Add reregistration flag to account creation response

service/src/main/java/org/whispersystems/textsecuregcm/controllers/RegistrationController.java

@@ -36,6 +36,7 @@ import java.util.Optional;
 import org.whispersystems.textsecuregcm.auth.BasicAuthorizationHeader;
 import org.whispersystems.textsecuregcm.auth.PhoneVerificationTokenManager;
 import org.whispersystems.textsecuregcm.auth.RegistrationLockVerificationManager;
+import org.whispersystems.textsecuregcm.entities.AccountCreationResponse;
 import org.whispersystems.textsecuregcm.entities.AccountIdentityResponse;
 import org.whispersystems.textsecuregcm.entities.PhoneVerificationRequest;
 import org.whispersystems.textsecuregcm.entities.RegistrationLockFailure;
@@ -100,7 +101,7 @@ public class RegistrationController {
   @ApiResponse(responseCode = "429", description = "Too many attempts", headers = @Header(
       name = "Retry-After",
       description = "If present, an positive integer indicating the number of seconds before a subsequent attempt could succeed"))
-  public AccountIdentityResponse register(
+  public AccountCreationResponse register(
       @HeaderParam(HttpHeaders.AUTHORIZATION) @NotNull final BasicAuthorizationHeader authorizationHeader,
       @HeaderParam(HeaderUtils.X_SIGNAL_AGENT) final String signalAgent,
       @HeaderParam(HttpHeaders.USER_AGENT) final String userAgent,
@@ -166,12 +167,14 @@ public class RegistrationController {
             Tag.of(VERIFICATION_TYPE_TAG_NAME, verificationType.name())))
         .increment();
 
-    return new AccountIdentityResponseBuilder(account)
+    final AccountIdentityResponse identityResponse = new AccountIdentityResponseBuilder(account)
         // If there was an existing account, return whether it could have had something in the storage service
         .storageCapable(existingAccount
             .map(a -> a.hasCapability(DeviceCapability.STORAGE))
             .orElse(false))
         .build();
+
+    return new AccountCreationResponse(identityResponse, existingAccount.isPresent());
   }
 
 }

service/src/main/java/org/whispersystems/textsecuregcm/entities/AccountCreationResponse.java

@@ -0,0 +1,32 @@
+/*
+ * Copyright 2025 Signal Messenger, LLC
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+package org.whispersystems.textsecuregcm.entities;
+
+import com.fasterxml.jackson.annotation.JsonUnwrapped;
+import io.swagger.v3.oas.annotations.media.Schema;
+
+// Note, this class cannot be converted into a record because @JsonUnwrapped does not work with records until 2.19. We are on 2.18 until Dropwizard’s BOM updates.
+// https://github.com/FasterXML/jackson-databind/issues/1467
+public class AccountCreationResponse {
+
+  @JsonUnwrapped
+  private AccountIdentityResponse identityResponse;
+
+  @Schema(description = "If true, there was an existing account registered for this number")
+  private boolean reregistration;
+
+  public AccountCreationResponse() {
+  }
+
+  public AccountCreationResponse(AccountIdentityResponse identityResponse, boolean reregistration) {
+    this.identityResponse = identityResponse;
+    this.reregistration = reregistration;
+  }
+
+  public boolean isReregistration() {
+    return reregistration;
+  }
+}

service/src/test/java/org/whispersystems/textsecuregcm/controllers/RegistrationControllerTest.java

@@ -50,6 +50,7 @@ import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.Arguments;
 import org.junit.jupiter.params.provider.CsvSource;
 import org.junit.jupiter.params.provider.MethodSource;
+import org.junit.jupiter.params.provider.ValueSource;
 import org.junitpioneer.jupiter.cartesian.ArgumentSets;
 import org.junitpioneer.jupiter.cartesian.CartesianTest;
 import org.signal.libsignal.protocol.IdentityKey;
@@ -59,6 +60,8 @@ import org.whispersystems.textsecuregcm.auth.PhoneVerificationTokenManager;
 import org.whispersystems.textsecuregcm.auth.RegistrationLockError;
 import org.whispersystems.textsecuregcm.auth.RegistrationLockVerificationManager;
 import org.whispersystems.textsecuregcm.entities.AccountAttributes;
+import org.whispersystems.textsecuregcm.entities.AccountCreationResponse;
+import org.whispersystems.textsecuregcm.entities.AccountIdentityResponse;
 import org.whispersystems.textsecuregcm.entities.ApnRegistrationId;
 import org.whispersystems.textsecuregcm.entities.DeviceActivationRequest;
 import org.whispersystems.textsecuregcm.entities.ECSignedPreKey;
@@ -748,6 +751,8 @@ class RegistrationControllerTest {
 
     try (Response response = request.post(Entity.json(registrationRequest))) {
       assertEquals(200, response.getStatus());
+      final AccountIdentityResponse identityResponse = response.readEntity(AccountIdentityResponse.class);
+      assertEquals(accountIdentifier, identityResponse.uuid());
     }
 
     verify(accountsManager).create(
@@ -760,6 +765,34 @@ class RegistrationControllerTest {
         any());
   }
 
+  @ParameterizedTest
+  @ValueSource(booleans = {true, false})
+  void reregistrationFlag(final boolean existingAccount) throws InterruptedException {
+    final RegistrationServiceSession registrationSession =
+        new RegistrationServiceSession(new byte[16], NUMBER, true, null, null, null, SESSION_EXPIRATION_SECONDS);
+    when(registrationServiceClient.getSession(any(), any()))
+        .thenReturn(CompletableFuture.completedFuture(Optional.of(registrationSession)));
+
+    final Optional<Account> maybeAccount = Optional.ofNullable(existingAccount ? mock(Account.class) : null);
+    when(accountsManager.getByE164(any())).thenReturn(maybeAccount);
+
+    final Account account = mock(Account.class);
+    when(account.getPrimaryDevice()).thenReturn(mock(Device.class));
+
+    when(accountsManager.create(any(), any(), any(), any(), any(), any(), any()))
+        .thenReturn(account);
+
+    final Invocation.Builder request = resources.getJerseyTest()
+        .target("/v1/registration")
+        .request()
+        .header(HttpHeaders.AUTHORIZATION, AuthHelper.getProvisioningAuthHeader(NUMBER, PASSWORD));
+    try (Response response = request.post(Entity.json(requestJson("sessionId")))) {
+      assertEquals(200, response.getStatus());
+      final AccountCreationResponse creationResponse = response.readEntity(AccountCreationResponse.class);
+      assertEquals(existingAccount, creationResponse.isReregistration());
+    }
+  }
+
   private static boolean accountAttributesEqual(final AccountAttributes a, final AccountAttributes b) {
     return a.getFetchesMessages() == b.getFetchesMessages()
         && a.getRegistrationId() == b.getRegistrationId()