Implement new API endpoints for Usernames.

app/src/main/java/org/thoughtcrime/securesms/jobs/RetrieveProfileJob.java

@@ -34,6 +34,7 @@ import org.thoughtcrime.securesms.jobmanager.JobManager;
 import org.thoughtcrime.securesms.jobmanager.impl.NetworkConstraint;
 import org.thoughtcrime.securesms.keyvalue.SignalStore;
 import org.thoughtcrime.securesms.profiles.ProfileName;
+import org.thoughtcrime.securesms.recipients.LiveRecipient;
 import org.thoughtcrime.securesms.recipients.Recipient;
 import org.thoughtcrime.securesms.recipients.RecipientId;
 import org.thoughtcrime.securesms.recipients.RecipientUtil;
@@ -341,11 +342,11 @@ public class RetrieveProfileJob extends BaseJob {
     SignalServiceProfile profile             = profileAndCredential.getProfile();
     ProfileKey           recipientProfileKey = ProfileKeyUtil.profileKeyOrNull(recipient.getProfileKey());
 
-    setProfileName(recipient, profile.getName());
+    boolean wroteNewProfileName = setProfileName(recipient, profile.getName());
+
     setProfileAbout(recipient, profile.getAbout(), profile.getAboutEmoji());
     setProfileAvatar(recipient, profile.getAvatar());
     setProfileBadges(recipient, profile.getBadges());
-    clearUsername(recipient);
     setProfileCapabilities(recipient, profile.getCapabilities());
     setUnidentifiedAccessMode(recipient, profile.getUnidentifiedAccess(), profile.isUnrestrictedUnidentifiedAccess());
 
@@ -353,6 +354,10 @@ public class RetrieveProfileJob extends BaseJob {
       profileAndCredential.getExpiringProfileKeyCredential()
                           .ifPresent(profileKeyCredential -> setExpiringProfileKeyCredential(recipient, recipientProfileKey, profileKeyCredential));
     }
+
+    if (recipient.hasNonUsernameDisplayName(context) || wroteNewProfileName) {
+      clearUsername(recipient);
+    }
   }
 
   private void setProfileBadges(@NonNull Recipient recipient, @Nullable List<SignalServiceProfile.Badge> serviceBadges) {
@@ -436,16 +441,16 @@ public class RetrieveProfileJob extends BaseJob {
     }
   }
 
-  private void setProfileName(Recipient recipient, String profileName) {
+  private boolean setProfileName(Recipient recipient, String profileName) {
     try {
       ProfileKey profileKey = ProfileKeyUtil.profileKeyOrNull(recipient.getProfileKey());
-      if (profileKey == null) return;
+      if (profileKey == null) return false;
 
       String plaintextProfileName = Util.emptyIfNull(ProfileUtil.decryptString(profileKey, profileName));
 
       if (TextUtils.isEmpty(plaintextProfileName)) {
         Log.w(TAG, "No name set on the profile for " + recipient.getId() + " -- Leaving it alone");
-        return;
+        return false;
       }
 
       ProfileName remoteProfileName = ProfileName.fromSerialized(plaintextProfileName);
@@ -470,12 +475,16 @@ public class RetrieveProfileJob extends BaseJob {
           Log.i(TAG, String.format(Locale.US, "Name changed, but wasn't relevant to write an event. blocked: %s, group: %s, self: %s, firstSet: %s, displayChange: %s",
                                    recipient.isBlocked(), recipient.isGroup(), recipient.isSelf(), localDisplayName.isEmpty(), !remoteDisplayName.equals(localDisplayName)));
         }
+
+        return true;
       }
     } catch (InvalidCiphertextException e) {
       Log.w(TAG, "Bad profile key for " + recipient.getId());
     } catch (IOException e) {
       Log.w(TAG, e);
     }
+
+    return false;
   }
 
   private void setProfileAbout(@NonNull Recipient recipient, @Nullable String encryptedAbout, @Nullable String encryptedEmoji) {

app/src/main/java/org/thoughtcrime/securesms/profiles/manage/UsernameEditFragment.java

@@ -1,6 +1,7 @@
 package org.thoughtcrime.securesms.profiles.manage;
 
 import android.content.res.ColorStateList;
+import android.graphics.Color;
 import android.graphics.drawable.Drawable;
 import android.os.Bundle;
 import android.view.LayoutInflater;
@@ -15,16 +16,15 @@ import android.widget.Toast;
 
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
-import androidx.appcompat.widget.Toolbar;
 import androidx.core.content.ContextCompat;
 import androidx.fragment.app.FragmentManager;
-import androidx.lifecycle.LifecycleOwner;
 import androidx.lifecycle.ViewModelProvider;
 import androidx.navigation.Navigation;
 import androidx.navigation.fragment.NavHostFragment;
 
-import com.google.android.material.button.MaterialButton;
 import com.google.android.material.dialog.MaterialAlertDialogBuilder;
+import com.google.android.material.progressindicator.CircularProgressIndicatorSpec;
+import com.google.android.material.progressindicator.IndeterminateDrawable;
 import com.google.android.material.textfield.TextInputLayout;
 
 import org.signal.core.util.DimensionUnit;
@@ -38,10 +38,8 @@ import org.thoughtcrime.securesms.util.LifecycleDisposable;
 import org.thoughtcrime.securesms.util.UsernameUtil;
 import org.thoughtcrime.securesms.util.ViewUtil;
 import org.thoughtcrime.securesms.util.views.CircularProgressMaterialButton;
-import org.thoughtcrime.securesms.util.views.LearnMoreTextView;
 
 import java.util.Objects;
-import java.util.function.Consumer;
 
 public class UsernameEditFragment extends LoggingFragment {
 
@@ -76,19 +74,20 @@ public class UsernameEditFragment extends LoggingFragment {
     lifecycleDisposable.add(viewModel.getUiState().subscribe(this::onUiStateChanged));
     viewModel.getEvents().observe(getViewLifecycleOwner(), this::onEvent);
 
-    binding.usernameSubmitButton.setOnClickListener(v -> viewModel.onUsernameSubmitted(binding.usernameText.getText().toString()));
+    binding.usernameSubmitButton.setOnClickListener(v -> viewModel.onUsernameSubmitted());
     binding.usernameDeleteButton.setOnClickListener(v -> viewModel.onUsernameDeleted());
 
-    binding.usernameText.setText(Recipient.self().getUsername().orElse(null));
+    UsernameState usernameState = Recipient.self().getUsername().<UsernameState>map(UsernameState.Set::new).orElse(UsernameState.NoUsername.INSTANCE);
+    binding.usernameText.setText(usernameState.getNickname());
     binding.usernameText.addTextChangedListener(new SimpleTextWatcher() {
       @Override
-      public void onTextChanged(String text) {
+      public void onTextChanged(@NonNull String text) {
-        viewModel.onUsernameUpdated(text);
+        viewModel.onNicknameUpdated(text);
       }
     });
     binding.usernameText.setOnEditorActionListener((v, actionId, event) -> {
       if (actionId == EditorInfo.IME_ACTION_DONE) {
-        viewModel.onUsernameSubmitted(binding.usernameText.getText().toString());
+        viewModel.onUsernameSubmitted();
         return true;
       }
       return false;
@@ -118,9 +117,10 @@ public class UsernameEditFragment extends LoggingFragment {
 
     layoutParams.topMargin    = suffixTextView.getPaddingTop();
     layoutParams.bottomMargin = suffixTextView.getPaddingBottom();
+    layoutParams.setMarginEnd(suffixTextView.getPaddingEnd());
 
     suffixProgress = new ImageView(requireContext());
-    suffixProgress.setImageDrawable(UsernameSuffix.getInProgressDrawable(requireContext()));
+    suffixProgress.setImageDrawable(getInProgressDrawable());
     suffixParent.addView(suffixProgress, 0, layoutParams);
 
     suffixTextView.setOnClickListener(this::onLearnMore);
@@ -148,7 +148,7 @@ public class UsernameEditFragment extends LoggingFragment {
     TextInputLayout                usernameInputWrapper = binding.usernameTextWrapper;
 
     usernameInput.setEnabled(true);
-    presentSuffix(state.getUsernameSuffix());
+    presentSuffix(state.getUsername());
 
     switch (state.getButtonState()) {
       case SUBMIT:
@@ -224,18 +224,14 @@ public class UsernameEditFragment extends LoggingFragment {
         usernameInputWrapper.setError(getResources().getString(R.string.UsernameEditFragment_this_username_is_taken));
         usernameInputWrapper.setErrorTextColor(ColorStateList.valueOf(getResources().getColor(R.color.signal_colorError)));
 
-        break;
-      case AVAILABLE:
-        usernameInputWrapper.setError(getResources().getString(R.string.UsernameEditFragment_this_username_is_available));
-        usernameInputWrapper.setErrorTextColor(ColorStateList.valueOf(getResources().getColor(R.color.signal_accent_green)));
         break;
     }
   }
 
-  private void presentSuffix(@NonNull UsernameSuffix usernameSuffix) {
+  private void presentSuffix(@NonNull UsernameState usernameState) {
-    binding.usernameTextWrapper.setSuffixText(usernameSuffix.getCharSequence());
+    binding.usernameTextWrapper.setSuffixText(usernameState.getDiscriminator());
 
-    boolean isInProgress = usernameSuffix.isInProgress();
+    boolean isInProgress = usernameState.isInProgress();
 
     if (isInProgress) {
       suffixProgress.setVisibility(View.VISIBLE);
@@ -244,11 +240,23 @@ public class UsernameEditFragment extends LoggingFragment {
     }
   }
 
+  private IndeterminateDrawable<CircularProgressIndicatorSpec> getInProgressDrawable() {
+    CircularProgressIndicatorSpec spec = new CircularProgressIndicatorSpec(requireContext(), null);
+    spec.indicatorInset = 0;
+    spec.indicatorSize = (int) DimensionUnit.DP.toPixels(16f);
+    spec.trackColor = ContextCompat.getColor(requireContext(), R.color.signal_colorOnSurfaceVariant);
+    spec.trackThickness = (int) DimensionUnit.DP.toPixels(1f);
+
+    IndeterminateDrawable<CircularProgressIndicatorSpec> drawable = IndeterminateDrawable.createCircularDrawable(requireContext(), spec);
+    drawable.setBounds(0, 0, spec.indicatorSize, spec.indicatorSize);
+
+    return drawable;
+  }
+
   private void onEvent(@NonNull UsernameEditViewModel.Event event) {
     switch (event) {
       case SUBMIT_SUCCESS:
         ResultContract.setUsernameCreated(getParentFragmentManager());
-        Toast.makeText(requireContext(), R.string.UsernameEditFragment_successfully_set_username, Toast.LENGTH_SHORT).show();
         NavHostFragment.findNavController(this).popBackStack();
         break;
       case SUBMIT_FAIL_TAKEN:

app/src/main/java/org/thoughtcrime/securesms/profiles/manage/UsernameEditRepository.java

@@ -1,18 +1,19 @@
 package org.thoughtcrime.securesms.profiles.manage;
 
-import android.app.Application;
-
 import androidx.annotation.NonNull;
 import androidx.annotation.WorkerThread;
 
+import org.signal.core.util.Result;
 import org.signal.core.util.concurrent.SignalExecutors;
 import org.signal.core.util.logging.Log;
 import org.thoughtcrime.securesms.database.SignalDatabase;
 import org.thoughtcrime.securesms.dependencies.ApplicationDependencies;
 import org.thoughtcrime.securesms.recipients.Recipient;
 import org.whispersystems.signalservice.api.SignalServiceAccountManager;
+import org.whispersystems.signalservice.api.push.exceptions.UsernameIsNotReservedException;
 import org.whispersystems.signalservice.api.push.exceptions.UsernameMalformedException;
 import org.whispersystems.signalservice.api.push.exceptions.UsernameTakenException;
+import org.whispersystems.signalservice.internal.push.ReserveUsernameResponse;
 
 import java.io.IOException;
 import java.util.concurrent.Executor;
@@ -21,18 +22,20 @@ class UsernameEditRepository {
 
   private static final String TAG = Log.tag(UsernameEditRepository.class);
 
-  private final Application                 application;
   private final SignalServiceAccountManager accountManager;
   private final Executor                    executor;
 
   UsernameEditRepository() {
-    this.application    = ApplicationDependencies.getApplication();
     this.accountManager = ApplicationDependencies.getSignalServiceAccountManager();
     this.executor       = SignalExecutors.UNBOUNDED;
   }
 
-  void setUsername(@NonNull String username, @NonNull Callback<UsernameSetResult> callback) {
+  void reserveUsername(@NonNull String nickname, @NonNull Callback<Result<ReserveUsernameResponse, UsernameSetResult>> callback) {
-    executor.execute(() -> callback.onComplete(setUsernameInternal(username)));
+    executor.execute(() -> callback.onComplete(reserveUsernameInternal(nickname)));
+  }
+
+  void confirmUsername(@NonNull ReserveUsernameResponse reserveUsernameResponse, @NonNull Callback<UsernameSetResult> callback) {
+    executor.execute(() -> callback.onComplete(confirmUsernameInternal(reserveUsernameResponse)));
   }
 
   void deleteUsername(@NonNull Callback<UsernameDeleteResult> callback) {
@@ -40,20 +43,38 @@ class UsernameEditRepository {
   }
 
   @WorkerThread
-  private @NonNull UsernameSetResult setUsernameInternal(@NonNull String username) {
+  private @NonNull Result<ReserveUsernameResponse, UsernameSetResult> reserveUsernameInternal(@NonNull String nickname) {
     try {
-      accountManager.setUsername(username);
+      ReserveUsernameResponse username = accountManager.reserveUsername(nickname);
-      SignalDatabase.recipients().setUsername(Recipient.self().getId(), username);
+      Log.i(TAG, "[reserveUsername] Successfully reserved username.");
-      Log.i(TAG, "[setUsername] Successfully set username.");
+      return Result.success(username);
+    } catch (UsernameTakenException e) {
+      Log.w(TAG, "[reserveUsername] Username taken.");
+      return Result.failure(UsernameSetResult.USERNAME_UNAVAILABLE);
+    } catch (UsernameMalformedException e) {
+      Log.w(TAG, "[reserveUsername] Username malformed.");
+      return Result.failure(UsernameSetResult.USERNAME_INVALID);
+    } catch (IOException e) {
+      Log.w(TAG, "[reserveUsername] Generic network exception.", e);
+      return Result.failure(UsernameSetResult.NETWORK_ERROR);
+    }
+  }
+
+  @WorkerThread
+  private @NonNull UsernameSetResult confirmUsernameInternal(@NonNull ReserveUsernameResponse reserveUsernameResponse) {
+    try {
+      accountManager.confirmUsername(reserveUsernameResponse);
+      SignalDatabase.recipients().setUsername(Recipient.self().getId(), reserveUsernameResponse.getUsername());
+      Log.i(TAG, "[confirmUsername] Successfully reserved username.");
       return UsernameSetResult.SUCCESS;
     } catch (UsernameTakenException e) {
-      Log.w(TAG, "[setUsername] Username taken.");
+      Log.w(TAG, "[confirmUsername] Username gone.");
       return UsernameSetResult.USERNAME_UNAVAILABLE;
-    } catch (UsernameMalformedException e) {
+    } catch (UsernameIsNotReservedException e) {
-      Log.w(TAG, "[setUsername] Username malformed.");
+      Log.w(TAG, "[confirmUsername] Username was not reserved.");
       return UsernameSetResult.USERNAME_INVALID;
     } catch (IOException e) {
-      Log.w(TAG, "[setUsername] Generic network exception.", e);
+      Log.w(TAG, "[confirmUsername] Generic network exception.", e);
       return UsernameSetResult.NETWORK_ERROR;
     }
   }
@@ -79,10 +100,6 @@ class UsernameEditRepository {
     SUCCESS, NETWORK_ERROR
   }
 
-  enum UsernameAvailableResult {
-    TRUE, FALSE, NETWORK_ERROR
-  }
-
   interface Callback<E> {
     void onComplete(E result);
   }

app/src/main/java/org/thoughtcrime/securesms/profiles/manage/UsernameEditViewModel.java

@@ -1,6 +1,5 @@
 package org.thoughtcrime.securesms.profiles.manage;
 
-import android.app.Application;
 import android.text.TextUtils;
 
 import androidx.annotation.NonNull;
@@ -9,86 +8,126 @@ import androidx.lifecycle.ViewModel;
 import androidx.lifecycle.ViewModelProvider;
 
 import org.signal.core.util.ThreadUtil;
-import org.signal.core.util.logging.Log;
-import org.thoughtcrime.securesms.dependencies.ApplicationDependencies;
 import org.thoughtcrime.securesms.recipients.Recipient;
 import org.thoughtcrime.securesms.util.SingleLiveEvent;
 import org.thoughtcrime.securesms.util.UsernameUtil;
 import org.thoughtcrime.securesms.util.UsernameUtil.InvalidReason;
 import org.thoughtcrime.securesms.util.rx.RxStore;
 
+import java.util.Objects;
 import java.util.Optional;
+import java.util.concurrent.TimeUnit;
 
 import io.reactivex.rxjava3.android.schedulers.AndroidSchedulers;
 import io.reactivex.rxjava3.core.Flowable;
+import io.reactivex.rxjava3.disposables.CompositeDisposable;
+import io.reactivex.rxjava3.disposables.Disposable;
+import io.reactivex.rxjava3.processors.PublishProcessor;
 import io.reactivex.rxjava3.schedulers.Schedulers;
 
-
+/**
+ * Manages the state around username updates.
+ *
+ * A note on naming conventions:
+ *
+ * Usernames are made up of two discrete components, a nickname and a discriminator. They are formatted thusly:
+ *
+ * [nickname]#[discriminator]
+ *
+ * The nickname is user-controlled, whereas the discriminator is controlled by the server.
+ */
 class UsernameEditViewModel extends ViewModel {
 
-  private static final String TAG = Log.tag(UsernameEditViewModel.class);
+  private static final long NICKNAME_PUBLISHER_DEBOUNCE_TIMEOUT_MILLIS = 500;
 
-  private final Application            application;
+  private final SingleLiveEvent<Event>   events;
-  private final SingleLiveEvent<Event> events;
+  private final UsernameEditRepository   repo;
-  private final UsernameEditRepository repo;
+  private final RxStore<State>           uiState;
-  private final RxStore<State>         uiState;
+  private final PublishProcessor<String> nicknamePublisher;
+  private final CompositeDisposable      disposables;
 
   private UsernameEditViewModel() {
-    this.application = ApplicationDependencies.getApplication();
+    this.repo              = new UsernameEditRepository();
-    this.repo        = new UsernameEditRepository();
+    this.uiState           = new RxStore<>(new State(ButtonState.SUBMIT_DISABLED, UsernameStatus.NONE, Recipient.self().getUsername().<UsernameState>map(UsernameState.Set::new).orElse(UsernameState.NoUsername.INSTANCE)), Schedulers.computation());
-    this.uiState     = new RxStore<>(new State(ButtonState.SUBMIT_DISABLED, UsernameStatus.NONE, UsernameSuffix.NONE), Schedulers.computation());
+    this.events            = new SingleLiveEvent<>();
-    this.events      = new SingleLiveEvent<>();
+    this.nicknamePublisher = PublishProcessor.create();
+    this.disposables       = new CompositeDisposable();
+
+    Disposable disposable = nicknamePublisher.debounce(NICKNAME_PUBLISHER_DEBOUNCE_TIMEOUT_MILLIS, TimeUnit.MILLISECONDS)
+                                             .subscribe(this::onNicknameChanged);
+    disposables.add(disposable);
   }
 
-  void onUsernameUpdated(@NonNull String username) {
+  @Override
+  protected void onCleared() {
+    super.onCleared();
+    disposables.clear();
+  }
+
+  void onNicknameUpdated(@NonNull String nickname) {
     uiState.update(state -> {
-      if (TextUtils.isEmpty(username) && Recipient.self().getUsername().isPresent()) {
+      if (TextUtils.isEmpty(nickname) && Recipient.self().getUsername().isPresent()) {
-        return new State(ButtonState.DELETE, UsernameStatus.NONE, state.usernameSuffix);
+        return new State(ButtonState.DELETE, UsernameStatus.NONE, UsernameState.NoUsername.INSTANCE);
       }
 
-      if (username.equals(Recipient.self().getUsername().orElse(null))) {
+      Optional<InvalidReason> invalidReason = UsernameUtil.checkUsername(nickname);
-        return new State(ButtonState.SUBMIT_DISABLED, UsernameStatus.NONE, state.usernameSuffix);
-      }
 
-      Optional<InvalidReason> invalidReason = UsernameUtil.checkUsername(username);
+      return invalidReason.map(reason -> new State(ButtonState.SUBMIT_DISABLED, mapUsernameError(reason), state.usernameState))
-
+                          .orElseGet(() -> new State(ButtonState.SUBMIT_DISABLED, UsernameStatus.NONE, state.usernameState));
-      return invalidReason.map(reason -> new State(ButtonState.SUBMIT_DISABLED, mapUsernameError(reason), state.usernameSuffix))
-                          .orElseGet(() -> new State(ButtonState.SUBMIT, UsernameStatus.NONE, state.usernameSuffix));
     });
+
+    nicknamePublisher.onNext(nickname);
   }
 
-  void onUsernameSubmitted(@NonNull String username) {
+  void onUsernameSubmitted() {
-    if (username.equals(Recipient.self().getUsername().orElse(null))) {
+    UsernameState usernameState = uiState.getState().getUsername();
-      uiState.update(state -> new State(ButtonState.SUBMIT_DISABLED, UsernameStatus.NONE, state.usernameSuffix));
+
+    if (!(usernameState instanceof UsernameState.Reserved)) {
+      uiState.update(state -> new State(ButtonState.SUBMIT_DISABLED, UsernameStatus.NONE, state.usernameState));
       return;
     }
 
-    Optional<InvalidReason> invalidReason = UsernameUtil.checkUsername(username);
+    if (Objects.equals(usernameState.getUsername(), Recipient.self().getUsername().orElse(null))) {
+      uiState.update(state -> new State(ButtonState.SUBMIT_DISABLED, UsernameStatus.NONE, state.usernameState));
+      return;
+    }
+
+    Optional<InvalidReason> invalidReason = UsernameUtil.checkUsername(usernameState.getNickname());
 
     if (invalidReason.isPresent()) {
-      uiState.update(state -> new State(ButtonState.SUBMIT_DISABLED, mapUsernameError(invalidReason.get()), state.usernameSuffix));
+      uiState.update(state -> new State(ButtonState.SUBMIT_DISABLED, mapUsernameError(invalidReason.get()), state.usernameState));
       return;
     }
 
-    uiState.update(state -> new State(ButtonState.SUBMIT_LOADING, UsernameStatus.NONE, state.usernameSuffix));
+    uiState.update(state -> new State(ButtonState.SUBMIT_LOADING, UsernameStatus.NONE, state.usernameState));
 
-    repo.setUsername(username, (result) -> {
+    repo.confirmUsername(((UsernameState.Reserved) usernameState).getReserveUsernameResponse(), (result) -> {
       ThreadUtil.runOnMain(() -> {
+        String nickname = usernameState.getNickname();
+
         switch (result) {
           case SUCCESS:
-            uiState.update(state -> new State(ButtonState.SUBMIT_DISABLED, UsernameStatus.NONE, state.usernameSuffix));
+            uiState.update(state -> new State(ButtonState.SUBMIT_DISABLED, UsernameStatus.NONE, state.usernameState));
             events.postValue(Event.SUBMIT_SUCCESS);
             break;
           case USERNAME_INVALID:
-            uiState.update(state -> new State(ButtonState.SUBMIT_DISABLED, UsernameStatus.INVALID_GENERIC, state.usernameSuffix));
+            uiState.update(state -> new State(ButtonState.SUBMIT_DISABLED, UsernameStatus.INVALID_GENERIC, state.usernameState));
             events.postValue(Event.SUBMIT_FAIL_INVALID);
+
+            if (nickname != null) {
+              onNicknameUpdated(nickname);
+            }
             break;
           case USERNAME_UNAVAILABLE:
-            uiState.update(state -> new State(ButtonState.SUBMIT_DISABLED, UsernameStatus.TAKEN, state.usernameSuffix));
+            uiState.update(state -> new State(ButtonState.SUBMIT_DISABLED, UsernameStatus.TAKEN, state.usernameState));
             events.postValue(Event.SUBMIT_FAIL_TAKEN);
+
+            if (nickname != null) {
+              onNicknameUpdated(nickname);
+            }
             break;
           case NETWORK_ERROR:
-            uiState.update(state -> new State(ButtonState.SUBMIT, UsernameStatus.NONE, state.usernameSuffix));
+            uiState.update(state -> new State(ButtonState.SUBMIT, UsernameStatus.NONE, state.usernameState));
             events.postValue(Event.NETWORK_FAILURE);
             break;
         }
@@ -97,17 +136,17 @@ class UsernameEditViewModel extends ViewModel {
   }
 
   void onUsernameDeleted() {
-    uiState.update(state -> new State(ButtonState.DELETE_LOADING, UsernameStatus.NONE, state.usernameSuffix));
+    uiState.update(state -> new State(ButtonState.DELETE_LOADING, UsernameStatus.NONE, state.usernameState));
 
     repo.deleteUsername((result) -> {
       ThreadUtil.runOnMain(() -> {
         switch (result) {
           case SUCCESS:
-            uiState.update(state -> new State(ButtonState.DELETE_DISABLED, UsernameStatus.NONE, state.usernameSuffix));
+            uiState.update(state -> new State(ButtonState.DELETE_DISABLED, UsernameStatus.NONE, state.usernameState));
             events.postValue(Event.DELETE_SUCCESS);
             break;
           case NETWORK_ERROR:
-            uiState.update(state -> new State(ButtonState.DELETE, UsernameStatus.NONE, state.usernameSuffix));
+            uiState.update(state -> new State(ButtonState.DELETE, UsernameStatus.NONE, state.usernameState));
             events.postValue(Event.NETWORK_FAILURE);
             break;
         }
@@ -123,28 +162,68 @@ class UsernameEditViewModel extends ViewModel {
     return events;
   }
 
+  private void onNicknameChanged(@NonNull String nickname) {
+    if (TextUtils.isEmpty(nickname)) {
+      return;
+    }
+
+    uiState.update(state -> new State(ButtonState.SUBMIT_DISABLED, UsernameStatus.NONE, UsernameState.Loading.INSTANCE));
+    repo.reserveUsername(nickname, result -> {
+      ThreadUtil.runOnMain(() -> {
+        result.either(
+            reserveUsernameJsonResponse -> {
+              uiState.update(state -> new State(ButtonState.SUBMIT, UsernameStatus.NONE, new UsernameState.Reserved(reserveUsernameJsonResponse)));
+              return null;
+            },
+            failure -> {
+              switch (failure) {
+                case SUCCESS:
+                  throw new AssertionError();
+                case USERNAME_INVALID:
+                  uiState.update(state -> new State(ButtonState.SUBMIT_DISABLED, UsernameStatus.INVALID_GENERIC, UsernameState.NoUsername.INSTANCE));
+                  break;
+                case USERNAME_UNAVAILABLE:
+                  uiState.update(state -> new State(ButtonState.SUBMIT_DISABLED, UsernameStatus.TAKEN, UsernameState.NoUsername.INSTANCE));
+                  break;
+                case NETWORK_ERROR:
+                  uiState.update(state -> new State(ButtonState.SUBMIT, UsernameStatus.NONE, UsernameState.NoUsername.INSTANCE));
+                  events.postValue(Event.NETWORK_FAILURE);
+                  break;
+              }
+
+              return null;
+            });
+      });
+    });
+  }
+
   private static UsernameStatus mapUsernameError(@NonNull InvalidReason invalidReason) {
     switch (invalidReason) {
-      case TOO_SHORT:          return UsernameStatus.TOO_SHORT;
+      case TOO_SHORT:
-      case TOO_LONG:           return UsernameStatus.TOO_LONG;
+        return UsernameStatus.TOO_SHORT;
-      case STARTS_WITH_NUMBER: return UsernameStatus.CANNOT_START_WITH_NUMBER;
+      case TOO_LONG:
-      case INVALID_CHARACTERS: return UsernameStatus.INVALID_CHARACTERS;
+        return UsernameStatus.TOO_LONG;
-      default:                 return UsernameStatus.INVALID_GENERIC;
+      case STARTS_WITH_NUMBER:
+        return UsernameStatus.CANNOT_START_WITH_NUMBER;
+      case INVALID_CHARACTERS:
+        return UsernameStatus.INVALID_CHARACTERS;
+      default:
+        return UsernameStatus.INVALID_GENERIC;
     }
   }
 
   static class State {
     private final ButtonState    buttonState;
     private final UsernameStatus usernameStatus;
-    private final UsernameSuffix usernameSuffix;
+    private final UsernameState  usernameState;
 
     private State(@NonNull ButtonState buttonState,
                   @NonNull UsernameStatus usernameStatus,
-                  @NonNull UsernameSuffix usernameSuffix)
+                  @NonNull UsernameState usernameState)
     {
       this.buttonState    = buttonState;
       this.usernameStatus = usernameStatus;
-      this.usernameSuffix = usernameSuffix;
+      this.usernameState  = usernameState;
     }
 
     @NonNull ButtonState getButtonState() {
@@ -155,13 +234,13 @@ class UsernameEditViewModel extends ViewModel {
       return usernameStatus;
     }
 
-    @NonNull UsernameSuffix getUsernameSuffix() {
+    @NonNull UsernameState getUsername() {
-      return usernameSuffix;
+      return usernameState;
     }
   }
 
   enum UsernameStatus {
-    NONE, AVAILABLE, TAKEN, TOO_SHORT, TOO_LONG, CANNOT_START_WITH_NUMBER, INVALID_CHARACTERS, INVALID_GENERIC
+    NONE, TAKEN, TOO_SHORT, TOO_LONG, CANNOT_START_WITH_NUMBER, INVALID_CHARACTERS, INVALID_GENERIC
   }
 
   enum ButtonState {
@@ -174,7 +253,7 @@ class UsernameEditViewModel extends ViewModel {
 
   static class Factory extends ViewModelProvider.NewInstanceFactory {
     @Override
-    public @NonNull<T extends ViewModel> T create(@NonNull Class<T> modelClass) {
+    public @NonNull <T extends ViewModel> T create(@NonNull Class<T> modelClass) {
       //noinspection ConstantConditions
       return modelClass.cast(new UsernameEditViewModel());
     }

app/src/main/java/org/thoughtcrime/securesms/profiles/manage/UsernameState.kt

@@ -0,0 +1,36 @@
+package org.thoughtcrime.securesms.profiles.manage
+
+import org.whispersystems.signalservice.internal.push.ReserveUsernameResponse
+
+/**
+ * Describes the state of the username suffix, which is a spanned CharSequence.
+ */
+sealed class UsernameState {
+
+  protected open val username: String? = null
+  open val isInProgress: Boolean = false
+
+  object Loading : UsernameState() {
+    override val isInProgress: Boolean = true
+  }
+
+  object NoUsername : UsernameState()
+
+  data class Reserved(
+    val reserveUsernameResponse: ReserveUsernameResponse
+  ) : UsernameState() {
+    override val username: String? = reserveUsernameResponse.username
+  }
+
+  data class Set(
+    override val username: String
+  ) : UsernameState()
+
+  fun getNickname(): String? {
+    return username?.split('#')?.firstOrNull()
+  }
+
+  fun getDiscriminator(): String? {
+    return username?.split('#')?.lastOrNull()
+  }
+}

app/src/main/java/org/thoughtcrime/securesms/profiles/manage/UsernameSuffix.kt

@@ -1,43 +0,0 @@
-package org.thoughtcrime.securesms.profiles.manage
-
-import android.content.Context
-import androidx.core.content.ContextCompat
-import com.google.android.material.progressindicator.CircularProgressIndicatorSpec
-import com.google.android.material.progressindicator.IndeterminateDrawable
-import org.signal.core.util.DimensionUnit
-import org.thoughtcrime.securesms.R
-
-/**
- * Describes the state of the username suffix, which is a spanned CharSequence.
- */
-data class UsernameSuffix(
-  val charSequence: CharSequence?
-) {
-
-  val isInProgress = charSequence == null
-
-  companion object {
-    @JvmField
-    val LOADING = UsernameSuffix(null)
-
-    @JvmField
-    val NONE = UsernameSuffix("")
-
-    @JvmStatic
-    fun fromCode(code: Int) = UsernameSuffix("#$code")
-
-    @JvmStatic
-    fun getInProgressDrawable(context: Context): IndeterminateDrawable<CircularProgressIndicatorSpec> {
-      val progressIndicatorSpec = CircularProgressIndicatorSpec(context, null).apply {
-        indicatorInset = 0
-        indicatorSize = DimensionUnit.DP.toPixels(16f).toInt()
-        trackColor = ContextCompat.getColor(context, R.color.signal_colorOnSurfaceVariant)
-        trackThickness = DimensionUnit.DP.toPixels(1f).toInt()
-      }
-
-      return IndeterminateDrawable.createCircularDrawable(context, progressIndicatorSpec).apply {
-        setBounds(0, 0, DimensionUnit.DP.toPixels(16f).toInt(), DimensionUnit.DP.toPixels(16f).toInt())
-      }
-    }
-  }
-}

app/src/main/java/org/thoughtcrime/securesms/recipients/Recipient.java

@@ -570,6 +570,37 @@ public class Recipient {
   }
 
   public @NonNull String getDisplayName(@NonNull Context context) {
+    String name = getNameFromLocalData(context);
+
+    if (Util.isEmpty(name)) {
+      name = context.getString(R.string.Recipient_unknown);
+    }
+
+    return StringUtil.isolateBidi(name);
+  }
+
+  public @NonNull String getDisplayNameOrUsername(@NonNull Context context) {
+    String name = getNameFromLocalData(context);
+
+    if (Util.isEmpty(name)) {
+      name = StringUtil.isolateBidi(username);
+    }
+
+    if (Util.isEmpty(name)) {
+      name = StringUtil.isolateBidi(context.getString(R.string.Recipient_unknown));
+    }
+
+    return StringUtil.isolateBidi(name);
+  }
+
+  public boolean hasNonUsernameDisplayName(@NonNull Context context) {
+    return getNameFromLocalData(context) != null;
+  }
+
+  /**
+   * @return local name for user ignoring the username.
+   */
+  private @Nullable String getNameFromLocalData(@NonNull Context context) {
     String name = getGroupName(context);
 
     if (Util.isEmpty(name)) {
@@ -588,40 +619,6 @@ public class Recipient {
       name = email;
     }
 
-    if (Util.isEmpty(name)) {
-      name = context.getString(R.string.Recipient_unknown);
-    }
-
-    return StringUtil.isolateBidi(name);
-  }
-
-  public @NonNull String getDisplayNameOrUsername(@NonNull Context context) {
-    String name = getGroupName(context);
-
-    if (Util.isEmpty(name)) {
-      name = systemContactName;
-    }
-
-    if (Util.isEmpty(name)) {
-      name = StringUtil.isolateBidi(getProfileName().toString());
-    }
-
-    if (Util.isEmpty(name) && !Util.isEmpty(e164)) {
-      name = PhoneNumberFormatter.prettyPrint(e164);
-    }
-
-    if (Util.isEmpty(name)) {
-      name = StringUtil.isolateBidi(email);
-    }
-
-    if (Util.isEmpty(name)) {
-      name = StringUtil.isolateBidi(username);
-    }
-
-    if (Util.isEmpty(name)) {
-      name = StringUtil.isolateBidi(context.getString(R.string.Recipient_unknown));
-    }
-
     return name;
   }
 

app/src/main/java/org/thoughtcrime/securesms/util/UsernameUtil.java

@@ -12,6 +12,7 @@ import org.thoughtcrime.securesms.dependencies.ApplicationDependencies;
 import org.thoughtcrime.securesms.recipients.Recipient;
 import org.thoughtcrime.securesms.recipients.RecipientId;
 import org.whispersystems.signalservice.api.profiles.SignalServiceProfile;
+import org.whispersystems.signalservice.api.push.ACI;
 import org.whispersystems.signalservice.api.push.ServiceId;
 
 import java.io.IOException;
@@ -67,8 +68,8 @@ public class UsernameUtil {
 
     try {
       Log.d(TAG, "No local user with this username. Searching remotely.");
-      SignalServiceProfile profile = ApplicationDependencies.getSignalServiceMessageReceiver().retrieveProfileByUsername(username, Optional.empty(), Locale.getDefault());
+      ACI aci = ApplicationDependencies.getSignalServiceAccountManager().getAciByUsername(username);
-      return Optional.ofNullable(profile.getServiceId());
+      return Optional.ofNullable(aci);
     } catch (IOException e) {
       return Optional.empty();
     }

core-util/src/main/java/org/signal/core/util/Result.kt

@@ -9,7 +9,10 @@ sealed class Result<out S, out F> {
   data class Success<out S>(val success: S) : Result<S, Nothing>()
 
   companion object {
+    @JvmStatic
     fun <S> success(value: S) = Success(value)
+
+    @JvmStatic
     fun <F> failure(value: F) = Failure(value)
   }
 

libsignal/service/src/main/java/org/whispersystems/signalservice/api/SignalServiceAccountManager.java

@@ -70,6 +70,7 @@ import org.whispersystems.signalservice.internal.push.PushServiceSocket;
 import org.whispersystems.signalservice.internal.push.RemoteAttestationUtil;
 import org.whispersystems.signalservice.internal.push.RemoteConfigResponse;
 import org.whispersystems.signalservice.internal.push.RequestVerificationCodeResponse;
+import org.whispersystems.signalservice.internal.push.ReserveUsernameResponse;
 import org.whispersystems.signalservice.internal.push.SignalServiceProtos;
 import org.whispersystems.signalservice.internal.push.VerifyAccountResponse;
 import org.whispersystems.signalservice.internal.push.WhoAmIResponse;
@@ -866,8 +867,20 @@ public class SignalServiceAccountManager {
     }
   }
 
-  public void setUsername(String username) throws IOException {
+  public ACI getAciByUsername(String username) throws IOException {
-    this.pushServiceSocket.setUsername(username);
+    return this.pushServiceSocket.getAciByUsername(username);
+  }
+
+  public void setUsername(String nickname, String existingUsername) throws IOException {
+    this.pushServiceSocket.setUsername(nickname, existingUsername);
+  }
+
+  public ReserveUsernameResponse reserveUsername(String nickname) throws IOException {
+    return this.pushServiceSocket.reserveUsername(nickname);
+  }
+
+  public void confirmUsername(ReserveUsernameResponse reserveUsernameResponse) throws IOException {
+    this.pushServiceSocket.confirmUsername(reserveUsernameResponse);
   }
 
   public void deleteUsername() throws IOException {

libsignal/service/src/main/java/org/whispersystems/signalservice/api/SignalServiceMessageReceiver.java

@@ -118,12 +118,6 @@ public class SignalServiceMessageReceiver {
     }
   }
 
-  public SignalServiceProfile retrieveProfileByUsername(String username, Optional<UnidentifiedAccess> unidentifiedAccess, Locale locale)
-      throws IOException
-  {
-    return socket.retrieveProfileByUsername(username, unidentifiedAccess, locale);
-  }
-
   public InputStream retrieveProfileAvatar(String path, File destination, ProfileKey profileKey, long maxSizeBytes)
       throws IOException
   {

libsignal/service/src/main/java/org/whispersystems/signalservice/api/push/exceptions/UsernameIsNotAssociatedWithAnAccountException.java

@@ -0,0 +1,7 @@
+package org.whispersystems.signalservice.api.push.exceptions;
+
+public class UsernameIsNotAssociatedWithAnAccountException extends NotFoundException {
+  public UsernameIsNotAssociatedWithAnAccountException() {
+    super("The given username is not associated with an account.");
+  }
+}

libsignal/service/src/main/java/org/whispersystems/signalservice/api/push/exceptions/UsernameIsNotReservedException.java

@@ -0,0 +1,7 @@
+package org.whispersystems.signalservice.api.push.exceptions;
+
+public class UsernameIsNotReservedException extends NonSuccessfulResponseCodeException {
+  public UsernameIsNotReservedException() {
+    super(409, "The given username is not associated with an account.");
+  }
+}

libsignal/service/src/main/java/org/whispersystems/signalservice/internal/push/ConfirmUsernameRequest.java

@@ -0,0 +1,16 @@
+package org.whispersystems.signalservice.internal.push;
+
+import com.fasterxml.jackson.annotation.JsonProperty;
+
+class ConfirmUsernameRequest {
+  @JsonProperty
+  private String usernameToConfirm;
+
+  @JsonProperty
+  private String reservationToken;
+
+  ConfirmUsernameRequest(String usernameToConfirm, String reservationToken) {
+    this.usernameToConfirm = usernameToConfirm;
+    this.reservationToken  = reservationToken;
+  }
+}

libsignal/service/src/main/java/org/whispersystems/signalservice/internal/push/GetAciByUsernameResponse.java

@@ -0,0 +1,18 @@
+package org.whispersystems.signalservice.internal.push;
+
+import com.fasterxml.jackson.annotation.JsonProperty;
+
+/**
+ * JSON POJO that represents the returned ACI from a call to
+ * /v1/account/username/[username]
+ */
+class GetAciByUsernameResponse {
+  @JsonProperty
+  private String uuid;
+
+  GetAciByUsernameResponse() {}
+
+  String getUuid() {
+    return uuid;
+  }
+}

libsignal/service/src/main/java/org/whispersystems/signalservice/internal/push/PushServiceSocket.java

@@ -53,6 +53,7 @@ import org.whispersystems.signalservice.api.payments.CurrencyConversions;
 import org.whispersystems.signalservice.api.profiles.ProfileAndCredential;
 import org.whispersystems.signalservice.api.profiles.SignalServiceProfile;
 import org.whispersystems.signalservice.api.profiles.SignalServiceProfileWrite;
+import org.whispersystems.signalservice.api.push.ACI;
 import org.whispersystems.signalservice.api.push.ServiceId;
 import org.whispersystems.signalservice.api.push.ServiceIdType;
 import org.whispersystems.signalservice.api.push.SignalServiceAddress;
@@ -79,6 +80,8 @@ import org.whispersystems.signalservice.api.push.exceptions.RemoteAttestationRes
 import org.whispersystems.signalservice.api.push.exceptions.ResumeLocationInvalidException;
 import org.whispersystems.signalservice.api.push.exceptions.ServerRejectedException;
 import org.whispersystems.signalservice.api.push.exceptions.UnregisteredUserException;
+import org.whispersystems.signalservice.api.push.exceptions.UsernameIsNotAssociatedWithAnAccountException;
+import org.whispersystems.signalservice.api.push.exceptions.UsernameIsNotReservedException;
 import org.whispersystems.signalservice.api.push.exceptions.UsernameMalformedException;
 import org.whispersystems.signalservice.api.push.exceptions.UsernameTakenException;
 import org.whispersystems.signalservice.api.storage.StorageAuthResponse;
@@ -139,6 +142,8 @@ import java.io.InputStream;
 import java.io.OutputStream;
 import java.io.UnsupportedEncodingException;
 import java.math.BigDecimal;
+import java.net.URLEncoder;
+import java.nio.charset.StandardCharsets;
 import java.security.KeyManagementException;
 import java.security.NoSuchAlgorithmException;
 import java.security.SecureRandom;
@@ -156,10 +161,12 @@ import java.util.concurrent.TimeUnit;
 import java.util.function.Function;
 
 import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 import javax.net.ssl.SSLContext;
 import javax.net.ssl.TrustManager;
 import javax.net.ssl.X509TrustManager;
 
+import io.reactivex.rxjava3.annotations.NonNull;
 import io.reactivex.rxjava3.core.Single;
 import io.reactivex.rxjava3.schedulers.Schedulers;
 import okhttp3.Call;
@@ -195,8 +202,10 @@ public class PushServiceSocket {
   private static final String REGISTRATION_LOCK_PATH     = "/v1/accounts/registration_lock";
   private static final String REQUEST_PUSH_CHALLENGE     = "/v1/accounts/fcm/preauth/%s/%s";
   private static final String WHO_AM_I                   = "/v1/accounts/whoami";
-  private static final String SET_USERNAME_PATH          = "/v1/accounts/username/%s";
+  private static final String GET_USERNAME_PATH          = "/v1/accounts/username/%s";
-  private static final String DELETE_USERNAME_PATH       = "/v1/accounts/username";
+  private static final String MODIFY_USERNAME_PATH       = "/v1/accounts/username";
+  private static final String RESERVE_USERNAME_PATH      = "/v1/accounts/username/reserved";
+  private static final String CONFIRM_USERNAME_PATH      = "/v1/accounts/username/confirm";
   private static final String DELETE_ACCOUNT_PATH        = "/v1/accounts/me";
   private static final String CHANGE_NUMBER_PATH         = "/v1/accounts/number";
   private static final String IDENTIFIER_REGISTERED_PATH = "/v1/accounts/account/%s";
@@ -221,7 +230,6 @@ public class PushServiceSocket {
   private static final String PAYMENTS_AUTH_PATH        = "/v1/payments/auth";
 
   private static final String PROFILE_PATH              = "/v1/profile/%s";
-  private static final String PROFILE_USERNAME_PATH     = "/v1/profile/username/%s";
   private static final String PROFILE_BATCH_CHECK_PATH  = "/v1/profile/identity_check/batch";
 
   private static final String SENDER_CERTIFICATE_PATH         = "/v1/certificate/delivery";
@@ -770,19 +778,6 @@ public class PushServiceSocket {
     });
   }
 
-  public SignalServiceProfile retrieveProfileByUsername(String username, Optional<UnidentifiedAccess> unidentifiedAccess, Locale locale)
-      throws NonSuccessfulResponseCodeException, PushNetworkException, MalformedResponseException
-  {
-    String response = makeServiceRequest(String.format(PROFILE_USERNAME_PATH, username), "GET", null, AcceptLanguagesUtil.getHeadersWithAcceptLanguage(locale), unidentifiedAccess);
-
-    try {
-      return JsonUtil.fromJson(response, SignalServiceProfile.class);
-    } catch (IOException e) {
-      Log.w(TAG, e);
-      throw new MalformedResponseException("Unable to parse entity", e);
-    }
-  }
-
   public ListenableFuture<ProfileAndCredential> retrieveVersionedProfileAndCredential(UUID target, ProfileKey profileKey, Optional<UnidentifiedAccess> unidentifiedAccess, Locale locale) {
     ProfileKeyVersion                  profileKeyIdentifier = profileKey.getProfileKeyVersion(target);
     ProfileKeyCredentialRequestContext requestContext       = clientZkProfileOperations.createProfileKeyCredentialRequestContext(random, target, profileKey);
@@ -899,17 +894,102 @@ public class PushServiceSocket {
         .onErrorReturn(ServiceResponse::forUnknownError);
   }
 
-  public void setUsername(String username) throws IOException {
+  /**
-    makeServiceRequest(String.format(SET_USERNAME_PATH, username), "PUT", "", NO_HEADERS, (responseCode, body) -> {
+   * Gets the ACI for the given username, if it exists. This is an unauthenticated request.
+   *
+   * This network request can have the following error responses:
+   * <ul>
+   *   <li>404 - The username given is not associated with an account</li>
+   *   <li>428 - Rate-limited, retry is available in the Retry-After header</li>
+   *   <li>400 - Bad Request. The request included authentication.</li>
+   * </ul>
+   *
+   * @param username The username to look up.
+   * @return The ACI for the given username if it exists.
+   * @throws IOException if a network exception occurs.
+   */
+  public @NonNull ACI getAciByUsername(String username) throws IOException {
+    String response = makeServiceRequestWithoutAuthentication(
+        String.format(GET_USERNAME_PATH, URLEncoder.encode(username, StandardCharsets.UTF_8.toString())),
+        "GET",
+        null,
+        (responseCode, body) -> {
+          if (responseCode == 404) {
+            throw new UsernameIsNotAssociatedWithAnAccountException();
+          }
+        }
+    );
+
+    GetAciByUsernameResponse getAciByUsernameResponse = JsonUtil.fromJsonResponse(response, GetAciByUsernameResponse.class);
+    return ACI.from(UUID.fromString(getAciByUsernameResponse.getUuid()));
+  }
+
+  /**
+   * Set the username for the account without seeing the discriminator first.
+   *
+   * @param nickname          The user-supplied nickname, which must meet the requirements for usernames.
+   * @param existingUsername  (Optional) If the account has a current username, indicates what the client thinks the current username is. Allows the server to
+   *                          deduplicate repeated requests.
+   * @return                  The username as set by the server, which includes both the nickname and discriminator.
+   * @throws IOException      Thrown when the username is invalid or taken, or when another network error occurs.
+   */
+  public @NonNull String setUsername(@NonNull String nickname, @Nullable String existingUsername) throws IOException {
+    SetUsernameRequest setUsernameRequest = new SetUsernameRequest(nickname, existingUsername);
+
+    String responseString = makeServiceRequest(MODIFY_USERNAME_PATH, "PUT", JsonUtil.toJson(setUsernameRequest), NO_HEADERS, (responseCode, body) -> {
       switch (responseCode) {
-        case 400: throw new UsernameMalformedException();
+        case 422: throw new UsernameMalformedException();
         case 409: throw new UsernameTakenException();
       }
     }, Optional.empty());
+
+    SetUsernameResponse response = JsonUtil.fromJsonResponse(responseString, SetUsernameResponse.class);
+    return response.getUsername();
+  }
+
+  /**
+   * Reserve a username for the account. This replaces an existing reservation if one exists. The username is guaranteed to be available for 5 minutes and can
+   * be confirmed with confirmUsername.
+   *
+   * @param nickname          The user-supplied nickname, which must meet the requirements for usernames.
+   * @return                  The reserved username. It is available for confirmation for 5 minutes.
+   * @throws IOException      Thrown when the username is invalid or taken, or when another network error occurs.
+   */
+  public @NonNull ReserveUsernameResponse reserveUsername(@NonNull String nickname) throws IOException {
+    ReserveUsernameRequest reserveUsernameRequest = new ReserveUsernameRequest(nickname);
+
+    String responseString = makeServiceRequest(RESERVE_USERNAME_PATH, "PUT", JsonUtil.toJson(reserveUsernameRequest), NO_HEADERS, (responseCode, body) -> {
+      switch (responseCode) {
+        case 422: throw new UsernameMalformedException();
+        case 409: throw new UsernameTakenException();
+      }
+    }, Optional.empty());
+
+    return JsonUtil.fromJsonResponse(responseString, ReserveUsernameResponse.class);
+  }
+
+  /**
+   * Set a previously reserved username for the account.
+   *
+   * @param reserveUsernameResponse The response object from the reservation
+   * @throws IOException                Thrown when the username is invalid or taken, or when another network error occurs.
+   */
+  public void confirmUsername(ReserveUsernameResponse reserveUsernameResponse) throws IOException {
+    ConfirmUsernameRequest confirmUsernameRequest = new ConfirmUsernameRequest(reserveUsernameResponse.getUsername(), reserveUsernameResponse.getReservationToken());
+
+    makeServiceRequest(CONFIRM_USERNAME_PATH, "PUT", JsonUtil.toJson(confirmUsernameRequest), NO_HEADERS, (responseCode, body) -> {
+      switch (responseCode) {
+        case 409: throw new UsernameIsNotReservedException();
+        case 410: throw new UsernameTakenException();
+      }
+    }, Optional.empty());
   }
 
+  /**
+   * Remove the username associated with the account.
+   */
   public void deleteUsername() throws IOException {
-    makeServiceRequest(DELETE_USERNAME_PATH, "DELETE", null);
+    makeServiceRequest(MODIFY_USERNAME_PATH, "DELETE", null);
   }
 
   public void deleteAccount() throws IOException {

libsignal/service/src/main/java/org/whispersystems/signalservice/internal/push/ReserveUsernameRequest.java

@@ -0,0 +1,16 @@
+package org.whispersystems.signalservice.internal.push;
+
+import com.fasterxml.jackson.annotation.JsonProperty;
+
+class ReserveUsernameRequest {
+  @JsonProperty
+  private String nickname;
+
+  ReserveUsernameRequest(String nickname) {
+    this.nickname = nickname;
+  }
+
+  String getNickname() {
+    return nickname;
+  }
+}

libsignal/service/src/main/java/org/whispersystems/signalservice/internal/push/ReserveUsernameResponse.java

@@ -0,0 +1,21 @@
+package org.whispersystems.signalservice.internal.push;
+
+import com.fasterxml.jackson.annotation.JsonProperty;
+
+public class ReserveUsernameResponse {
+  @JsonProperty
+  private String username;
+
+  @JsonProperty
+  private String reservationToken;
+
+  ReserveUsernameResponse() {}
+
+  public String getUsername() {
+    return username;
+  }
+
+  String getReservationToken() {
+    return reservationToken;
+  }
+}

libsignal/service/src/main/java/org/whispersystems/signalservice/internal/push/SetUsernameRequest.java

@@ -0,0 +1,24 @@
+package org.whispersystems.signalservice.internal.push;
+
+import com.fasterxml.jackson.annotation.JsonProperty;
+
+class SetUsernameRequest {
+  @JsonProperty
+  private String nickname;
+
+  @JsonProperty
+  private String existingUsername;
+
+  SetUsernameRequest(String nickname, String existingUsername) {
+    this.nickname         = nickname;
+    this.existingUsername = existingUsername;
+  }
+
+  String getNickname() {
+    return nickname;
+  }
+
+  String getExistingUsername() {
+    return existingUsername;
+  }
+}

libsignal/service/src/main/java/org/whispersystems/signalservice/internal/push/SetUsernameResponse.java

@@ -0,0 +1,14 @@
+package org.whispersystems.signalservice.internal.push;
+
+import com.fasterxml.jackson.annotation.JsonProperty;
+
+class SetUsernameResponse {
+  @JsonProperty
+  private String username;
+
+  SetUsernameResponse() {}
+
+  String getUsername() {
+    return username;
+  }
+}