improve sync error handling

app/src/main/java/it/niedermann/owncloud/notes/main/MainActivity.java

@@ -2,6 +2,7 @@
  * Nextcloud Notes - Android Client
  *
  * SPDX-FileCopyrightText: 2015-2024 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-FileCopyrightText: 2026 Alper Ozturk <alper.ozturk@nextcloud.com>
  * SPDX-License-Identifier: GPL-3.0-or-later
  */
 package it.niedermann.owncloud.notes.main;
@@ -215,7 +216,7 @@ protected void onCreate(Bundle savedInstanceState) {
         mainViewModel.getSyncStatus().observe(this, syncStatus -> swipeRefreshLayout.setRefreshing(syncStatus));
         mainViewModel.getSyncErrors().observe(this, exceptions -> {
             if (mainViewModel.containsNonInfrastructureRelatedItems(exceptions)) {
-                BrandedSnackbar.make(coordinatorLayout, R.string.error_synchronization, Snackbar.LENGTH_LONG)
+                BrandedSnackbar.make(coordinatorLayout, SyncErrorMessage.of(exceptions), Snackbar.LENGTH_LONG)
                         .setAnchorView(binding.activityNotesListView.fabCreate)
                         .setAction(R.string.simple_more, v -> ExceptionDialogFragment.newInstance(exceptions)
                                 .show(getSupportFragmentManager(), ExceptionDialogFragment.class.getSimpleName()))
@@ -324,7 +325,7 @@ public void onError(@NonNull Throwable t) {
                                     .setAnchorView(binding.activityNotesListView.fabCreate)
                                     .show();
                         } else {
-                            BrandedSnackbar.make(coordinatorLayout, R.string.error_synchronization, Snackbar.LENGTH_LONG)
+                            BrandedSnackbar.make(coordinatorLayout, SyncErrorMessage.of(t), Snackbar.LENGTH_LONG)
                                     .setAction(R.string.simple_more, v -> ExceptionDialogFragment.newInstance(t)
                                             .show(getSupportFragmentManager(), ExceptionDialogFragment.class.getSimpleName()))
                                     .setAnchorView(binding.activityNotesListView.fabCreate)
@@ -608,7 +609,7 @@ public void onError(@NonNull Throwable t) {
                                         .setAnchorView(binding.activityNotesListView.fabCreate)
                                         .show();
                             } else {
-                                BrandedSnackbar.make(coordinatorLayout, R.string.error_synchronization, Snackbar.LENGTH_LONG)
+                                BrandedSnackbar.make(coordinatorLayout, SyncErrorMessage.of(t), Snackbar.LENGTH_LONG)
                                         .setAction(R.string.simple_more, v -> ExceptionDialogFragment.newInstance(t)
                                                 .show(getSupportFragmentManager(), ExceptionDialogFragment.class.getSimpleName()))
                                         .setAnchorView(binding.activityNotesListView.fabCreate)

app/src/main/java/it/niedermann/owncloud/notes/main/SyncErrorMessage.kt

@@ -0,0 +1,38 @@
+/*
+ * Nextcloud - Android Client
+ *
+ * SPDX-FileCopyrightText: 2026 Alper Ozturk <alper.ozturk@nextcloud.com>
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+package it.niedermann.owncloud.notes.main
+
+import androidx.annotation.StringRes
+import com.nextcloud.android.sso.exceptions.NextcloudApiNotRespondingException
+import com.nextcloud.android.sso.exceptions.NextcloudHttpRequestFailedException
+import com.nextcloud.android.sso.exceptions.NextcloudNetworkException
+import com.nextcloud.android.sso.exceptions.TokenMismatchException
+import it.niedermann.owncloud.notes.persistence.NoteSyncException
+import it.niedermann.owncloud.notes.persistence.SyncFailureReason
+
+object SyncErrorMessage {
+    @JvmStatic
+    @StringRes
+    fun of(exceptions: Collection<Throwable>): Int =
+        (exceptions.map { it.syncFailureReason() }.distinct().singleOrNull() ?: SyncFailureReason.UNKNOWN).message
+
+    @JvmStatic
+    @StringRes
+    fun of(exception: Throwable): Int = exception.syncFailureReason().message
+
+    private fun Throwable.syncFailureReason(): SyncFailureReason =
+        generateSequence(this) { it.cause }.firstNotNullOfOrNull { it.directSyncFailureReason() }
+            ?: SyncFailureReason.UNKNOWN
+
+    private fun Throwable.directSyncFailureReason(): SyncFailureReason? = when (this) {
+        is NoteSyncException -> reason
+        is NextcloudHttpRequestFailedException -> SyncFailureReason.fromStatusCode(statusCode)
+        is NextcloudNetworkException, is NextcloudApiNotRespondingException -> SyncFailureReason.SERVER_UNREACHABLE
+        is TokenMismatchException -> SyncFailureReason.TOKEN_MISMATCH
+        else -> null
+    }
+}

app/src/main/java/it/niedermann/owncloud/notes/persistence/NoteSyncException.kt

@@ -0,0 +1,14 @@
+/*
+ * Nextcloud - Android Client
+ *
+ * SPDX-FileCopyrightText: 2026 Alper Ozturk <alper.ozturk@nextcloud.com>
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+package it.niedermann.owncloud.notes.persistence
+
+import retrofit2.Response
+
+class NoteSyncException(noteTitle: String, response: Response<*>) :
+    Exception("Could not sync \"$noteTitle\" (HTTP ${response.code()}): ${response.message()}") {
+    val reason = SyncFailureReason.fromStatusCode(response.code())
+}

app/src/main/java/it/niedermann/owncloud/notes/persistence/NotesRepository.java

@@ -250,6 +250,7 @@ public LiveData<ImportStatus> addAccount(@NonNull String url, @NonNull String us
                     return importTask.importNotes(new IResponseCallback<>() {
                         @Override
                         public void onSuccess(Void result) {
+                            syncActive.put(account.getId(), false);
                             callback.onSuccess(account);
                         }