Explain vault backup permission error

app/src/main/java/com/beemdevelopment/aegis/Preferences.java

@@ -11,6 +11,7 @@
 
 import com.beemdevelopment.aegis.util.JsonUtils;
 import com.beemdevelopment.aegis.util.TimeUtils;
+import com.beemdevelopment.aegis.vault.VaultBackupPermissionException;
 
 import org.json.JSONArray;
 import org.json.JSONException;
@@ -507,14 +508,16 @@ public static class BackupResult {
         private final Date _time;
         private boolean _isBuiltIn;
         private final String _error;
+        private final boolean _isPermissionError;
 
         public BackupResult(@Nullable Exception e) {
-            this(new Date(), e == null ? null : e.toString());
+            this(new Date(), e == null ? null : e.toString(), e instanceof VaultBackupPermissionException);
         }
 
-        private BackupResult(Date time, @Nullable String error) {
+        private BackupResult(Date time, @Nullable String error, boolean isPermissionError) {
             _time = time;
             _error = error;
+            _isPermissionError = isPermissionError;
         }
 
         @Nullable
@@ -542,12 +545,17 @@ private void setIsBuiltIn(boolean isBuiltIn) {
             _isBuiltIn = isBuiltIn;
         }
 
+        public boolean isPermissionError() {
+            return _isPermissionError;
+        }
+
         public String toJson() {
             JSONObject obj = new JSONObject();
 
             try {
                 obj.put("time", _time.getTime());
                 obj.put("error", _error == null ? JSONObject.NULL : _error);
+                obj.put("isPermissionError", _isPermissionError);
             } catch (JSONException e) {
                 throw new RuntimeException(e);
             }
@@ -559,7 +567,8 @@ public static BackupResult fromJson(String json) throws JSONException {
             JSONObject obj = new JSONObject(json);
             long time = obj.getLong("time");
             String error = JsonUtils.optString(obj, "error");
-            return new BackupResult(new Date(time), error);
+            boolean isPermissionError = obj.optBoolean("isPermissionError");
+            return new BackupResult(new Date(time), error, isPermissionError);
         }
     }
 

app/src/main/java/com/beemdevelopment/aegis/ui/dialogs/Dialogs.java

@@ -407,7 +407,8 @@ public static void showErrorDialog(Context context, String message, CharSequence
 
     public static void showBackupErrorDialog(Context context, Preferences.BackupResult backupRes, DialogInterface.OnClickListener listener) {
         String system = context.getString(backupRes.isBuiltIn() ? R.string.backup_system_builtin : R.string.backup_system_android);
-        String message = context.getString(R.string.backup_error_dialog_details, system, backupRes.getElapsedSince(context));
+        @StringRes int details = backupRes.isPermissionError() ? R.string.backup_permission_error_dialog_details : R.string.backup_error_dialog_details;
+        String message = context.getString(details, system, backupRes.getElapsedSince(context));
         Dialogs.showErrorDialog(context, message, backupRes.getError(), listener);
     }
 

app/src/main/java/com/beemdevelopment/aegis/vault/VaultBackupManager.java

@@ -53,22 +53,23 @@ public void scheduleBackup(File tempFile, Uri dirUri, int versionsToKeep) {
             try {
                 createBackup(tempFile, dirUri, versionsToKeep);
                 _prefs.setBuiltInBackupResult(new Preferences.BackupResult(null));
-            } catch (VaultRepositoryException e) {
+            } catch (VaultRepositoryException | VaultBackupPermissionException e) {
                 e.printStackTrace();
                 _prefs.setBuiltInBackupResult(new Preferences.BackupResult(e));
             }
         });
     }
 
-    private void createBackup(File tempFile, Uri dirUri, int versionsToKeep) throws VaultRepositoryException {
+    private void createBackup(File tempFile, Uri dirUri, int versionsToKeep)
+            throws VaultRepositoryException, VaultBackupPermissionException {
         FileInfo fileInfo = new FileInfo(FILENAME_PREFIX);
         DocumentFile dir = DocumentFile.fromTreeUri(_context, dirUri);
 
         try {
             Log.i(TAG, String.format("Creating backup at %s: %s", Uri.decode(dir.getUri().toString()), fileInfo.toString()));
 
             if (!hasPermissionsAt(dirUri)) {
-                throw new VaultRepositoryException("No persisted URI permissions");
+                throw new VaultBackupPermissionException("No persisted URI permissions");
             }
 
             // If we create a file with a name that already exists, SAF will append a number
@@ -92,7 +93,7 @@ private void createBackup(File tempFile, Uri dirUri, int versionsToKeep) throws
             } catch (IOException e) {
                 throw new VaultRepositoryException(e);
             }
-        } catch (VaultRepositoryException e) {
+        } catch (VaultRepositoryException | VaultBackupPermissionException e) {
             Log.e(TAG, String.format("Unable to create backup: %s", e.toString()));
             throw e;
         } finally {

app/src/main/java/com/beemdevelopment/aegis/vault/VaultBackupPermissionException.java

@@ -0,0 +1,7 @@
+package com.beemdevelopment.aegis.vault;
+
+public class VaultBackupPermissionException extends Exception {
+    public VaultBackupPermissionException(String message) {
+        super(message);
+    }
+}

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

@@ -390,6 +390,11 @@
         comment="The first parameter is the type of backup (e.g. built-in or Android backup). The second parameter is an elapsed time in the style of 'x seconds/minutes/days ago'.">
         A recent vault backup attempt using %s failed because an error occurred. The backup was attempted %s. Please check your backup settings to make sure backups can complete successfully.
     </string>
+    <string
+        name="backup_permission_error_dialog_details"
+        comment="The first parameter is the type of backup (e.g. built-in or Android backup). The second parameter is an elapsed time in the style of 'x seconds/minutes/days ago'.">
+        A recent vault backup attempt using %s failed because Aegis did not have permission to write to the backup destination. The backup was attempted %s. This error can occur if you moved/renamed the backup destination or if you recently restored Aegis from a backup. Please reconfigure the backup destination.
+    </string>
     <string name="backup_system_builtin">Aegis\' built-in automatic backups</string>
     <string name="backup_system_android">Android\'s cloud backup system</string>
     <string