Factor out code into new

AppDataRestoreManager

which was in RestoreViewModel before.
Now all three steps of app restore have their own dedicated manager class making the ViewModel more readable.

app/src/main/java/com/stevesoltys/seedvault/restore/AppDataRestoreManager.kt

@@ -0,0 +1,313 @@
+/*
+ * SPDX-FileCopyrightText: 2024 The Calyx Institute
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package com.stevesoltys.seedvault.restore
+
+import android.app.backup.BackupManager
+import android.app.backup.BackupTransport
+import android.app.backup.IBackupManager
+import android.app.backup.IRestoreObserver
+import android.app.backup.IRestoreSession
+import android.app.backup.RestoreSet
+import android.content.Context
+import android.os.RemoteException
+import android.os.UserHandle
+import android.util.Log
+import androidx.annotation.WorkerThread
+import androidx.lifecycle.LiveData
+import androidx.lifecycle.MutableLiveData
+import com.stevesoltys.seedvault.BackupMonitor
+import com.stevesoltys.seedvault.MAGIC_PACKAGE_MANAGER
+import com.stevesoltys.seedvault.R
+import com.stevesoltys.seedvault.metadata.PackageState
+import com.stevesoltys.seedvault.restore.install.isInstalled
+import com.stevesoltys.seedvault.settings.SettingsManager
+import com.stevesoltys.seedvault.transport.TRANSPORT_ID
+import com.stevesoltys.seedvault.transport.restore.RestoreCoordinator
+import com.stevesoltys.seedvault.ui.AppBackupState
+import com.stevesoltys.seedvault.ui.AppBackupState.FAILED
+import com.stevesoltys.seedvault.ui.AppBackupState.FAILED_NOT_ALLOWED
+import com.stevesoltys.seedvault.ui.AppBackupState.FAILED_NOT_INSTALLED
+import com.stevesoltys.seedvault.ui.AppBackupState.FAILED_NO_DATA
+import com.stevesoltys.seedvault.ui.AppBackupState.FAILED_QUOTA_EXCEEDED
+import com.stevesoltys.seedvault.ui.AppBackupState.IN_PROGRESS
+import com.stevesoltys.seedvault.ui.AppBackupState.NOT_YET_BACKED_UP
+import com.stevesoltys.seedvault.ui.AppBackupState.SUCCEEDED
+import com.stevesoltys.seedvault.ui.notification.getAppName
+import java.util.LinkedList
+
+private val TAG = AppDataRestoreManager::class.simpleName
+
+internal class AppDataRestoreManager(
+    private val context: Context,
+    private val backupManager: IBackupManager,
+    private val settingsManager: SettingsManager,
+    private val restoreCoordinator: RestoreCoordinator,
+) {
+
+    private var session: IRestoreSession? = null
+    private val monitor = BackupMonitor()
+
+    private val mRestoreProgress = MutableLiveData<LinkedList<AppRestoreResult>>().apply {
+        value = LinkedList<AppRestoreResult>().apply {
+            add(
+                AppRestoreResult(
+                    packageName = MAGIC_PACKAGE_MANAGER,
+                    name = getAppName(context, MAGIC_PACKAGE_MANAGER),
+                    state = IN_PROGRESS
+                )
+            )
+        }
+    }
+    val restoreProgress: LiveData<LinkedList<AppRestoreResult>> get() = mRestoreProgress
+    private val mRestoreBackupResult = MutableLiveData<RestoreBackupResult>()
+    val restoreBackupResult: LiveData<RestoreBackupResult> get() = mRestoreBackupResult
+
+    @WorkerThread
+    fun startRestore(restorableBackup: RestorableBackup) {
+        val token = restorableBackup.token
+
+        Log.d(TAG, "Starting new restore session to restore backup $token")
+
+        // if we had no token before (i.e. restore from setup wizard),
+        // use the token of the current restore set from now on
+        if (settingsManager.getToken() == null) {
+            settingsManager.setNewToken(token)
+        }
+
+        // start a new restore session
+        val session = try {
+            getOrStartSession()
+        } catch (e: RemoteException) {
+            Log.e(TAG, "Error starting new session", e)
+            mRestoreBackupResult.postValue(
+                RestoreBackupResult(context.getString(R.string.restore_set_error))
+            )
+            return
+        }
+
+        val packages = restorableBackup.packageMetadataMap.keys.toList()
+        val observer = RestoreObserver(
+            restoreCoordinator = restoreCoordinator,
+            restorableBackup = restorableBackup,
+            session = session,
+            packages = packages,
+            monitor = monitor
+        )
+
+        // We need to retrieve the restore sets before starting the restore.
+        // Otherwise, restorePackages() won't work as they need the restore sets cached internally.
+        if (session.getAvailableRestoreSets(observer, monitor) != 0) {
+            Log.e(TAG, "getAvailableRestoreSets() returned non-zero value")
+
+            mRestoreBackupResult.postValue(
+                RestoreBackupResult(context.getString(R.string.restore_set_error))
+            )
+        }
+    }
+
+    @Throws(RemoteException::class)
+    private fun getOrStartSession(): IRestoreSession {
+        @Suppress("UNRESOLVED_REFERENCE")
+        val session = this.session
+            ?: backupManager.beginRestoreSessionForUser(UserHandle.myUserId(), null, TRANSPORT_ID)
+            ?: throw RemoteException("beginRestoreSessionForUser returned null")
+        this.session = session
+        return session
+    }
+
+    @WorkerThread
+    // this should be called one package at a time and never concurrently for different packages
+    private fun onRestoreStarted(packageName: String, backup: RestorableBackup) {
+        // list is never null and always has at least one package
+        val list = mRestoreProgress.value!!
+
+        // check previous package first and change status
+        updateLatestPackage(list, backup)
+
+        // add current package
+        list.addFirst(
+            AppRestoreResult(packageName, getAppName(context, packageName), IN_PROGRESS)
+        )
+        mRestoreProgress.postValue(list)
+    }
+
+    @WorkerThread
+    private fun updateLatestPackage(list: LinkedList<AppRestoreResult>, backup: RestorableBackup) {
+        val latestResult = list[0]
+        if (restoreCoordinator.isFailedPackage(latestResult.packageName)) {
+            list[0] = latestResult.copy(state = getFailedStatus(latestResult.packageName, backup))
+        } else {
+            list[0] = latestResult.copy(state = SUCCEEDED)
+        }
+    }
+
+    @WorkerThread
+    private fun getFailedStatus(packageName: String, backup: RestorableBackup): AppBackupState {
+        val metadata = backup.packageMetadataMap[packageName] ?: return FAILED
+        return when (metadata.state) {
+            PackageState.NO_DATA -> FAILED_NO_DATA
+            PackageState.WAS_STOPPED -> NOT_YET_BACKED_UP
+            PackageState.NOT_ALLOWED -> FAILED_NOT_ALLOWED
+            PackageState.QUOTA_EXCEEDED -> FAILED_QUOTA_EXCEEDED
+            PackageState.UNKNOWN_ERROR -> FAILED
+            PackageState.APK_AND_DATA -> if (context.packageManager.isInstalled(packageName)) {
+                FAILED
+            } else FAILED_NOT_INSTALLED
+        }
+    }
+
+    @WorkerThread
+    private fun onRestoreComplete(result: RestoreBackupResult, backup: RestorableBackup) {
+        // update status of latest package
+        val list = mRestoreProgress.value!!
+        updateLatestPackage(list, backup)
+
+        // add missing packages as failed
+        val seenPackages = list.map { it.packageName }.toSet()
+        val expectedPackages = backup.packageMetadataMap.keys
+        expectedPackages.removeAll(seenPackages)
+        for (packageName: String in expectedPackages) {
+            // TODO don't add if it was a NO_DATA system app
+            val failedStatus = getFailedStatus(packageName, backup)
+            val appResult =
+                AppRestoreResult(packageName, getAppName(context, packageName), failedStatus)
+            list.addFirst(appResult)
+        }
+        mRestoreProgress.postValue(list)
+
+        mRestoreBackupResult.postValue(result)
+    }
+
+    fun closeSession() {
+        session?.endRestoreSession()
+        session = null
+    }
+
+    // TODO  sort apps alphabetically
+    @WorkerThread
+    private inner class RestoreObserver(
+        private val restoreCoordinator: RestoreCoordinator,
+        private val restorableBackup: RestorableBackup,
+        private val session: IRestoreSession,
+        private val packages: List<String>,
+        private val monitor: BackupMonitor,
+    ) : IRestoreObserver.Stub() {
+
+        /**
+         * The current package index.
+         *
+         * Used for splitting the packages into chunks.
+         */
+        private var packageIndex: Int = 0
+
+        /**
+         * Map of results for each chunk.
+         *
+         * The key is the chunk index, the value is the result.
+         */
+        private val chunkResults = mutableMapOf<Int, Int>()
+
+        /**
+         * Supply a list of the restore datasets available from the current transport.
+         * This method is invoked as a callback following the application's use of the
+         * [IRestoreSession.getAvailableRestoreSets] method.
+         *
+         * @param restoreSets An array of [RestoreSet] objects
+         *   describing all of the available datasets that are candidates for restoring to
+         *   the current device. If no applicable datasets exist, restoreSets will be null.
+         */
+        override fun restoreSetsAvailable(restoreSets: Array<out RestoreSet>?) {
+            // this gets executed after we got the restore sets
+            // now we can start the restore of all available packages
+            restoreNextPackages()
+        }
+
+        /**
+         * Restore the next chunk of packages.
+         *
+         * We need to restore in chunks, otherwise [BackupTransport.startRestore] in the
+         * framework's [PerformUnifiedRestoreTask] may fail due to an oversize Binder
+         * transaction, causing the entire restoration to fail.
+         */
+        private fun restoreNextPackages() {
+            // Make sure metadata for selected backup is cached before starting each chunk.
+            val backupMetadata = restorableBackup.backupMetadata
+            restoreCoordinator.beforeStartRestore(backupMetadata)
+
+            val nextChunkIndex = (packageIndex + PACKAGES_PER_CHUNK).coerceAtMost(packages.size)
+            val packageChunk = packages.subList(packageIndex, nextChunkIndex).toTypedArray()
+            packageIndex += packageChunk.size
+
+            val token = backupMetadata.token
+            val result = session.restorePackages(token, this, packageChunk, monitor)
+
+            if (result != BackupManager.SUCCESS) {
+                Log.e(TAG, "restorePackages() returned non-zero value: $result")
+            }
+        }
+
+        /**
+         * The restore operation has begun.
+         *
+         * @param numPackages The total number of packages
+         * being processed in this restore operation.
+         */
+        override fun restoreStarting(numPackages: Int) {
+            // noop
+        }
+
+        /**
+         * An indication of which package is being restored currently,
+         * out of the total number provided in the [restoreStarting] callback.
+         * This method is not guaranteed to be called.
+         *
+         * @param nowBeingRestored The index, between 1 and the numPackages parameter
+         *   to the [restoreStarting] callback, of the package now being restored.
+         * @param currentPackage The name of the package now being restored.
+         */
+        override fun onUpdate(nowBeingRestored: Int, currentPackage: String) {
+            // nowBeingRestored reporting is buggy, so don't use it
+            onRestoreStarted(currentPackage, restorableBackup)
+        }
+
+        /**
+         * The restore operation has completed.
+         *
+         * @param result Zero on success; a nonzero error code if the restore operation
+         *   as a whole failed.
+         */
+        override fun restoreFinished(result: Int) {
+            val chunkIndex = packageIndex / PACKAGES_PER_CHUNK
+            chunkResults[chunkIndex] = result
+
+            // Restore next chunk if successful and there are more packages to restore.
+            if (packageIndex < packages.size) {
+                restoreNextPackages()
+                return
+            }
+
+            // Restore finished, time to get the result.
+            onRestoreComplete(getRestoreResult(), restorableBackup)
+            closeSession()
+        }
+
+        private fun getRestoreResult(): RestoreBackupResult {
+            val failedChunks = chunkResults
+                .filter { it.value != BackupManager.SUCCESS }
+                .map { "chunk ${it.key} failed with error ${it.value}" }
+
+            return if (failedChunks.isNotEmpty()) {
+                Log.e(TAG, "Restore failed: $failedChunks")
+
+                return RestoreBackupResult(
+                    errorMsg = context.getString(R.string.restore_finished_error)
+                )
+            } else {
+                RestoreBackupResult(errorMsg = null)
+            }
+        }
+    }
+}

app/src/main/java/com/stevesoltys/seedvault/restore/RestoreViewModel.kt

@@ -6,34 +6,18 @@
 package com.stevesoltys.seedvault.restore
 
 import android.app.Application
-import android.app.backup.BackupManager
-import android.app.backup.BackupTransport
 import android.app.backup.IBackupManager
-import android.app.backup.IRestoreObserver
-import android.app.backup.IRestoreSession
-import android.app.backup.RestoreSet
 import android.content.Intent
 import android.graphics.drawable.Drawable
-import android.os.RemoteException
-import android.os.UserHandle
 import android.util.Log
 import androidx.annotation.UiThread
-import androidx.annotation.WorkerThread
 import androidx.appcompat.content.res.AppCompatResources.getDrawable
 import androidx.lifecycle.LiveData
 import androidx.lifecycle.MutableLiveData
 import androidx.lifecycle.asLiveData
 import androidx.lifecycle.viewModelScope
-import com.stevesoltys.seedvault.BackupMonitor
-import com.stevesoltys.seedvault.MAGIC_PACKAGE_MANAGER
 import com.stevesoltys.seedvault.R
 import com.stevesoltys.seedvault.crypto.KeyManager
-import com.stevesoltys.seedvault.metadata.PackageState.APK_AND_DATA
-import com.stevesoltys.seedvault.metadata.PackageState.NOT_ALLOWED
-import com.stevesoltys.seedvault.metadata.PackageState.NO_DATA
-import com.stevesoltys.seedvault.metadata.PackageState.QUOTA_EXCEEDED
-import com.stevesoltys.seedvault.metadata.PackageState.UNKNOWN_ERROR
-import com.stevesoltys.seedvault.metadata.PackageState.WAS_STOPPED
 import com.stevesoltys.seedvault.plugins.StoragePluginManager
 import com.stevesoltys.seedvault.restore.DisplayFragment.RESTORE_APPS
 import com.stevesoltys.seedvault.restore.DisplayFragment.RESTORE_BACKUP
@@ -43,25 +27,13 @@ import com.stevesoltys.seedvault.restore.DisplayFragment.SELECT_APPS
 import com.stevesoltys.seedvault.restore.install.ApkRestore
 import com.stevesoltys.seedvault.restore.install.InstallIntentCreator
 import com.stevesoltys.seedvault.restore.install.InstallResult
-import com.stevesoltys.seedvault.restore.install.isInstalled
 import com.stevesoltys.seedvault.settings.SettingsManager
 import com.stevesoltys.seedvault.storage.StorageRestoreService
-import com.stevesoltys.seedvault.transport.TRANSPORT_ID
 import com.stevesoltys.seedvault.transport.restore.RestoreCoordinator
-import com.stevesoltys.seedvault.ui.AppBackupState
-import com.stevesoltys.seedvault.ui.AppBackupState.FAILED
-import com.stevesoltys.seedvault.ui.AppBackupState.FAILED_NOT_ALLOWED
-import com.stevesoltys.seedvault.ui.AppBackupState.FAILED_NOT_INSTALLED
-import com.stevesoltys.seedvault.ui.AppBackupState.FAILED_NO_DATA
-import com.stevesoltys.seedvault.ui.AppBackupState.FAILED_QUOTA_EXCEEDED
-import com.stevesoltys.seedvault.ui.AppBackupState.IN_PROGRESS
-import com.stevesoltys.seedvault.ui.AppBackupState.NOT_YET_BACKED_UP
-import com.stevesoltys.seedvault.ui.AppBackupState.SUCCEEDED
 import com.stevesoltys.seedvault.ui.LiveEvent
 import com.stevesoltys.seedvault.ui.MutableLiveEvent
 import com.stevesoltys.seedvault.ui.PACKAGE_NAME_SYSTEM
 import com.stevesoltys.seedvault.ui.RequireProvisioningViewModel
-import com.stevesoltys.seedvault.ui.notification.getAppName
 import com.stevesoltys.seedvault.ui.systemData
 import com.stevesoltys.seedvault.worker.IconManager
 import com.stevesoltys.seedvault.worker.NUM_PACKAGES_PER_TRANSACTION
@@ -85,7 +57,7 @@ internal class RestoreViewModel(
     app: Application,
     settingsManager: SettingsManager,
     keyManager: KeyManager,
-    private val backupManager: IBackupManager,
+    backupManager: IBackupManager,
     private val restoreCoordinator: RestoreCoordinator,
     private val apkRestore: ApkRestore,
     private val iconManager: IconManager,
@@ -97,10 +69,10 @@ internal class RestoreViewModel(
 
     override val isRestoreOperation = true
 
-    private var session: IRestoreSession? = null
-    private val monitor = BackupMonitor()
     private val appSelectionManager =
         AppSelectionManager(app, pluginManager, iconManager, viewModelScope)
+    private val appDataRestoreManager =
+        AppDataRestoreManager(app, backupManager, settingsManager, restoreCoordinator)
 
     private val mDisplayFragment = MutableLiveEvent<DisplayFragment>()
     internal val displayFragment: LiveEvent<DisplayFragment> = mDisplayFragment
@@ -118,34 +90,14 @@ internal class RestoreViewModel(
 
     internal val installIntentCreator by lazy { InstallIntentCreator(app.packageManager) }
 
-    private val mRestoreProgress = MutableLiveData<LinkedList<AppRestoreResult>>().apply {
+    internal val restoreProgress: LiveData<LinkedList<AppRestoreResult>>
-        value = LinkedList<AppRestoreResult>().apply {
+        get() = appDataRestoreManager.restoreProgress
-            add(
-                AppRestoreResult(
-                    packageName = MAGIC_PACKAGE_MANAGER,
-                    name = getAppName(app, MAGIC_PACKAGE_MANAGER),
-                    state = IN_PROGRESS
-                )
-            )
-        }
-    }
-    internal val restoreProgress: LiveData<LinkedList<AppRestoreResult>> get() = mRestoreProgress
 
-    private val mRestoreBackupResult = MutableLiveData<RestoreBackupResult>()
+    internal val restoreBackupResult: LiveData<RestoreBackupResult>
-    internal val restoreBackupResult: LiveData<RestoreBackupResult> get() = mRestoreBackupResult
+        get() = appDataRestoreManager.restoreBackupResult
 
     override val snapshots = storageBackup.getBackupSnapshots().asLiveData(ioDispatcher)
 
-    @Throws(RemoteException::class)
-    private fun getOrStartSession(): IRestoreSession {
-        @Suppress("UNRESOLVED_REFERENCE")
-        val session = this.session
-            ?: backupManager.beginRestoreSessionForUser(UserHandle.myUserId(), null, TRANSPORT_ID)
-            ?: throw RemoteException("beginRestoreSessionForUser returned null")
-        this.session = session
-        return session
-    }
-
     internal fun loadRestoreSets() = viewModelScope.launch(ioDispatcher) {
         val backups = restoreCoordinator.getAvailableMetadata()?.mapNotNull { (token, metadata) ->
             when (metadata.time) {
@@ -208,260 +160,16 @@ internal class RestoreViewModel(
         mDisplayFragment.postEvent(RESTORE_BACKUP)
 
         viewModelScope.launch(ioDispatcher) {
-            startRestore()
+            val backup = chosenRestorableBackup.value ?: error("No Backup chosen")
+            appDataRestoreManager.startRestore(backup)
         }
     }
 
-    @WorkerThread
-    private fun startRestore() {
-        val token = mChosenRestorableBackup.value?.token
-            ?: throw IllegalStateException("No chosen backup")
-
-        Log.d(TAG, "Starting new restore session to restore backup $token")
-
-        // if we had no token before (i.e. restore from setup wizard),
-        // use the token of the current restore set from now on
-        if (settingsManager.getToken() == null) {
-            settingsManager.setNewToken(token)
-        }
-
-        // start a new restore session
-        val session = try {
-            getOrStartSession()
-        } catch (e: RemoteException) {
-            Log.e(TAG, "Error starting new session", e)
-            mRestoreBackupResult.postValue(
-                RestoreBackupResult(app.getString(R.string.restore_set_error))
-            )
-            return
-        }
-
-        val restorableBackup = mChosenRestorableBackup.value
-        val packages = restorableBackup?.packageMetadataMap?.keys?.toList()
-            ?: run {
-                Log.e(TAG, "Chosen backup has empty package metadata map")
-                mRestoreBackupResult.postValue(
-                    RestoreBackupResult(app.getString(R.string.restore_set_error))
-                )
-                return
-            }
-
-        val observer = RestoreObserver(
-            restoreCoordinator = restoreCoordinator,
-            restorableBackup = restorableBackup,
-            session = session,
-            packages = packages,
-            monitor = monitor
-        )
-
-        // We need to retrieve the restore sets before starting the restore.
-        // Otherwise, restorePackages() won't work as they need the restore sets cached internally.
-        if (session.getAvailableRestoreSets(observer, monitor) != 0) {
-            Log.e(TAG, "getAvailableRestoreSets() returned non-zero value")
-
-            mRestoreBackupResult.postValue(
-                RestoreBackupResult(app.getString(R.string.restore_set_error))
-            )
-        }
-    }
-
-    @WorkerThread
-    // this should be called one package at a time and never concurrently for different packages
-    private fun onRestoreStarted(packageName: String) {
-        // list is never null and always has at least one package
-        val list = mRestoreProgress.value!!
-
-        // check previous package first and change status
-        updateLatestPackage(list)
-
-        // add current package
-        list.addFirst(AppRestoreResult(packageName, getAppName(app, packageName), IN_PROGRESS))
-        mRestoreProgress.postValue(list)
-    }
-
-    @WorkerThread
-    private fun updateLatestPackage(list: LinkedList<AppRestoreResult>) {
-        val latestResult = list[0]
-        if (restoreCoordinator.isFailedPackage(latestResult.packageName)) {
-            list[0] = latestResult.copy(state = getFailedStatus(latestResult.packageName))
-        } else {
-            list[0] = latestResult.copy(state = SUCCEEDED)
-        }
-    }
-
-    @WorkerThread
-    private fun getFailedStatus(
-        packageName: String,
-        restorableBackup: RestorableBackup = chosenRestorableBackup.value!!,
-    ): AppBackupState {
-        val metadata = restorableBackup.packageMetadataMap[packageName] ?: return FAILED
-        return when (metadata.state) {
-            NO_DATA -> FAILED_NO_DATA
-            WAS_STOPPED -> NOT_YET_BACKED_UP
-            NOT_ALLOWED -> FAILED_NOT_ALLOWED
-            QUOTA_EXCEEDED -> FAILED_QUOTA_EXCEEDED
-            UNKNOWN_ERROR -> FAILED
-            APK_AND_DATA -> {
-                if (app.packageManager.isInstalled(packageName)) FAILED else FAILED_NOT_INSTALLED
-            }
-        }
-    }
-
-    @WorkerThread
-    private fun onRestoreComplete(result: RestoreBackupResult) {
-        // update status of latest package
-        val list = mRestoreProgress.value!!
-        updateLatestPackage(list)
-
-        // add missing packages as failed
-        val seenPackages = list.map { it.packageName }
-        val restorableBackup = chosenRestorableBackup.value!!
-        val expectedPackages = restorableBackup.packageMetadataMap.keys
-        expectedPackages.removeAll(seenPackages)
-        for (packageName: String in expectedPackages) {
-            // TODO don't add if it was a NO_DATA system app
-            val failedStatus = getFailedStatus(packageName, restorableBackup)
-            list.addFirst(AppRestoreResult(packageName, getAppName(app, packageName), failedStatus))
-        }
-        mRestoreProgress.postValue(list)
-
-        mRestoreBackupResult.postValue(result)
-    }
-
     override fun onCleared() {
         super.onCleared()
         @OptIn(DelicateCoroutinesApi::class)
         GlobalScope.launch(ioDispatcher) { iconManager.removeIcons() }
-        closeSession()
+        appDataRestoreManager.closeSession()
-    }
-
-    private fun closeSession() {
-        session?.endRestoreSession()
-        session = null
-    }
-
-    @WorkerThread
-    private inner class RestoreObserver(
-        private val restoreCoordinator: RestoreCoordinator,
-        private val restorableBackup: RestorableBackup,
-        private val session: IRestoreSession,
-        private val packages: List<String>,
-        private val monitor: BackupMonitor,
-    ) : IRestoreObserver.Stub() {
-
-        /**
-         * The current package index.
-         *
-         * Used for splitting the packages into chunks.
-         */
-        private var packageIndex: Int = 0
-
-        /**
-         * Map of results for each chunk.
-         *
-         * The key is the chunk index, the value is the result.
-         */
-        private val chunkResults = mutableMapOf<Int, Int>()
-
-        /**
-         * Supply a list of the restore datasets available from the current transport.
-         * This method is invoked as a callback following the application's use of the
-         * [IRestoreSession.getAvailableRestoreSets] method.
-         *
-         * @param restoreSets An array of [RestoreSet] objects
-         *   describing all of the available datasets that are candidates for restoring to
-         *   the current device. If no applicable datasets exist, restoreSets will be null.
-         */
-        override fun restoreSetsAvailable(restoreSets: Array<out RestoreSet>?) {
-            // this gets executed after we got the restore sets
-            // now we can start the restore of all available packages
-            restoreNextPackages()
-        }
-
-        /**
-         * Restore the next chunk of packages.
-         *
-         * We need to restore in chunks, otherwise [BackupTransport.startRestore] in the
-         * framework's [PerformUnifiedRestoreTask] may fail due to an oversize Binder
-         * transaction, causing the entire restoration to fail.
-         */
-        private fun restoreNextPackages() {
-            // Make sure metadata for selected backup is cached before starting each chunk.
-            val backupMetadata = restorableBackup.backupMetadata
-            restoreCoordinator.beforeStartRestore(backupMetadata)
-
-            val nextChunkIndex = (packageIndex + PACKAGES_PER_CHUNK).coerceAtMost(packages.size)
-            val packageChunk = packages.subList(packageIndex, nextChunkIndex).toTypedArray()
-            packageIndex += packageChunk.size
-
-            val token = backupMetadata.token
-            val result = session.restorePackages(token, this, packageChunk, monitor)
-
-            if (result != BackupManager.SUCCESS) {
-                Log.e(TAG, "restorePackages() returned non-zero value: $result")
-            }
-        }
-
-        /**
-         * The restore operation has begun.
-         *
-         * @param numPackages The total number of packages
-         * being processed in this restore operation.
-         */
-        override fun restoreStarting(numPackages: Int) {
-            // noop
-        }
-
-        /**
-         * An indication of which package is being restored currently,
-         * out of the total number provided in the [restoreStarting] callback.
-         * This method is not guaranteed to be called.
-         *
-         * @param nowBeingRestored The index, between 1 and the numPackages parameter
-         *   to the [restoreStarting] callback, of the package now being restored.
-         * @param currentPackage The name of the package now being restored.
-         */
-        override fun onUpdate(nowBeingRestored: Int, currentPackage: String) {
-            // nowBeingRestored reporting is buggy, so don't use it
-            onRestoreStarted(currentPackage)
-        }
-
-        /**
-         * The restore operation has completed.
-         *
-         * @param result Zero on success; a nonzero error code if the restore operation
-         *   as a whole failed.
-         */
-        override fun restoreFinished(result: Int) {
-            val chunkIndex = packageIndex / PACKAGES_PER_CHUNK
-            chunkResults[chunkIndex] = result
-
-            // Restore next chunk if successful and there are more packages to restore.
-            if (packageIndex < packages.size) {
-                restoreNextPackages()
-                return
-            }
-
-            // Restore finished, time to get the result.
-            onRestoreComplete(getRestoreResult())
-            closeSession()
-        }
-
-        private fun getRestoreResult(): RestoreBackupResult {
-            val failedChunks = chunkResults
-                .filter { it.value != BackupManager.SUCCESS }
-                .map { "chunk ${it.key} failed with error ${it.value}" }
-
-            return if (failedChunks.isNotEmpty()) {
-                Log.e(TAG, "Restore failed: $failedChunks")
-
-                return RestoreBackupResult(
-                    errorMsg = app.getString(R.string.restore_finished_error)
-                )
-            } else {
-                RestoreBackupResult(errorMsg = null)
-            }
-        }
     }
 
     @UiThread