Get rid of device folders, use unix epoch as backup token and store it

app/build.gradle

@@ -106,10 +106,10 @@ dependencies {
     implementation 'commons-io:commons-io:2.6'
     implementation 'io.github.novacrypto:BIP39:2019.01.27'
 
-    implementation 'androidx.core:core-ktx:1.0.2'
+    implementation 'androidx.core:core-ktx:1.1.0'
-    implementation 'androidx.preference:preference-ktx:1.0.0'
+    implementation 'androidx.preference:preference-ktx:1.1.0'
     implementation 'com.google.android.material:material:1.0.0'
-    implementation 'androidx.lifecycle:lifecycle-extensions:2.0.0'
+    implementation 'androidx.lifecycle:lifecycle-extensions:2.1.0'
     implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
 
     lintChecks 'com.github.thirdegg:lint-rules:0.0.4-alpha'

app/src/androidTest/java/com/stevesoltys/backup/DocumentsStorageTest.kt

@@ -4,6 +4,7 @@ import androidx.documentfile.provider.DocumentFile
 import androidx.test.platform.app.InstrumentationRegistry
 import androidx.test.runner.AndroidJUnit4
 import com.stevesoltys.backup.settings.getBackupFolderUri
+import com.stevesoltys.backup.settings.getBackupToken
 import com.stevesoltys.backup.transport.backup.plugins.DocumentsStorage
 import com.stevesoltys.backup.transport.backup.plugins.createOrGetFile
 import org.junit.After
@@ -20,9 +21,9 @@ private const val filename = "test-file"
 class DocumentsStorageTest {
 
     private val context = InstrumentationRegistry.getInstrumentation().targetContext
+    private val token = getBackupToken(context)
     private val folderUri = getBackupFolderUri(context)
-    private val deviceName = "device name"
+    private val storage = DocumentsStorage(context, folderUri, token)
-    private val storage = DocumentsStorage(context, folderUri, deviceName)
 
     private lateinit var file: DocumentFile
 

app/src/main/java/com/stevesoltys/backup/metadata/Metadata.kt

@@ -3,12 +3,11 @@ package com.stevesoltys.backup.metadata
 import android.os.Build
 import android.os.Build.VERSION.SDK_INT
 import com.stevesoltys.backup.header.VERSION
-import com.stevesoltys.backup.transport.DEFAULT_RESTORE_SET_TOKEN
 import java.io.InputStream
 
 data class BackupMetadata(
         internal val version: Byte = VERSION,
-        internal val token: Long = DEFAULT_RESTORE_SET_TOKEN,
+        internal val token: Long,
         internal val androidVersion: Int = SDK_INT,
         internal val deviceName: String = "${Build.MANUFACTURER} ${Build.MODEL}"
 )
@@ -22,5 +21,8 @@ class FormatException(cause: Throwable) : Exception(cause)
 
 class EncryptedBackupMetadata private constructor(val token: Long, val inputStream: InputStream?, val error: Boolean) {
     constructor(token: Long, inputStream: InputStream) : this(token, inputStream, false)
-    constructor(token: Long, error: Boolean) : this(token, null, false)
+    /**
+     * Indicates that there was an error retrieving the encrypted backup metadata.
+     */
+    constructor(token: Long) : this(token, null, true)
 }

app/src/main/java/com/stevesoltys/backup/metadata/MetadataWriter.kt

@@ -3,7 +3,6 @@ package com.stevesoltys.backup.metadata
 import androidx.annotation.VisibleForTesting
 import com.stevesoltys.backup.Utf8
 import com.stevesoltys.backup.crypto.Crypto
-import com.stevesoltys.backup.transport.DEFAULT_RESTORE_SET_TOKEN
 import org.json.JSONObject
 import java.io.IOException
 import java.io.OutputStream
@@ -11,7 +10,7 @@ import java.io.OutputStream
 interface MetadataWriter {
 
     @Throws(IOException::class)
-    fun write(outputStream: OutputStream, token: Long = DEFAULT_RESTORE_SET_TOKEN)
+    fun write(outputStream: OutputStream, token: Long)
 
 }
 

app/src/main/java/com/stevesoltys/backup/settings/SettingsFragment.kt

@@ -10,9 +10,8 @@ import android.util.Log
 import android.view.Menu
 import android.view.MenuInflater
 import android.view.MenuItem
-import android.widget.Toast
-import android.widget.Toast.LENGTH_SHORT
 import androidx.lifecycle.ViewModelProviders
+import androidx.preference.Preference
 import androidx.preference.Preference.OnPreferenceChangeListener
 import androidx.preference.PreferenceFragmentCompat
 import androidx.preference.TwoStatePreference
@@ -37,7 +36,7 @@ class SettingsFragment : PreferenceFragmentCompat() {
 
         viewModel = ViewModelProviders.of(requireActivity()).get(SettingsViewModel::class.java)
 
-        backup = findPreference("backup") as TwoStatePreference
+        backup = findPreference("backup")!!
         backup.onPreferenceChangeListener = OnPreferenceChangeListener { _, newValue ->
             val enabled = newValue as Boolean
             try {
@@ -50,13 +49,13 @@ class SettingsFragment : PreferenceFragmentCompat() {
             }
         }
 
-        val backupLocation = findPreference("backup_location")
+        val backupLocation = findPreference<Preference>("backup_location")!!
         backupLocation.setOnPreferenceClickListener {
             viewModel.chooseBackupLocation()
             true
         }
 
-        autoRestore = findPreference("auto_restore") as TwoStatePreference
+        autoRestore = findPreference("auto_restore")!!
         autoRestore.onPreferenceChangeListener = OnPreferenceChangeListener { _, newValue ->
             val enabled = newValue as Boolean
             try {

app/src/main/java/com/stevesoltys/backup/settings/SettingsManager.kt

@@ -3,8 +3,10 @@ package com.stevesoltys.backup.settings
 import android.content.Context
 import android.net.Uri
 import android.preference.PreferenceManager.getDefaultSharedPreferences
+import java.util.*
 
 private const val PREF_KEY_BACKUP_URI = "backupUri"
+private const val PREF_KEY_BACKUP_TOKEN = "backupToken"
 private const val PREF_KEY_DEVICE_NAME = "deviceName"
 private const val PREF_KEY_BACKUP_PASSWORD = "backupLegacyPassword"
 
@@ -21,6 +23,24 @@ fun getBackupFolderUri(context: Context): Uri? {
     return Uri.parse(uriStr)
 }
 
+/**
+ * Generates and returns a new backup token while saving it as well.
+ * Subsequent calls to [getBackupToken] will return this new token once saved.
+ */
+fun getAndSaveNewBackupToken(context: Context): Long = Date().time.apply {
+    getDefaultSharedPreferences(context)
+            .edit()
+            .putLong(PREF_KEY_BACKUP_TOKEN, this)
+            .apply()
+}
+
+/**
+ * Returns the current backup token or 0 if none exists.
+ */
+fun getBackupToken(context: Context): Long {
+    return getDefaultSharedPreferences(context).getLong(PREF_KEY_BACKUP_TOKEN, 0L)
+}
+
 fun setDeviceName(context: Context, name: String) {
     getDefaultSharedPreferences(context)
             .edit()

app/src/main/java/com/stevesoltys/backup/transport/ConfigurableBackupTransport.kt

@@ -13,7 +13,6 @@ import android.util.Log
 import com.stevesoltys.backup.settings.SettingsActivity
 
 val TRANSPORT_ID: String = ConfigurableBackupTransport::class.java.name
-const val DEFAULT_RESTORE_SET_TOKEN: Long = 1
 
 private const val TRANSPORT_DIRECTORY_NAME = "com.stevesoltys.backup.transport.ConfigurableBackupTransport"
 private val TAG = ConfigurableBackupTransport::class.java.simpleName

app/src/main/java/com/stevesoltys/backup/transport/PluginManager.kt

@@ -9,7 +9,7 @@ import com.stevesoltys.backup.header.HeaderWriterImpl
 import com.stevesoltys.backup.metadata.MetadataReaderImpl
 import com.stevesoltys.backup.metadata.MetadataWriterImpl
 import com.stevesoltys.backup.settings.getBackupFolderUri
-import com.stevesoltys.backup.settings.getDeviceName
+import com.stevesoltys.backup.settings.getBackupToken
 import com.stevesoltys.backup.transport.backup.BackupCoordinator
 import com.stevesoltys.backup.transport.backup.FullBackup
 import com.stevesoltys.backup.transport.backup.InputFactory
@@ -26,7 +26,7 @@ class PluginManager(context: Context) {
 
     // We can think about using an injection framework such as Dagger to simplify this.
 
-    private val storage = DocumentsStorage(context, getBackupFolderUri(context), getDeviceName(context)!!)
+    private val storage = DocumentsStorage(context, getBackupFolderUri(context), getBackupToken(context))
 
     private val headerWriter = HeaderWriterImpl()
     private val headerReader = HeaderReaderImpl()
@@ -42,7 +42,7 @@ class PluginManager(context: Context) {
     private val fullBackup = FullBackup(backupPlugin.fullBackupPlugin, inputFactory, headerWriter, crypto)
     private val notificationManager = (context.applicationContext as Backup).notificationManager
 
-    internal val backupCoordinator = BackupCoordinator(backupPlugin, kvBackup, fullBackup, metadataWriter, notificationManager)
+    internal val backupCoordinator = BackupCoordinator(context, backupPlugin, kvBackup, fullBackup, metadataWriter, notificationManager)
 
 
     private val restorePlugin = DocumentsProviderRestorePlugin(storage)
@@ -50,6 +50,6 @@ class PluginManager(context: Context) {
     private val kvRestore = KVRestore(restorePlugin.kvRestorePlugin, outputFactory, headerReader, crypto)
     private val fullRestore = FullRestore(restorePlugin.fullRestorePlugin, outputFactory, headerReader, crypto)
 
-    internal val restoreCoordinator = RestoreCoordinator(restorePlugin, kvRestore, fullRestore, metadataReader)
+    internal val restoreCoordinator = RestoreCoordinator(context, restorePlugin, kvRestore, fullRestore, metadataReader)
 
 }

app/src/main/java/com/stevesoltys/backup/transport/backup/BackupCoordinator.kt

@@ -2,11 +2,13 @@ package com.stevesoltys.backup.transport.backup
 
 import android.app.backup.BackupTransport.TRANSPORT_ERROR
 import android.app.backup.BackupTransport.TRANSPORT_OK
+import android.content.Context
 import android.content.pm.PackageInfo
 import android.os.ParcelFileDescriptor
 import android.util.Log
 import com.stevesoltys.backup.BackupNotificationManager
 import com.stevesoltys.backup.metadata.MetadataWriter
+import com.stevesoltys.backup.settings.getBackupToken
 import java.io.IOException
 
 private val TAG = BackupCoordinator::class.java.simpleName
@@ -16,6 +18,7 @@ private val TAG = BackupCoordinator::class.java.simpleName
  * @author Torsten Grote
  */
 class BackupCoordinator(
+        private val context: Context,
         private val plugin: BackupPlugin,
         private val kv: KVBackup,
         private val full: FullBackup,
@@ -51,7 +54,7 @@ class BackupCoordinator(
         Log.i(TAG, "Initialize Device!")
         return try {
             plugin.initializeDevice()
-            writeBackupMetadata()
+            writeBackupMetadata(getBackupToken(context))
             // [finishBackup] will only be called when we return [TRANSPORT_OK] here
             // so we remember that we initialized successfully
             calledInitialize = true
@@ -148,9 +151,9 @@ class BackupCoordinator(
     }
 
     @Throws(IOException::class)
-    private fun writeBackupMetadata() {
+    private fun writeBackupMetadata(token: Long) {
         val outputStream = plugin.getMetadataOutputStream()
-        metadataWriter.write(outputStream)
+        metadataWriter.write(outputStream, token)
     }
 
 }

app/src/main/java/com/stevesoltys/backup/transport/backup/plugins/DocumentsProviderBackupPlugin.kt

@@ -25,8 +25,8 @@ class DocumentsProviderBackupPlugin(
         storage.rootBackupDir ?: throw IOException()
 
         // create backup folders
-        val kvDir = storage.defaultKvBackupDir
+        val kvDir = storage.currentKvBackupDir
-        val fullDir = storage.defaultFullBackupDir
+        val fullDir = storage.currentFullBackupDir
 
         // wipe existing data
         storage.getSetDir()?.findFile(FILE_BACKUP_METADATA)?.delete()

app/src/main/java/com/stevesoltys/backup/transport/backup/plugins/DocumentsProviderFullBackup.kt

@@ -16,7 +16,7 @@ class DocumentsProviderFullBackup(
 
     @Throws(IOException::class)
     override fun getOutputStream(targetPackage: PackageInfo): OutputStream {
-        val file = storage.defaultFullBackupDir?.createOrGetFile(targetPackage.packageName)
+        val file = storage.currentFullBackupDir?.createOrGetFile(targetPackage.packageName)
                 ?: throw IOException()
         return storage.getOutputStream(file)
     }
@@ -25,7 +25,7 @@ class DocumentsProviderFullBackup(
     override fun removeDataOfPackage(packageInfo: PackageInfo) {
         val packageName = packageInfo.packageName
         Log.i(TAG, "Deleting $packageName...")
-        val file = storage.defaultFullBackupDir?.findFile(packageName) ?: return
+        val file = storage.currentFullBackupDir?.findFile(packageName) ?: return
         if (!file.delete()) throw IOException("Failed to delete $packageName")
     }
 

app/src/main/java/com/stevesoltys/backup/transport/backup/plugins/DocumentsProviderKVBackup.kt

@@ -15,7 +15,7 @@ class DocumentsProviderKVBackup(private val storage: DocumentsStorage) : KVBacku
 
     @Throws(IOException::class)
     override fun hasDataForPackage(packageInfo: PackageInfo): Boolean {
-        val packageFile = storage.defaultKvBackupDir?.findFile(packageInfo.packageName)
+        val packageFile = storage.currentKvBackupDir?.findFile(packageInfo.packageName)
                 ?: return false
         return packageFile.listFiles().isNotEmpty()
     }
@@ -30,7 +30,7 @@ class DocumentsProviderKVBackup(private val storage: DocumentsStorage) : KVBacku
     override fun removeDataOfPackage(packageInfo: PackageInfo) {
         // we cannot use the cached this.packageFile here,
         // because this can be called before [ensureRecordStorageForPackage]
-        val packageFile = storage.defaultKvBackupDir?.findFile(packageInfo.packageName) ?: return
+        val packageFile = storage.currentKvBackupDir?.findFile(packageInfo.packageName) ?: return
         packageFile.delete()
     }
 

app/src/main/java/com/stevesoltys/backup/transport/backup/plugins/DocumentsStorage.kt

@@ -5,7 +5,7 @@ import android.content.pm.PackageInfo
 import android.net.Uri
 import android.util.Log
 import androidx.documentfile.provider.DocumentFile
-import com.stevesoltys.backup.transport.DEFAULT_RESTORE_SET_TOKEN
+import com.stevesoltys.backup.settings.getAndSaveNewBackupToken
 import java.io.IOException
 import java.io.InputStream
 import java.io.OutputStream
@@ -13,15 +13,13 @@ import java.io.OutputStream
 const val DIRECTORY_FULL_BACKUP = "full"
 const val DIRECTORY_KEY_VALUE_BACKUP = "kv"
 const val FILE_BACKUP_METADATA = ".backup.metadata"
+const val FILE_NO_MEDIA = ".nomedia"
 private const val ROOT_DIR_NAME = ".AndroidBackup"
-private const val NO_MEDIA = ".nomedia"
 private const val MIME_TYPE = "application/octet-stream"
 
 private val TAG = DocumentsStorage::class.java.simpleName
 
-class DocumentsStorage(context: Context, parentFolder: Uri?, deviceName: String) {
+class DocumentsStorage(private val context: Context, parentFolder: Uri?, token: Long) {
-
-    private val contentResolver = context.contentResolver
 
     internal val rootBackupDir: DocumentFile? by lazy {
         val folderUri = parentFolder ?: return@lazy null
@@ -30,7 +28,7 @@ class DocumentsStorage(context: Context, parentFolder: Uri?, deviceName: String)
         try {
             val rootDir = parent.createOrGetDirectory(ROOT_DIR_NAME)
             // create .nomedia file to prevent Android's MediaScanner from trying to index the backup
-            rootDir.createOrGetFile(NO_MEDIA)
+            rootDir.createOrGetFile(FILE_NO_MEDIA)
             rootDir
         } catch (e: IOException) {
             Log.e(TAG, "Error creating root backup dir.", e)
@@ -38,73 +36,71 @@ class DocumentsStorage(context: Context, parentFolder: Uri?, deviceName: String)
         }
     }
 
-    private val deviceDir: DocumentFile? by lazy {
+    private val currentToken: Long by lazy {
+        if (token != 0L) token
+        else getAndSaveNewBackupToken(context).apply {
+            Log.d(TAG, "Using a fresh backup token: $this")
+        }
+    }
+
+    private val currentSetDir: DocumentFile? by lazy {
+        val currentSetName = currentToken.toString()
         try {
-            rootBackupDir?.createOrGetDirectory(deviceName)
+            rootBackupDir?.createOrGetDirectory(currentSetName)
         } catch (e: IOException) {
             Log.e(TAG, "Error creating current restore set dir.", e)
             null
         }
     }
 
-    private val defaultSetDir: DocumentFile? by lazy {
+    val currentFullBackupDir: DocumentFile? by lazy {
-        val currentSetName = DEFAULT_RESTORE_SET_TOKEN.toString()
         try {
-            deviceDir?.createOrGetDirectory(currentSetName)
+            currentSetDir?.createOrGetDirectory(DIRECTORY_FULL_BACKUP)
-        } catch (e: IOException) {
-            Log.e(TAG, "Error creating current restore set dir.", e)
-            null
-        }
-    }
-
-    val defaultFullBackupDir: DocumentFile? by lazy {
-        try {
-            defaultSetDir?.createOrGetDirectory(DIRECTORY_FULL_BACKUP)
         } catch (e: IOException) {
             Log.e(TAG, "Error creating full backup dir.", e)
             null
         }
     }
 
-    val defaultKvBackupDir: DocumentFile? by lazy {
+    val currentKvBackupDir: DocumentFile? by lazy {
         try {
-            defaultSetDir?.createOrGetDirectory(DIRECTORY_KEY_VALUE_BACKUP)
+            currentSetDir?.createOrGetDirectory(DIRECTORY_KEY_VALUE_BACKUP)
         } catch (e: IOException) {
             Log.e(TAG, "Error creating K/V backup dir.", e)
             null
         }
     }
 
-    fun getSetDir(token: Long = DEFAULT_RESTORE_SET_TOKEN): DocumentFile? {
+    fun getSetDir(token: Long = currentToken): DocumentFile? {
-        if (token == DEFAULT_RESTORE_SET_TOKEN) return defaultSetDir
+        if (token == currentToken) return currentSetDir
-        return deviceDir?.findFile(token.toString())
+        return rootBackupDir?.findFile(token.toString())
     }
 
-    fun getKVBackupDir(token: Long = DEFAULT_RESTORE_SET_TOKEN): DocumentFile? {
+    fun getKVBackupDir(token: Long = currentToken): DocumentFile? {
-        if (token == DEFAULT_RESTORE_SET_TOKEN) return defaultKvBackupDir ?: throw IOException()
+        if (token == currentToken) return currentKvBackupDir ?: throw IOException()
         return getSetDir(token)?.findFile(DIRECTORY_KEY_VALUE_BACKUP)
     }
 
     @Throws(IOException::class)
-    fun getOrCreateKVBackupDir(token: Long = DEFAULT_RESTORE_SET_TOKEN): DocumentFile {
+    fun getOrCreateKVBackupDir(token: Long = currentToken): DocumentFile {
-        if (token == DEFAULT_RESTORE_SET_TOKEN) return defaultKvBackupDir ?: throw IOException()
+        if (token == currentToken) return currentKvBackupDir ?: throw IOException()
         val setDir = getSetDir(token) ?: throw IOException()
         return setDir.createOrGetDirectory(DIRECTORY_KEY_VALUE_BACKUP)
     }
 
-    fun getFullBackupDir(token: Long = DEFAULT_RESTORE_SET_TOKEN): DocumentFile? {
+    fun getFullBackupDir(token: Long = currentToken): DocumentFile? {
-        if (token == DEFAULT_RESTORE_SET_TOKEN) return defaultFullBackupDir ?: throw IOException()
+        if (token == currentToken) return currentFullBackupDir ?: throw IOException()
         return getSetDir(token)?.findFile(DIRECTORY_FULL_BACKUP)
     }
 
     @Throws(IOException::class)
     fun getInputStream(file: DocumentFile): InputStream {
-        return contentResolver.openInputStream(file.uri) ?: throw IOException()
+        return context.contentResolver.openInputStream(file.uri) ?: throw IOException()
     }
 
     @Throws(IOException::class)
     fun getOutputStream(file: DocumentFile): OutputStream {
-        return contentResolver.openOutputStream(file.uri) ?: throw IOException()
+        return context.contentResolver.openOutputStream(file.uri) ?: throw IOException()
     }
 
 }

app/src/main/java/com/stevesoltys/backup/transport/restore/RestoreCoordinator.kt

@@ -5,12 +5,14 @@ import android.app.backup.BackupTransport.TRANSPORT_OK
 import android.app.backup.RestoreDescription
 import android.app.backup.RestoreDescription.*
 import android.app.backup.RestoreSet
+import android.content.Context
 import android.content.pm.PackageInfo
 import android.os.ParcelFileDescriptor
 import android.util.Log
 import com.stevesoltys.backup.header.UnsupportedVersionException
 import com.stevesoltys.backup.metadata.FormatException
 import com.stevesoltys.backup.metadata.MetadataReader
+import com.stevesoltys.backup.settings.getBackupToken
 import libcore.io.IoUtils.closeQuietly
 import java.io.IOException
 
@@ -21,6 +23,7 @@ private class RestoreCoordinatorState(
 private val TAG = RestoreCoordinator::class.java.simpleName
 
 internal class RestoreCoordinator(
+        private val context: Context,
         private val plugin: RestorePlugin,
         private val kv: KVRestore,
         private val full: FullRestore,
@@ -64,8 +67,15 @@ internal class RestoreCoordinator(
         return restoreSets.toTypedArray()
     }
 
+    /**
+     * Get the identifying token of the backup set currently being stored from this device.
+     * This is used in the case of applications wishing to restore their last-known-good data.
+     *
+     * @return A token that can be used for restore,
+     * or 0 if there is no backup set available corresponding to the current device state.
+     */
     fun getCurrentRestoreSet(): Long {
-        return plugin.getCurrentRestoreSet()
+        return getBackupToken(context)
                 .apply { Log.i(TAG, "Got current restore set token: $this") }
     }
 

app/src/main/java/com/stevesoltys/backup/transport/restore/RestorePlugin.kt

@@ -16,13 +16,4 @@ interface RestorePlugin {
      **/
     fun getAvailableBackups(): Sequence<EncryptedBackupMetadata>?
 
-    /**
-     * Get the identifying token of the backup set currently being stored from this device.
-     * This is used in the case of applications wishing to restore their last-known-good data.
-     *
-     * @return A token that can be used for restore,
-     * or 0 if there is no backup set available corresponding to the current device state.
-     */
-    fun getCurrentRestoreSet(): Long
-
 }

app/src/main/java/com/stevesoltys/backup/transport/restore/plugins/DocumentsProviderRestorePlugin.kt

@@ -3,9 +3,9 @@ package com.stevesoltys.backup.transport.restore.plugins
 import android.util.Log
 import androidx.documentfile.provider.DocumentFile
 import com.stevesoltys.backup.metadata.EncryptedBackupMetadata
-import com.stevesoltys.backup.transport.DEFAULT_RESTORE_SET_TOKEN
 import com.stevesoltys.backup.transport.backup.plugins.DocumentsStorage
 import com.stevesoltys.backup.transport.backup.plugins.FILE_BACKUP_METADATA
+import com.stevesoltys.backup.transport.backup.plugins.FILE_NO_MEDIA
 import com.stevesoltys.backup.transport.restore.FullRestorePlugin
 import com.stevesoltys.backup.transport.restore.KVRestorePlugin
 import com.stevesoltys.backup.transport.restore.RestorePlugin
@@ -25,30 +25,41 @@ class DocumentsProviderRestorePlugin(private val storage: DocumentsStorage) : Re
 
     override fun getAvailableBackups(): Sequence<EncryptedBackupMetadata>? {
         val rootDir = storage.rootBackupDir ?: return null
-        val files = ArrayList<DocumentFile>()
+        val files = ArrayList<Pair<Long, DocumentFile>>()
-        for (file in rootDir.listFiles()) {
+        for (set in rootDir.listFiles()) {
-            file.isDirectory || continue
+            if (!set.isDirectory || set.name == null) {
-            val set = file.findFile(DEFAULT_RESTORE_SET_TOKEN.toString()) ?: continue
+                if (set.name != FILE_NO_MEDIA) {
-            val metadata = set.findFile(FILE_BACKUP_METADATA) ?: continue
+                    Log.w(TAG, "Found invalid backup set folder: ${set.name}")
-            files.add(metadata)
+                }
+                continue
+            }
+            val token = try {
+                set.name!!.toLong()
+            } catch (e: NumberFormatException) {
+                Log.w(TAG, "Found invalid backup set folder: ${set.name}", e)
+                continue
+            }
+            val metadata = set.findFile(FILE_BACKUP_METADATA)
+            if (metadata == null) {
+                Log.w(TAG, "Missing metadata file in backup set folder: ${set.name}")
+            } else {
+                files.add(Pair(token, metadata))
+            }
         }
         val iterator = files.iterator()
         return generateSequence {
             if (!iterator.hasNext()) return@generateSequence null  // end sequence
-            val metadata = iterator.next()
+            val pair = iterator.next()
-            val token = metadata.parentFile!!.name!!.toLong()
+            val token = pair.first
+            val metadata = pair.second
             try {
                 val stream = storage.getInputStream(metadata)
                 EncryptedBackupMetadata(token, stream)
             } catch (e: IOException) {
                 Log.e(TAG, "Error getting InputStream for backup metadata.", e)
-                EncryptedBackupMetadata(token, true)
+                EncryptedBackupMetadata(token)
             }
         }
     }
 
-    override fun getCurrentRestoreSet(): Long {
-        return DEFAULT_RESTORE_SET_TOKEN
-    }
-
 }

app/src/main/java/com/stevesoltys/backup/ui/BackupViewModel.kt

@@ -1,6 +1,8 @@
 package com.stevesoltys.backup.ui
 
 import android.app.Application
+import android.app.backup.BackupProgress
+import android.app.backup.IBackupObserver
 import android.content.Intent
 import android.content.Intent.FLAG_GRANT_READ_URI_PERMISSION
 import android.content.Intent.FLAG_GRANT_WRITE_URI_PERMISSION
@@ -13,6 +15,7 @@ import com.stevesoltys.backup.isOnExternalStorage
 import com.stevesoltys.backup.settings.getBackupFolderUri
 import com.stevesoltys.backup.settings.setBackupFolderUri
 import com.stevesoltys.backup.transport.ConfigurableBackupTransportService
+import com.stevesoltys.backup.transport.TRANSPORT_ID
 
 private val TAG = BackupViewModel::class.java.simpleName
 
@@ -55,10 +58,11 @@ abstract class BackupViewModel(protected val app: Application) : AndroidViewMode
             // stop backup service to be sure the old location will get updated
             app.stopService(Intent(app, ConfigurableBackupTransportService::class.java))
 
-            // notify the UI that the location has been set
-            locationWasSet.setEvent(LocationResult(true, initialSetUp))
-
             Log.d(TAG, "New storage location chosen: $folderUri")
+
+            // initialize the new location
+            // TODO don't do this when restoring
+            Backup.backupManager.initializeTransports(arrayOf(TRANSPORT_ID), InitializationObserver(initialSetUp))
         } else {
             Log.w(TAG, "Location was rejected: $folderUri")
 
@@ -71,6 +75,27 @@ abstract class BackupViewModel(protected val app: Application) : AndroidViewMode
         return true
     }
 
+    private inner class InitializationObserver(private val initialSetUp: Boolean) : IBackupObserver.Stub() {
+        override fun onUpdate(currentBackupPackage: String, backupProgress: BackupProgress) {
+            // noop
+        }
+        override fun onResult(target: String, status: Int) {
+            // noop
+        }
+        override fun backupFinished(status: Int) {
+            if (Log.isLoggable(TAG, Log.INFO)) {
+                Log.i(TAG, "Initialization finished. Status: $status")
+            }
+            if (status == 0) {
+                // notify the UI that the location has been set
+                locationWasSet.postEvent(LocationResult(true, initialSetUp))
+            } else {
+                // notify the UI that the location was invalid
+                locationWasSet.postEvent(LocationResult(false, initialSetUp))
+            }
+        }
+    }
+
 }
 
 class LocationResult(val validLocation: Boolean, val initialSetup: Boolean)

app/src/test/java/com/stevesoltys/backup/transport/CoordinatorIntegrationTest.kt

@@ -43,18 +43,18 @@ internal class CoordinatorIntegrationTest : TransportTest() {
     private val fullBackupPlugin = mockk<FullBackupPlugin>()
     private val fullBackup = FullBackup(fullBackupPlugin, inputFactory, headerWriter, cryptoImpl)
     private val notificationManager = mockk<BackupNotificationManager>()
-    private val backup = BackupCoordinator(backupPlugin, kvBackup, fullBackup, metadataWriter, notificationManager)
+    private val backup = BackupCoordinator(context, backupPlugin, kvBackup, fullBackup, metadataWriter, notificationManager)
 
     private val restorePlugin = mockk<RestorePlugin>()
     private val kvRestorePlugin = mockk<KVRestorePlugin>()
     private val kvRestore = KVRestore(kvRestorePlugin, outputFactory, headerReader, cryptoImpl)
     private val fullRestorePlugin = mockk<FullRestorePlugin>()
     private val fullRestore = FullRestore(fullRestorePlugin, outputFactory, headerReader, cryptoImpl)
-    private val restore = RestoreCoordinator(restorePlugin, kvRestore, fullRestore, metadataReader)
+    private val restore = RestoreCoordinator(context, restorePlugin, kvRestore, fullRestore, metadataReader)
 
     private val backupDataInput = mockk<BackupDataInput>()
     private val fileDescriptor = mockk<ParcelFileDescriptor>(relaxed = true)
-    private val token = DEFAULT_RESTORE_SET_TOKEN
+    private val token = Random.nextLong()
     private val appData = ByteArray(42).apply { Random.nextBytes(this) }
     private val appData2 = ByteArray(1337).apply { Random.nextBytes(this) }
     private val key = "RestoreKey"

app/src/test/java/com/stevesoltys/backup/transport/TransportTest.kt

@@ -1,5 +1,6 @@
 package com.stevesoltys.backup.transport
 
+import android.content.Context
 import android.content.pm.PackageInfo
 import android.util.Log
 import com.stevesoltys.backup.crypto.Crypto
@@ -13,6 +14,7 @@ import org.junit.jupiter.api.TestInstance.Lifecycle.PER_METHOD
 abstract class TransportTest {
 
     protected val crypto = mockk<Crypto>()
+    protected val context = mockk<Context>(relaxed = true)
 
     protected val packageInfo = PackageInfo().apply { packageName = "org.example" }
 

app/src/test/java/com/stevesoltys/backup/transport/backup/BackupCoordinatorTest.kt

@@ -23,14 +23,14 @@ internal class BackupCoordinatorTest: BackupTest() {
     private val metadataWriter = mockk<MetadataWriter>()
     private val notificationManager = mockk<BackupNotificationManager>()
 
-    private val backup = BackupCoordinator(plugin, kv, full, metadataWriter, notificationManager)
+    private val backup = BackupCoordinator(context, plugin, kv, full, metadataWriter, notificationManager)
 
     private val metadataOutputStream = mockk<OutputStream>()
 
     @Test
     fun `device initialization succeeds and delegates to plugin`() {
         every { plugin.initializeDevice() } just Runs
-        expectWritingMetadata()
+        expectWritingMetadata(0L)
         every { kv.hasState() } returns false
         every { full.hasState() } returns false
 
@@ -116,9 +116,9 @@ internal class BackupCoordinatorTest: BackupTest() {
         assertEquals(result, backup.finishBackup())
     }
 
-    private fun expectWritingMetadata() {
+    private fun expectWritingMetadata(token: Long = this.token) {
         every { plugin.getMetadataOutputStream() } returns metadataOutputStream
-        every { metadataWriter.write(metadataOutputStream) } just Runs
+        every { metadataWriter.write(metadataOutputStream, token) } just Runs
     }
 
 }

app/src/test/java/com/stevesoltys/backup/transport/backup/BackupTest.kt

@@ -1,11 +1,12 @@
 package com.stevesoltys.backup.transport.backup
 
 import android.os.ParcelFileDescriptor
-import com.stevesoltys.backup.transport.TransportTest
 import com.stevesoltys.backup.header.HeaderWriter
 import com.stevesoltys.backup.header.VersionHeader
+import com.stevesoltys.backup.transport.TransportTest
 import io.mockk.mockk
 import java.io.OutputStream
+import kotlin.random.Random
 
 internal abstract class BackupTest : TransportTest() {
 
@@ -14,6 +15,7 @@ internal abstract class BackupTest : TransportTest() {
     protected val data = mockk<ParcelFileDescriptor>()
     protected val outputStream = mockk<OutputStream>()
 
+    protected val token = Random.nextLong()
     protected val header = VersionHeader(packageName = packageInfo.packageName)
     protected val quota = 42L
 

app/src/test/java/com/stevesoltys/backup/transport/restore/RestoreCoordinatorTest.kt

@@ -27,7 +27,7 @@ internal class RestoreCoordinatorTest : TransportTest() {
     private val full = mockk<FullRestore>()
     private val metadataReader = mockk<MetadataReader>()
 
-    private val restore = RestoreCoordinator(plugin, kv, full, metadataReader)
+    private val restore = RestoreCoordinator(context, plugin, kv, full, metadataReader)
 
     private val token = Random.nextLong()
     private val inputStream = mockk<InputStream>()
@@ -56,11 +56,8 @@ internal class RestoreCoordinatorTest : TransportTest() {
 
     @Test
     fun `getCurrentRestoreSet() delegates to plugin`() {
-        val currentRestoreSet = Random.nextLong()
+        // We don't mock the SettingsManager, so the default value is returned here
-
+        assertEquals(0L, restore.getCurrentRestoreSet())
-        every { plugin.getCurrentRestoreSet() } returns currentRestoreSet
-
-        assertEquals(currentRestoreSet, restore.getCurrentRestoreSet())
     }
 
     @Test