Clear existing storage snapshots from storage medium

because that scenario isn't supported at the moment

app/src/main/java/com/stevesoltys/seedvault/App.kt

@@ -47,7 +47,7 @@ open class App : Application() {
 
         viewModel { SettingsViewModel(this@App, get(), get(), get(), get(), get(), get()) }
         viewModel { RecoveryCodeViewModel(this@App, get(), get(), get()) }
-        viewModel { BackupStorageViewModel(this@App, get(), get(), get()) }
+        viewModel { BackupStorageViewModel(this@App, get(), get(), get(), get()) }
         viewModel { RestoreStorageViewModel(this@App, get(), get()) }
         viewModel { RestoreViewModel(this@App, get(), get(), get(), get(), get(), get()) }
         viewModel { FileSelectionViewModel(this@App, get()) }

app/src/main/java/com/stevesoltys/seedvault/ui/storage/BackupStorageViewModel.kt

@@ -16,6 +16,7 @@ import com.stevesoltys.seedvault.transport.backup.BackupCoordinator
 import com.stevesoltys.seedvault.transport.requestBackup
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.launch
+import org.calyxos.backup.storage.api.StorageBackup
 import java.io.IOException
 
 private val TAG = BackupStorageViewModel::class.java.simpleName
@@ -24,6 +25,7 @@ internal class BackupStorageViewModel(
     private val app: Application,
     private val backupManager: IBackupManager,
     private val backupCoordinator: BackupCoordinator,
+    private val storageBackup: StorageBackup,
     settingsManager: SettingsManager
 ) : StorageViewModel(app, settingsManager) {
 
@@ -32,6 +34,9 @@ internal class BackupStorageViewModel(
     override fun onLocationSet(uri: Uri) {
         val isUsb = saveStorage(uri)
         viewModelScope.launch(Dispatchers.IO) {
+            // remove old storage snapshots and clear cache
+            storageBackup.deleteAllSnapshots()
+            storageBackup.clearCache()
             try {
                 // will also generate a new backup token for the new restore set
                 backupCoordinator.startNewRestoreSet()

app/src/main/java/com/stevesoltys/seedvault/ui/storage/StorageCheckFragment.kt

@@ -3,6 +3,7 @@ package com.stevesoltys.seedvault.ui.storage
 import android.os.Bundle
 import android.view.LayoutInflater
 import android.view.View
+import android.view.View.GONE
 import android.view.View.INVISIBLE
 import android.view.View.VISIBLE
 import android.view.ViewGroup
@@ -37,7 +38,7 @@ class StorageCheckFragment : Fragment() {
         inflater: LayoutInflater,
         container: ViewGroup?,
         savedInstanceState: Bundle?
-    ): View? {
+    ): View {
         val v: View = inflater.inflate(R.layout.fragment_storage_check, container, false)
 
         titleView = v.findViewById(R.id.titleView)
@@ -55,6 +56,7 @@ class StorageCheckFragment : Fragment() {
 
         val errorMsg = requireArguments().getString(ERROR_MSG)
         if (errorMsg != null) {
+            view.findViewById<View>(R.id.patienceView).visibility = GONE
             progressBar.visibility = INVISIBLE
             errorView.text = errorMsg
             errorView.visibility = VISIBLE

app/src/main/java/com/stevesoltys/seedvault/ui/storage/StorageRootsFragment.kt

@@ -83,6 +83,9 @@ internal class StorageRootsFragment : Fragment(), StorageRootClickedListener {
             backView.setOnClickListener { requireActivity().finishAfterTransition() }
         } else {
             warningIcon.visibility = VISIBLE
+            if (viewModel.hasStorageSet) {
+                warningText.setText(R.string.storage_fragment_warning_delete)
+            }
             warningText.visibility = VISIBLE
             divider.visibility = VISIBLE
         }

app/src/main/java/com/stevesoltys/seedvault/ui/storage/StorageViewModel.kt

@@ -41,6 +41,8 @@ internal abstract class StorageViewModel(
     private var storageRoot: StorageRoot? = null
 
     internal var isSetupWizard: Boolean = false
+    internal val hasStorageSet: Boolean
+        get() = settingsManager.getStorage() != null
     abstract val isRestoreOperation: Boolean
 
     companion object {

app/src/main/res/layout/fragment_storage_check.xml

@@ -29,6 +29,17 @@
         app:layout_constraintTop_toBottomOf="@+id/imageView"
         tools:text="@string/storage_check_fragment_backup_title" />
 
+    <TextView
+        android:id="@+id/patienceView"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:layout_margin="16dp"
+        android:gravity="center_horizontal"
+        android:text="@string/storage_check_fragment_patience"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toBottomOf="@+id/titleView" />
+
     <ProgressBar
         android:id="@+id/progressBar"
         style="?android:progressBarStyleLarge"
@@ -37,10 +48,10 @@
         android:layout_marginStart="16dp"
         android:layout_marginTop="32dp"
         android:layout_marginEnd="16dp"
-        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintBottom_toTopOf="@+id/backButton"
         app:layout_constraintEnd_toEndOf="parent"
         app:layout_constraintStart_toStartOf="parent"
-        app:layout_constraintTop_toBottomOf="@+id/titleView"
+        app:layout_constraintTop_toBottomOf="@+id/patienceView"
         app:layout_constraintVertical_bias="0.0" />
 
     <TextView
@@ -56,7 +67,7 @@
         app:layout_constraintBottom_toBottomOf="parent"
         app:layout_constraintEnd_toEndOf="parent"
         app:layout_constraintStart_toStartOf="parent"
-        app:layout_constraintTop_toBottomOf="@+id/titleView"
+        app:layout_constraintTop_toBottomOf="@+id/patienceView"
         app:layout_constraintVertical_bias="0.0"
         tools:text="@string/storage_check_fragment_backup_error"
         tools:visibility="visible" />

app/src/main/res/layout/fragment_storage_root.xml

@@ -22,24 +22,24 @@
         android:layout_width="0dp"
         android:layout_height="wrap_content"
         android:layout_margin="16dp"
+        android:gravity="center"
         android:text="@string/storage_fragment_backup_title"
         android:textSize="24sp"
-        android:gravity="center"
-        tools:text="Choose where to store backup (is a short title, but it can be longer)"
         app:layout_constraintEnd_toEndOf="parent"
         app:layout_constraintStart_toStartOf="parent"
-        app:layout_constraintTop_toBottomOf="@+id/imageView" />
+        app:layout_constraintTop_toBottomOf="@+id/imageView"
+        tools:text="Choose where to store backup (is a short title, but it can be longer)" />
 
     <ImageView
         android:id="@+id/warningIcon"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_marginStart="16dp"
-        android:layout_marginTop="24dp"
         android:src="@drawable/ic_warning"
         android:visibility="gone"
+        app:layout_constraintBottom_toBottomOf="@+id/warningText"
         app:layout_constraintStart_toStartOf="parent"
-        app:layout_constraintTop_toBottomOf="@+id/titleView"
+        app:layout_constraintTop_toTopOf="@+id/warningText"
         tools:ignore="ContentDescription"
         tools:visibility="visible" />
 

app/src/main/res/values/strings.xml

@@ -46,6 +46,7 @@
     <string name="storage_fragment_backup_title">Choose where to store backups</string>
     <string name="storage_fragment_restore_title">Where to find your backups?</string>
     <string name="storage_fragment_warning">People with access to your storage location can learn which apps you use, but do not get access to the apps\' data.</string>
+    <string name="storage_fragment_warning_delete">Existing backups in this location will be deleted.</string>
     <string name="storage_fake_drive_title">USB flash drive</string>
     <string name="storage_fake_drive_summary">Needs to be plugged in</string>
     <string name="storage_available_bytes"><xliff:g example="1 GB" id="size">%1$s</xliff:g> free</string>
@@ -54,6 +55,7 @@
     <string name="storage_fake_nextcloud_summary_installed">Tap to set up account</string>
     <string name="storage_fake_nextcloud_summary_unavailable">Account not available. Set one up (or disable passcode).</string>
     <string name="storage_check_fragment_backup_title">Initializing backup location…</string>
+    <string name="storage_check_fragment_patience">This may take some time…</string>
     <string name="storage_check_fragment_restore_title">Looking for backups…</string>
     <string name="storage_check_fragment_backup_error">An error occurred while accessing the backup location.</string>
     <string name="storage_check_fragment_permission_error">Unable to get the permission to write to the backup location.</string>

storage/README.md

@@ -8,3 +8,8 @@ Please see the [design document](doc/design.md) for more information.
 There is also a [demo app](demo) that illustrates the working of the library
 and does not need to be a system app with elevated permissions.
 It can be built and installed as a regular app requesting permissions at runtime.
+
+## Limitations
+
+The design document mentions several limitations of this initial implementation.
+One of them is that you cannot backup more than one device to the same storage location.

storage/demo/src/main/java/de/grobox/storagebackuptester/MainViewModel.kt

@@ -89,7 +89,12 @@ class MainViewModel(application: Application) : BackupContentViewModel(applicati
     }
 
     fun setBackupLocation(uri: Uri?) {
-        if (uri != null) clearDb()
+        if (uri != null) {
+            viewModelScope.launch(Dispatchers.IO) {
+                storageBackup.deleteAllSnapshots()
+                storageBackup.clearCache()
+            }
+        }
         settingsManager.setBackupLocation(uri)
     }
 

storage/lib/src/main/java/org/calyxos/backup/storage/api/StorageBackup.kt

@@ -26,6 +26,7 @@ import org.calyxos.backup.storage.scanner.DocumentScanner
 import org.calyxos.backup.storage.scanner.FileScanner
 import org.calyxos.backup.storage.scanner.MediaScanner
 import org.calyxos.backup.storage.toStoredUri
+import java.io.IOException
 import java.util.concurrent.atomic.AtomicBoolean
 
 private const val TAG = "StorageBackup"
@@ -33,7 +34,7 @@ private const val TAG = "StorageBackup"
 @Suppress("BlockingMethodInNonBlockingContext")
 public class StorageBackup(
     private val context: Context,
-    plugin: StoragePlugin,
+    private val plugin: StoragePlugin,
     private val dispatcher: CoroutineDispatcher = Dispatchers.IO,
 ) {
 
@@ -98,9 +99,31 @@ public class StorageBackup(
         list.joinToString(", ", limit = 5)
     }
 
-    @Deprecated("TODO remove for release")
+    /**
-    public fun clearCache() {
+     * Run this on a new storage location to ensure that there are no old snapshots
-        db.clearAllTables()
+     * (potentially encrypted with an old key) laying around.
+     * Using a storage location with existing data is not supported.
+     */
+    public suspend fun deleteAllSnapshots(): Unit = withContext(dispatcher) {
+        try {
+            plugin.getAvailableBackupSnapshots().forEach {
+                try {
+                    plugin.deleteBackupSnapshot(it)
+                } catch (e: IOException) {
+                    Log.e(TAG, "Error deleting snapshot $it", e)
+                }
+            }
+        } catch (e: IOException) {
+            Log.e(TAG, "Error deleting all snapshots", e)
+        }
+    }
+
+    /**
+     * It is advised to clear existing cache when selecting a new storage location.
+     */
+    public suspend fun clearCache(): Unit = withContext(dispatcher) {
+        db.getChunksCache().clear()
+        db.getFilesCache().clear()
     }
 
     public suspend fun runBackup(backupObserver: BackupObserver?): Boolean =

storage/lib/src/main/java/org/calyxos/backup/storage/db/FilesCache.kt

@@ -37,6 +37,9 @@ internal interface FilesCache {
     @Update
     fun update(file: CachedFile)
 
+    @Query("DELETE FROM CachedFile")
+    fun clear()
+
     @Query("UPDATE CachedFile SET last_seen = :now WHERE uri IN (:uris)")
     fun updateLastSeen(uris: Collection<Uri>, now: Long = System.currentTimeMillis())
 

storage/lib/src/main/java/org/calyxos/backup/storage/plugin/SnapshotRetriever.kt

@@ -1,5 +1,6 @@
 package org.calyxos.backup.storage.plugin
 
+import com.google.protobuf.InvalidProtocolBufferException
 import org.calyxos.backup.storage.api.StoragePlugin
 import org.calyxos.backup.storage.backup.BackupSnapshot
 import org.calyxos.backup.storage.crypto.StreamCrypto
@@ -13,7 +14,11 @@ internal class SnapshotRetriever(
     private val streamCrypto: StreamCrypto = StreamCrypto,
 ) {
 
-    @Throws(IOException::class, GeneralSecurityException::class)
+    @Throws(
+        IOException::class,
+        GeneralSecurityException::class,
+        InvalidProtocolBufferException::class,
+    )
     suspend fun getSnapshot(streamKey: ByteArray, timestamp: Long): BackupSnapshot {
         return storagePlugin.getBackupSnapshotInputStream(timestamp).use { inputStream ->
             val version = inputStream.readVersion()