Support rendering URLs inside sync barcodes (#5944)

Task/Issue URL: https://app.asana.com/1/137249556945/project/608920331025315/task/1209921184459923?focus=true

### Description
Allows sync setup codes which appear in the QR barcode to be URL-based. 
- Note, this is disabled by default.
- Note, this PR doesn’t handle scanning a URL-based barcode which will be in a higher branch on this stack.

### Steps to test this PR
Get two devices (or one device + one emulator) as you’ll need to scan barcodes.

#### Feature disabled, everything works as normal
- [x] The feature is disabled by default, so just fresh install the app from this branch on both devices
- For each of the following scenarios, make sure you can set up sync AND ensure that the “code to include” in logcat is NOT a URL:
  - [x] Scanning barcode when both devices signed out
  - [x] Scanning barcode when both devices signed in
  - [x] Scanning barcode when scanning device is the only one signed out
  - [x] Scanning barcode when scanning device is the only one signed in
  - [x] Manually entering codes for the same scenarios…

#### Feature enabled
- [x] Enable `syncSetupBarcodeIsUrlBased` feature flag on a device. Note, we expect the URL to be in the barcode but the other device won’t be able to scan it successfully (implemented in a higher branch on this stack) so don’t worry about that part.
 - Repeat the scenarios above, 
     - [ ] ensuring the barcode is a URL when showing the barcode (e.g., scan it from system camera app and inspect it). URL should match the spec from the [tech design](https://app.asana.com/1/137249556945/project/608920331025315/task/1209922290919800?focus=true).
     - [ ] ensuring when manually sharing the code it does NOT use a URL

Author: CDRussell

sync/sync-impl/src/main/java/com/duckduckgo/sync/impl/EncodingExtension.kt

@@ -25,3 +25,28 @@ internal fun String.encodeB64(): String {
 internal fun String.decodeB64(): String {
     return String(Base64.decode(this, Base64.DEFAULT))
 }
+
+/**
+ * This assumes the string is already base64-encoded
+ */
+internal fun String.applyUrlSafetyFromB64(): String {
+    return this
+        .replace('+', '-')
+        .replace('/', '_')
+        .trimEnd('=')
+}
+
+internal fun String.removeUrlSafetyToRestoreB64(): String {
+    return this
+        .replace('-', '+')
+        .replace('_', '/')
+        .restoreBase64Padding()
+}
+
+private fun String.restoreBase64Padding(): String {
+    return when (length % 4) {
+        2 -> "$this=="
+        3 -> "$this="
+        else -> this
+    }
+}

sync/sync-impl/src/main/java/com/duckduckgo/sync/impl/SyncAccountRepository.kt

@@ -37,7 +37,9 @@ import com.duckduckgo.sync.impl.CodeType.UNKNOWN
 import com.duckduckgo.sync.impl.ExchangeResult.*
 import com.duckduckgo.sync.impl.Result.Error
 import com.duckduckgo.sync.impl.Result.Success
+import com.duckduckgo.sync.impl.SyncAccountRepository.AuthCode
 import com.duckduckgo.sync.impl.pixels.*
+import com.duckduckgo.sync.impl.ui.qrcode.SyncBarcodeUrlWrapper
 import com.duckduckgo.sync.store.*
 import com.squareup.anvil.annotations.*
 import com.squareup.moshi.*
@@ -59,16 +61,28 @@ interface SyncAccountRepository {
     fun logout(deviceId: String): Result<Boolean>
     fun deleteAccount(): Result<Boolean>
     fun latestToken(): String
-    fun getRecoveryCode(): Result<String>
+    fun getRecoveryCode(): Result<AuthCode>
     fun getThisConnectedDevice(): ConnectedDevice?
     fun getConnectedDevices(): Result<List<ConnectedDevice>>
-    fun getConnectQR(): Result<String>
+    fun getConnectQR(): Result<AuthCode>
     fun pollConnectionKeys(): Result<Boolean>
-    fun generateExchangeInvitationCode(): Result<String>
+    fun generateExchangeInvitationCode(): Result<AuthCode>
     fun pollSecondDeviceExchangeAcknowledgement(): Result<Boolean>
     fun pollForRecoveryCodeAndLogin(): Result<ExchangeResult>
     fun renameDevice(device: ConnectedDevice): Result<Boolean>
     fun logoutAndJoinNewAccount(stringCode: String): Result<Boolean>
+
+    data class AuthCode(
+        /**
+         * A code that is suitable for displaying in a QR code.
+         */
+        val qrCode: String,
+
+        /**
+         * Just the code (b64-encoded)
+         */
+        val rawCode: String,
+    )
 }
 
 @ContributesBinding(AppScope::class)
@@ -85,6 +99,7 @@ class AppSyncAccountRepository @Inject constructor(
     private val dispatcherProvider: DispatcherProvider,
     private val syncFeature: SyncFeature,
     private val deviceKeyGenerator: DeviceKeyGenerator,
+    private val syncCodeUrlWrapper: SyncBarcodeUrlWrapper,
 ) : SyncAccountRepository {
 
     /**
@@ -300,13 +315,16 @@ class AppSyncAccountRepository @Inject constructor(
         )
     }
 
-    override fun getRecoveryCode(): Result<String> {
+    override fun getRecoveryCode(): Result<AuthCode> {
         val primaryKey = syncStore.primaryKey ?: return Error(reason = "Get Recovery Code: Not existing primary Key").alsoFireAccountErrorPixel()
         val userID = syncStore.userId ?: return Error(reason = "Get Recovery Code: Not existing userId").alsoFireAccountErrorPixel()
-        return Success(Adapters.recoveryCodeAdapter.toJson(LinkCode(RecoveryCode(primaryKey, userID))).encodeB64())
+        val b64Encoded = Adapters.recoveryCodeAdapter.toJson(LinkCode(RecoveryCode(primaryKey, userID))).encodeB64()
+
+        // no additional formatting on the QR code for recovery codes, so qrCode always identical to rawCode
+        return Success(AuthCode(qrCode = b64Encoded, rawCode = b64Encoded))
     }
 
-    override fun generateExchangeInvitationCode(): Result<String> {
+    override fun generateExchangeInvitationCode(): Result<AuthCode> {
         // Sync: InviteFlow - A (https://app.asana.com/0/72649045549333/1209571867429615)
         Timber.d("Sync-exchange: InviteFlow - A. Generating invitation code")
 
@@ -321,14 +339,19 @@ class AppSyncAccountRepository @Inject constructor(
         val invitationWrapper = InvitationCodeWrapper(invitationCode)
 
         return kotlin.runCatching {
-            val code = Adapters.invitationCodeAdapter.toJson(invitationWrapper).encodeB64()
-            Success(code)
+            val b64Encoded = Adapters.invitationCodeAdapter.toJson(invitationWrapper).encodeB64()
+            val qrCode = if (syncFeature.syncSetupBarcodeIsUrlBased().isEnabled()) {
+                syncCodeUrlWrapper.wrapCodeInUrl(b64Encoded)
+            } else {
+                b64Encoded
+            }
+            Success(AuthCode(qrCode = qrCode, rawCode = b64Encoded))
         }.getOrElse {
             Error(code = EXCHANGE_FAILED.code, reason = "Error generating invitation code").alsoFireAccountErrorPixel()
         }
     }
 
-    override fun getConnectQR(): Result<String> {
+    override fun getConnectQR(): Result<AuthCode> {
         val prepareForConnect = kotlin.runCatching {
             nativeLib.prepareForConnect().also {
                 it.checkResult("Creating ConnectQR code failed")
@@ -344,7 +367,13 @@ class AppSyncAccountRepository @Inject constructor(
             LinkCode(connect = ConnectCode(deviceId = deviceId, secretKey = prepareForConnect.publicKey)),
         ) ?: return Error(reason = "Error generating Linking Code").alsoFireAccountErrorPixel()
 
-        return Success(linkingQRCode.encodeB64())
+        val b64Encoded = linkingQRCode.encodeB64()
+        val qrCode = if (syncFeature.syncSetupBarcodeIsUrlBased().isEnabled()) {
+            syncCodeUrlWrapper.wrapCodeInUrl(b64Encoded)
+        } else {
+            b64Encoded
+        }
+        return Success(AuthCode(qrCode = qrCode, rawCode = b64Encoded))
     }
 
     private fun connectDevice(connectKeys: ConnectCode): Result<Boolean> {
@@ -465,7 +494,7 @@ class AppSyncAccountRepository @Inject constructor(
 
                 // recovery code comes b64 encoded, so we need to decode it, then encrypt, which automatically b64 encodes the encrypted form
                 return kotlin.runCatching {
-                    val json = recoveryCode.data.decodeB64()
+                    val json = recoveryCode.data.rawCode.decodeB64()
                     val encryptedJson = nativeLib.seal(json, publicKey)
                     syncApi.sendEncryptedMessage(keyId, encryptedJson)
                 }.getOrElse {

sync/sync-impl/src/main/java/com/duckduckgo/sync/impl/SyncFeature.kt

@@ -20,7 +20,6 @@ import com.duckduckgo.anvil.annotations.ContributesRemoteFeature
 import com.duckduckgo.di.scopes.AppScope
 import com.duckduckgo.feature.toggles.api.Toggle
 import com.duckduckgo.feature.toggles.api.Toggle.DefaultFeatureValue
-import com.duckduckgo.feature.toggles.api.Toggle.InternalAlwaysEnabled
 
 @ContributesRemoteFeature(
     scope = AppScope::class,
@@ -54,4 +53,7 @@ interface SyncFeature {
 
     @Toggle.DefaultValue(DefaultFeatureValue.TRUE)
     fun automaticallyUpdateSyncSettings(): Toggle
+
+    @Toggle.DefaultValue(DefaultFeatureValue.FALSE)
+    fun syncSetupBarcodeIsUrlBased(): Toggle
 }

sync/sync-impl/src/main/java/com/duckduckgo/sync/impl/ui/SyncActivityViewModel.kt

@@ -310,9 +310,9 @@ class SyncActivityViewModel @Inject constructor(
 
     fun generateRecoveryCode(viewContext: Context) {
         viewModelScope.launch(dispatchers.io()) {
-            syncAccountRepository.getRecoveryCode().onSuccess { recoveryCodeB64 ->
+            syncAccountRepository.getRecoveryCode().onSuccess { authCode ->
                 kotlin.runCatching {
-                    recoveryCodePDF.generateAndStoreRecoveryCodePDF(viewContext, recoveryCodeB64)
+                    recoveryCodePDF.generateAndStoreRecoveryCodePDF(viewContext, authCode.rawCode)
                 }.onSuccess { generateRecoveryCodePDF ->
                     command.send(RecoveryCodePDFSuccess(generateRecoveryCodePDF))
                 }.onFailure {

sync/sync-impl/src/main/java/com/duckduckgo/sync/impl/ui/SyncConnectViewModel.kt

@@ -48,7 +48,7 @@ import com.duckduckgo.sync.impl.ui.SyncConnectViewModel.Command.LoginSuccess
 import com.duckduckgo.sync.impl.ui.SyncConnectViewModel.Command.ReadTextCode
 import com.duckduckgo.sync.impl.ui.SyncConnectViewModel.Command.ShowError
 import com.duckduckgo.sync.impl.ui.SyncConnectViewModel.Command.ShowMessage
-import javax.inject.*
+import javax.inject.Inject
 import kotlinx.coroutines.channels.BufferOverflow.DROP_OLDEST
 import kotlinx.coroutines.channels.Channel
 import kotlinx.coroutines.delay
@@ -127,9 +127,9 @@ class SyncConnectViewModel @Inject constructor(
 
     private suspend fun showQRCode() {
         syncAccountRepository.getConnectQR()
-            .onSuccess { connectQR ->
+            .onSuccess { code ->
                 val qrBitmap = withContext(dispatchers.io()) {
-                    qrEncoder.encodeAsBitmap(connectQR, dimen.qrSizeSmall, dimen.qrSizeSmall)
+                    qrEncoder.encodeAsBitmap(code.qrCode, dimen.qrSizeSmall, dimen.qrSizeSmall)
                 }
                 viewState.emit(viewState.value.copy(qrCodeBitmap = qrBitmap))
             }.onFailure {
@@ -146,8 +146,8 @@ class SyncConnectViewModel @Inject constructor(
     fun onCopyCodeClicked() {
         viewModelScope.launch(dispatchers.io()) {
             syncAccountRepository.getConnectQR().getOrNull()?.let { code ->
-                Timber.d("Sync: recovery available for sharing manually: $code")
-                clipboard.copyToClipboard(code)
+                Timber.d("Sync: code available for sharing manually: $code")
+                clipboard.copyToClipboard(code.rawCode)
                 command.send(ShowMessage(R.string.sync_code_copied_message))
             } ?: command.send(FinishWithError)
         }

sync/sync-impl/src/main/java/com/duckduckgo/sync/impl/ui/SyncInternalSettingsViewModel.kt

@@ -204,7 +204,7 @@ constructor(
     fun onShowQRClicked() {
         viewModelScope.launch(dispatchers.io()) {
             val recoveryCode = syncAccountRepository.getRecoveryCode().getOrNull() ?: return@launch
-            command.send(ShowQR(recoveryCode))
+            command.send(ShowQR(recoveryCode.qrCode))
         }
     }
 
@@ -242,7 +242,9 @@ constructor(
                     return@launch
                 }
 
-                is Success -> qrCodeResult.data
+                is Success -> {
+                    qrCodeResult.data.qrCode
+                }
             }
             updateViewState()
             command.send(ShowQR(qrCode))

sync/sync-impl/src/main/java/com/duckduckgo/sync/impl/ui/SyncWithAnotherActivityViewModel.kt

@@ -40,6 +40,7 @@ import com.duckduckgo.sync.impl.R.string
 import com.duckduckgo.sync.impl.Result.Error
 import com.duckduckgo.sync.impl.Result.Success
 import com.duckduckgo.sync.impl.SyncAccountRepository
+import com.duckduckgo.sync.impl.SyncAccountRepository.AuthCode
 import com.duckduckgo.sync.impl.SyncFeature
 import com.duckduckgo.sync.impl.onFailure
 import com.duckduckgo.sync.impl.onSuccess
@@ -77,7 +78,7 @@ class SyncWithAnotherActivityViewModel @Inject constructor(
     private val command = Channel<Command>(1, DROP_OLDEST)
     fun commands(): Flow<Command> = command.receiveAsFlow()
 
-    private var barcodeContents: String? = null
+    private var barcodeContents: AuthCode? = null
 
     private val viewState = MutableStateFlow(ViewState())
     fun viewState(): Flow<ViewState> = viewState.onStart {
@@ -108,17 +109,20 @@ class SyncWithAnotherActivityViewModel @Inject constructor(
     }
 
     private suspend fun showQRCode() {
-        val shouldExchangeKeysToSyncAnotherDevice = syncFeature.exchangeKeysToSyncWithAnotherDevice().isEnabled()
-
-        if (!shouldExchangeKeysToSyncAnotherDevice) {
+        // get the code as a Result, and pair it with the type of code we're dealing with
+        val result = if (!syncFeature.exchangeKeysToSyncWithAnotherDevice().isEnabled()) {
             syncAccountRepository.getRecoveryCode()
         } else {
             syncAccountRepository.generateExchangeInvitationCode()
-        }.onSuccess { connectQR ->
-            barcodeContents = connectQR
+        }
+
+        result.onSuccess { authCode ->
+            barcodeContents = authCode
+
             val qrBitmap = withContext(dispatchers.io()) {
-                qrEncoder.encodeAsBitmap(connectQR, dimen.qrSizeSmall, dimen.qrSizeSmall)
+                qrEncoder.encodeAsBitmap(authCode.qrCode, dimen.qrSizeSmall, dimen.qrSizeSmall)
             }
+
             viewState.emit(viewState.value.copy(qrCodeBitmap = qrBitmap))
         }.onFailure {
             command.send(Command.FinishWithError)
@@ -133,8 +137,8 @@ class SyncWithAnotherActivityViewModel @Inject constructor(
 
     fun onCopyCodeClicked() {
         viewModelScope.launch(dispatchers.io()) {
-            barcodeContents?.let { code ->
-                clipboard.copyToClipboard(code)
+            barcodeContents?.let { contents ->
+                clipboard.copyToClipboard(contents.rawCode)
                 command.send(ShowMessage(string.sync_code_copied_message))
             } ?: command.send(FinishWithError)
         }

sync/sync-impl/src/main/java/com/duckduckgo/sync/impl/ui/qrcode/SyncBarcodeUrl.kt

@@ -0,0 +1,67 @@
+/*
+ * Copyright (c) 2025 DuckDuckGo
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.duckduckgo.sync.impl.ui.qrcode
+
+import androidx.core.net.toUri
+
+data class SyncBarcodeUrl(
+    val webSafeB64EncodedCode: String,
+    val urlEncodedDeviceName: String? = null,
+) {
+
+    fun asUrl(): String {
+        val sb = StringBuilder(URL_BASE)
+            .append("&")
+            .append(CODE_PARAM).append("=").append(webSafeB64EncodedCode)
+
+        if (urlEncodedDeviceName?.isNotBlank() == true) {
+            sb.append("&")
+            sb.append(DEVICE_NAME_PARAM).append("=").append(urlEncodedDeviceName)
+        }
+
+        return sb.toString()
+    }
+
+    companion object {
+        const val URL_BASE = "https://duckduckgo.com/sync/pairing/#"
+        private const val CODE_PARAM = "code"
+        private const val DEVICE_NAME_PARAM = "deviceName"
+
+        fun parseUrl(fullSyncUrl: String): SyncBarcodeUrl? {
+            return kotlin.runCatching {
+                if (!fullSyncUrl.startsWith(URL_BASE)) {
+                    return null
+                }
+
+                val uri = fullSyncUrl.toUri()
+                val fragment = uri.fragment ?: return null
+                val fragmentParts = fragment.split("&")
+
+                val code = fragmentParts
+                    .find { it.startsWith("code=") }
+                    ?.substringAfter("code=")
+                    ?: return null
+
+                val deviceName = fragmentParts
+                    .find { it.startsWith("deviceName=") }
+                    ?.substringAfter("deviceName=")
+
+                SyncBarcodeUrl(webSafeB64EncodedCode = code, urlEncodedDeviceName = deviceName)
+            }.getOrNull()
+        }
+    }
+}