Add QR scanning to username link flow.

2025-12-24 21:15:48 +00:00 · 2023-04-03 09:56:44 -04:00
parent bb8fdcabcb
commit dc2e249566
15 changed files with 882 additions and 36 deletions
--- a/app/build.gradle
+++ b/app/build.gradle
@@ -559,6 +559,7 @@ dependencies {
    }
    implementation libs.dnsjava
    implementation libs.kotlinx.collections.immutable
+    implementation libs.accompanist.permissions

    spinnerImplementation project(":spinner")

--- a/app/src/main/java/org/thoughtcrime/securesms/components/settings/app/usernamelinks/QrCode.kt
+++ b/app/src/main/java/org/thoughtcrime/securesms/components/settings/app/usernamelinks/QrCode.kt
@@ -2,6 +2,7 @@ package org.thoughtcrime.securesms.components.settings.app.usernamelinks

 import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.size
 import androidx.compose.foundation.layout.width
 import androidx.compose.material3.Surface
 import androidx.compose.runtime.Composable
@@ -93,12 +94,12 @@ private fun DrawScope.drawQr(
  }

  // Logo border
-  val deadzonePaddingPercent = 0.02f
+  val deadzonePaddingPercent = 0.03f
  val logoBorderRadiusPx = ((deadzonePercent - deadzonePaddingPercent) * size.width) / 2
  drawCircle(
    color = foregroundColor,
    radius = logoBorderRadiusPx,
-    style = Stroke(width = cellWidthPx * 0.7f),
+    style = Stroke(width = 4.dp.toPx()),
    center = this.center
  )

@@ -156,9 +157,7 @@ private fun Preview() {
  Surface {
    QrCode(
      data = QrCodeData.forData("https://signal.org", 64),
-      modifier = Modifier
-        .width(100.dp)
-        .height(100.dp),
+      modifier = Modifier.size(200.dp),
      deadzonePercent = 0.3f
    )
  }
--- a/app/src/main/java/org/thoughtcrime/securesms/components/settings/app/usernamelinks/main/QrScanResult.kt
+++ b/app/src/main/java/org/thoughtcrime/securesms/components/settings/app/usernamelinks/main/QrScanResult.kt
@@ -0,0 +1,16 @@
+package org.thoughtcrime.securesms.components.settings.app.usernamelinks.main
+
+import org.thoughtcrime.securesms.recipients.Recipient
+
+/**
+ * Result of taking data from the QR scanner and trying to resolve it to a recipient.
+ */
+sealed class QrScanResult {
+  class Success(val recipient: Recipient) : QrScanResult()
+
+  class NotFound(val username: String) : QrScanResult()
+
+  object InvalidData : QrScanResult()
+
+  object NetworkError : QrScanResult()
+}
--- a/app/src/main/java/org/thoughtcrime/securesms/components/settings/app/usernamelinks/main/UsernameLinkSettingsFragment.kt
+++ b/app/src/main/java/org/thoughtcrime/securesms/components/settings/app/usernamelinks/main/UsernameLinkSettingsFragment.kt
@@ -1,25 +1,61 @@
 package org.thoughtcrime.securesms.components.settings.app.usernamelinks.main

+import android.os.Bundle
+import android.view.View
+import androidx.compose.animation.AnimatedVisibility
+import androidx.compose.animation.slideInHorizontally
+import androidx.compose.animation.slideOutHorizontally
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.defaultMinSize
+import androidx.compose.foundation.layout.fillMaxHeight
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.shape.RoundedCornerShape
+import androidx.compose.material3.ButtonDefaults
 import androidx.compose.material3.ExperimentalMaterial3Api
+import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.Scaffold
 import androidx.compose.material3.SnackbarHost
 import androidx.compose.material3.SnackbarHostState
+import androidx.compose.material3.Surface
+import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
 import androidx.compose.runtime.rememberCoroutineScope
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.res.stringResource
 import androidx.compose.ui.tooling.preview.Preview
+import androidx.compose.ui.unit.dp
 import androidx.fragment.app.viewModels
 import androidx.navigation.NavController
 import androidx.navigation.fragment.findNavController
+import com.google.accompanist.permissions.ExperimentalPermissionsApi
+import com.google.accompanist.permissions.PermissionState
+import com.google.accompanist.permissions.isGranted
+import com.google.accompanist.permissions.rememberPermissionState
 import kotlinx.coroutines.CoroutineScope
+import org.signal.core.ui.Buttons
+import org.signal.core.ui.Dialogs
+import org.signal.core.ui.theme.SignalTheme
+import org.signal.core.util.concurrent.LifecycleDisposable
+import org.thoughtcrime.securesms.R
+import org.thoughtcrime.securesms.components.settings.app.usernamelinks.main.UsernameLinkSettingsState.ActiveTab
 import org.thoughtcrime.securesms.compose.ComposeFragment

-@OptIn(ExperimentalMaterial3Api::class)
+@OptIn(
+  ExperimentalMaterial3Api::class,
+  ExperimentalPermissionsApi::class
+)
 class UsernameLinkSettingsFragment : ComposeFragment() {

-  val viewModel: UsernameLinkSettingsViewModel by viewModels()
+  private val viewModel: UsernameLinkSettingsViewModel by viewModels()
+  private val disposables: LifecycleDisposable = LifecycleDisposable()

  @Composable
  override fun FragmentContent() {
@@ -29,23 +65,121 @@ class UsernameLinkSettingsFragment : ComposeFragment() {
    val navController: NavController by remember { mutableStateOf(findNavController()) }

    Scaffold(
-      snackbarHost = { SnackbarHost(hostState = snackbarHostState) }
+      snackbarHost = { SnackbarHost(hostState = snackbarHostState) },
+      topBar = { TopAppBarContent(state.activeTab) }
    ) { contentPadding ->
-      UsernameLinkShareScreen(
-        state = state,
-        snackbarHostState = snackbarHostState,
-        scope = scope,
-        contentPadding = contentPadding,
-        navController = navController
-      )
+
+      if (state.indeterminateProgress) {
+        Dialogs.IndeterminateProgressDialog()
+      }
+
+      AnimatedVisibility(
+        visible = state.activeTab == ActiveTab.Code,
+        enter = slideInHorizontally(initialOffsetX = { fullWidth -> -fullWidth }),
+        exit = slideOutHorizontally(targetOffsetX = { fullWidth -> -fullWidth })
+      ) {
+        UsernameLinkShareScreen(
+          state = state,
+          snackbarHostState = snackbarHostState,
+          scope = scope,
+          modifier = Modifier.padding(contentPadding),
+          navController = navController
+        )
+      }
+
+      AnimatedVisibility(
+        visible = state.activeTab == ActiveTab.Scan,
+        enter = slideInHorizontally(initialOffsetX = { fullWidth -> fullWidth }),
+        exit = slideOutHorizontally(targetOffsetX = { fullWidth -> fullWidth })
+      ) {
+        UsernameQrScanScreen(
+          lifecycleOwner = viewLifecycleOwner,
+          disposables = disposables.disposables,
+          qrScanResult = state.qrScanResult,
+          onQrCodeScanned = { data -> viewModel.onQrCodeScanned(data) },
+          onQrResultHandled = { viewModel.onQrResultHandled() },
+          modifier = Modifier.padding(contentPadding)
+        )
+      }
    }
  }

+  override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
+    disposables.bindTo(viewLifecycleOwner)
+  }
+
  override fun onResume() {
    super.onResume()
    viewModel.onResume()
  }

+  @Composable
+  private fun TopAppBarContent(activeTab: ActiveTab) {
+    val cameraPermissionState: PermissionState = rememberPermissionState(permission = android.Manifest.permission.CAMERA)
+
+    Box(
+      modifier = Modifier
+        .fillMaxWidth()
+        .height(64.dp)
+    ) {
+      Row(
+        modifier = Modifier
+          .fillMaxWidth()
+          .fillMaxHeight(),
+        horizontalArrangement = Arrangement.Center,
+        verticalAlignment = Alignment.CenterVertically
+      ) {
+        TabButton(
+          label = stringResource(R.string.UsernameLinkSettings_code_tab_name),
+          active = activeTab == ActiveTab.Code,
+          onClick = { viewModel.onTabSelected(ActiveTab.Code) },
+          modifier = Modifier.padding(end = 8.dp)
+        )
+        TabButton(
+          label = stringResource(R.string.UsernameLinkSettings_scan_tab_name),
+          active = activeTab == ActiveTab.Scan,
+          onClick = {
+            if (cameraPermissionState.status.isGranted) {
+              viewModel.onTabSelected(ActiveTab.Scan)
+            } else {
+              cameraPermissionState.launchPermissionRequest()
+            }
+          }
+        )
+      }
+    }
+  }
+
+  @Composable
+  private fun TabButton(label: String, active: Boolean, onClick: () -> Unit, modifier: Modifier = Modifier) {
+    val colors = if (active) {
+      ButtonDefaults.filledTonalButtonColors()
+    } else {
+      ButtonDefaults.buttonColors(
+        containerColor = SignalTheme.colors.colorSurface2,
+        contentColor = MaterialTheme.colorScheme.onSurface
+      )
+    }
+    Buttons.MediumTonal(
+      onClick = onClick,
+      modifier = modifier.defaultMinSize(minWidth = 100.dp),
+      shape = RoundedCornerShape(12.dp),
+      colors = colors
+    ) {
+      Text(label)
+    }
+  }
+
+  @Preview
+  @Composable
+  private fun AppBarPreview() {
+    SignalTheme(isDarkMode = false) {
+      Surface {
+        TopAppBarContent(activeTab = ActiveTab.Code)
+      }
+    }
+  }
+
  @Preview
  @Composable
  fun PreviewAll() {
--- a/app/src/main/java/org/thoughtcrime/securesms/components/settings/app/usernamelinks/main/UsernameLinkSettingsState.kt
+++ b/app/src/main/java/org/thoughtcrime/securesms/components/settings/app/usernamelinks/main/UsernameLinkSettingsState.kt
@@ -7,8 +7,15 @@ import org.thoughtcrime.securesms.components.settings.app.usernamelinks.Username
 * Represents the UI state of the [UsernameLinkSettingsFragment].
 */
 data class UsernameLinkSettingsState(
+  val activeTab: ActiveTab,
  val username: String,
  val usernameLink: String,
  val qrCodeData: QrCodeData?,
-  val qrCodeColorScheme: UsernameQrCodeColorScheme
-)
+  val qrCodeColorScheme: UsernameQrCodeColorScheme,
+  val qrScanResult: QrScanResult? = null,
+  val indeterminateProgress: Boolean = false
+) {
+  enum class ActiveTab {
+    Code, Scan
+  }
+}
--- a/app/src/main/java/org/thoughtcrime/securesms/components/settings/app/usernamelinks/main/UsernameLinkSettingsViewModel.kt
+++ b/app/src/main/java/org/thoughtcrime/securesms/components/settings/app/usernamelinks/main/UsernameLinkSettingsViewModel.kt
@@ -9,17 +9,27 @@ import io.reactivex.rxjava3.disposables.CompositeDisposable
 import io.reactivex.rxjava3.kotlin.plusAssign
 import io.reactivex.rxjava3.schedulers.Schedulers
 import io.reactivex.rxjava3.subjects.BehaviorSubject
+import org.signal.core.util.logging.Log
+import org.signal.libsignal.usernames.BaseUsernameException
 import org.thoughtcrime.securesms.components.settings.app.usernamelinks.QrCodeData
+import org.thoughtcrime.securesms.components.settings.app.usernamelinks.main.UsernameLinkSettingsState.ActiveTab
+import org.thoughtcrime.securesms.dependencies.ApplicationDependencies
 import org.thoughtcrime.securesms.keyvalue.SignalStore
 import org.thoughtcrime.securesms.recipients.Recipient
 import org.thoughtcrime.securesms.util.UsernameUtil
+import org.whispersystems.signalservice.api.push.ACI
+import org.whispersystems.signalservice.api.push.exceptions.NonSuccessfulResponseCodeException
+import java.io.IOException

 class UsernameLinkSettingsViewModel : ViewModel() {

+  private val TAG = Log.tag(UsernameLinkSettingsViewModel::class.java)
+
  private val username: BehaviorSubject<String> = BehaviorSubject.createDefault(Recipient.self().username.get())

  private val _state = mutableStateOf(
    UsernameLinkSettingsState(
+      activeTab = ActiveTab.Code,
      username = username.value!!,
      usernameLink = UsernameUtil.generateLink(username.value!!),
      qrCodeData = null,
@@ -54,6 +64,61 @@ class UsernameLinkSettingsViewModel : ViewModel() {
    )
  }

+  fun onTabSelected(tab: ActiveTab) {
+    _state.value = _state.value.copy(
+      activeTab = tab
+    )
+  }
+
+  fun onQrCodeScanned(url: String) {
+    _state.value = _state.value.copy(
+      indeterminateProgress = true
+    )
+
+    disposable += Single
+      .fromCallable {
+        val username: String? = UsernameUtil.parseLink(url)
+
+        if (username == null) {
+          Log.w(TAG, "Failed to parse username from url")
+          return@fromCallable QrScanResult.InvalidData
+        }
+
+        return@fromCallable try {
+          val hashed: String = UsernameUtil.hashUsernameToBase64(username)
+          val aci: ACI = ApplicationDependencies.getSignalServiceAccountManager().getAciByUsernameHash(hashed)
+          QrScanResult.Success(Recipient.externalUsername(aci, username))
+        } catch (e: BaseUsernameException) {
+          Log.w(TAG, "Invalid username", e)
+          QrScanResult.InvalidData
+        } catch (e: NonSuccessfulResponseCodeException) {
+          Log.w(TAG, "Non-successful response during username resolution", e)
+          if (e.code == 404) {
+            QrScanResult.NotFound(username)
+          } else {
+            QrScanResult.NetworkError
+          }
+        } catch (e: IOException) {
+          Log.w(TAG, "Network error during username resolution", e)
+          QrScanResult.NetworkError
+        }
+      }
+      .subscribeOn(Schedulers.io())
+      .observeOn(AndroidSchedulers.mainThread())
+      .subscribe { result ->
+        _state.value = _state.value.copy(
+          qrScanResult = result,
+          indeterminateProgress = false
+        )
+      }
+  }
+
+  fun onQrResultHandled() {
+    _state.value = _state.value.copy(
+      qrScanResult = null
+    )
+  }
+
  private fun generateQrCodeData(url: String): Single<QrCodeData> {
    return Single.fromCallable {
      QrCodeData.forData(url, 64)
--- a/app/src/main/java/org/thoughtcrime/securesms/components/settings/app/usernamelinks/main/UsernameLinkShareScreen.kt
+++ b/app/src/main/java/org/thoughtcrime/securesms/components/settings/app/usernamelinks/main/UsernameLinkShareScreen.kt
@@ -5,7 +5,6 @@ import androidx.compose.foundation.background
 import androidx.compose.foundation.clickable
 import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Column
-import androidx.compose.foundation.layout.PaddingValues
 import androidx.compose.foundation.layout.Row
 import androidx.compose.foundation.layout.fillMaxWidth
 import androidx.compose.foundation.layout.padding
@@ -36,6 +35,7 @@ import org.thoughtcrime.securesms.R
 import org.thoughtcrime.securesms.components.settings.app.usernamelinks.QrCodeBadge
 import org.thoughtcrime.securesms.components.settings.app.usernamelinks.QrCodeData
 import org.thoughtcrime.securesms.components.settings.app.usernamelinks.UsernameQrCodeColorScheme
+import org.thoughtcrime.securesms.components.settings.app.usernamelinks.main.UsernameLinkSettingsState.ActiveTab
 import org.thoughtcrime.securesms.util.UsernameUtil
 import org.thoughtcrime.securesms.util.Util
 import org.thoughtcrime.securesms.util.navigation.safeNavigate
@@ -49,12 +49,10 @@ fun UsernameLinkShareScreen(
  snackbarHostState: SnackbarHostState,
  scope: CoroutineScope,
  navController: NavController,
-  modifier: Modifier = Modifier,
-  contentPadding: PaddingValues = PaddingValues(0.dp)
+  modifier: Modifier = Modifier
 ) {
  Column(
    modifier = modifier
-      .padding(contentPadding)
      .verticalScroll(rememberScrollState())
  ) {
    QrCodeBadge(
@@ -85,7 +83,8 @@ fun UsernameLinkShareScreen(
      text = stringResource(id = R.string.UsernameLinkSettings_qr_description),
      textAlign = TextAlign.Center,
      style = MaterialTheme.typography.bodyMedium,
-      modifier = Modifier.padding(top = 24.dp, bottom = 36.dp, start = 43.dp, end = 43.dp)
+      modifier = Modifier.padding(top = 24.dp, bottom = 36.dp, start = 43.dp, end = 43.dp),
+      color = MaterialTheme.colorScheme.onSurfaceVariant
    )

    Row(
@@ -186,6 +185,7 @@ private fun ScreenPreviewDarkTheme() {
 private fun previewState(): UsernameLinkSettingsState {
  val link = UsernameUtil.generateLink("maya.45")
  return UsernameLinkSettingsState(
+    activeTab = ActiveTab.Code,
    username = "maya.45",
    usernameLink = link,
    qrCodeData = QrCodeData.forData(link, 64),
--- a/app/src/main/java/org/thoughtcrime/securesms/components/settings/app/usernamelinks/main/UsernameQrScanScreen.kt
+++ b/app/src/main/java/org/thoughtcrime/securesms/components/settings/app/usernamelinks/main/UsernameQrScanScreen.kt
@@ -1,14 +1,144 @@
 package org.thoughtcrime.securesms.components.settings.app.usernamelinks.main

+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.fillMaxHeight
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.padding
+import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
+import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
+import androidx.compose.ui.draw.drawWithContent
+import androidx.compose.ui.geometry.CornerRadius
+import androidx.compose.ui.geometry.Offset
+import androidx.compose.ui.geometry.Size
+import androidx.compose.ui.graphics.BlendMode
+import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.graphics.drawscope.DrawScope
+import androidx.compose.ui.graphics.drawscope.Fill
+import androidx.compose.ui.graphics.drawscope.Stroke
+import androidx.compose.ui.platform.LocalContext
+import androidx.compose.ui.res.stringResource
+import androidx.compose.ui.unit.dp
+import androidx.compose.ui.viewinterop.AndroidView
+import androidx.lifecycle.LifecycleOwner
+import io.reactivex.rxjava3.disposables.CompositeDisposable
+import io.reactivex.rxjava3.kotlin.plusAssign
+import org.signal.core.ui.Dialogs
+import org.signal.qr.QrScannerView
+import org.thoughtcrime.securesms.R
+import org.thoughtcrime.securesms.mediasend.camerax.CameraXModelBlocklist
+import org.thoughtcrime.securesms.util.CommunicationActions

 /**
 * A screen that allows you to scan a QR code to start a chat.
 */
@Composable
-fun UsernameQrScanScreen(modifier: Modifier = Modifier) {
-  // TODO
-  Text(text = "QR Scanner Placeholder")
+fun UsernameQrScanScreen(
+  lifecycleOwner: LifecycleOwner,
+  disposables: CompositeDisposable,
+  qrScanResult: QrScanResult?,
+  onQrCodeScanned: (String) -> Unit,
+  onQrResultHandled: () -> Unit,
+  modifier: Modifier = Modifier
+) {
+  when (qrScanResult) {
+    QrScanResult.InvalidData -> {
+      QrScanResultDialog(stringResource(R.string.UsernameLinkSettings_qr_result_invalid), onDismiss = onQrResultHandled)
+    }
+    QrScanResult.NetworkError -> {
+      QrScanResultDialog(stringResource(R.string.UsernameLinkSettings_qr_result_network_error), onDismiss = onQrResultHandled)
+    }
+    is QrScanResult.NotFound -> {
+      QrScanResultDialog(stringResource(R.string.UsernameLinkSettings_qr_result_not_found, qrScanResult.username), onDismiss = onQrResultHandled)
+    }
+    is QrScanResult.Success -> {
+      CommunicationActions.startConversation(LocalContext.current, qrScanResult.recipient, null)
+      onQrResultHandled()
+    }
+    null -> {}
+  }
+
+  Column(
+    modifier = modifier
+      .fillMaxWidth()
+      .fillMaxHeight()
+  ) {
+    AndroidView(
+      factory = { context ->
+        val view = QrScannerView(context)
+        disposables += view.qrData.subscribe { data ->
+          onQrCodeScanned(data)
+        }
+        view
+      },
+      update = { view ->
+        view.start(lifecycleOwner = lifecycleOwner, forceLegacy = CameraXModelBlocklist.isBlocklisted())
+      },
+      modifier = Modifier
+        .fillMaxWidth()
+        .weight(1f, true)
+        .drawWithContent {
+          drawContent()
+          drawQrCrosshair()
+        }
+    )
+
+    Row(
+      modifier = Modifier
+        .fillMaxWidth()
+        .padding(16.dp),
+      verticalAlignment = Alignment.CenterVertically,
+      horizontalArrangement = Arrangement.Center
+    ) {
+      Text(
+        text = stringResource(R.string.UsernameLinkSettings_qr_scan_description),
+        style = MaterialTheme.typography.bodyMedium,
+        color = MaterialTheme.colorScheme.onSurfaceVariant
+      )
+    }
+  }
+}
+
+@Composable
+private fun QrScanResultDialog(message: String, onDismiss: () -> Unit) {
+  Dialogs.SimpleMessageDialog(
+    message = message,
+    dismiss = stringResource(id = android.R.string.ok),
+    onDismiss = onDismiss
+  )
+}
+
+private fun DrawScope.drawQrCrosshair() {
+  val crosshairWidth: Float = size.minDimension * 0.6f
+  val clearWidth: Float = crosshairWidth * 0.75f
+
+  // Draw a full white rounded rect...
+  drawRoundRect(
+    color = Color.White,
+    topLeft = center - Offset(crosshairWidth / 2, crosshairWidth / 2),
+    style = Stroke(width = 3.dp.toPx()),
+    size = Size(crosshairWidth, crosshairWidth),
+    cornerRadius = CornerRadius(10.dp.toPx(), 10.dp.toPx())
+  )
+
+  // ...then cut out the middle parts with BlendMode.Clear to leave us with just the corners
+  drawRect(
+    color = Color.White,
+    topLeft = Offset(center.x - clearWidth / 2, 0f),
+    style = Fill,
+    size = Size(clearWidth, size.height),
+    blendMode = BlendMode.Clear
+  )
+
+  drawRect(
+    color = Color.White,
+    topLeft = Offset(0f, center.y - clearWidth / 2),
+    style = Fill,
+    size = Size(size.width, clearWidth),
+    blendMode = BlendMode.Clear
+  )
 }
--- a/app/src/main/java/org/thoughtcrime/securesms/profiles/manage/ManageProfileFragment.java
+++ b/app/src/main/java/org/thoughtcrime/securesms/profiles/manage/ManageProfileFragment.java
@@ -247,14 +247,7 @@ public class ManageProfileFragment extends LoggingFragment {
      binding.manageProfileUsernameShare.setVisibility(View.GONE);
    } else {
      binding.manageProfileUsername.setText(username);
-
-      try {
-        binding.manageProfileUsernameSubtitle.setText(UsernameUtil.generateLink(username));
-      } catch (BaseUsernameException e) {
-        Log.w(TAG, "Could not format username link", e);
-        binding.manageProfileUsernameSubtitle.setText(R.string.ManageProfileFragment_your_username);
-      }
-
+      binding.manageProfileUsernameSubtitle.setText(UsernameUtil.generateLink(username));
      binding.manageProfileUsernameShare.setVisibility(View.VISIBLE);
    }
  }
--- a/app/src/main/java/org/thoughtcrime/securesms/util/Base64.java
+++ b/app/src/main/java/org/thoughtcrime/securesms/util/Base64.java
@@ -14,6 +14,10 @@ public final class Base64 {
    return org.whispersystems.util.Base64.decode(s);
  }

+  public static @NonNull byte[] decodeWithoutPadding(@NonNull String s) throws IOException {
+    return org.whispersystems.util.Base64.decodeWithoutPadding(s);
+  }
+
  public static @NonNull String encodeBytes(@NonNull byte[] source) {
    return org.whispersystems.util.Base64.encodeBytes(source);
  }
--- a/app/src/main/java/org/thoughtcrime/securesms/util/UsernameUtil.java
+++ b/app/src/main/java/org/thoughtcrime/securesms/util/UsernameUtil.java
@@ -18,8 +18,10 @@ import org.whispersystems.signalservice.api.push.ServiceId;
 import org.whispersystems.util.Base64UrlSafe;

 import java.io.IOException;
+import java.nio.charset.StandardCharsets;
 import java.util.Locale;
 import java.util.Optional;
+import java.util.regex.Matcher;
 import java.util.regex.Pattern;

 public class UsernameUtil {
@@ -31,6 +33,7 @@ public class UsernameUtil {

  private static final Pattern FULL_PATTERN        = Pattern.compile(String.format(Locale.US, "^[a-zA-Z_][a-zA-Z0-9_]{%d,%d}$", MIN_LENGTH - 1, MAX_LENGTH - 1), Pattern.CASE_INSENSITIVE);
  private static final Pattern DIGIT_START_PATTERN = Pattern.compile("^[0-9].*$");
+  private static final Pattern URL_PATTERN         = Pattern.compile("(https://)?signal.me/#u/([a-zA-Z0-9+/]*={0,2})");


  private static final String BASE_URL_SCHEMELESS = "signal.me/#u/";
@@ -80,6 +83,14 @@ public class UsernameUtil {
    }
  }

+  /**
+   * Hashes a username to a url-safe base64 string.
+   * @throws BaseUsernameException If the username is invalid and un-hashable.
+   */
+  public static String hashUsernameToBase64(String username) throws BaseUsernameException {
+    return Base64UrlSafe.encodeBytesWithoutPadding(Username.hash(username));
+  }
+
  @WorkerThread
  public static @NonNull Optional<ServiceId> fetchAciForUsernameHash(@NonNull String base64UrlSafeEncodedUsernameHash) {
    try {
@@ -91,13 +102,33 @@ public class UsernameUtil {
    }
  }

-  public static String generateLink(String username) throws BaseUsernameException {
-    byte[] hash   = Username.hash(username);
-    String base64 = Base64UrlSafe.encodeBytesWithoutPadding(hash);
+  public static String generateLink(String username) {
+    String base64 = Base64UrlSafe.encodeBytesWithoutPadding(username.getBytes(StandardCharsets.UTF_8));

    return BASE_URL + base64;
  }

+  /**
+   * Parses the username from a link if possible, otherwise null.
+   */
+  public static @Nullable String parseLink(String url) {
+    Matcher matcher = URL_PATTERN.matcher(url);
+    if (!matcher.matches()) {
+      return null;
+    }
+
+    String base64 = matcher.group(2);
+    if (base64 == null) {
+      return null;
+    }
+
+    try {
+      return new String(Base64.decodeWithoutPadding(base64));
+    } catch (IOException e) {
+      return null;
+    }
+  }
+
  public enum InvalidReason {
    TOO_SHORT, TOO_LONG, INVALID_CHARACTERS, STARTS_WITH_NUMBER
  }
--- a/app/src/main/res/values/strings.xml
+++ b/app/src/main/res/values/strings.xml
@@ -6095,6 +6095,12 @@
    <string name="UsernameLinkSettings_qr_scan_description">Scan the QR Code on your contact’s device.</string>
    <!-- App bar title for the username QR code color picker screen -->
    <string name="UsernameLinkSettings_color_picker_app_bar_title">Color</string>
+    <!-- Body of a dialog that is displayed when we failed to read a username QR code. -->
+    <string name="UsernameLinkSettings_qr_result_invalid">The QR code was invalid.</string>
+    <!-- Body of a dialog that is displayed when the username we looked up could not be found. -->
+    <string name="UsernameLinkSettings_qr_result_not_found">A user with username $1$s could not be found.</string>
+    <!-- Body of a dialog that is displayed when we experienced a network error when looking up a username. -->
+    <string name="UsernameLinkSettings_qr_result_network_error">Experienced a network error. Please try again.</string>

    <!-- EOF -->
 </resources>