public PublicKeyCredentialCreationOptions getRegistrationRequest()

in Fido/app/src/main/java/com/fido/example/fido2apiexample/GAEService.java [97:203]
79 lines of code
11 McCabe index (conditional complexity)

    public PublicKeyCredentialCreationOptions getRegistrationRequest(List<String> excludedKeys) {
        try {
            if (fido2Service == null) {
                return null;
            }
            List<String> registerRequestContent =
                    fido2Service.getRegistrationRequest().execute().getItems();
            if (registerRequestContent == null || registerRequestContent.isEmpty()) {
                Log.i(TAG, "registerRequestContent is null or empty");
                return null;
            }
            for (String value : registerRequestContent) {
                Log.i(TAG, "registerRequestContent " + value);
            }
            // A sample register request:
            // {"rp":{"id":"webauthndemo.appspot.com","name":"webauthndemo.appspot.com"},
            //
            // "user":{"name":"littlecattest","displayName":"littlecattest","id":"bGl0dGxlY2F0dGVzdEBnbWFpbC5jb20="},
            //     "challenge":"Zys9NEvoE6KRhZtVMJZ3KKHg+spgXu2R0R7AQ2Mudlg=",
            //     "pubKeyCredParams":[{"type":"public-key","alg":-7},{"type":"public-key","alg":-35},
            //     {"type":"public-key","alg":-36},{"type":"public-key","alg":-40},
            //     {"type":"public-key","alg":-41},{"type":"public-key","alg":-42},
            //     {"type":"public-key","alg":-37},{"type":"public-key","alg":-38},
            //     {"type":"public-key","alg":-39}],
            //     "session":{"id":5634387206995968,
            //     "challenge":"Zys9NEvoE6KRhZtVMJZ3KKHg+spgXu2R0R7AQ2Mudlg=",
            //     "origin":"webauthndemo.appspot.com"}}*/

            JSONObject registerRequestJson = new JSONObject(registerRequestContent.get(0));
            PublicKeyCredentialCreationOptions.Builder builder =
                    new PublicKeyCredentialCreationOptions.Builder();

            // Parse challenge
            builder.setChallenge(
                    BaseEncoding.base64().decode(registerRequestJson.getString(KEY_REQUEST_CHALLENGE)));

            // Parse RP
            JSONObject rpJson = registerRequestJson.getJSONObject(KEY_RP);
            String rpId = rpJson.getString(KEY_RP_ID);
            String rpName = rpJson.getString(KEY_RP_NAME);
            String rpIcon = null;
            if (rpJson.has(KEY_RP_ICON)) {
                rpIcon = rpJson.getString(KEY_RP_ICON);
            }
            PublicKeyCredentialRpEntity entity = new PublicKeyCredentialRpEntity(rpId, rpName, rpIcon);
            builder.setRp(entity);

            // Parse user
            JSONObject userJson = registerRequestJson.getJSONObject(KEY_USER);
            String displayName = userJson.getString(KEY_USER_DISPLAY_NAME);
            PublicKeyCredentialUserEntity userEntity =
                    new PublicKeyCredentialUserEntity(
                            displayName.getBytes() /* id */,
                            displayName /* name */,
                            null /* icon */,
                            displayName);
            builder.setUser(userEntity);

            // Parse parameters
            List<PublicKeyCredentialParameters> parameters = new ArrayList<>();
            if (registerRequestJson.has(KEY_PARAMETERS)) {
                JSONArray params = registerRequestJson.getJSONArray(KEY_PARAMETERS);
                for (int i = 0; i < params.length(); i++) {
                    JSONObject param = params.getJSONObject(i);
                    String type = param.getString(KEY_PARAMETERS_TYPE);
                    // TODO: this is a hack, use KEY_PARAMETERS_ALGORITHM = "alg"
                    PublicKeyCredentialParameters parameter =
                            new PublicKeyCredentialParameters(type, EC2Algorithm.ES256.getAlgoValue());
                    parameters.add(parameter);
                }
            }
            builder.setParameters(parameters);

            // Parse timeout
            Double timeout = null;
            if (registerRequestJson.has(KEY_TIMEOUT)) {
                timeout = Double.valueOf(registerRequestJson.getLong(KEY_TIMEOUT));
            }
            builder.setTimeoutSeconds(timeout);

            // Parse exclude list
            List<PublicKeyCredentialDescriptor> descriptors =
                    FluentIterable.from(excludedKeys)
                            .transform(
                                    k ->
                                            new PublicKeyCredentialDescriptor(
                                                    PublicKeyCredentialType.PUBLIC_KEY.toString(),
                                                    BaseEncoding.base64Url().decode(k),
                                                    /* transports= */ null))
                            .toList();
            builder.setExcludeList(descriptors);

            AuthenticatorSelectionCriteria.Builder criteria =
                    new AuthenticatorSelectionCriteria.Builder();
            if (registerRequestJson.has(KEY_ATTACHMENT)) {
                criteria.setAttachment(
                        Attachment.fromString(registerRequestJson.getString(KEY_ATTACHMENT)));
            }
            builder.setAuthenticatorSelection(criteria.build());
            return builder.build();
        } catch (IOException
                | JSONException
                | Attachment.UnsupportedAttachmentException e) {
            Log.e(TAG, "Error extracting information from server's registration request", e);
        }
        return null;
    }