 2: non - anon user signing in with a credential that does not
                        // belong to an existing user, but the email matches an existing user
                        // that has another social IDP. We need to link this new IDP to this
                        // existing user.
                        // CASE 3: CASE 2 with an anonymous user. We link the new IDP to the
                        // same account before handling invoking a merge failure.
                        ProviderUtils.fetchSortedProviders(getAuth(), getArguments(), email)
                                .addOnSuccessListener(providers -> {
                                    if (providers.contains(response.getProviderType())) {
                                        // Case 1
                                        handleMergeFailure(credential);
                                    } else if (providers.isEmpty()) {
                                        setResult(Resource.forFailure(
                                                new FirebaseUiException(
                                                        ErrorCodes.DEVELOPER_ERROR,
                                                        "No supported providers.")));
                                    } else {
                                        // Case 2 & 3 - we need to link
                                        startWelcomeBackFlowForLinking(
                                                providers.get(0), response);
                                    }
                                })
                                .addOnFailureListener(e1 -> setResult(Resource.forFailure(
                                        e1)));
                    }
                });
    }