public void start()

in auth/src/main/java/com/firebase/ui/auth/data/remote/SignInKickstarter.java [57:121]
54 lines of code
9 McCabe index (conditional complexity)

    public void start() {
        if (!TextUtils.isEmpty(getArguments().emailLink)) {
            setResult(Resource.forFailure(new IntentRequiredException(
                    EmailLinkCatcherActivity.createIntent(getApplication(), getArguments()),
                    RequestCodes.EMAIL_FLOW)));
            return;
        }

        // Signing in with Generic IDP puts the app in the background - it can be reclaimed by the
        // OS during the sign in flow.
        Task<AuthResult> pendingResultTask = getAuth().getPendingAuthResult();
        if (pendingResultTask != null) {
            pendingResultTask
                    .addOnSuccessListener(
                            authResult -> {
                                final IdpResponse response = new IdpResponse.Builder(
                                        new User.Builder(
                                                authResult.getCredential().getProvider(),
                                                authResult.getUser().getEmail()).build())
                                        .build();
                                handleSuccess(response, authResult);

                            })
                    .addOnFailureListener(
                            e -> setResult(Resource.forFailure(e)));
            return;
        }


        // Only support password credentials if email auth is enabled
        boolean supportPasswords = ProviderUtils.getConfigFromIdps(
                getArguments().providers, EmailAuthProvider.PROVIDER_ID) != null;
        List<String> accountTypes = getCredentialAccountTypes();

        // If the request will be empty, avoid the step entirely
        boolean willRequestCredentials = supportPasswords || accountTypes.size() > 0;

        if (getArguments().enableCredentials && willRequestCredentials) {
            setResult(Resource.forLoading());

            GoogleApiUtils.getCredentialsClient(getApplication())
                    .request(new CredentialRequest.Builder()
                            .setPasswordLoginSupported(supportPasswords)
                            .setAccountTypes(accountTypes.toArray(new String[accountTypes.size()]))
                            .build())
                    .addOnCompleteListener(task -> {
                        try {
                            handleCredential(
                                    task.getResult(ApiException.class).getCredential());
                        } catch (ResolvableApiException e) {
                            if (e.getStatusCode() == CommonStatusCodes.RESOLUTION_REQUIRED) {
                                setResult(Resource.forFailure(
                                        new PendingIntentRequiredException(
                                                e.getResolution(), RequestCodes.CRED_HINT)));
                            } else {
                                startAuthMethodChoice();
                            }
                        } catch (ApiException e) {
                            startAuthMethodChoice();
                        }
                    });
        } else {
            startAuthMethodChoice();
        }
    }