#1170 Migrate NotesServerSyncHelper to NotesRepository

25 files changed, 1282 insertions, 969 deletions

diff --git a/app/build.gradle b/app/build.gradle
index d5944241..a1f7d7da 100644
--- a/app/build.gradle
+++ b/app/build.gradle
@@ -102,6 +102,7 @@ dependencies {
 
     // Testing
     testImplementation 'junit:junit:4.13.2'
+    testImplementation 'org.mockito:mockito-core:3.9.0'
     testImplementation 'org.robolectric:robolectric:4.5.1'
     testImplementation 'androidx.test:core:1.3.0'
     testImplementation 'androidx.test.ext:junit:1.1.2'
diff --git a/app/src/main/java/it/niedermann/owncloud/notes/accountswitcher/AccountSwitcherDialog.java b/app/src/main/java/it/niedermann/owncloud/notes/accountswitcher/AccountSwitcherDialog.java
index 79467d86..f5643d86 100644
--- a/app/src/main/java/it/niedermann/owncloud/notes/accountswitcher/AccountSwitcherDialog.java
+++ b/app/src/main/java/it/niedermann/owncloud/notes/accountswitcher/AccountSwitcherDialog.java
@@ -21,7 +21,7 @@ import it.niedermann.owncloud.notes.R;
 import it.niedermann.owncloud.notes.branding.BrandedDialogFragment;
 import it.niedermann.owncloud.notes.databinding.DialogAccountSwitcherBinding;
 import it.niedermann.owncloud.notes.manageaccounts.ManageAccountsActivity;
-import it.niedermann.owncloud.notes.persistence.NotesDatabase;
+import it.niedermann.owncloud.notes.persistence.NotesRepository;
 import it.niedermann.owncloud.notes.persistence.entity.Account;
 
 import static it.niedermann.owncloud.notes.branding.BrandingUtil.applyBrandToLayerDrawable;
@@ -33,7 +33,7 @@ public class AccountSwitcherDialog extends BrandedDialogFragment {
 
     private static final String KEY_CURRENT_ACCOUNT_ID = "current_account_id";
 
-    private NotesDatabase db;
+    private NotesRepository repo;
     private DialogAccountSwitcherBinding binding;
     private AccountSwitcherListener accountSwitcherListener;
     private long currentAccountId;
@@ -55,7 +55,7 @@ public class AccountSwitcherDialog extends BrandedDialogFragment {
             this.currentAccountId = args.getLong(KEY_CURRENT_ACCOUNT_ID);
         }
 
-        db = NotesDatabase.getInstance(requireActivity());
+        repo = NotesRepository.getInstance(requireContext());
     }
 
     @NonNull
@@ -63,7 +63,7 @@ public class AccountSwitcherDialog extends BrandedDialogFragment {
     public Dialog onCreateDialog(Bundle savedInstanceState) {
         binding = DialogAccountSwitcherBinding.inflate(requireActivity().getLayoutInflater());
 
-        final LiveData<Account> account$ = db.getAccountDao().getAccountById$(currentAccountId);
+        final LiveData<Account> account$ = repo.getAccountById$(currentAccountId);
         account$.observe(requireActivity(), (currentLocalAccount) -> {
             account$.removeObservers(requireActivity());
 
@@ -81,7 +81,7 @@ public class AccountSwitcherDialog extends BrandedDialogFragment {
                 dismiss();
             }));
             binding.accountsList.setAdapter(adapter);
-            final LiveData<List<Account>> localAccounts$ = db.getAccountDao().getAccounts$();
+            final LiveData<List<Account>> localAccounts$ = repo.getAccounts$();
             localAccounts$.observe(requireActivity(), (localAccounts) -> {
                 localAccounts$.removeObservers(requireActivity());
                 for (Account localAccount : localAccounts) {
diff --git a/app/src/main/java/it/niedermann/owncloud/notes/edit/BaseNoteFragment.java b/app/src/main/java/it/niedermann/owncloud/notes/edit/BaseNoteFragment.java
index 383d9e1b..1b4b8289 100644
--- a/app/src/main/java/it/niedermann/owncloud/notes/edit/BaseNoteFragment.java
+++ b/app/src/main/java/it/niedermann/owncloud/notes/edit/BaseNoteFragment.java
@@ -41,7 +41,7 @@ import it.niedermann.owncloud.notes.edit.category.CategoryDialogFragment;
 import it.niedermann.owncloud.notes.edit.category.CategoryDialogFragment.CategoryDialogListener;
 import it.niedermann.owncloud.notes.edit.title.EditTitleDialogFragment;
 import it.niedermann.owncloud.notes.edit.title.EditTitleDialogFragment.EditTitleListener;
-import it.niedermann.owncloud.notes.persistence.NotesDatabase;
+import it.niedermann.owncloud.notes.persistence.NotesRepository;
 import it.niedermann.owncloud.notes.persistence.entity.Account;
 import it.niedermann.owncloud.notes.persistence.entity.Note;
 import it.niedermann.owncloud.notes.shared.model.ApiVersion;
@@ -76,7 +76,7 @@ public abstract class BaseNoteFragment extends BrandedFragment implements Catego
     @Nullable
     private Note originalNote;
     private int originalScrollY;
-    protected NotesDatabase db;
+    protected NotesRepository repo;
     private NoteFragmentListener listener;
     private boolean titleModified = false;
 
@@ -90,7 +90,7 @@ public abstract class BaseNoteFragment extends BrandedFragment implements Catego
         } catch (ClassCastException e) {
             throw new ClassCastException(context.getClass() + " must implement " + NoteFragmentListener.class);
         }
-        db = NotesDatabase.getInstance(context);
+        repo = NotesRepository.getInstance(context);
     }
 
     @Override
@@ -99,7 +99,7 @@ public abstract class BaseNoteFragment extends BrandedFragment implements Catego
         new Thread(() -> {
             try {
                 SingleSignOnAccount ssoAccount = SingleAccountHelper.getCurrentSingleSignOnAccount(requireContext().getApplicationContext());
-                this.localAccount = db.getAccountDao().getAccountByName(ssoAccount.name);
+                this.localAccount = repo.getAccountByName(ssoAccount.name);
 
                 if (savedInstanceState == null) {
                     long id = requireArguments().getLong(PARAM_NOTE_ID);
@@ -107,11 +107,11 @@ public abstract class BaseNoteFragment extends BrandedFragment implements Catego
                         long accountId = requireArguments().getLong(PARAM_ACCOUNT_ID);
                         if (accountId > 0) {
                             /* Switch account if account id has been provided */
-                            this.localAccount = db.getAccountDao().getAccountById(accountId);
+                            this.localAccount = repo.getAccountById(accountId);
                             SingleAccountHelper.setCurrentAccount(requireContext().getApplicationContext(), localAccount.getAccountName());
                         }
                         isNew = false;
-                        note = originalNote = db.getNoteDao().getNoteById(id);
+                        note = originalNote = repo.getNoteById(id);
                         requireActivity().runOnUiThread(() -> onNoteLoaded(note));
                         requireActivity().invalidateOptionsMenu();
                     } else {
@@ -126,7 +126,7 @@ public abstract class BaseNoteFragment extends BrandedFragment implements Catego
                                 requireActivity().invalidateOptionsMenu();
                             }
                         } else {
-                            note = db.addNote(localAccount.getId(), cloudNote);
+                            note = repo.addNote(localAccount.getId(), cloudNote);
                             originalNote = null;
                             requireActivity().runOnUiThread(() -> onNoteLoaded(note));
                             requireActivity().invalidateOptionsMenu();
@@ -213,19 +213,19 @@ public abstract class BaseNoteFragment extends BrandedFragment implements Catego
         if (itemId == R.id.menu_cancel) {
             new Thread(() -> {
                 if (originalNote == null) {
-                    db.deleteNoteAndSync(localAccount, note.getId());
+                    repo.deleteNoteAndSync(localAccount, note.getId());
                 } else {
-                    db.updateNoteAndSync(localAccount, originalNote, null, null, null);
+                    repo.updateNoteAndSync(localAccount, originalNote, null, null, null);
                 }
             }).start();
             listener.close();
             return true;
         } else if (itemId == R.id.menu_delete) {
-            db.deleteNoteAndSync(localAccount, note.getId());
+            repo.deleteNoteAndSync(localAccount, note.getId());
             listener.close();
             return true;
         } else if (itemId == R.id.menu_favorite) {
-            db.toggleFavoriteAndSync(localAccount, note.getId());
+            repo.toggleFavoriteAndSync(localAccount, note.getId());
             listener.onNoteUpdated(note);
             prepareFavoriteOption(item);
             return true;
@@ -288,7 +288,7 @@ public abstract class BaseNoteFragment extends BrandedFragment implements Catego
 
     public void onCloseNote() {
         if (!titleModified && originalNote == null && getContent().isEmpty()) {
-            db.deleteNoteAndSync(localAccount, note.getId());
+            repo.deleteNoteAndSync(localAccount, note.getId());
         }
     }
 
@@ -304,13 +304,13 @@ public abstract class BaseNoteFragment extends BrandedFragment implements Catego
             if (note.getContent().equals(newContent)) {
                 if (note.getScrollY() != originalScrollY) {
                     Log.v(TAG, "... only saving new scroll state, since content did not change");
-                    db.getNoteDao().updateScrollY(note.getId(), note.getScrollY());
+                    repo.updateScrollY(note.getId(), note.getScrollY());
                 } else {
                     Log.v(TAG, "... not saving, since nothing has changed");
                 }
             } else {
                 // FIXME requires database queries on main thread!
-                note = db.updateNoteAndSync(localAccount, note, newContent, null, callback);
+                note = repo.updateNoteAndSync(localAccount, note, newContent, null, callback);
                 listener.onNoteUpdated(note);
                 requireActivity().invalidateOptionsMenu();
             }
@@ -354,7 +354,7 @@ public abstract class BaseNoteFragment extends BrandedFragment implements Catego
 
     @Override
     public void onCategoryChosen(String category) {
-        db.setCategory(localAccount, note.getId(), category);
+        repo.setCategory(localAccount, note.getId(), category);
         note.setCategory(category);
         listener.onNoteUpdated(note);
     }
@@ -364,13 +364,13 @@ public abstract class BaseNoteFragment extends BrandedFragment implements Catego
         titleModified = true;
         note.setTitle(newTitle);
         new Thread(() -> {
-            note = db.updateNoteAndSync(localAccount, note, note.getContent(), newTitle, null);
+            note = repo.updateNoteAndSync(localAccount, note, note.getContent(), newTitle, null);
             requireActivity().runOnUiThread(() -> listener.onNoteUpdated(note));
         }).start();
     }
 
     public void moveNote(Account account) {
-        db.moveNoteToAnotherAccount(account, note);
+        repo.moveNoteToAnotherAccount(account, note);
         listener.close();
     }
 
diff --git a/app/src/main/java/it/niedermann/owncloud/notes/edit/NotePreviewFragment.java b/app/src/main/java/it/niedermann/owncloud/notes/edit/NotePreviewFragment.java
index fca142e9..f1626149 100644
--- a/app/src/main/java/it/niedermann/owncloud/notes/edit/NotePreviewFragment.java
+++ b/app/src/main/java/it/niedermann/owncloud/notes/edit/NotePreviewFragment.java
@@ -125,7 +125,7 @@ public class NotePreviewFragment extends SearchableBaseNoteFragment implements O
     protected void registerInternalNoteLinkHandler() {
         binding.singleNoteContent.registerOnLinkClickCallback((link) -> {
             try {
-                final long noteLocalId = db.getNoteDao().getLocalIdByRemoteId(this.note.getAccountId(), Long.parseLong(link));
+                final long noteLocalId = repo.getLocalIdByRemoteId(this.note.getAccountId(), Long.parseLong(link));
                 Log.i(TAG, "Found note for remoteId \"" + link + "\" in account \"" + this.note.getAccountId() + "\" with localId + \"" + noteLocalId + "\". Attempt to open " + EditNoteActivity.class.getSimpleName() + " for this note.");
                 startActivity(new Intent(requireActivity().getApplicationContext(), EditNoteActivity.class).putExtra(EditNoteActivity.PARAM_NOTE_ID, noteLocalId));
                 return true;
@@ -153,20 +153,20 @@ public class NotePreviewFragment extends SearchableBaseNoteFragment implements O
 
     @Override
     public void onRefresh() {
-        if (noteLoaded && db.getNoteServerSyncHelper().isSyncPossible() && SSOUtil.isConfigured(getContext())) {
+        if (noteLoaded && repo.isSyncPossible() && SSOUtil.isConfigured(getContext())) {
             binding.swiperefreshlayout.setRefreshing(true);
             new Thread(() -> {
                 try {
-                    final Account account = db.getAccountDao().getAccountByName(SingleAccountHelper.getCurrentSingleSignOnAccount(requireContext()).name);
-                    db.getNoteServerSyncHelper().addCallbackPull(account, () -> new Thread(() -> {
-                        note = db.getNoteDao().getNoteById(note.getId());
+                    final Account account = repo.getAccountByName(SingleAccountHelper.getCurrentSingleSignOnAccount(requireContext()).name);
+                    repo.addCallbackPull(account, () -> new Thread(() -> {
+                        note = repo.getNoteById(note.getId());
                         changedText = note.getContent();
                         requireActivity().runOnUiThread(() -> {
                             binding.singleNoteContent.setMarkdownString(note.getContent());
                             binding.swiperefreshlayout.setRefreshing(false);
                         });
                     }).start());
-                    db.getNoteServerSyncHelper().scheduleSync(account, false);
+                    repo.scheduleSync(account, false);
                 } catch (NextcloudFilesAppAccountNotFoundException | NoCurrentAccountSelectedException e) {
                     e.printStackTrace();
                 }
diff --git a/app/src/main/java/it/niedermann/owncloud/notes/edit/category/CategoryViewModel.java b/app/src/main/java/it/niedermann/owncloud/notes/edit/category/CategoryViewModel.java
index 96900a3b..ea5efd37 100644
--- a/app/src/main/java/it/niedermann/owncloud/notes/edit/category/CategoryViewModel.java
+++ b/app/src/main/java/it/niedermann/owncloud/notes/edit/category/CategoryViewModel.java
@@ -11,7 +11,7 @@ import androidx.lifecycle.MutableLiveData;
 import java.util.List;
 
 import it.niedermann.owncloud.notes.main.navigation.NavigationItem;
-import it.niedermann.owncloud.notes.persistence.NotesDatabase;
+import it.niedermann.owncloud.notes.persistence.NotesRepository;
 
 import static androidx.lifecycle.Transformations.map;
 import static androidx.lifecycle.Transformations.switchMap;
@@ -19,14 +19,14 @@ import static it.niedermann.owncloud.notes.shared.util.DisplayUtils.convertToCat
 
 public class CategoryViewModel extends AndroidViewModel {
 
-    private final NotesDatabase db;
+    private final NotesRepository repo;
 
     @NonNull
     private final MutableLiveData<String> searchTerm = new MutableLiveData<>("");
 
     public CategoryViewModel(@NonNull Application application) {
         super(application);
-        db = NotesDatabase.getInstance(application);
+        repo = NotesRepository.getInstance(application);
     }
 
     public void postSearchTerm(@NonNull String searchTerm) {
@@ -36,7 +36,7 @@ public class CategoryViewModel extends AndroidViewModel {
     @NonNull
     public LiveData<List<NavigationItem.CategoryNavigationItem>> getCategories(long accountId) {
         return switchMap(this.searchTerm, searchTerm ->
-                map(db.getNoteDao().searchCategories$(accountId, TextUtils.isEmpty(searchTerm) ? "%" : "%" + searchTerm + "%"),
+                map(repo.searchCategories$(accountId, TextUtils.isEmpty(searchTerm) ? "%" : "%" + searchTerm + "%"),
                         categories -> convertToCategoryNavigationItem(getApplication(), categories)));
     }
 }
diff --git a/app/src/main/java/it/niedermann/owncloud/notes/importaccount/ImportAccountViewModel.java b/app/src/main/java/it/niedermann/owncloud/notes/importaccount/ImportAccountViewModel.java
index 04b30d8d..abcf68e3 100644
--- a/app/src/main/java/it/niedermann/owncloud/notes/importaccount/ImportAccountViewModel.java
+++ b/app/src/main/java/it/niedermann/owncloud/notes/importaccount/ImportAccountViewModel.java
@@ -6,7 +6,7 @@ import androidx.annotation.NonNull;
 import androidx.lifecycle.AndroidViewModel;
 import androidx.lifecycle.LiveData;
 
-import it.niedermann.owncloud.notes.persistence.NotesDatabase;
+import it.niedermann.owncloud.notes.persistence.NotesRepository;
 import it.niedermann.owncloud.notes.persistence.entity.Account;
 import it.niedermann.owncloud.notes.shared.model.Capabilities;
 
@@ -15,14 +15,14 @@ public class ImportAccountViewModel extends AndroidViewModel {
     private static final String TAG = ImportAccountViewModel.class.getSimpleName();
 
     @NonNull
-    private final NotesDatabase db;
+    private final NotesRepository repo;
 
     public ImportAccountViewModel(@NonNull Application application) {
         super(application);
-        this.db = NotesDatabase.getInstance(application.getApplicationContext());
+        this.repo = NotesRepository.getInstance(application);
     }
 
     public LiveData<Account> addAccount(@NonNull String url, @NonNull String username, @NonNull String accountName, @NonNull Capabilities capabilities) {
-        return db.addAccount(url, username, accountName, capabilities);
+        return repo.addAccount(url, username, accountName, capabilities);
     }
 }
diff --git a/app/src/main/java/it/niedermann/owncloud/notes/main/MainViewModel.java b/app/src/main/java/it/niedermann/owncloud/notes/main/MainViewModel.java
index 77104856..2e43d78d 100644
--- a/app/src/main/java/it/niedermann/owncloud/notes/main/MainViewModel.java
+++ b/app/src/main/java/it/niedermann/owncloud/notes/main/MainViewModel.java
@@ -34,8 +34,7 @@ import it.niedermann.owncloud.notes.exception.IntendedOfflineException;
 import it.niedermann.owncloud.notes.main.navigation.NavigationAdapter;
 import it.niedermann.owncloud.notes.main.navigation.NavigationItem;
 import it.niedermann.owncloud.notes.persistence.CapabilitiesClient;
-import it.niedermann.owncloud.notes.persistence.NotesDatabase;
-import it.niedermann.owncloud.notes.persistence.NotesServerSyncHelper;
+import it.niedermann.owncloud.notes.persistence.NotesRepository;
 import it.niedermann.owncloud.notes.persistence.entity.Account;
 import it.niedermann.owncloud.notes.persistence.entity.CategoryWithNotesCount;
 import it.niedermann.owncloud.notes.persistence.entity.Note;
@@ -73,7 +72,7 @@ public class MainViewModel extends AndroidViewModel {
     private static final String KEY_EXPANDED_CATEGORY = "expandedCategory";
 
     @NonNull
-    private final NotesDatabase db;
+    private final NotesRepository repo;
 
     @NonNull
     private final MutableLiveData<Account> currentAccount = new MutableLiveData<>();
@@ -86,7 +85,7 @@ public class MainViewModel extends AndroidViewModel {
 
     public MainViewModel(@NonNull Application application, @NonNull SavedStateHandle savedStateHandle) {
         super(application);
-        this.db = NotesDatabase.getInstance(application);
+        this.repo = NotesRepository.getInstance(application);
         this.state = savedStateHandle;
     }
 
@@ -175,7 +174,7 @@ public class MainViewModel extends AndroidViewModel {
     @NonNull
     @MainThread
     public LiveData<Pair<NavigationCategory, CategorySortingMethod>> getCategorySortingMethodOfSelectedCategory() {
-        return switchMap(getSelectedCategory(), selectedCategory -> map(db.getCategoryOrder(selectedCategory), sortingMethod -> new Pair<>(selectedCategory, sortingMethod)));
+        return switchMap(getSelectedCategory(), selectedCategory -> map(repo.getCategoryOrder(selectedCategory), sortingMethod -> new Pair<>(selectedCategory, sortingMethod)));
     }
 
     public LiveData<Void> modifyCategoryOrder(@NonNull NavigationCategory selectedCategory, @NonNull CategorySortingMethod sortingMethod) {
@@ -184,7 +183,7 @@ public class MainViewModel extends AndroidViewModel {
                 return new MutableLiveData<>(null);
             } else {
                 Log.v(TAG, "[modifyCategoryOrder] - currentAccount: " + currentAccount.getAccountName());
-                db.modifyCategoryOrder(currentAccount.getId(), selectedCategory, sortingMethod);
+                repo.modifyCategoryOrder(currentAccount.getId(), selectedCategory, sortingMethod);
                 return new MutableLiveData<>(null);
             }
         });
@@ -225,22 +224,22 @@ public class MainViewModel extends AndroidViewModel {
                                     case RECENT: {
                                         Log.v(TAG, "[getNotesListLiveData] - category: " + RECENT);
                                         fromDatabase = sortingMethod.second == SORT_MODIFIED_DESC
-                                                ? db.getNoteDao().searchRecentByModified$(accountId, searchQueryOrWildcard)
-                                                : db.getNoteDao().searchRecentLexicographically$(accountId, searchQueryOrWildcard);
+                                                ? repo.searchRecentByModified$(accountId, searchQueryOrWildcard)
+                                                : repo.searchRecentLexicographically$(accountId, searchQueryOrWildcard);
                                         break;
                                     }
                                     case FAVORITES: {
                                         Log.v(TAG, "[getNotesListLiveData] - category: " + FAVORITES);
                                         fromDatabase = sortingMethod.second == SORT_MODIFIED_DESC
-                                                ? db.getNoteDao().searchFavoritesByModified$(accountId, searchQueryOrWildcard)
-                                                : db.getNoteDao().searchFavoritesLexicographically$(accountId, searchQueryOrWildcard);
+                                                ? repo.searchFavoritesByModified$(accountId, searchQueryOrWildcard)
+                                                : repo.searchFavoritesLexicographically$(accountId, searchQueryOrWildcard);
                                         break;
                                     }
                                     case UNCATEGORIZED: {
                                         Log.v(TAG, "[getNotesListLiveData] - category: " + UNCATEGORIZED);
                                         fromDatabase = sortingMethod.second == SORT_MODIFIED_DESC
-                                                ? db.getNoteDao().searchUncategorizedByModified$(accountId, searchQueryOrWildcard)
-                                                : db.getNoteDao().searchUncategorizedLexicographically$(accountId, searchQueryOrWildcard);
+                                                ? repo.searchUncategorizedByModified$(accountId, searchQueryOrWildcard)
+                                                : repo.searchUncategorizedLexicographically$(accountId, searchQueryOrWildcard);
                                         break;
                                     }
                                     case DEFAULT_CATEGORY:
@@ -251,8 +250,8 @@ public class MainViewModel extends AndroidViewModel {
                                         }
                                         Log.v(TAG, "[getNotesListLiveData] - category: " + category);
                                         fromDatabase = sortingMethod.second == SORT_MODIFIED_DESC
-                                                ? db.getNoteDao().searchCategoryByModified$(accountId, searchQueryOrWildcard, category)
-                                                : db.getNoteDao().searchCategoryLexicographically$(accountId, searchQueryOrWildcard, category);
+                                                ? repo.searchCategoryByModified$(accountId, searchQueryOrWildcard, category)
+                                                : repo.searchCategoryLexicographically$(accountId, searchQueryOrWildcard, category);
                                         break;
                                     }
                                 }
@@ -294,11 +293,11 @@ public class MainViewModel extends AndroidViewModel {
                 Log.v(TAG, "[getNavigationCategories] - currentAccount: " + currentAccount.getAccountName());
                 return switchMap(getExpandedCategory(), expandedCategory -> {
                     Log.v(TAG, "[getNavigationCategories] - expandedCategory: " + expandedCategory);
-                    return switchMap(db.getNoteDao().count$(currentAccount.getId()), (count) -> {
+                    return switchMap(repo.count$(currentAccount.getId()), (count) -> {
                         Log.v(TAG, "[getNavigationCategories] - count: " + count);
-                        return switchMap(db.getNoteDao().countFavorites$(currentAccount.getId()), (favoritesCount) -> {
+                        return switchMap(repo.countFavorites$(currentAccount.getId()), (favoritesCount) -> {
                             Log.v(TAG, "[getNavigationCategories] - favoritesCount: " + favoritesCount);
-                            return distinctUntilChanged(map(db.getNoteDao().getCategories$(currentAccount.getId()), fromDatabase ->
+                            return distinctUntilChanged(map(repo.getCategories$(currentAccount.getId()), fromDatabase ->
                                     fromCategoriesWithNotesCount(getApplication(), expandedCategory, fromDatabase, count, favoritesCount)
                             ));
                         });
@@ -390,22 +389,21 @@ public class MainViewModel extends AndroidViewModel {
      */
     public void synchronizeCapabilities(@NonNull Account localAccount, @NonNull IResponseCallback<Void> callback) {
         new Thread(() -> {
-            final NotesServerSyncHelper syncHelper = db.getNoteServerSyncHelper();
-            if (!syncHelper.isSyncPossible()) {
-                syncHelper.updateNetworkStatus();
+            if (!repo.isSyncPossible()) {
+                repo.updateNetworkStatus();
             }
-            if (syncHelper.isSyncPossible()) {
+            if (repo.isSyncPossible()) {
                 try {
                     final Capabilities capabilities = CapabilitiesClient.getCapabilities(getApplication(), AccountImporter.getSingleSignOnAccount(getApplication(), localAccount.getAccountName()), localAccount.getCapabilitiesETag());
-                    db.getAccountDao().updateCapabilitiesETag(localAccount.getId(), capabilities.getETag());
-                    db.getAccountDao().updateBrand(localAccount.getId(), capabilities.getColor(), capabilities.getTextColor());
+                    repo.updateCapabilitiesETag(localAccount.getId(), capabilities.getETag());
+                    repo.updateBrand(localAccount.getId(), capabilities.getColor(), capabilities.getTextColor());
                     localAccount.setColor(capabilities.getColor());
                     localAccount.setTextColor(capabilities.getTextColor());
                     BrandingUtil.saveBrandColors(getApplication(), localAccount.getColor(), localAccount.getTextColor());
-                    db.updateApiVersion(localAccount.getId(), capabilities.getApiVersion());
+                    repo.updateApiVersion(localAccount.getId(), capabilities.getApiVersion());
                     callback.onSuccess(null);
                 } catch (NextcloudFilesAppAccountNotFoundException e) {
-                    db.getAccountDao().deleteAccount(localAccount);
+                    repo.deleteAccount(localAccount);
                     callback.onError(e);
                 } catch (Exception e) {
                     if (e instanceof NextcloudHttpRequestFailedException && ((NextcloudHttpRequestFailedException) e).getStatusCode() == HttpURLConnection.HTTP_NOT_MODIFIED) {
@@ -416,7 +414,7 @@ public class MainViewModel extends AndroidViewModel {
                     }
                 }
             } else {
-                if (syncHelper.isNetworkConnected() && syncHelper.isSyncOnlyOnWifi()) {
+                if (repo.isNetworkConnected() && repo.isSyncOnlyOnWifi()) {
                     callback.onError(new IntendedOfflineException("Network is connected, but sync is not possible."));
                 } else {
                     callback.onError(new NetworkErrorException("Sync is not possible, because network is not connected."));
@@ -431,15 +429,14 @@ public class MainViewModel extends AndroidViewModel {
     public void synchronizeNotes(@NonNull Account currentAccount, @NonNull IResponseCallback<Void> callback) {
         new Thread(() -> {
             Log.v(TAG, "[synchronize] - currentAccount: " + currentAccount.getAccountName());
-            final NotesServerSyncHelper syncHelper = db.getNoteServerSyncHelper();
-            if (!syncHelper.isSyncPossible()) {
-                syncHelper.updateNetworkStatus();
+            if (!repo.isSyncPossible()) {
+                repo.updateNetworkStatus();
             }
-            if (syncHelper.isSyncPossible()) {
-                syncHelper.scheduleSync(currentAccount, false);
+            if (repo.isSyncPossible()) {
+                repo.scheduleSync(currentAccount, false);
                 callback.onSuccess(null);
             } else { // Sync is not possible
-                if (syncHelper.isNetworkConnected() && syncHelper.isSyncOnlyOnWifi()) {
+                if (repo.isNetworkConnected() && repo.isSyncOnlyOnWifi()) {
                     callback.onError(new IntendedOfflineException("Network is connected, but sync is not possible."));
                 } else {
                     callback.onError(new NetworkErrorException("Sync is not possible, because network is not connected."));
@@ -449,25 +446,25 @@ public class MainViewModel extends AndroidViewModel {
     }
 
     public LiveData<Boolean> getSyncStatus() {
-        return db.getNoteServerSyncHelper().getSyncStatus();
+        return repo.getSyncStatus();
     }
 
     public LiveData<ArrayList<Throwable>> getSyncErrors() {
-        return db.getNoteServerSyncHelper().getSyncErrors();
+        return repo.getSyncErrors();
     }
 
     public LiveData<Boolean> hasMultipleAccountsConfigured() {
-        return map(db.getAccountDao().countAccounts$(), (counter) -> counter != null && counter > 1);
+        return map(repo.countAccounts$(), (counter) -> counter != null && counter > 1);
     }
 
     @WorkerThread
     public Account getLocalAccountByAccountName(String accountName) {
-        return db.getAccountDao().getAccountByName(accountName);
+        return repo.getAccountByName(accountName);
     }
 
     @WorkerThread
     public List<Account> getAccounts() {
-        return db.getAccountDao().getAccounts();
+        return repo.getAccounts();
     }
 
     public LiveData<Void> setCategory(Iterable<Long> noteIds, @NonNull String category) {
@@ -477,7 +474,7 @@ public class MainViewModel extends AndroidViewModel {
             } else {
                 Log.v(TAG, "[setCategory] - currentAccount: " + currentAccount.getAccountName());
                 for (Long noteId : noteIds) {
-                    db.setCategory(currentAccount, noteId, category);
+                    repo.setCategory(currentAccount, noteId, category);
                 }
                 return new MutableLiveData<>(null);
             }
@@ -485,9 +482,9 @@ public class MainViewModel extends AndroidViewModel {
     }
 
     public LiveData<Note> moveNoteToAnotherAccount(Account account, Long noteId) {
-        return switchMap(db.getNoteDao().getNoteById$(noteId), (note) -> {
+        return switchMap(repo.getNoteById$(noteId), (note) -> {
             Log.v(TAG, "[moveNoteToAnotherAccount] - note: " + note);
-            return db.moveNoteToAnotherAccount(account, note);
+            return repo.moveNoteToAnotherAccount(account, note);
         });
     }
 
@@ -497,7 +494,7 @@ public class MainViewModel extends AndroidViewModel {
                 return new MutableLiveData<>(null);
             } else {
                 Log.v(TAG, "[toggleFavoriteAndSync] - currentAccount: " + currentAccount.getAccountName());
-                db.toggleFavoriteAndSync(currentAccount, noteId);
+                repo.toggleFavoriteAndSync(currentAccount, noteId);
                 return new MutableLiveData<>(null);
             }
         });
@@ -509,7 +506,7 @@ public class MainViewModel extends AndroidViewModel {
                 return new MutableLiveData<>(null);
             } else {
                 Log.v(TAG, "[deleteNoteAndSync] - currentAccount: " + currentAccount.getAccountName());
-                db.deleteNoteAndSync(currentAccount, id);
+                repo.deleteNoteAndSync(currentAccount, id);
                 return new MutableLiveData<>(null);
             }
         });
@@ -522,7 +519,7 @@ public class MainViewModel extends AndroidViewModel {
             } else {
                 Log.v(TAG, "[deleteNotesAndSync] - currentAccount: " + currentAccount.getAccountName());
                 for (Long id : ids) {
-                    db.deleteNoteAndSync(currentAccount, id);
+                    repo.deleteNoteAndSync(currentAccount, id);
                 }
                 return new MutableLiveData<>(null);
             }
@@ -530,7 +527,7 @@ public class MainViewModel extends AndroidViewModel {
     }
 
     public LiveData<Account> addAccount(@NonNull String url, @NonNull String username, @NonNull String accountName, @NonNull Capabilities capabilities) {
-        return db.addAccount(url, username, accountName, capabilities);
+        return repo.addAccount(url, username, accountName, capabilities);
     }
 
     public LiveData<Note> getFullNote$(long id) {
@@ -539,7 +536,7 @@ public class MainViewModel extends AndroidViewModel {
 
     @WorkerThread
     public Note getFullNote(long id) {
-        return db.getNoteDao().getNoteById(id);
+        return repo.getNoteById(id);
     }
 
     public LiveData<List<Note>> getFullNotesWithCategory(@NonNull Collection<Long> ids) {
@@ -552,7 +549,7 @@ public class MainViewModel extends AndroidViewModel {
                 new Thread(() -> notes.postValue(
                         ids
                                 .stream()
-                                .map(id -> db.getNoteDao().getNoteById(id))
+                                .map(repo::getNoteById)
                                 .collect(Collectors.toList())
                 )).start();
                 return notes;
@@ -566,7 +563,7 @@ public class MainViewModel extends AndroidViewModel {
                 return new MutableLiveData<>();
             } else {
                 Log.v(TAG, "[addNoteAndSync] - currentAccount: " + currentAccount.getAccountName());
-                return db.addNoteAndSync(currentAccount, note);
+                return repo.addNoteAndSync(currentAccount, note);
             }
         });
     }
@@ -575,25 +572,25 @@ public class MainViewModel extends AndroidViewModel {
         return switchMap(getCurrentAccount(), currentAccount -> {
             if (currentAccount != null) {
                 Log.v(TAG, "[updateNoteAndSync] - currentAccount: " + currentAccount.getAccountName());
-                db.updateNoteAndSync(currentAccount, oldNote, newContent, newTitle, null);
+                repo.updateNoteAndSync(currentAccount, oldNote, newContent, newTitle, null);
             }
             return new MutableLiveData<>(null);
         });
     }
 
     public void createOrUpdateSingleNoteWidgetData(SingleNoteWidgetData data) {
-        db.getWidgetSingleNoteDao().createOrUpdateSingleNoteWidgetData(data);
+        repo.createOrUpdateSingleNoteWidgetData(data);
     }
 
     public LiveData<Integer> getAccountsCount() {
-        return db.getAccountDao().countAccounts$();
+        return repo.countAccounts$();
     }
 
     @WorkerThread
     public String collectNoteContents(@NonNull List<Long> noteIds) {
         final StringBuilder noteContents = new StringBuilder();
         for (Long noteId : noteIds) {
-            final Note fullNote = db.getNoteDao().getNoteById(noteId);
+            final Note fullNote = repo.getNoteById(noteId);
             final String tempFullNote = fullNote.getContent();
             if (!TextUtils.isEmpty(tempFullNote)) {
                 if (noteContents.length() > 0) {
diff --git a/app/src/main/java/it/niedermann/owncloud/notes/manageaccounts/ManageAccountsActivity.java b/app/src/main/java/it/niedermann/owncloud/notes/manageaccounts/ManageAccountsActivity.java
index 4c307b07..dee5661f 100644
--- a/app/src/main/java/it/niedermann/owncloud/notes/manageaccounts/ManageAccountsActivity.java
+++ b/app/src/main/java/it/niedermann/owncloud/notes/manageaccounts/ManageAccountsActivity.java
@@ -63,7 +63,7 @@ public class ManageAccountsActivity extends LockedActivity {
             @Override
             public void onSuccess(Long unsynchronizedChangesCount) {
                 runOnUiThread(() -> {
-                    if (unsynchronizedChangesCount != null && unsynchronizedChangesCount > 0) {
+                    if (unsynchronizedChangesCount > 0) {
                         new BrandedDeleteAlertDialogBuilder(ManageAccountsActivity.this)
                                 .setTitle(getString(R.string.remove_account, accountToDelete.getUserName()))
                                 .setMessage(getResources().getQuantityString(R.plurals.remove_account_message, (int) unsynchronizedChangesCount.longValue(), accountToDelete.getAccountName(), unsynchronizedChangesCount))
diff --git a/app/src/main/java/it/niedermann/owncloud/notes/manageaccounts/ManageAccountsViewModel.java b/app/src/main/java/it/niedermann/owncloud/notes/manageaccounts/ManageAccountsViewModel.java
index 3e7e430a..2ee45cf8 100644
--- a/app/src/main/java/it/niedermann/owncloud/notes/manageaccounts/ManageAccountsViewModel.java
+++ b/app/src/main/java/it/niedermann/owncloud/notes/manageaccounts/ManageAccountsViewModel.java
@@ -15,6 +15,7 @@ import com.nextcloud.android.sso.helper.SingleAccountHelper;
 import java.util.List;
 
 import it.niedermann.owncloud.notes.persistence.NotesDatabase;
+import it.niedermann.owncloud.notes.persistence.NotesRepository;
 import it.niedermann.owncloud.notes.persistence.entity.Account;
 import it.niedermann.owncloud.notes.shared.model.IResponseCallback;
 
@@ -25,28 +26,28 @@ public class ManageAccountsViewModel extends AndroidViewModel {
     private static final String TAG = ManageAccountsViewModel.class.getSimpleName();
 
     @NonNull
-    private final NotesDatabase db;
+    private final NotesRepository repo;
 
     public ManageAccountsViewModel(@NonNull Application application) {
         super(application);
-        this.db = NotesDatabase.getInstance(application);
+        this.repo = NotesRepository.getInstance(application);
     }
 
     public void getCurrentAccount(@NonNull Context context, @NonNull IResponseCallback<Account> callback) {
         try {
-            callback.onSuccess(db.getAccountDao().getAccountByName((SingleAccountHelper.getCurrentSingleSignOnAccount(context).name)));
+            callback.onSuccess(repo.getAccountByName((SingleAccountHelper.getCurrentSingleSignOnAccount(context).name)));
         } catch (NextcloudFilesAppAccountNotFoundException | NoCurrentAccountSelectedException e) {
             callback.onError(e);
         }
     }
 
     public LiveData<List<Account>> getAccounts$() {
-        return distinctUntilChanged(db.getAccountDao().getAccounts$());
+        return distinctUntilChanged(repo.getAccounts$());
     }
 
     public void deleteAccount(@NonNull Account account, @NonNull Context context) {
         new Thread(() -> {
-            final List<Account> accounts = db.getAccountDao().getAccounts();
+            final List<Account> accounts = repo.getAccounts();
             for (int i = 0; i < accounts.size(); i++) {
                 if (accounts.get(i).getId() == account.getId()) {
                     if (i > 0) {
@@ -56,7 +57,7 @@ public class ManageAccountsViewModel extends AndroidViewModel {
                     } else {
                         selectAccount(null, context);
                     }
-                    db.deleteAccount(accounts.get(i));
+                    repo.deleteAccount(accounts.get(i));
                     break;
                 }
             }
@@ -68,6 +69,6 @@ public class ManageAccountsViewModel extends AndroidViewModel {
     }
 
     public void countUnsynchronizedNotes(long accountId, @NonNull IResponseCallback<Long> callback) {
-        new Thread(() -> callback.onSuccess(db.getNoteDao().countUnsynchronizedNotes(accountId))).start();
+        new Thread(() -> callback.onSuccess(repo.countUnsynchronizedNotes(accountId))).start();
     }
 }
\ No newline at end of file
diff --git a/app/src/main/java/it/niedermann/owncloud/notes/persistence/CapabilitiesWorker.java b/app/src/main/java/it/niedermann/owncloud/notes/persistence/CapabilitiesWorker.java
index a9590225..8c38fbde 100644
--- a/app/src/main/java/it/niedermann/owncloud/notes/persistence/CapabilitiesWorker.java
+++ b/app/src/main/java/it/niedermann/owncloud/notes/persistence/CapabilitiesWorker.java
@@ -42,15 +42,15 @@ public class CapabilitiesWorker extends Worker {
     @NonNull
     @Override
     public Result doWork() {
-        final NotesDatabase db = NotesDatabase.getInstance(getApplicationContext());
-        for (Account account : db.getAccountDao().getAccounts()) {
+        final NotesRepository repo = NotesRepository.getInstance(getApplicationContext());
+        for (Account account : repo.getAccounts()) {
             try {
                 final SingleSignOnAccount ssoAccount = AccountImporter.getSingleSignOnAccount(getApplicationContext(), account.getAccountName());
                 Log.i(TAG, "Refreshing capabilities for " + ssoAccount.name);
                 final Capabilities capabilities = CapabilitiesClient.getCapabilities(getApplicationContext(), ssoAccount, account.getCapabilitiesETag());
-                db.getAccountDao().updateCapabilitiesETag(account.getId(), capabilities.getETag());
-                db.getAccountDao().updateBrand(account.getId(), capabilities.getColor(), capabilities.getTextColor());
-                db.updateApiVersion(account.getId(), capabilities.getApiVersion());
+                repo.updateCapabilitiesETag(account.getId(), capabilities.getETag());
+                repo.updateBrand(account.getId(), capabilities.getColor(), capabilities.getTextColor());
+                repo.updateApiVersion(account.getId(), capabilities.getApiVersion());
                 Log.i(TAG, capabilities.toString());
             } catch (Exception e) {
                 if (e instanceof NextcloudHttpRequestFailedException) {
diff --git a/app/src/main/java/it/niedermann/owncloud/notes/persistence/NotesDatabase.java b/app/src/main/java/it/niedermann/owncloud/notes/persistence/NotesDatabase.java
index c6f80280..4f4aaa78 100644
--- a/app/src/main/java/it/niedermann/owncloud/notes/persistence/NotesDatabase.java
+++ b/app/src/main/java/it/niedermann/owncloud/notes/persistence/NotesDatabase.java
@@ -1,43 +1,15 @@
 package it.niedermann.owncloud.notes.persistence;
 
 import android.content.Context;
-import android.content.Intent;
-import android.content.SharedPreferences;
-import android.content.pm.ShortcutInfo;
-import android.content.pm.ShortcutManager;
-import android.graphics.drawable.Icon;
-import android.text.TextUtils;
 import android.util.Log;
 
-import androidx.annotation.AnyThread;
-import androidx.annotation.MainThread;
 import androidx.annotation.NonNull;
-import androidx.annotation.Nullable;
-import androidx.annotation.WorkerThread;
-import androidx.lifecycle.LiveData;
-import androidx.lifecycle.MutableLiveData;
-import androidx.preference.PreferenceManager;
 import androidx.room.Database;
 import androidx.room.Room;
 import androidx.room.RoomDatabase;
 import androidx.room.TypeConverters;
 import androidx.sqlite.db.SupportSQLiteDatabase;
 
-import com.nextcloud.android.sso.AccountImporter;
-import com.nextcloud.android.sso.exceptions.NextcloudFilesAppAccountNotFoundException;
-
-import org.json.JSONArray;
-import org.json.JSONException;
-
-import java.util.ArrayList;
-import java.util.Calendar;
-import java.util.Collections;
-import java.util.List;
-import java.util.Map;
-
-import it.niedermann.android.sharedpreferences.SharedPreferenceIntLiveData;
-import it.niedermann.owncloud.notes.R;
-import it.niedermann.owncloud.notes.edit.EditNoteActivity;
 import it.niedermann.owncloud.notes.persistence.dao.AccountDao;
 import it.niedermann.owncloud.notes.persistence.dao.CategoryOptionsDao;
 import it.niedermann.owncloud.notes.persistence.dao.NoteDao;
@@ -61,24 +33,6 @@ import it.niedermann.owncloud.notes.persistence.migration.Migration_18_19;
 import it.niedermann.owncloud.notes.persistence.migration.Migration_19_20;
 import it.niedermann.owncloud.notes.persistence.migration.Migration_20_21;
 import it.niedermann.owncloud.notes.persistence.migration.Migration_9_10;
-import it.niedermann.owncloud.notes.shared.model.ApiVersion;
-import it.niedermann.owncloud.notes.shared.model.Capabilities;
-import it.niedermann.owncloud.notes.shared.model.CategorySortingMethod;
-import it.niedermann.owncloud.notes.shared.model.DBStatus;
-import it.niedermann.owncloud.notes.shared.model.ENavigationCategoryType;
-import it.niedermann.owncloud.notes.shared.model.ISyncCallback;
-import it.niedermann.owncloud.notes.shared.model.NavigationCategory;
-import it.niedermann.owncloud.notes.shared.util.NoteUtil;
-
-import static android.os.Build.VERSION.SDK_INT;
-import static android.os.Build.VERSION_CODES.O;
-import static androidx.lifecycle.Transformations.map;
-import static androidx.lifecycle.Transformations.switchMap;
-import static it.niedermann.owncloud.notes.edit.EditNoteActivity.ACTION_SHORTCUT;
-import static it.niedermann.owncloud.notes.shared.util.NoteUtil.generateNoteExcerpt;
-import static it.niedermann.owncloud.notes.widget.notelist.NoteListWidget.updateNoteListWidgets;
-import static it.niedermann.owncloud.notes.widget.singlenote.SingleNoteWidget.updateSingleNoteWidgets;
-import static java.util.stream.Collectors.toMap;
 
 @Database(
         entities = {
@@ -94,13 +48,16 @@ public abstract class NotesDatabase extends RoomDatabase {
 
     private static final String TAG = NotesDatabase.class.getSimpleName();
     private static final String NOTES_DB_NAME = "OWNCLOUD_NOTES";
-    private static NotesDatabase instance;
-    private static Context context;
-    private static NotesServerSyncHelper serverSyncHelper;
-    private static String defaultNonEmptyTitle;
+    private static volatile NotesDatabase instance;
+
+    public static NotesDatabase getInstance(@NonNull Context context) {
+        if (instance == null) {
+            instance = create(context.getApplicationContext());
+        }
+        return instance;
+    }
 
     private static NotesDatabase create(final Context context) {
-        defaultNonEmptyTitle = NoteUtil.generateNonEmptyNoteTitle("", context);
         return Room.databaseBuilder(
                 context,
                 NotesDatabase.class,
@@ -110,9 +67,9 @@ public abstract class NotesDatabase extends RoomDatabase {
                         new Migration_10_11(context),
                         new Migration_11_12(context),
                         new Migration_12_13(context),
-                        new Migration_13_14(context, () -> instance.notifyWidgets()),
+                        new Migration_13_14(context),
                         new Migration_14_15(),
-                        new Migration_15_16(context, () -> instance.notifyWidgets()),
+                        new Migration_15_16(context),
                         new Migration_16_17(),
                         new Migration_17_18(),
                         new Migration_18_19(context),
@@ -144,404 +101,4 @@ public abstract class NotesDatabase extends RoomDatabase {
     public abstract WidgetSingleNoteDao getWidgetSingleNoteDao();
 
     public abstract WidgetNotesListDao getWidgetNotesListDao();
-
-    public static NotesDatabase getInstance(@NonNull Context context) {
-        if (instance == null) {
-            instance = create(context.getApplicationContext());
-            NotesDatabase.context = context.getApplicationContext();
-            NotesDatabase.serverSyncHelper = NotesServerSyncHelper.getInstance(instance);
-        }
-        return instance;
-    }
-
-    public NotesServerSyncHelper getNoteServerSyncHelper() {
-        return NotesDatabase.serverSyncHelper;
-    }
-
-    /**
-     * Creates a new Note in the Database and adds a Synchronization Flag.
-     *
-     * @param note Note
-     */
-    @NonNull
-    @MainThread
-    public LiveData<Note> addNoteAndSync(Account account, Note note) {
-        final Note entity = new Note(0, null, note.getModified(), note.getTitle(), note.getContent(), note.getCategory(), note.getFavorite(), note.getETag(), DBStatus.LOCAL_EDITED, account.getId(), generateNoteExcerpt(note.getContent(), note.getTitle()), 0);
-        final MutableLiveData<Note> ret = new MutableLiveData<>();
-        new Thread(() -> ret.postValue(addNote(account.getId(), entity))).start();
-        return map(ret, newNote -> {
-            notifyWidgets();
-            serverSyncHelper.scheduleSync(account, true);
-            return newNote;
-        });
-    }
-
-    /**
-     * Inserts a note directly into the Database.
-     * Excerpt will be generated, {@link DBStatus#LOCAL_EDITED} will be applied in case the note has
-     * already has a local ID, otherwise {@link DBStatus#VOID} will be applied.
-     * No Synchronisation will be triggered! Use {@link #addNoteAndSync(Account, Note)}!
-     *
-     * @param note {@link Note} to be added.
-     */
-    @NonNull
-    @WorkerThread
-    public Note addNote(long accountId, @NonNull Note note) {
-        note.setStatus(note.getId() > 0 ? DBStatus.LOCAL_EDITED : DBStatus.VOID);
-        note.setAccountId(accountId);
-        note.setExcerpt(generateNoteExcerpt(note.getContent(), note.getTitle()));
-        return getNoteDao().getNoteById(getNoteDao().addNote(note));
-    }
-
-    @MainThread
-    public LiveData<Note> moveNoteToAnotherAccount(Account account, @NonNull Note note) {
-        return switchMap(getNoteDao().getContent$(note.getId()), (content) -> {
-            final Note fullNote = new Note(null, note.getModified(), note.getTitle(), content, note.getCategory(), note.getFavorite(), null);
-            deleteNoteAndSync(account, note.getId());
-            return addNoteAndSync(account, fullNote);
-        });
-    }
-
-    /**
-     * @return a {@link Map} of remote IDs as keys and local IDs as values of all {@link Note}s of
-     * the given {@param accountId} which are not {@link DBStatus#LOCAL_DELETED}
-     */
-    @NonNull
-    @WorkerThread
-    public Map<Long, Long> getIdMap(long accountId) {
-        validateAccountId(accountId);
-        return getNoteDao()
-                .getRemoteIdAndId(accountId)
-                .stream()
-                .filter(note -> note.getRemoteId() != null)
-                .collect(toMap(Note::getRemoteId, Note::getId));
-    }
-
-    @AnyThread
-    public void toggleFavoriteAndSync(Account account, long noteId) {
-        new Thread(() -> {
-            getNoteDao().toggleFavorite(noteId);
-            serverSyncHelper.scheduleSync(account, true);
-        }).start();
-    }
-
-    /**
-     * Set the category for a given note.
-     * This method will search in the database to find out the category id in the db.
-     * If there is no such category existing, this method will create it and search again.
-     *
-     * @param account  The single sign on account
-     * @param noteId   The note which will be updated
-     * @param category The category title which should be used to find the category id.
-     */
-    @AnyThread
-    public void setCategory(@NonNull Account account, long noteId, @NonNull String category) {
-        new Thread(() -> {
-            getNoteDao().updateStatus(noteId, DBStatus.LOCAL_EDITED);
-            getNoteDao().updateCategory(noteId, category);
-            serverSyncHelper.scheduleSync(account, true);
-        }).start();
-    }
-
-    /**
-     * Updates a single Note with a new content.
-     * The title is derived from the new content automatically, and modified date as well as DBStatus are updated, too -- if the content differs to the state in the database.
-     *
-     * @param oldNote    Note to be changed
-     * @param newContent New content. If this is <code>null</code>, then <code>oldNote</code> is saved again (useful for undoing changes).
-     * @param newTitle   New title. If this is <code>null</code>, then either the old title is reused (in case the note has been synced before) or a title is generated (in case it is a new note)
-     * @param callback   When the synchronization is finished, this callback will be invoked (optional).
-     * @return changed {@link Note} if differs from database, otherwise the old {@link Note}.
-     */
-    @WorkerThread
-    public Note updateNoteAndSync(Account localAccount, @NonNull Note oldNote, @Nullable String newContent, @Nullable String newTitle, @Nullable ISyncCallback callback) {
-        final Note newNote;
-        if (newContent == null) {
-            newNote = new Note(oldNote.getId(), oldNote.getRemoteId(), oldNote.getModified(), oldNote.getTitle(), oldNote.getContent(), oldNote.getCategory(), oldNote.getFavorite(), oldNote.getETag(), DBStatus.LOCAL_EDITED, localAccount.getId(), oldNote.getExcerpt(), oldNote.getScrollY());
-        } else {
-            final String title;
-            if (newTitle != null) {
-                title = newTitle;
-            } else {
-                if ((oldNote.getRemoteId() == null || localAccount.getPreferredApiVersion() == null || localAccount.getPreferredApiVersion().compareTo(new ApiVersion("1.0", 0, 0)) < 0) &&
-                        (defaultNonEmptyTitle.equals(oldNote.getTitle()))) {
-                    title = NoteUtil.generateNonEmptyNoteTitle(newContent, context);
-                } else {
-                    title = oldNote.getTitle();
-                }
-            }
-            newNote = new Note(oldNote.getId(), oldNote.getRemoteId(), Calendar.getInstance(), title, newContent, oldNote.getCategory(), oldNote.getFavorite(), oldNote.getETag(), DBStatus.LOCAL_EDITED, localAccount.getId(), generateNoteExcerpt(newContent, title), oldNote.getScrollY());
-        }
-        int rows = getNoteDao().updateNote(newNote);
-        // if data was changed, set new status and schedule sync (with callback); otherwise invoke callback directly.
-        if (rows > 0) {
-            notifyWidgets();
-            if (callback != null) {
-                serverSyncHelper.addCallbackPush(localAccount, callback);
-            }
-            serverSyncHelper.scheduleSync(localAccount, true);
-            return newNote;
-        } else {
-            if (callback != null) {
-                callback.onFinish();
-            }
-            return oldNote;
-        }
-    }
-
-    /**
-     * Marks a Note in the Database as Deleted. In the next Synchronization it will be deleted
-     * from the Server.
-     *
-     * @param id long - ID of the Note that should be deleted
-     */
-    @AnyThread
-    public void deleteNoteAndSync(Account account, long id) {
-        new Thread(() -> {
-            getNoteDao().updateStatus(id, DBStatus.LOCAL_DELETED);
-            notifyWidgets();
-            serverSyncHelper.scheduleSync(account, true);
-
-            if (SDK_INT >= O) {
-                ShortcutManager shortcutManager = context.getSystemService(ShortcutManager.class);
-                if (shortcutManager != null) {
-                    shortcutManager.getPinnedShortcuts().forEach((shortcut) -> {
-                        String shortcutId = id + "";
-                        if (shortcut.getId().equals(shortcutId)) {
-                            Log.v(TAG, "Removing shortcut for " + shortcutId);
-                            shortcutManager.disableShortcuts(Collections.singletonList(shortcutId), context.getResources().getString(R.string.note_has_been_deleted));
-                        }
-                    });
-                } else {
-                    Log.e(TAG, ShortcutManager.class.getSimpleName() + "is null.");
-                }
-            }
-        }).start();
-    }
-
-    /**
-     * Notify about changed notes.
-     */
-    @AnyThread
-    protected void notifyWidgets() {
-        new Thread(() -> {
-            updateSingleNoteWidgets(context);
-            updateNoteListWidgets(context);
-        }).start();
-    }
-
-    @AnyThread
-    void updateDynamicShortcuts(long accountId) {
-        new Thread(() -> {
-            if (SDK_INT >= android.os.Build.VERSION_CODES.N_MR1) {
-                ShortcutManager shortcutManager = context.getApplicationContext().getSystemService(ShortcutManager.class);
-                if (shortcutManager != null) {
-                    if (!shortcutManager.isRateLimitingActive()) {
-                        List<ShortcutInfo> newShortcuts = new ArrayList<>();
-
-                        for (Note note : getNoteDao().getRecentNotes(accountId)) {
-                            if (!TextUtils.isEmpty(note.getTitle())) {
-                                Intent intent = new Intent(context.getApplicationContext(), EditNoteActivity.class);
-                                intent.putExtra(EditNoteActivity.PARAM_NOTE_ID, note.getId());
-                                intent.setAction(ACTION_SHORTCUT);
-
-                                newShortcuts.add(new ShortcutInfo.Builder(context.getApplicationContext(), note.getId() + "")
-                                        .setShortLabel(note.getTitle() + "")
-                                        .setIcon(Icon.createWithResource(context.getApplicationContext(), note.getFavorite() ? R.drawable.ic_star_yellow_24dp : R.drawable.ic_star_grey_ccc_24dp))
-                                        .setIntent(intent)
-                                        .build());
-                            } else {
-                                // Prevent crash https://github.com/stefan-niedermann/nextcloud-notes/issues/613
-                                Log.e(TAG, "shortLabel cannot be empty " + note);
-                            }
-                        }
-                        Log.d(TAG, "Update dynamic shortcuts");
-                        shortcutManager.removeAllDynamicShortcuts();
-                        shortcutManager.addDynamicShortcuts(newShortcuts);
-                    }
-                }
-            }
-        }).start();
-    }
-
-    @AnyThread
-    public LiveData<Account> addAccount(@NonNull String url, @NonNull String username, @NonNull String accountName, @NonNull Capabilities capabilities) {
-        return getAccountDao().getAccountById$(getAccountDao().insert(new Account(url, username, accountName, capabilities)));
-    }
-
-    /**
-     * @param apiVersion has to be a JSON array as a string <code>["0.2", "1.0", ...]</code>
-     * @return whether or not the given {@link ApiVersion} has been written to the database
-     * @throws IllegalArgumentException if the apiVersion does not match the expected format
-     */
-    public boolean updateApiVersion(long accountId, @Nullable String apiVersion) throws IllegalArgumentException {
-        validateAccountId(accountId);
-        if (apiVersion != null) {
-            try {
-                JSONArray apiVersions = new JSONArray(apiVersion);
-                for (int i = 0; i < apiVersions.length(); i++) {
-                    ApiVersion.of(apiVersions.getString(i));
-                }
-                if (apiVersions.length() > 0) {
-                    final int updatedRows = getAccountDao().updateApiVersion(accountId, apiVersion);
-                    if (updatedRows == 1) {
-                        Log.i(TAG, "Updated apiVersion to \"" + apiVersion + "\" for accountId = " + accountId);
-                    } else {
-                        Log.e(TAG, "Updated " + updatedRows + " but expected only 1 for accountId = " + accountId + " and apiVersion = \"" + apiVersion + "\"");
-                    }
-                    return true;
-                } else {
-                    Log.i(TAG, "Given API version is a valid JSON array but does not contain any valid API versions. Do not update database.");
-                }
-            } catch (NumberFormatException e) {
-                throw new IllegalArgumentException("API version does contain a non-valid version: " + apiVersion);
-            } catch (JSONException e) {
-                throw new IllegalArgumentException("API version must contain be a JSON array: " + apiVersion);
-            }
-        } else {
-            Log.v(TAG, "Given API version is null. Do not update database");
-        }
-        return false;
-    }
-
-    /**
-     * @param localAccount the {@link Account} that should be deleted
-     * @throws IllegalArgumentException if no account has been deleted by the given accountId
-     */
-    @AnyThread
-    public void deleteAccount(@NonNull Account localAccount) throws IllegalArgumentException {
-        validateAccountId(localAccount.getId());
-        new Thread(() -> {
-            int deletedAccounts = getAccountDao().deleteAccount(localAccount);
-            if (deletedAccounts < 1) {
-                Log.e(TAG, "AccountId '" + localAccount.getId() + "' did not delete any account");
-                throw new IllegalArgumentException("The given accountId does not delete any row");
-            } else if (deletedAccounts > 1) {
-                Log.e(TAG, "AccountId '" + localAccount.getId() + "' deleted unexpectedly '" + deletedAccounts + "' accounts");
-            }
-
-            try {
-                SSOClient.invalidateAPICache(AccountImporter.getSingleSignOnAccount(context, localAccount.getAccountName()));
-            } catch (NextcloudFilesAppAccountNotFoundException e) {
-                e.printStackTrace();
-                SSOClient.invalidateAPICache();
-            }
-
-            // TODO this should already be handled by foreign key cascade, no?
-            final int deletedNotes = getNoteDao().deleteByAccountId(localAccount.getId());
-            Log.v(TAG, "Deleted " + deletedNotes + " notes from account " + localAccount.getId());
-        }).start();
-    }
-
-    private static void validateAccountId(long accountId) {
-        if (accountId < 1) {
-            throw new IllegalArgumentException("accountId must be greater than 0");
-        }
-    }
-
-    /**
-     * Modifies the sorting method for one category, the category can be normal category or
-     * one of "All notes", "Favorite", and "Uncategorized".
-     * If category is one of these three, sorting method will be modified in android.content.SharedPreference.
-     * The user can determine use which sorting method to show the notes for a category.
-     * When the user changes the sorting method, this method should be called.
-     *
-     * @param accountId        The user accountID
-     * @param selectedCategory The category to be modified
-     * @param sortingMethod    The sorting method in {@link CategorySortingMethod} enum format
-     */
-    @AnyThread
-    public void modifyCategoryOrder(long accountId, @NonNull NavigationCategory selectedCategory, @NonNull CategorySortingMethod sortingMethod) {
-        validateAccountId(accountId);
-
-        new Thread(() -> {
-            final Context ctx = context.getApplicationContext();
-            final SharedPreferences.Editor sp = PreferenceManager.getDefaultSharedPreferences(ctx).edit();
-            int orderIndex = sortingMethod.getId();
-
-            switch (selectedCategory.getType()) {
-                case FAVORITES: {
-                    sp.putInt(ctx.getString(R.string.action_sorting_method) + ' ' + ctx.getString(R.string.label_favorites), orderIndex);
-                    break;
-                }
-                case UNCATEGORIZED: {
-                    sp.putInt(ctx.getString(R.string.action_sorting_method) + ' ' + ctx.getString(R.string.action_uncategorized), orderIndex);
-                    break;
-                }
-                case RECENT: {
-                    sp.putInt(ctx.getString(R.string.action_sorting_method) + ' ' + ctx.getString(R.string.label_all_notes), orderIndex);
-                    break;
-                }
-                case DEFAULT_CATEGORY:
-                default: {
-                    final String category = selectedCategory.getCategory();
-                    if (category != null) {
-                        if (getCategoryOptionsDao().modifyCategoryOrder(accountId, category, sortingMethod) == 0) {
-                            // Nothing updated means we didn't have this yet
-                            final CategoryOptions categoryOptions = new CategoryOptions();
-                            categoryOptions.setAccountId(accountId);
-                            categoryOptions.setCategory(category);
-                            categoryOptions.setSortingMethod(sortingMethod);
-                            getCategoryOptionsDao().addCategoryOptions(categoryOptions);
-                        }
-                    } else {
-                        throw new IllegalStateException("Tried to modify category order for " + ENavigationCategoryType.DEFAULT_CATEGORY + "but category is null.");
-                    }
-                    break;
-                }
-            }
-            sp.apply();
-        }).start();
-    }
-
-    /**
-     * Gets the sorting method of a {@link NavigationCategory}, the category can be normal
-     * {@link CategoryOptions} or one of {@link ENavigationCategoryType}.
-     * If the category no normal {@link CategoryOptions}, sorting method will be got from
-     * {@link SharedPreferences}.
-     * <p>
-     * The sorting method of the category can be used to decide to use which sorting method to show
-     * the notes for each categories.
-     *
-     * @param selectedCategory The category
-     * @return The sorting method in CategorySortingMethod enum format
-     */
-    @NonNull
-    @MainThread
-    public LiveData<CategorySortingMethod> getCategoryOrder(@NonNull NavigationCategory selectedCategory) {
-        final SharedPreferences sp = PreferenceManager.getDefaultSharedPreferences(context);
-        String prefKey;
-
-        switch (selectedCategory.getType()) {
-            // TODO make this account specific
-            case RECENT: {
-                prefKey = context.getString(R.string.action_sorting_method) + ' ' + context.getString(R.string.label_all_notes);
-                break;
-            }
-            case FAVORITES: {
-                prefKey = context.getString(R.string.action_sorting_method) + ' ' + context.getString(R.string.label_favorites);
-                break;
-            }
-            case UNCATEGORIZED: {
-                prefKey = context.getString(R.string.action_sorting_method) + ' ' + context.getString(R.string.action_uncategorized);
-                break;
-            }
-            case DEFAULT_CATEGORY:
-            default: {
-                final String category = selectedCategory.getCategory();
-                if (category != null) {
-                    return getCategoryOptionsDao().getCategoryOrder(selectedCategory.getAccountId(), category);
-                } else {
-                    Log.e(TAG, "Cannot read " + CategorySortingMethod.class.getSimpleName() + " for " + ENavigationCategoryType.DEFAULT_CATEGORY + ".");
-                    return new MutableLiveData<>(CategorySortingMethod.SORT_MODIFIED_DESC);
-                }
-            }
-        }
-
-        return map(new SharedPreferenceIntLiveData(sp, prefKey, CategorySortingMethod.SORT_MODIFIED_DESC.getId()), CategorySortingMethod::findById);
-    }
-
-    public Context getContext() {
-        return NotesDatabase.context;
-    }
 }
diff --git a/app/src/main/java/it/niedermann/owncloud/notes/persistence/NotesRepository.java b/app/src/main/java/it/niedermann/owncloud/notes/persistence/NotesRepository.java
new file mode 100644
index 00000000..55b786dc
--- /dev/null
+++ b/app/src/main/java/it/niedermann/owncloud/notes/persistence/NotesRepository.java
@@ -0,0 +1,951 @@
+package it.niedermann.owncloud.notes.persistence;
+
+import android.accounts.NetworkErrorException;
+import android.content.BroadcastReceiver;
+import android.content.Context;
+import android.content.Intent;
+import android.content.IntentFilter;
+import android.content.SharedPreferences;
+import android.content.pm.ShortcutInfo;
+import android.content.pm.ShortcutManager;
+import android.graphics.drawable.Icon;
+import android.net.ConnectivityManager;
+import android.net.NetworkInfo;
+import android.text.TextUtils;
+import android.util.Log;
+
+import androidx.annotation.AnyThread;
+import androidx.annotation.ColorInt;
+import androidx.annotation.MainThread;
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import androidx.annotation.WorkerThread;
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.MutableLiveData;
+import androidx.preference.PreferenceManager;
+
+import com.nextcloud.android.sso.AccountImporter;
+import com.nextcloud.android.sso.exceptions.NextcloudFilesAppAccountNotFoundException;
+import com.nextcloud.android.sso.exceptions.NoCurrentAccountSelectedException;
+import com.nextcloud.android.sso.helper.SingleAccountHelper;
+import com.nextcloud.android.sso.model.SingleSignOnAccount;
+
+import org.json.JSONArray;
+import org.json.JSONException;
+
+import java.util.ArrayList;
+import java.util.Calendar;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+
+import it.niedermann.android.sharedpreferences.SharedPreferenceIntLiveData;
+import it.niedermann.owncloud.notes.R;
+import it.niedermann.owncloud.notes.edit.EditNoteActivity;
+import it.niedermann.owncloud.notes.persistence.entity.Account;
+import it.niedermann.owncloud.notes.persistence.entity.CategoryOptions;
+import it.niedermann.owncloud.notes.persistence.entity.CategoryWithNotesCount;
+import it.niedermann.owncloud.notes.persistence.entity.Note;
+import it.niedermann.owncloud.notes.persistence.entity.NotesListWidgetData;
+import it.niedermann.owncloud.notes.persistence.entity.SingleNoteWidgetData;
+import it.niedermann.owncloud.notes.shared.model.ApiVersion;
+import it.niedermann.owncloud.notes.shared.model.Capabilities;
+import it.niedermann.owncloud.notes.shared.model.CategorySortingMethod;
+import it.niedermann.owncloud.notes.shared.model.DBStatus;
+import it.niedermann.owncloud.notes.shared.model.ENavigationCategoryType;
+import it.niedermann.owncloud.notes.shared.model.ISyncCallback;
+import it.niedermann.owncloud.notes.shared.model.NavigationCategory;
+import it.niedermann.owncloud.notes.shared.model.SyncResultStatus;
+import it.niedermann.owncloud.notes.shared.util.NoteUtil;
+import it.niedermann.owncloud.notes.shared.util.SSOUtil;
+
+import static android.os.Build.VERSION.SDK_INT;
+import static android.os.Build.VERSION_CODES.O;
+import static androidx.lifecycle.Transformations.distinctUntilChanged;
+import static androidx.lifecycle.Transformations.map;
+import static androidx.lifecycle.Transformations.switchMap;
+import static it.niedermann.owncloud.notes.edit.EditNoteActivity.ACTION_SHORTCUT;
+import static it.niedermann.owncloud.notes.shared.util.NoteUtil.generateNoteExcerpt;
+import static it.niedermann.owncloud.notes.widget.notelist.NoteListWidget.updateNoteListWidgets;
+import static it.niedermann.owncloud.notes.widget.singlenote.SingleNoteWidget.updateSingleNoteWidgets;
+import static java.util.stream.Collectors.toMap;
+
+@SuppressWarnings("UnusedReturnValue")
+public class NotesRepository {
+
+    private static final String TAG = NotesRepository.class.getSimpleName();
+
+    private static NotesRepository instance;
+
+    private final ExecutorService executor = Executors.newSingleThreadExecutor();
+    private final Context context;
+    private final NotesDatabase db;
+    private final String defaultNonEmptyTitle;
+
+    /**
+     * Track network connection changes using a {@link BroadcastReceiver}
+     */
+    private boolean isSyncPossible = false;
+    private boolean networkConnected = false;
+    private String syncOnlyOnWifiKey;
+    private boolean syncOnlyOnWifi;
+    private final MutableLiveData<Boolean> syncStatus = new MutableLiveData<>(false);
+    private final MutableLiveData<ArrayList<Throwable>> syncErrors = new MutableLiveData<>();
+
+    /**
+     * @see <a href="https://stackoverflow.com/a/3104265">Do not make this a local variable.</a>
+     */
+    @SuppressWarnings("FieldCanBeLocal")
+    private final SharedPreferences.OnSharedPreferenceChangeListener onSharedPreferenceChangeListener = (SharedPreferences prefs, String key) -> {
+        if (syncOnlyOnWifiKey.equals(key)) {
+            syncOnlyOnWifi = prefs.getBoolean(syncOnlyOnWifiKey, false);
+            updateNetworkStatus();
+        }
+    };
+
+    private final BroadcastReceiver networkReceiver = new BroadcastReceiver() {
+        @Override
+        public void onReceive(Context context, Intent intent) {
+            updateNetworkStatus();
+            if (isSyncPossible() && SSOUtil.isConfigured(context)) {
+                new Thread(() -> {
+                    try {
+                        scheduleSync(getAccountByName(SingleAccountHelper.getCurrentSingleSignOnAccount(context).name), false);
+                    } catch (NextcloudFilesAppAccountNotFoundException | NoCurrentAccountSelectedException e) {
+                        Log.v(TAG, "Can not select current SingleSignOn account after network changed, do not sync.");
+                    }
+                }).start();
+            }
+        }
+    };
+
+    // current state of the synchronization
+    private final Map<Long, Boolean> syncActive = new HashMap<>();
+    private final Map<Long, Boolean> syncScheduled = new HashMap<>();
+
+    // list of callbacks for both parts of synchronization
+    private final Map<Long, List<ISyncCallback>> callbacksPush = new HashMap<>();
+    private final Map<Long, List<ISyncCallback>> callbacksPull = new HashMap<>();
+
+
+    public static synchronized NotesRepository getInstance(@NonNull Context context) {
+        if (instance == null) {
+            instance = new NotesRepository(context);
+        }
+        return instance;
+    }
+
+    private NotesRepository(final Context context) {
+        this.context = context.getApplicationContext();
+        this.db = NotesDatabase.getInstance(this.context);
+        this.defaultNonEmptyTitle = NoteUtil.generateNonEmptyNoteTitle("", this.context);
+        this.syncOnlyOnWifiKey = context.getApplicationContext().getResources().getString(R.string.pref_key_wifi_only);
+
+        // Registers BroadcastReceiver to track network connection changes.
+        context.getApplicationContext().registerReceiver(networkReceiver, new IntentFilter(ConnectivityManager.CONNECTIVITY_ACTION));
+
+        SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(this.context.getApplicationContext());
+        prefs.registerOnSharedPreferenceChangeListener(onSharedPreferenceChangeListener);
+        syncOnlyOnWifi = prefs.getBoolean(syncOnlyOnWifiKey, false);
+
+        updateNetworkStatus();
+    }
+
+
+    // Accounts
+
+    public List<Account> getAccounts() {
+        return db.getAccountDao().getAccounts();
+    }
+
+    public int deleteAccount(Account localAccount) {
+        return db.getAccountDao().deleteAccount(localAccount);
+    }
+
+    public Account getAccountByName(String accountName) {
+        return db.getAccountDao().getAccountByName(accountName);
+    }
+
+    public Account getAccountById(long accountId) {
+        return db.getAccountDao().getAccountById(accountId);
+    }
+
+    public LiveData<List<Account>> getAccounts$() {
+        return db.getAccountDao().getAccounts$();
+    }
+
+    public LiveData<Account> getAccountById$(long accountId) {
+        return db.getAccountDao().getAccountById$(accountId);
+    }
+
+    public LiveData<Integer> countAccounts$() {
+        return db.getAccountDao().countAccounts$();
+    }
+
+    public void updateBrand(long id, @ColorInt Integer color, @ColorInt Integer textColor) {
+        db.getAccountDao().updateBrand(id, color, textColor);
+    }
+
+    public void updateETag(long id, String eTag) {
+        db.getAccountDao().updateETag(id, eTag);
+    }
+
+    public void updateCapabilitiesETag(long id, String capabilitiesETag) {
+        db.getAccountDao().updateCapabilitiesETag(id, capabilitiesETag);
+    }
+
+    public void updateModified(long id, long modified) {
+        db.getAccountDao().updateModified(id, modified);
+    }
+
+
+    // Notes
+
+    public LiveData<Note> getNoteById$(long id) {
+        return db.getNoteDao().getNoteById$(id);
+    }
+
+    public Note getNoteById(long id) {
+        return db.getNoteDao().getNoteById(id);
+    }
+
+    public LiveData<Integer> count$(long accountId) {
+        return db.getNoteDao().count$(accountId);
+    }
+
+    public LiveData<Integer> countFavorites$(long accountId) {
+        return db.getNoteDao().countFavorites$(accountId);
+    }
+
+    public void updateScrollY(long id, int scrollY) {
+        db.getNoteDao().updateScrollY(id, scrollY);
+    }
+
+    public LiveData<List<CategoryWithNotesCount>> searchCategories$(Long accountId, String searchTerm) {
+        return db.getNoteDao().searchCategories$(accountId, searchTerm);
+    }
+
+    public LiveData<List<Note>> searchRecentByModified$(long accountId, String query) {
+        return db.getNoteDao().searchRecentByModified$(accountId, query);
+    }
+
+    public List<Note> searchRecentByModified(long accountId, String query) {
+        return db.getNoteDao().searchRecentByModified(accountId, query);
+    }
+
+    public LiveData<List<Note>> searchRecentLexicographically$(long accountId, String query) {
+        return db.getNoteDao().searchRecentLexicographically$(accountId, query);
+    }
+
+    public LiveData<List<Note>> searchFavoritesByModified$(long accountId, String query) {
+        return db.getNoteDao().searchFavoritesByModified$(accountId, query);
+    }
+
+    public List<Note> searchFavoritesByModified(long accountId, String query) {
+        return db.getNoteDao().searchFavoritesByModified(accountId, query);
+    }
+
+    public LiveData<List<Note>> searchFavoritesLexicographically$(long accountId, String query) {
+        return db.getNoteDao().searchFavoritesLexicographically$(accountId, query);
+    }
+
+    public LiveData<List<Note>> searchUncategorizedByModified$(long accountId, String query) {
+        return db.getNoteDao().searchUncategorizedByModified$(accountId, query);
+    }
+
+    public List<Note> searchUncategorizedByModified(long accountId, String query) {
+        return db.getNoteDao().searchUncategorizedByModified(accountId, query);
+    }
+
+    public LiveData<List<Note>> searchUncategorizedLexicographically$(long accountId, String query) {
+        return db.getNoteDao().searchUncategorizedLexicographically$(accountId, query);
+    }
+
+    public LiveData<List<Note>> searchCategoryByModified$(long accountId, String query, String category) {
+        return db.getNoteDao().searchCategoryByModified$(accountId, query, category);
+    }
+
+    public List<Note> searchCategoryByModified(long accountId, String query, String category) {
+        return db.getNoteDao().searchCategoryByModified(accountId, query, category);
+    }
+
+    public LiveData<List<Note>> searchCategoryLexicographically$(long accountId, String query, String category) {
+        return db.getNoteDao().searchCategoryLexicographically$(accountId, query, category);
+    }
+
+    public LiveData<List<CategoryWithNotesCount>> getCategories$(Long accountId) {
+        return db.getNoteDao().getCategories$(accountId);
+    }
+
+    public void updateRemoteId(long id, Long remoteId) {
+        db.getNoteDao().updateRemoteId(id, remoteId);
+    }
+
+    public Long getLocalIdByRemoteId(long accountId, long remoteId) {
+        return db.getNoteDao().getLocalIdByRemoteId(accountId, remoteId);
+    }
+
+    public List<Note> getLocalModifiedNotes(long accountId) {
+        return db.getNoteDao().getLocalModifiedNotes(accountId);
+    }
+
+    public void deleteByNoteId(long id, DBStatus forceDBStatus) {
+        db.getNoteDao().deleteByNoteId(id, forceDBStatus);
+    }
+
+    public int updateIfNotModifiedLocallyDuringSync(long noteId, Long targetModified, String targetTitle, boolean targetFavorite, String targetETag, String targetContent, String targetExcerpt, String contentBeforeSyncStart, String categoryBeforeSyncStart, boolean favoriteBeforeSyncStart) {
+        return db.getNoteDao().updateIfNotModifiedLocallyDuringSync(noteId, targetModified, targetTitle, targetFavorite, targetETag, targetContent, targetExcerpt, contentBeforeSyncStart, categoryBeforeSyncStart, favoriteBeforeSyncStart);
+    }
+
+    public int updateIfNotModifiedLocallyAndAnyRemoteColumnHasChanged(long id, Long modified, String title, boolean favorite, String category, String eTag, String content, String excerpt) {
+        return db.getNoteDao().updateIfNotModifiedLocallyAndAnyRemoteColumnHasChanged(id, modified, title, favorite, category, eTag, content, excerpt);
+    }
+
+    public long countUnsynchronizedNotes(long accountId) {
+        final Long unsynchronizedNotesCount = db.getNoteDao().countUnsynchronizedNotes(accountId);
+        return unsynchronizedNotesCount == null ? 0 : unsynchronizedNotesCount;
+    }
+
+
+    // SingleNoteWidget
+
+    public void createOrUpdateSingleNoteWidgetData(SingleNoteWidgetData data) {
+        db.getWidgetSingleNoteDao().createOrUpdateSingleNoteWidgetData(data);
+    }
+
+    public void removeSingleNoteWidget(int id) {
+        db.getWidgetSingleNoteDao().removeSingleNoteWidget(id);
+    }
+
+    public SingleNoteWidgetData getSingleNoteWidgetData(int id) {
+        return db.getWidgetSingleNoteDao().getSingleNoteWidgetData(id);
+    }
+
+
+    // ListWidget
+
+    public void createOrUpdateNoteListWidgetData(NotesListWidgetData data) {
+        db.getWidgetNotesListDao().createOrUpdateNoteListWidgetData(data);
+    }
+
+    public void removeNoteListWidget(int appWidgetId) {
+        db.getWidgetNotesListDao().removeNoteListWidget(appWidgetId);
+    }
+
+    public NotesListWidgetData getNoteListWidgetData(int appWidgetId) {
+        return db.getWidgetNotesListDao().getNoteListWidgetData(appWidgetId);
+    }
+
+    /**
+     * Creates a new Note in the Database and adds a Synchronization Flag.
+     *
+     * @param note Note
+     */
+    @NonNull
+    @MainThread
+    public LiveData<Note> addNoteAndSync(Account account, Note note) {
+        final Note entity = new Note(0, null, note.getModified(), note.getTitle(), note.getContent(), note.getCategory(), note.getFavorite(), note.getETag(), DBStatus.LOCAL_EDITED, account.getId(), generateNoteExcerpt(note.getContent(), note.getTitle()), 0);
+        final MutableLiveData<Note> ret = new MutableLiveData<>();
+        new Thread(() -> ret.postValue(addNote(account.getId(), entity))).start();
+        return map(ret, newNote -> {
+            notifyWidgets();
+            scheduleSync(account, true);
+            return newNote;
+        });
+    }
+
+    /**
+     * Inserts a note directly into the Database.
+     * Excerpt will be generated, {@link DBStatus#LOCAL_EDITED} will be applied in case the note has
+     * already has a local ID, otherwise {@link DBStatus#VOID} will be applied.
+     * No Synchronisation will be triggered! Use {@link #addNoteAndSync(Account, Note)}!
+     *
+     * @param note {@link Note} to be added.
+     */
+    @NonNull
+    @WorkerThread
+    public Note addNote(long accountId, @NonNull Note note) {
+        note.setStatus(note.getId() > 0 ? DBStatus.LOCAL_EDITED : DBStatus.VOID);
+        note.setAccountId(accountId);
+        note.setExcerpt(generateNoteExcerpt(note.getContent(), note.getTitle()));
+        return db.getNoteDao().getNoteById(db.getNoteDao().addNote(note));
+    }
+
+    @MainThread
+    public LiveData<Note> moveNoteToAnotherAccount(Account account, @NonNull Note note) {
+        return switchMap(db.getNoteDao().getContent$(note.getId()), (content) -> {
+            final Note fullNote = new Note(null, note.getModified(), note.getTitle(), content, note.getCategory(), note.getFavorite(), null);
+            deleteNoteAndSync(account, note.getId());
+            return addNoteAndSync(account, fullNote);
+        });
+    }
+
+    /**
+     * @return a {@link Map} of remote IDs as keys and local IDs as values of all {@link Note}s of
+     * the given {@param accountId} which are not {@link DBStatus#LOCAL_DELETED}
+     */
+    @NonNull
+    @WorkerThread
+    public Map<Long, Long> getIdMap(long accountId) {
+        validateAccountId(accountId);
+        return db.getNoteDao()
+                .getRemoteIdAndId(accountId)
+                .stream()
+                .filter(note -> note.getRemoteId() != null)
+                .collect(toMap(Note::getRemoteId, Note::getId));
+    }
+
+    @AnyThread
+    public void toggleFavoriteAndSync(Account account, long noteId) {
+        new Thread(() -> {
+            db.getNoteDao().toggleFavorite(noteId);
+            scheduleSync(account, true);
+        }).start();
+    }
+
+    /**
+     * Set the category for a given note.
+     * This method will search in the database to find out the category id in the db.
+     * If there is no such category existing, this method will create it and search again.
+     *
+     * @param account  The single sign on account
+     * @param noteId   The note which will be updated
+     * @param category The category title which should be used to find the category id.
+     */
+    @AnyThread
+    public void setCategory(@NonNull Account account, long noteId, @NonNull String category) {
+        new Thread(() -> {
+            db.getNoteDao().updateStatus(noteId, DBStatus.LOCAL_EDITED);
+            db.getNoteDao().updateCategory(noteId, category);
+            scheduleSync(account, true);
+        }).start();
+    }
+
+    /**
+     * Updates a single Note with a new content.
+     * The title is derived from the new content automatically, and modified date as well as DBStatus are updated, too -- if the content differs to the state in the database.
+     *
+     * @param oldNote    Note to be changed
+     * @param newContent New content. If this is <code>null</code>, then <code>oldNote</code> is saved again (useful for undoing changes).
+     * @param newTitle   New title. If this is <code>null</code>, then either the old title is reused (in case the note has been synced before) or a title is generated (in case it is a new note)
+     * @param callback   When the synchronization is finished, this callback will be invoked (optional).
+     * @return changed {@link Note} if differs from database, otherwise the old {@link Note}.
+     */
+    @WorkerThread
+    public Note updateNoteAndSync(Account localAccount, @NonNull Note oldNote, @Nullable String newContent, @Nullable String newTitle, @Nullable ISyncCallback callback) {
+        final Note newNote;
+        if (newContent == null) {
+            newNote = new Note(oldNote.getId(), oldNote.getRemoteId(), oldNote.getModified(), oldNote.getTitle(), oldNote.getContent(), oldNote.getCategory(), oldNote.getFavorite(), oldNote.getETag(), DBStatus.LOCAL_EDITED, localAccount.getId(), oldNote.getExcerpt(), oldNote.getScrollY());
+        } else {
+            final String title;
+            if (newTitle != null) {
+                title = newTitle;
+            } else {
+                if ((oldNote.getRemoteId() == null || localAccount.getPreferredApiVersion() == null || localAccount.getPreferredApiVersion().compareTo(new ApiVersion("1.0", 0, 0)) < 0) &&
+                        (defaultNonEmptyTitle.equals(oldNote.getTitle()))) {
+                    title = NoteUtil.generateNonEmptyNoteTitle(newContent, context);
+                } else {
+                    title = oldNote.getTitle();
+                }
+            }
+            newNote = new Note(oldNote.getId(), oldNote.getRemoteId(), Calendar.getInstance(), title, newContent, oldNote.getCategory(), oldNote.getFavorite(), oldNote.getETag(), DBStatus.LOCAL_EDITED, localAccount.getId(), generateNoteExcerpt(newContent, title), oldNote.getScrollY());
+        }
+        int rows = db.getNoteDao().updateNote(newNote);
+        // if data was changed, set new status and schedule sync (with callback); otherwise invoke callback directly.
+        if (rows > 0) {
+            notifyWidgets();
+            if (callback != null) {
+                addCallbackPush(localAccount, callback);
+            }
+            scheduleSync(localAccount, true);
+            return newNote;
+        } else {
+            if (callback != null) {
+                callback.onFinish();
+            }
+            return oldNote;
+        }
+    }
+
+    /**
+     * Marks a Note in the Database as Deleted. In the next Synchronization it will be deleted
+     * from the Server.
+     *
+     * @param id long - ID of the Note that should be deleted
+     */
+    @AnyThread
+    public void deleteNoteAndSync(Account account, long id) {
+        new Thread(() -> {
+            db.getNoteDao().updateStatus(id, DBStatus.LOCAL_DELETED);
+            notifyWidgets();
+            scheduleSync(account, true);
+
+            if (SDK_INT >= O) {
+                ShortcutManager shortcutManager = context.getSystemService(ShortcutManager.class);
+                if (shortcutManager != null) {
+                    shortcutManager.getPinnedShortcuts().forEach((shortcut) -> {
+                        String shortcutId = id + "";
+                        if (shortcut.getId().equals(shortcutId)) {
+                            Log.v(TAG, "Removing shortcut for " + shortcutId);
+                            shortcutManager.disableShortcuts(Collections.singletonList(shortcutId), context.getResources().getString(R.string.note_has_been_deleted));
+                        }
+                    });
+                } else {
+                    Log.e(TAG, ShortcutManager.class.getSimpleName() + "is null.");
+                }
+            }
+        }).start();
+    }
+
+    /**
+     * Notify about changed notes.
+     */
+    @AnyThread
+    protected void notifyWidgets() {
+        new Thread(() -> {
+            updateSingleNoteWidgets(context);
+            updateNoteListWidgets(context);
+        }).start();
+    }
+
+    @AnyThread
+    void updateDynamicShortcuts(long accountId) {
+        new Thread(() -> {
+            if (SDK_INT >= android.os.Build.VERSION_CODES.N_MR1) {
+                ShortcutManager shortcutManager = context.getApplicationContext().getSystemService(ShortcutManager.class);
+                if (shortcutManager != null) {
+                    if (!shortcutManager.isRateLimitingActive()) {
+                        List<ShortcutInfo> newShortcuts = new ArrayList<>();
+
+                        for (Note note : db.getNoteDao().getRecentNotes(accountId)) {
+                            if (!TextUtils.isEmpty(note.getTitle())) {
+                                Intent intent = new Intent(context.getApplicationContext(), EditNoteActivity.class);
+                                intent.putExtra(EditNoteActivity.PARAM_NOTE_ID, note.getId());
+                                intent.setAction(ACTION_SHORTCUT);
+
+                                newShortcuts.add(new ShortcutInfo.Builder(context.getApplicationContext(), note.getId() + "")
+                                        .setShortLabel(note.getTitle() + "")
+                                        .setIcon(Icon.createWithResource(context.getApplicationContext(), note.getFavorite() ? R.drawable.ic_star_yellow_24dp : R.drawable.ic_star_grey_ccc_24dp))
+                                        .setIntent(intent)
+                                        .build());
+                            } else {
+                                // Prevent crash https://github.com/stefan-niedermann/nextcloud-notes/issues/613
+                                Log.e(TAG, "shortLabel cannot be empty " + note);
+                            }
+                        }
+                        Log.d(TAG, "Update dynamic shortcuts");
+                        shortcutManager.removeAllDynamicShortcuts();
+                        shortcutManager.addDynamicShortcuts(newShortcuts);
+                    }
+                }
+            }
+        }).start();
+    }
+
+    @AnyThread
+    public LiveData<Account> addAccount(@NonNull String url, @NonNull String username, @NonNull String accountName, @NonNull Capabilities capabilities) {
+        return db.getAccountDao().getAccountById$(db.getAccountDao().insert(new Account(url, username, accountName, capabilities)));
+    }
+
+    /**
+     * @param apiVersion has to be a JSON array as a string <code>["0.2", "1.0", ...]</code>
+     * @return whether or not the given {@link ApiVersion} has been written to the database
+     * @throws IllegalArgumentException if the apiVersion does not match the expected format
+     */
+    public boolean updateApiVersion(long accountId, @Nullable String apiVersion) throws IllegalArgumentException {
+        validateAccountId(accountId);
+        if (apiVersion != null) {
+            try {
+                JSONArray apiVersions = new JSONArray(apiVersion);
+                for (int i = 0; i < apiVersions.length(); i++) {
+                    ApiVersion.of(apiVersions.getString(i));
+                }
+                if (apiVersions.length() > 0) {
+                    final int updatedRows = db.getAccountDao().updateApiVersion(accountId, apiVersion);
+                    if (updatedRows == 1) {
+                        Log.i(TAG, "Updated apiVersion to \"" + apiVersion + "\" for accountId = " + accountId);
+                    } else {
+                        Log.e(TAG, "Updated " + updatedRows + " but expected only 1 for accountId = " + accountId + " and apiVersion = \"" + apiVersion + "\"");
+                    }
+                    return true;
+                } else {
+                    Log.i(TAG, "Given API version is a valid JSON array but does not contain any valid API versions. Do not update database.");
+                }
+            } catch (NumberFormatException e) {
+                throw new IllegalArgumentException("API version does contain a non-valid version: " + apiVersion);
+            } catch (JSONException e) {
+                throw new IllegalArgumentException("API version must contain be a JSON array: " + apiVersion);
+            }
+        } else {
+            Log.v(TAG, "Given API version is null. Do not update database");
+        }
+        return false;
+    }
+
+    /**
+     * @param localAccount the {@link Account} that should be deleted
+     * @throws IllegalArgumentException if no account has been deleted by the given accountId
+     */
+    @AnyThread
+    public LiveData<Void> deleteAccount$(@NonNull Account localAccount) throws IllegalArgumentException {
+        validateAccountId(localAccount.getId());
+        MutableLiveData<Void> ret = new MutableLiveData<>();
+        new Thread(() -> {
+            int deletedAccounts = db.getAccountDao().deleteAccount(localAccount);
+            if (deletedAccounts < 1) {
+                Log.e(TAG, "AccountId '" + localAccount.getId() + "' did not delete any account");
+                throw new IllegalArgumentException("The given accountId does not delete any row");
+            } else if (deletedAccounts > 1) {
+                Log.e(TAG, "AccountId '" + localAccount.getId() + "' deleted unexpectedly '" + deletedAccounts + "' accounts");
+            }
+
+            try {
+                SSOClient.invalidateAPICache(AccountImporter.getSingleSignOnAccount(context, localAccount.getAccountName()));
+            } catch (NextcloudFilesAppAccountNotFoundException e) {
+                e.printStackTrace();
+                SSOClient.invalidateAPICache();
+            }
+
+            // TODO this should already be handled by foreign key cascade, no?
+            final int deletedNotes = db.getNoteDao().deleteByAccountId(localAccount.getId());
+            Log.v(TAG, "Deleted " + deletedNotes + " notes from account " + localAccount.getId());
+            ret.postValue(null);
+        }).start();
+        return ret;
+    }
+
+    private static void validateAccountId(long accountId) {
+        if (accountId < 1) {
+            throw new IllegalArgumentException("accountId must be greater than 0");
+        }
+    }
+
+    /**
+     * Modifies the sorting method for one category, the category can be normal category or
+     * one of "All notes", "Favorite", and "Uncategorized".
+     * If category is one of these three, sorting method will be modified in android.content.SharedPreference.
+     * The user can determine use which sorting method to show the notes for a category.
+     * When the user changes the sorting method, this method should be called.
+     *
+     * @param accountId        The user accountID
+     * @param selectedCategory The category to be modified
+     * @param sortingMethod    The sorting method in {@link CategorySortingMethod} enum format
+     */
+    @AnyThread
+    public void modifyCategoryOrder(long accountId, @NonNull NavigationCategory selectedCategory, @NonNull CategorySortingMethod sortingMethod) {
+        validateAccountId(accountId);
+
+        new Thread(() -> {
+            final Context ctx = context.getApplicationContext();
+            final SharedPreferences.Editor sp = PreferenceManager.getDefaultSharedPreferences(ctx).edit();
+            int orderIndex = sortingMethod.getId();
+
+            switch (selectedCategory.getType()) {
+                case FAVORITES: {
+                    sp.putInt(ctx.getString(R.string.action_sorting_method) + ' ' + ctx.getString(R.string.label_favorites), orderIndex);
+                    break;
+                }
+                case UNCATEGORIZED: {
+                    sp.putInt(ctx.getString(R.string.action_sorting_method) + ' ' + ctx.getString(R.string.action_uncategorized), orderIndex);
+                    break;
+                }
+                case RECENT: {
+                    sp.putInt(ctx.getString(R.string.action_sorting_method) + ' ' + ctx.getString(R.string.label_all_notes), orderIndex);
+                    break;
+                }
+                case DEFAULT_CATEGORY:
+                default: {
+                    final String category = selectedCategory.getCategory();
+                    if (category != null) {
+                        if (db.getCategoryOptionsDao().modifyCategoryOrder(accountId, category, sortingMethod) == 0) {
+                            // Nothing updated means we didn't have this yet
+                            final CategoryOptions categoryOptions = new CategoryOptions();
+                            categoryOptions.setAccountId(accountId);
+                            categoryOptions.setCategory(category);
+                            categoryOptions.setSortingMethod(sortingMethod);
+                            db.getCategoryOptionsDao().addCategoryOptions(categoryOptions);
+                        }
+                    } else {
+                        throw new IllegalStateException("Tried to modify category order for " + ENavigationCategoryType.DEFAULT_CATEGORY + "but category is null.");
+                    }
+                    break;
+                }
+            }
+            sp.apply();
+        }).start();
+    }
+
+    /**
+     * Gets the sorting method of a {@link NavigationCategory}, the category can be normal
+     * {@link CategoryOptions} or one of {@link ENavigationCategoryType}.
+     * If the category no normal {@link CategoryOptions}, sorting method will be got from
+     * {@link SharedPreferences}.
+     * <p>
+     * The sorting method of the category can be used to decide to use which sorting method to show
+     * the notes for each categories.
+     *
+     * @param selectedCategory The category
+     * @return The sorting method in CategorySortingMethod enum format
+     */
+    @NonNull
+    @MainThread
+    public LiveData<CategorySortingMethod> getCategoryOrder(@NonNull NavigationCategory selectedCategory) {
+        final SharedPreferences sp = PreferenceManager.getDefaultSharedPreferences(context);
+        String prefKey;
+
+        switch (selectedCategory.getType()) {
+            // TODO make this account specific
+            case RECENT: {
+                prefKey = context.getString(R.string.action_sorting_method) + ' ' + context.getString(R.string.label_all_notes);
+                break;
+            }
+            case FAVORITES: {
+                prefKey = context.getString(R.string.action_sorting_method) + ' ' + context.getString(R.string.label_favorites);
+                break;
+            }
+            case UNCATEGORIZED: {
+                prefKey = context.getString(R.string.action_sorting_method) + ' ' + context.getString(R.string.action_uncategorized);
+                break;
+            }
+            case DEFAULT_CATEGORY:
+            default: {
+                final String category = selectedCategory.getCategory();
+                if (category != null) {
+                    return db.getCategoryOptionsDao().getCategoryOrder(selectedCategory.getAccountId(), category);
+                } else {
+                    Log.e(TAG, "Cannot read " + CategorySortingMethod.class.getSimpleName() + " for " + ENavigationCategoryType.DEFAULT_CATEGORY + ".");
+                    return new MutableLiveData<>(CategorySortingMethod.SORT_MODIFIED_DESC);
+                }
+            }
+        }
+
+        return map(new SharedPreferenceIntLiveData(sp, prefKey, CategorySortingMethod.SORT_MODIFIED_DESC.getId()), CategorySortingMethod::findById);
+    }
+
+    public Context getContext() {
+        return context;
+    }
+
+
+    @Override
+    protected void finalize() throws Throwable {
+        context.getApplicationContext().unregisterReceiver(networkReceiver);
+        super.finalize();
+    }
+
+    /**
+     * Synchronization is only possible, if there is an active network connection.
+     * <p>
+     * This method respects the user preference "Sync on Wi-Fi only".
+     * <p>
+     * NoteServerSyncHelper observes changes in the network connection.
+     * The current state can be retrieved with this method.
+     *
+     * @return true if sync is possible, otherwise false.
+     */
+    public boolean isSyncPossible() {
+        return isSyncPossible;
+    }
+
+    public boolean isNetworkConnected() {
+        return networkConnected;
+    }
+
+    public boolean isSyncOnlyOnWifi() {
+        return syncOnlyOnWifi;
+    }
+
+    /**
+     * Adds a callback method to the NoteServerSyncHelper for the synchronization part push local changes to the server.
+     * All callbacks will be executed once the synchronization operations are done.
+     * After execution the callback will be deleted, so it has to be added again if it shall be
+     * executed the next time all synchronize operations are finished.
+     *
+     * @param callback Implementation of ISyncCallback, contains one method that shall be executed.
+     */
+    public void addCallbackPush(Account account, ISyncCallback callback) {
+        if (account == null) {
+            Log.i(TAG, "ssoAccount is null. Is this a local account?");
+            callback.onScheduled();
+            callback.onFinish();
+        } else {
+            if (!callbacksPush.containsKey(account.getId())) {
+                callbacksPush.put(account.getId(), new ArrayList<>());
+            }
+            Objects.requireNonNull(callbacksPush.get(account.getId())).add(callback);
+        }
+    }
+
+    /**
+     * Adds a callback method to the NoteServerSyncHelper for the synchronization part pull remote changes from the server.
+     * All callbacks will be executed once the synchronization operations are done.
+     * After execution the callback will be deleted, so it has to be added again if it shall be
+     * executed the next time all synchronize operations are finished.
+     *
+     * @param callback Implementation of ISyncCallback, contains one method that shall be executed.
+     */
+    public void addCallbackPull(Account account, ISyncCallback callback) {
+        if (account == null) {
+            Log.i(TAG, "ssoAccount is null. Is this a local account?");
+            callback.onScheduled();
+            callback.onFinish();
+        } else {
+            if (!callbacksPull.containsKey(account.getId())) {
+                callbacksPull.put(account.getId(), new ArrayList<>());
+            }
+            Objects.requireNonNull(callbacksPull.get(account.getId())).add(callback);
+        }
+    }
+
+    /**
+     * Schedules a synchronization and start it directly, if the network is connected and no
+     * synchronization is currently running.
+     *
+     * @param onlyLocalChanges Whether to only push local changes to the server or to also load the whole list of notes from the server.
+     */
+    public void scheduleSync(Account account, boolean onlyLocalChanges) {
+        if (account == null) {
+            Log.i(TAG, SingleSignOnAccount.class.getSimpleName() + " is null. Is this a local account?");
+        } else {
+            if (syncActive.get(account.getId()) == null) {
+                syncActive.put(account.getId(), false);
+            }
+            Log.d(TAG, "Sync requested (" + (onlyLocalChanges ? "onlyLocalChanges" : "full") + "; " + (Boolean.TRUE.equals(syncActive.get(account.getId())) ? "sync active" : "sync NOT active") + ") ...");
+            if (isSyncPossible() && (!Boolean.TRUE.equals(syncActive.get(account.getId())) || onlyLocalChanges)) {
+                try {
+                    SingleSignOnAccount ssoAccount = AccountImporter.getSingleSignOnAccount(context, account.getAccountName());
+                    Log.d(TAG, "... starting now");
+                    final NotesClient notesClient = NotesClient.newInstance(account.getPreferredApiVersion(), context);
+                    final NotesServerSyncTask syncTask = new NotesServerSyncTask(notesClient, this, account, ssoAccount, onlyLocalChanges) {
+                        @Override
+                        void onPreExecute() {
+                            syncStatus.postValue(true);
+                            if (!syncScheduled.containsKey(localAccount.getId()) || syncScheduled.get(localAccount.getId()) == null) {
+                                syncScheduled.put(localAccount.getId(), false);
+                            }
+                            if (!onlyLocalChanges && Boolean.TRUE.equals(syncScheduled.get(localAccount.getId()))) {
+                                syncScheduled.put(localAccount.getId(), false);
+                            }
+                            syncActive.put(localAccount.getId(), true);
+                        }
+
+                        @Override
+                        void onPostExecute(SyncResultStatus status) {
+                            for (Throwable e : exceptions) {
+                                Log.e(TAG, e.getMessage(), e);
+                            }
+                            if (!status.pullSuccessful || !status.pushSuccessful) {
+                                syncErrors.postValue(exceptions);
+                            }
+                            syncActive.put(localAccount.getId(), false);
+                            // notify callbacks
+                            if (callbacks.containsKey(localAccount.getId()) && callbacks.get(localAccount.getId()) != null) {
+                                for (ISyncCallback callback : Objects.requireNonNull(callbacks.get(localAccount.getId()))) {
+                                    callback.onFinish();
+                                }
+                            }
+                            notifyWidgets();
+                            updateDynamicShortcuts(localAccount.getId());
+                            // start next sync if scheduled meanwhile
+                            if (syncScheduled.containsKey(localAccount.getId()) && syncScheduled.get(localAccount.getId()) != null && Boolean.TRUE.equals(syncScheduled.get(localAccount.getId()))) {
+                                scheduleSync(localAccount, false);
+                            }
+                            syncStatus.postValue(false);
+                        }
+                    };
+                    syncTask.addCallbacks(account, callbacksPush.get(account.getId()));
+                    callbacksPush.put(account.getId(), new ArrayList<>());
+                    if (!onlyLocalChanges) {
+                        syncTask.addCallbacks(account, callbacksPull.get(account.getId()));
+                        callbacksPull.put(account.getId(), new ArrayList<>());
+                    }
+                    executor.submit(syncTask);
+                } catch (NextcloudFilesAppAccountNotFoundException e) {
+                    Log.e(TAG, "... Could not find " + SingleSignOnAccount.class.getSimpleName() + " for account name " + account.getAccountName());
+                    e.printStackTrace();
+                }
+            } else if (!onlyLocalChanges) {
+                Log.d(TAG, "... scheduled");
+                syncScheduled.put(account.getId(), true);
+                if (callbacksPush.containsKey(account.getId()) && callbacksPush.get(account.getId()) != null) {
+                    final List<ISyncCallback> callbacks = callbacksPush.get(account.getId());
+                    if (callbacks != null) {
+                        for (ISyncCallback callback : callbacks) {
+                            callback.onScheduled();
+                        }
+                    } else {
+                        Log.w(TAG, "List of push-callbacks was set for account \"" + account.getAccountName() + "\" but it was null");
+                    }
+                }
+            } else {
+                Log.d(TAG, "... do nothing");
+                if (callbacksPush.containsKey(account.getId()) && callbacksPush.get(account.getId()) != null) {
+                    final List<ISyncCallback> callbacks = callbacksPush.get(account.getId());
+                    if (callbacks != null) {
+                        for (ISyncCallback callback : callbacks) {
+                            callback.onScheduled();
+                        }
+                    } else {
+                        Log.w(TAG, "List of push-callbacks was set for account \"" + account.getAccountName() + "\" but it was null");
+                    }
+                }
+            }
+        }
+    }
+
+    public void updateNetworkStatus() {
+        try {
+            final ConnectivityManager connMgr = (ConnectivityManager) context.getApplicationContext().getSystemService(Context.CONNECTIVITY_SERVICE);
+
+            if (connMgr == null) {
+                throw new NetworkErrorException("ConnectivityManager is null");
+            }
+
+            final NetworkInfo activeInfo = connMgr.getActiveNetworkInfo();
+
+            if (activeInfo == null) {
+                throw new NetworkErrorException("NetworkInfo is null");
+            }
+
+            if (activeInfo.isConnected()) {
+                networkConnected = true;
+
+                final NetworkInfo networkInfo = connMgr.getNetworkInfo((ConnectivityManager.TYPE_WIFI));
+
+                if (networkInfo == null) {
+                    throw new NetworkErrorException("connMgr.getNetworkInfo(ConnectivityManager.TYPE_WIFI) is null");
+                }
+
+                isSyncPossible = !syncOnlyOnWifi || networkInfo.isConnected();
+
+                if (isSyncPossible) {
+                    Log.d(TAG, "Network connection established.");
+                } else {
+                    Log.d(TAG, "Network connected, but not used because only synced on wifi.");
+                }
+            } else {
+                networkConnected = false;
+                isSyncPossible = false;
+                Log.d(TAG, "No network connection.");
+            }
+        } catch (NetworkErrorException e) {
+            e.printStackTrace();
+            networkConnected = false;
+            isSyncPossible = false;
+        }
+    }
+
+    @NonNull
+    public LiveData<Boolean> getSyncStatus() {
+        return distinctUntilChanged(this.syncStatus);
+    }
+
+    @NonNull
+    public LiveData<ArrayList<Throwable>> getSyncErrors() {
+        return this.syncErrors;
+    }
+}
diff --git a/app/src/main/java/it/niedermann/owncloud/notes/persistence/NotesServerSyncHelper.java b/app/src/main/java/it/niedermann/owncloud/notes/persistence/NotesServerSyncHelper.java
deleted file mode 100644
index e9fab1b0..00000000
--- a/app/src/main/java/it/niedermann/owncloud/notes/persistence/NotesServerSyncHelper.java
+++ /dev/null
@@ -1,346 +0,0 @@
-package it.niedermann.owncloud.notes.persistence;
-
-import android.accounts.NetworkErrorException;
-import android.content.BroadcastReceiver;
-import android.content.Context;
-import android.content.Intent;
-import android.content.IntentFilter;
-import android.content.SharedPreferences;
-import android.net.ConnectivityManager;
-import android.net.NetworkInfo;
-import android.util.Log;
-
-import androidx.annotation.NonNull;
-import androidx.lifecycle.LiveData;
-import androidx.lifecycle.MutableLiveData;
-import androidx.preference.PreferenceManager;
-
-import com.nextcloud.android.sso.AccountImporter;
-import com.nextcloud.android.sso.exceptions.NextcloudFilesAppAccountNotFoundException;
-import com.nextcloud.android.sso.exceptions.NoCurrentAccountSelectedException;
-import com.nextcloud.android.sso.helper.SingleAccountHelper;
-import com.nextcloud.android.sso.model.SingleSignOnAccount;
-
-import java.util.ArrayList;
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
-import java.util.Objects;
-import java.util.concurrent.ExecutorService;
-import java.util.concurrent.Executors;
-
-import it.niedermann.owncloud.notes.R;
-import it.niedermann.owncloud.notes.persistence.entity.Account;
-import it.niedermann.owncloud.notes.shared.model.ISyncCallback;
-import it.niedermann.owncloud.notes.shared.model.SyncResultStatus;
-import it.niedermann.owncloud.notes.shared.util.SSOUtil;
-
-import static androidx.lifecycle.Transformations.distinctUntilChanged;
-
-/**
- * Helps to synchronize the Database to the Server.
- */
-public class NotesServerSyncHelper {
-
-    private static final String TAG = NotesServerSyncHelper.class.getSimpleName();
-
-    private final ExecutorService executor = Executors.newSingleThreadExecutor();
-
-    private static NotesServerSyncHelper instance;
-
-    private final NotesDatabase db;
-    private final Context context;
-
-    /**
-     * Track network connection changes using a {@link BroadcastReceiver}
-     */
-    private boolean isSyncPossible = false;
-    private boolean networkConnected = false;
-    private String syncOnlyOnWifiKey;
-    private boolean syncOnlyOnWifi;
-    private final MutableLiveData<Boolean> syncStatus = new MutableLiveData<>(false);
-    private final MutableLiveData<ArrayList<Throwable>> syncErrors = new MutableLiveData<>();
-
-    /**
-     * @see <a href="https://stackoverflow.com/a/3104265">Do not make this a local variable.</a>
-     */
-    @SuppressWarnings("FieldCanBeLocal")
-    private final SharedPreferences.OnSharedPreferenceChangeListener onSharedPreferenceChangeListener = (SharedPreferences prefs, String key) -> {
-        if (syncOnlyOnWifiKey.equals(key)) {
-            syncOnlyOnWifi = prefs.getBoolean(syncOnlyOnWifiKey, false);
-            updateNetworkStatus();
-        }
-    };
-
-    private final BroadcastReceiver networkReceiver = new BroadcastReceiver() {
-        @Override
-        public void onReceive(Context context, Intent intent) {
-            updateNetworkStatus();
-            if (isSyncPossible() && SSOUtil.isConfigured(context)) {
-                new Thread(() -> {
-                    try {
-                        scheduleSync(db.getAccountDao().getAccountByName(SingleAccountHelper.getCurrentSingleSignOnAccount(context).name), false);
-                    } catch (NextcloudFilesAppAccountNotFoundException | NoCurrentAccountSelectedException e) {
-                        Log.v(TAG, "Can not select current SingleSignOn account after network changed, do not sync.");
-                    }
-                }).start();
-            }
-        }
-    };
-
-    // current state of the synchronization
-    private final Map<Long, Boolean> syncActive = new HashMap<>();
-    private final Map<Long, Boolean> syncScheduled = new HashMap<>();
-
-    // list of callbacks for both parts of synchronization
-    private final Map<Long, List<ISyncCallback>> callbacksPush = new HashMap<>();
-    private final Map<Long, List<ISyncCallback>> callbacksPull = new HashMap<>();
-
-    private NotesServerSyncHelper(NotesDatabase db) {
-        this.db = db;
-        this.context = db.getContext();
-        this.syncOnlyOnWifiKey = context.getApplicationContext().getResources().getString(R.string.pref_key_wifi_only);
-
-        // Registers BroadcastReceiver to track network connection changes.
-        context.getApplicationContext().registerReceiver(networkReceiver, new IntentFilter(ConnectivityManager.CONNECTIVITY_ACTION));
-
-        SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(this.context.getApplicationContext());
-        prefs.registerOnSharedPreferenceChangeListener(onSharedPreferenceChangeListener);
-        syncOnlyOnWifi = prefs.getBoolean(syncOnlyOnWifiKey, false);
-
-        updateNetworkStatus();
-    }
-
-    /**
-     * Get (or create) instance from NoteServerSyncHelper.
-     * This has to be a singleton in order to realize correct registering and unregistering of
-     * the BroadcastReceiver, which listens on changes of network connectivity.
-     *
-     * @param db {@link NotesDatabase}
-     * @return NoteServerSyncHelper
-     */
-    public static synchronized NotesServerSyncHelper getInstance(NotesDatabase db) {
-        if (instance == null) {
-            instance = new NotesServerSyncHelper(db);
-        }
-        return instance;
-    }
-
-    @Override
-    protected void finalize() throws Throwable {
-        context.getApplicationContext().unregisterReceiver(networkReceiver);
-        super.finalize();
-    }
-
-    /**
-     * Synchronization is only possible, if there is an active network connection.
-     * <p>
-     * This method respects the user preference "Sync on Wi-Fi only".
-     * <p>
-     * NoteServerSyncHelper observes changes in the network connection.
-     * The current state can be retrieved with this method.
-     *
-     * @return true if sync is possible, otherwise false.
-     */
-    public boolean isSyncPossible() {
-        return isSyncPossible;
-    }
-
-    public boolean isNetworkConnected() {
-        return networkConnected;
-    }
-
-    public boolean isSyncOnlyOnWifi() {
-        return syncOnlyOnWifi;
-    }
-
-    /**
-     * Adds a callback method to the NoteServerSyncHelper for the synchronization part push local changes to the server.
-     * All callbacks will be executed once the synchronization operations are done.
-     * After execution the callback will be deleted, so it has to be added again if it shall be
-     * executed the next time all synchronize operations are finished.
-     *
-     * @param callback Implementation of ISyncCallback, contains one method that shall be executed.
-     */
-    public void addCallbackPush(Account account, ISyncCallback callback) {
-        if (account == null) {
-            Log.i(TAG, "ssoAccount is null. Is this a local account?");
-            callback.onScheduled();
-            callback.onFinish();
-        } else {
-            if (!callbacksPush.containsKey(account.getId())) {
-                callbacksPush.put(account.getId(), new ArrayList<>());
-            }
-            Objects.requireNonNull(callbacksPush.get(account.getId())).add(callback);
-        }
-    }
-
-    /**
-     * Adds a callback method to the NoteServerSyncHelper for the synchronization part pull remote changes from the server.
-     * All callbacks will be executed once the synchronization operations are done.
-     * After execution the callback will be deleted, so it has to be added again if it shall be
-     * executed the next time all synchronize operations are finished.
-     *
-     * @param callback Implementation of ISyncCallback, contains one method that shall be executed.
-     */
-    public void addCallbackPull(Account account, ISyncCallback callback) {
-        if (account == null) {
-            Log.i(TAG, "ssoAccount is null. Is this a local account?");
-            callback.onScheduled();
-            callback.onFinish();
-        } else {
-            if (!callbacksPull.containsKey(account.getId())) {
-                callbacksPull.put(account.getId(), new ArrayList<>());
-            }
-            Objects.requireNonNull(callbacksPull.get(account.getId())).add(callback);
-        }
-    }
-
-    /**
-     * Schedules a synchronization and start it directly, if the network is connected and no
-     * synchronization is currently running.
-     *
-     * @param onlyLocalChanges Whether to only push local changes to the server or to also load the whole list of notes from the server.
-     */
-    public void scheduleSync(Account account, boolean onlyLocalChanges) {
-        if (account == null) {
-            Log.i(TAG, SingleSignOnAccount.class.getSimpleName() + " is null. Is this a local account?");
-        } else {
-            if (syncActive.get(account.getId()) == null) {
-                syncActive.put(account.getId(), false);
-            }
-            Log.d(TAG, "Sync requested (" + (onlyLocalChanges ? "onlyLocalChanges" : "full") + "; " + (Boolean.TRUE.equals(syncActive.get(account.getId())) ? "sync active" : "sync NOT active") + ") ...");
-            if (isSyncPossible() && (!Boolean.TRUE.equals(syncActive.get(account.getId())) || onlyLocalChanges)) {
-                try {
-                    SingleSignOnAccount ssoAccount = AccountImporter.getSingleSignOnAccount(context, account.getAccountName());
-                    Log.d(TAG, "... starting now");
-                    final NotesClient notesClient = NotesClient.newInstance(account.getPreferredApiVersion(), context);
-                    final NotesServerSyncTask syncTask = new NotesServerSyncTask(notesClient, db, account, ssoAccount, onlyLocalChanges) {
-                        @Override
-                        void onPreExecute() {
-                            syncStatus.postValue(true);
-                            if (!syncScheduled.containsKey(localAccount.getId()) || syncScheduled.get(localAccount.getId()) == null) {
-                                syncScheduled.put(localAccount.getId(), false);
-                            }
-                            if (!onlyLocalChanges && Boolean.TRUE.equals(syncScheduled.get(localAccount.getId()))) {
-                                syncScheduled.put(localAccount.getId(), false);
-                            }
-                            syncActive.put(localAccount.getId(), true);
-                        }
-
-                        @Override
-                        void onPostExecute(SyncResultStatus status) {
-                            for (Throwable e : exceptions) {
-                                Log.e(TAG, e.getMessage(), e);
-                            }
-                            if (!status.pullSuccessful || !status.pushSuccessful) {
-                                syncErrors.postValue(exceptions);
-                            }
-                            syncActive.put(localAccount.getId(), false);
-                            // notify callbacks
-                            if (callbacks.containsKey(localAccount.getId()) && callbacks.get(localAccount.getId()) != null) {
-                                for (ISyncCallback callback : Objects.requireNonNull(callbacks.get(localAccount.getId()))) {
-                                    callback.onFinish();
-                                }
-                            }
-                            db.notifyWidgets();
-                            db.updateDynamicShortcuts(localAccount.getId());
-                            // start next sync if scheduled meanwhile
-                            if (syncScheduled.containsKey(localAccount.getId()) && syncScheduled.get(localAccount.getId()) != null && Boolean.TRUE.equals(syncScheduled.get(localAccount.getId()))) {
-                                scheduleSync(localAccount, false);
-                            }
-                            syncStatus.postValue(false);
-                        }
-                    };
-                    syncTask.addCallbacks(account, callbacksPush.get(account.getId()));
-                    callbacksPush.put(account.getId(), new ArrayList<>());
-                    if (!onlyLocalChanges) {
-                        syncTask.addCallbacks(account, callbacksPull.get(account.getId()));
-                        callbacksPull.put(account.getId(), new ArrayList<>());
-                    }
-                    executor.submit(syncTask);
-                } catch (NextcloudFilesAppAccountNotFoundException e) {
-                    Log.e(TAG, "... Could not find " + SingleSignOnAccount.class.getSimpleName() + " for account name " + account.getAccountName());
-                    e.printStackTrace();
-                }
-            } else if (!onlyLocalChanges) {
-                Log.d(TAG, "... scheduled");
-                syncScheduled.put(account.getId(), true);
-                if (callbacksPush.containsKey(account.getId()) && callbacksPush.get(account.getId()) != null) {
-                    final List<ISyncCallback> callbacks = callbacksPush.get(account.getId());
-                    if (callbacks != null) {
-                        for (ISyncCallback callback : callbacks) {
-                            callback.onScheduled();
-                        }
-                    } else {
-                        Log.w(TAG, "List of push-callbacks was set for account \"" + account.getAccountName() + "\" but it was null");
-                    }
-                }
-            } else {
-                Log.d(TAG, "... do nothing");
-                if (callbacksPush.containsKey(account.getId()) && callbacksPush.get(account.getId()) != null) {
-                    final List<ISyncCallback> callbacks = callbacksPush.get(account.getId());
-                    if (callbacks != null) {
-                        for (ISyncCallback callback : callbacks) {
-                            callback.onScheduled();
-                        }
-                    } else {
-                        Log.w(TAG, "List of push-callbacks was set for account \"" + account.getAccountName() + "\" but it was null");
-                    }
-                }
-            }
-        }
-    }
-
-    public void updateNetworkStatus() {
-        try {
-            final ConnectivityManager connMgr = (ConnectivityManager) context.getApplicationContext().getSystemService(Context.CONNECTIVITY_SERVICE);
-
-            if (connMgr == null) {
-                throw new NetworkErrorException("ConnectivityManager is null");
-            }
-
-            final NetworkInfo activeInfo = connMgr.getActiveNetworkInfo();
-
-            if (activeInfo == null) {
-                throw new NetworkErrorException("NetworkInfo is null");
-            }
-
-            if (activeInfo.isConnected()) {
-                networkConnected = true;
-
-                final NetworkInfo networkInfo = connMgr.getNetworkInfo((ConnectivityManager.TYPE_WIFI));
-
-                if (networkInfo == null) {
-                    throw new NetworkErrorException("connMgr.getNetworkInfo(ConnectivityManager.TYPE_WIFI) is null");
-                }
-
-                isSyncPossible = !syncOnlyOnWifi || networkInfo.isConnected();
-
-                if (isSyncPossible) {
-                    Log.d(TAG, "Network connection established.");
-                } else {
-                    Log.d(TAG, "Network connected, but not used because only synced on wifi.");
-                }
-            } else {
-                networkConnected = false;
-                isSyncPossible = false;
-                Log.d(TAG, "No network connection.");
-            }
-        } catch (NetworkErrorException e) {
-            e.printStackTrace();
-            networkConnected = false;
-            isSyncPossible = false;
-        }
-    }
-
-    @NonNull
-    public LiveData<Boolean> getSyncStatus() {
-        return distinctUntilChanged(this.syncStatus);
-    }
-
-    @NonNull
-    public LiveData<ArrayList<Throwable>> getSyncErrors() {
-        return this.syncErrors;
-    }
-}
diff --git a/app/src/main/java/it/niedermann/owncloud/notes/persistence/NotesServerSyncTask.java b/app/src/main/java/it/niedermann/owncloud/notes/persistence/NotesServerSyncTask.java
index dcc44979..2b4e6201 100644
--- a/app/src/main/java/it/niedermann/owncloud/notes/persistence/NotesServerSyncTask.java
+++ b/app/src/main/java/it/niedermann/owncloud/notes/persistence/NotesServerSyncTask.java
@@ -39,7 +39,7 @@ abstract class NotesServerSyncTask extends Thread {
     @NonNull
     private final NotesClient notesClient;
     @NonNull
-    private final NotesDatabase db;
+    private final NotesRepository repo;
     @NonNull
     protected final Account localAccount;
     @NonNull
@@ -50,10 +50,10 @@ abstract class NotesServerSyncTask extends Thread {
     @NonNull
     protected final ArrayList<Throwable> exceptions = new ArrayList<>();
 
-    NotesServerSyncTask(@NonNull NotesClient notesClient, @NonNull NotesDatabase db, @NonNull Account localAccount, @NonNull SingleSignOnAccount ssoAccount, boolean onlyLocalChanges) {
+    NotesServerSyncTask(@NonNull NotesClient notesClient, @NonNull NotesRepository repo, @NonNull Account localAccount, @NonNull SingleSignOnAccount ssoAccount, boolean onlyLocalChanges) {
         super(TAG);
         this.notesClient = notesClient;
-        this.db = db;
+        this.repo = repo;
         this.localAccount = localAccount;
         this.ssoAccount = ssoAccount;
         this.onlyLocalChanges = onlyLocalChanges;
@@ -89,7 +89,7 @@ abstract class NotesServerSyncTask extends Thread {
         Log.d(TAG, "pushLocalChanges()");
 
         boolean success = true;
-        final List<Note> notes = db.getNoteDao().getLocalModifiedNotes(localAccount.getId());
+        final List<Note> notes = repo.getLocalModifiedNotes(localAccount.getId());
         for (Note note : notes) {
             Log.d(TAG, "   Process Local Note: " + note);
             try {
@@ -112,10 +112,10 @@ abstract class NotesServerSyncTask extends Thread {
                         } else {
                             Log.v(TAG, "   ...Note does not have a remoteId yet → create");
                             remoteNote = notesClient.createNote(ssoAccount, note).getNote();
-                            db.getNoteDao().updateRemoteId(note.getId(), remoteNote.getRemoteId());
+                            repo.updateRemoteId(note.getId(), remoteNote.getRemoteId());
                         }
                         // Please note, that db.updateNote() realized an optimistic conflict resolution, which is required for parallel changes of this Note from the UI.
-                        db.getNoteDao().updateIfNotModifiedLocallyDuringSync(note.getId(), remoteNote.getModified().getTimeInMillis(), remoteNote.getTitle(), remoteNote.getFavorite(), remoteNote.getETag(), remoteNote.getContent(), generateNoteExcerpt(remoteNote.getContent(), remoteNote.getTitle()), note.getContent(), note.getCategory(), note.getFavorite());
+                        repo.updateIfNotModifiedLocallyDuringSync(note.getId(), remoteNote.getModified().getTimeInMillis(), remoteNote.getTitle(), remoteNote.getFavorite(), remoteNote.getETag(), remoteNote.getContent(), generateNoteExcerpt(remoteNote.getContent(), remoteNote.getTitle()), note.getContent(), note.getCategory(), note.getFavorite());
                         break;
                     case LOCAL_DELETED:
                         if (note.getRemoteId() == null) {
@@ -133,7 +133,7 @@ abstract class NotesServerSyncTask extends Thread {
                             }
                         }
                         // Please note, that db.deleteNote() realizes an optimistic conflict resolution, which is required for parallel changes of this Note from the UI.
-                        db.getNoteDao().deleteByNoteId(note.getId(), LOCAL_DELETED);
+                        repo.deleteByNoteId(note.getId(), LOCAL_DELETED);
                         break;
                     default:
                         throw new IllegalStateException("Unknown State of Note " + note + ": " + note.getStatus());
@@ -162,10 +162,10 @@ abstract class NotesServerSyncTask extends Thread {
     private boolean pullRemoteChanges() {
         Log.d(TAG, "pullRemoteChanges() for account " + localAccount.getAccountName());
         try {
-            final Map<Long, Long> idMap = db.getIdMap(localAccount.getId());
+            final Map<Long, Long> idMap = repo.getIdMap(localAccount.getId());
 
             // FIXME re-reading the localAccount is only a workaround for a not-up-to-date eTag in localAccount.
-            final Account accountFromDatabase = db.getAccountDao().getAccountById(localAccount.getId());
+            final Account accountFromDatabase = repo.getAccountById(localAccount.getId());
             if (accountFromDatabase == null) {
                 callbacks.remove(localAccount.getId());
                 return true;
@@ -186,14 +186,14 @@ abstract class NotesServerSyncTask extends Thread {
                     Log.v(TAG, "   ... found → Update");
                     Long localId = idMap.get(remoteNote.getRemoteId());
                     if (localId != null) {
-                        db.getNoteDao().updateIfNotModifiedLocallyAndAnyRemoteColumnHasChanged(
+                        repo.updateIfNotModifiedLocallyAndAnyRemoteColumnHasChanged(
                                 localId, remoteNote.getModified().getTimeInMillis(), remoteNote.getTitle(), remoteNote.getFavorite(), remoteNote.getCategory(), remoteNote.getETag(), remoteNote.getContent(), generateNoteExcerpt(remoteNote.getContent(), remoteNote.getTitle()));
                     } else {
                         Log.e(TAG, "Tried to update note from server, but local id of note is null. " + remoteNote);
                     }
                 } else {
                     Log.v(TAG, "   ... create");
-                    db.addNote(localAccount.getId(), remoteNote);
+                    repo.addNote(localAccount.getId(), remoteNote);
                 }
             }
             Log.d(TAG, "   Remove remotely deleted Notes (only those without local changes)");
@@ -201,17 +201,17 @@ abstract class NotesServerSyncTask extends Thread {
             for (Map.Entry<Long, Long> entry : idMap.entrySet()) {
                 if (!remoteIDs.contains(entry.getKey())) {
                     Log.v(TAG, "   ... remove " + entry.getValue());
-                    db.getNoteDao().deleteByNoteId(entry.getValue(), DBStatus.VOID);
+                    repo.deleteByNoteId(entry.getValue(), DBStatus.VOID);
                 }
             }
 
             // update ETag and Last-Modified in order to reduce size of next response
             localAccount.setETag(response.getETag());
             localAccount.setModified(response.getLastModified());
-            db.getAccountDao().updateETag(localAccount.getId(), localAccount.getETag());
-            db.getAccountDao().updateModified(localAccount.getId(), localAccount.getModified().getTimeInMillis());
+            repo.updateETag(localAccount.getId(), localAccount.getETag());
+            repo.updateModified(localAccount.getId(), localAccount.getModified().getTimeInMillis());
             try {
-                if (db.updateApiVersion(localAccount.getId(), response.getSupportedApiVersions())) {
+                if (repo.updateApiVersion(localAccount.getId(), response.getSupportedApiVersions())) {
                     localAccount.setApiVersion(response.getSupportedApiVersions());
                 }
             } catch (Exception e) {
diff --git a/app/src/main/java/it/niedermann/owncloud/notes/persistence/SyncWorker.java b/app/src/main/java/it/niedermann/owncloud/notes/persistence/SyncWorker.java
index 1b86e0aa..1d4a8bc7 100644
--- a/app/src/main/java/it/niedermann/owncloud/notes/persistence/SyncWorker.java
+++ b/app/src/main/java/it/niedermann/owncloud/notes/persistence/SyncWorker.java
@@ -34,11 +34,11 @@ public class SyncWorker extends Worker {
     @NonNull
     @Override
     public Result doWork() {
-        NotesDatabase db = NotesDatabase.getInstance(getApplicationContext());
-        for (Account account : db.getAccountDao().getAccounts()) {
+        NotesRepository repo = NotesRepository.getInstance(getApplicationContext());
+        for (Account account : repo.getAccounts()) {
             Log.v(TAG, "Starting background synchronization for " + account.getAccountName());
-            db.getNoteServerSyncHelper().addCallbackPull(account, () -> Log.v(TAG, "Finished background synchronization for " + account.getAccountName()));
-            db.getNoteServerSyncHelper().scheduleSync(account, false);
+            repo.addCallbackPull(account, () -> Log.v(TAG, "Finished background synchronization for " + account.getAccountName()));
+            repo.scheduleSync(account, false);
         }
         // TODO return result depending on callbackPull
         return Result.success();
diff --git a/app/src/main/java/it/niedermann/owncloud/notes/persistence/dao/NoteDao.java b/app/src/main/java/it/niedermann/owncloud/notes/persistence/dao/NoteDao.java
index 8cc73bf8..45979aa8 100644
--- a/app/src/main/java/it/niedermann/owncloud/notes/persistence/dao/NoteDao.java
+++ b/app/src/main/java/it/niedermann/owncloud/notes/persistence/dao/NoteDao.java
@@ -10,7 +10,6 @@ import androidx.room.Update;
 import java.util.List;
 import java.util.Set;
 
-import it.niedermann.owncloud.notes.persistence.NotesServerSyncHelper;
 import it.niedermann.owncloud.notes.persistence.entity.Account;
 import it.niedermann.owncloud.notes.persistence.entity.CategoryWithNotesCount;
 import it.niedermann.owncloud.notes.persistence.entity.Note;
diff --git a/app/src/main/java/it/niedermann/owncloud/notes/persistence/migration/Migration_13_14.java b/app/src/main/java/it/niedermann/owncloud/notes/persistence/migration/Migration_13_14.java
index 85e02617..3d0147fb 100644
--- a/app/src/main/java/it/niedermann/owncloud/notes/persistence/migration/Migration_13_14.java
+++ b/app/src/main/java/it/niedermann/owncloud/notes/persistence/migration/Migration_13_14.java
@@ -1,7 +1,9 @@
 package it.niedermann.owncloud.notes.persistence.migration;
 
+import android.appwidget.AppWidgetManager;
 import android.content.ContentValues;
 import android.content.Context;
+import android.content.Intent;
 import android.content.SharedPreferences;
 import android.util.Log;
 
@@ -14,19 +16,18 @@ import androidx.sqlite.db.SupportSQLiteDatabase;
 import java.util.Map;
 
 import it.niedermann.owncloud.notes.preferences.DarkModeSetting;
+import it.niedermann.owncloud.notes.widget.notelist.NoteListWidget;
+import it.niedermann.owncloud.notes.widget.singlenote.SingleNoteWidget;
 
 public class Migration_13_14 extends Migration {
 
     private static final String TAG = Migration_13_14.class.getSimpleName();
     @NonNull
     private final Context context;
-    @NonNull
-    private final Runnable notifyWidgets;
 
-    public Migration_13_14(@NonNull Context context, @NonNull Runnable notifyWidgets) {
+    public Migration_13_14(@NonNull Context context) {
         super(13, 14);
         this.context = context;
-        this.notifyWidgets = notifyWidgets;
     }
 
     /**
@@ -86,6 +87,7 @@ public class Migration_13_14 extends Migration {
             }
         }
         editor.apply();
-        notifyWidgets.run();
+        context.sendBroadcast(new Intent(context, SingleNoteWidget.class).setAction(AppWidgetManager.ACTION_APPWIDGET_UPDATE));
+        context.sendBroadcast(new Intent(context, NoteListWidget.class).setAction(AppWidgetManager.ACTION_APPWIDGET_UPDATE));
     }
 }
diff --git a/app/src/main/java/it/niedermann/owncloud/notes/persistence/migration/Migration_15_16.java b/app/src/main/java/it/niedermann/owncloud/notes/persistence/migration/Migration_15_16.java
index 2732151f..48b7195b 100644
--- a/app/src/main/java/it/niedermann/owncloud/notes/persistence/migration/Migration_15_16.java
+++ b/app/src/main/java/it/niedermann/owncloud/notes/persistence/migration/Migration_15_16.java
@@ -1,7 +1,9 @@
 package it.niedermann.owncloud.notes.persistence.migration;
 
+import android.appwidget.AppWidgetManager;
 import android.content.ContentValues;
 import android.content.Context;
+import android.content.Intent;
 import android.content.SharedPreferences;
 import android.database.Cursor;
 import android.util.Log;
@@ -15,19 +17,18 @@ import androidx.sqlite.db.SupportSQLiteDatabase;
 import java.util.Map;
 
 import it.niedermann.owncloud.notes.preferences.DarkModeSetting;
+import it.niedermann.owncloud.notes.widget.notelist.NoteListWidget;
+import it.niedermann.owncloud.notes.widget.singlenote.SingleNoteWidget;
 
 public class Migration_15_16 extends Migration {
 
     private static final String TAG = Migration_15_16.class.getSimpleName();
     @NonNull
     private final Context context;
-    @NonNull
-    private final Runnable notifyWidgets;
 
-    public Migration_15_16(@NonNull Context context, @NonNull Runnable notifyWidgets) {
+    public Migration_15_16(@NonNull Context context) {
         super(15, 16);
         this.context = context;
-        this.notifyWidgets = notifyWidgets;
     }
 
     /**
@@ -104,6 +105,7 @@ public class Migration_15_16 extends Migration {
             }
         }
         editor.apply();
-        notifyWidgets.run();
+        context.sendBroadcast(new Intent(context, SingleNoteWidget.class).setAction(AppWidgetManager.ACTION_APPWIDGET_UPDATE));
+        context.sendBroadcast(new Intent(context, NoteListWidget.class).setAction(AppWidgetManager.ACTION_APPWIDGET_UPDATE));
     }
 }
diff --git a/app/src/main/java/it/niedermann/owncloud/notes/widget/notelist/NoteListViewModel.java b/app/src/main/java/it/niedermann/owncloud/notes/widget/notelist/NoteListViewModel.java
index ad3830a4..9ec3e355 100644
--- a/app/src/main/java/it/niedermann/owncloud/notes/widget/notelist/NoteListViewModel.java
+++ b/app/src/main/java/it/niedermann/owncloud/notes/widget/notelist/NoteListViewModel.java
@@ -14,7 +14,7 @@ import it.niedermann.owncloud.notes.R;
 import it.niedermann.owncloud.notes.main.MainActivity;
 import it.niedermann.owncloud.notes.main.navigation.NavigationAdapter;
 import it.niedermann.owncloud.notes.main.navigation.NavigationItem;
-import it.niedermann.owncloud.notes.persistence.NotesDatabase;
+import it.niedermann.owncloud.notes.persistence.NotesRepository;
 
 import static androidx.lifecycle.Transformations.distinctUntilChanged;
 import static androidx.lifecycle.Transformations.map;
@@ -28,20 +28,20 @@ public class NoteListViewModel extends AndroidViewModel {
     private static final String TAG = NoteListViewModel.class.getSimpleName();
 
     @NonNull
-    private final NotesDatabase db;
+    private final NotesRepository repo;
 
     public NoteListViewModel(@NonNull Application application) {
         super(application);
-        this.db = NotesDatabase.getInstance(application);
+        this.repo = NotesRepository.getInstance(application);
     }
 
     public LiveData<List<NavigationItem>> getAdapterCategories(Long accountId) {
         return distinctUntilChanged(
-                switchMap(distinctUntilChanged(db.getNoteDao().count$(accountId)), (count) -> {
+                switchMap(distinctUntilChanged(repo.count$(accountId)), (count) -> {
                     Log.v(TAG, "[getAdapterCategories] countLiveData: " + count);
-                    return switchMap(distinctUntilChanged(db.getNoteDao().countFavorites$(accountId)), (favoritesCount) -> {
+                    return switchMap(distinctUntilChanged(repo.countFavorites$(accountId)), (favoritesCount) -> {
                         Log.v(TAG, "[getAdapterCategories] getFavoritesCountLiveData: " + favoritesCount);
-                        return map(distinctUntilChanged(db.getNoteDao().getCategories$(accountId)), fromDatabase -> {
+                        return map(distinctUntilChanged(repo.getCategories$(accountId)), fromDatabase -> {
                             final List<NavigationItem.CategoryNavigationItem> categories = convertToCategoryNavigationItem(getApplication(), fromDatabase);
 
                             final List<NavigationItem> items = new ArrayList<>(fromDatabase.size() + 3);
diff --git a/app/src/main/java/it/niedermann/owncloud/notes/widget/notelist/NoteListWidget.java b/app/src/main/java/it/niedermann/owncloud/notes/widget/notelist/NoteListWidget.java
index 98ebf2fe..7cc84de3 100644
--- a/app/src/main/java/it/niedermann/owncloud/notes/widget/notelist/NoteListWidget.java
+++ b/app/src/main/java/it/niedermann/owncloud/notes/widget/notelist/NoteListWidget.java
@@ -13,20 +13,20 @@ import android.widget.RemoteViews;
 import java.util.NoSuchElementException;
 
 import it.niedermann.owncloud.notes.R;
-import it.niedermann.owncloud.notes.persistence.NotesDatabase;
+import it.niedermann.owncloud.notes.persistence.NotesRepository;
 import it.niedermann.owncloud.notes.persistence.entity.NotesListWidgetData;
 
 public class NoteListWidget extends AppWidgetProvider {
     private static final String TAG = NoteListWidget.class.getSimpleName();
 
     static void updateAppWidget(Context context, AppWidgetManager awm, int[] appWidgetIds) {
-        final NotesDatabase db = NotesDatabase.getInstance(context);
+        final NotesRepository repo = NotesRepository.getInstance(context);
 
         RemoteViews views;
 
         for (int appWidgetId : appWidgetIds) {
             try {
-                final NotesListWidgetData data = db.getWidgetNotesListDao().getNoteListWidgetData(appWidgetId);
+                final NotesListWidgetData data = repo.getNoteListWidgetData(appWidgetId);
 
                 final Intent serviceIntent = new Intent(context, NoteListWidgetService.class);
                 serviceIntent.putExtra(AppWidgetManager.EXTRA_APPWIDGET_ID, appWidgetId);
@@ -80,10 +80,10 @@ public class NoteListWidget extends AppWidgetProvider {
     @Override
     public void onDeleted(Context context, int[] appWidgetIds) {
         super.onDeleted(context, appWidgetIds);
-        final NotesDatabase db = NotesDatabase.getInstance(context);
+        final NotesRepository repo = NotesRepository.getInstance(context);
 
         for (int appWidgetId : appWidgetIds) {
-            new Thread(() -> db.getWidgetNotesListDao().removeNoteListWidget(appWidgetId)).start();
+            new Thread(() -> repo.removeNoteListWidget(appWidgetId)).start();
         }
     }
 
diff --git a/app/src/main/java/it/niedermann/owncloud/notes/widget/notelist/NoteListWidgetConfigurationActivity.java b/app/src/main/java/it/niedermann/owncloud/notes/widget/notelist/NoteListWidgetConfigurationActivity.java
index 2c2aa086..a750ee1e 100644
--- a/app/src/main/java/it/niedermann/owncloud/notes/widget/notelist/NoteListWidgetConfigurationActivity.java
+++ b/app/src/main/java/it/niedermann/owncloud/notes/widget/notelist/NoteListWidgetConfigurationActivity.java
@@ -21,11 +21,9 @@ import it.niedermann.owncloud.notes.databinding.ActivityNoteListConfigurationBin
 import it.niedermann.owncloud.notes.main.navigation.NavigationAdapter;
 import it.niedermann.owncloud.notes.main.navigation.NavigationClickListener;
 import it.niedermann.owncloud.notes.main.navigation.NavigationItem;
-import it.niedermann.owncloud.notes.persistence.NotesDatabase;
+import it.niedermann.owncloud.notes.persistence.NotesRepository;
 import it.niedermann.owncloud.notes.persistence.entity.Account;
-import it.niedermann.owncloud.notes.persistence.entity.CategoryOptions;
 import it.niedermann.owncloud.notes.persistence.entity.NotesListWidgetData;
-import it.niedermann.owncloud.notes.shared.model.CategorySortingMethod;
 
 import static it.niedermann.owncloud.notes.persistence.entity.NotesListWidgetData.MODE_DISPLAY_ALL;
 import static it.niedermann.owncloud.notes.persistence.entity.NotesListWidgetData.MODE_DISPLAY_CATEGORY;
@@ -43,14 +41,14 @@ public class NoteListWidgetConfigurationActivity extends LockedActivity {
     private ActivityNoteListConfigurationBinding binding;
     private NoteListViewModel viewModel;
     private NavigationAdapter adapterCategories;
-    private NotesDatabase db = null;
+    private NotesRepository repo = null;
 
     @Override
     protected void onCreate(@Nullable Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setResult(RESULT_CANCELED);
 
-        db = NotesDatabase.getInstance(this);
+        repo = NotesRepository.getInstance(this);
         final Bundle extras = getIntent().getExtras();
 
         if (extras != null) {
@@ -107,7 +105,7 @@ public class NoteListWidgetConfigurationActivity extends LockedActivity {
                 data.setThemeMode(NotesApplication.getAppTheme(getApplicationContext()).getModeId());
 
                 new Thread(() -> {
-                    db.getWidgetNotesListDao().createOrUpdateNoteListWidgetData(data);
+                    repo.createOrUpdateNoteListWidgetData(data);
 
                     final Intent updateIntent = new Intent(AppWidgetManager.ACTION_APPWIDGET_UPDATE, null, getApplicationContext(), NoteListWidget.class)
                             .putExtra(AppWidgetManager.EXTRA_APPWIDGET_ID, appWidgetId);
@@ -126,7 +124,7 @@ public class NoteListWidgetConfigurationActivity extends LockedActivity {
 
         new Thread(() -> {
             try {
-                this.localAccount = db.getAccountDao().getAccountByName(SingleAccountHelper.getCurrentSingleSignOnAccount(this).name);
+                this.localAccount = repo.getAccountByName(SingleAccountHelper.getCurrentSingleSignOnAccount(this).name);
             } catch (NextcloudFilesAppAccountNotFoundException | NoCurrentAccountSelectedException e) {
                 e.printStackTrace();
                 Toast.makeText(this, R.string.widget_not_logged_in, Toast.LENGTH_LONG).show();
diff --git a/app/src/main/java/it/niedermann/owncloud/notes/widget/notelist/NoteListWidgetFactory.java b/app/src/main/java/it/niedermann/owncloud/notes/widget/notelist/NoteListWidgetFactory.java
index 7917b25a..b7482233 100644
--- a/app/src/main/java/it/niedermann/owncloud/notes/widget/notelist/NoteListWidgetFactory.java
+++ b/app/src/main/java/it/niedermann/owncloud/notes/widget/notelist/NoteListWidgetFactory.java
@@ -19,7 +19,7 @@ import java.util.List;
 import it.niedermann.owncloud.notes.R;
 import it.niedermann.owncloud.notes.edit.EditNoteActivity;
 import it.niedermann.owncloud.notes.main.MainActivity;
-import it.niedermann.owncloud.notes.persistence.NotesDatabase;
+import it.niedermann.owncloud.notes.persistence.NotesRepository;
 import it.niedermann.owncloud.notes.persistence.entity.Account;
 import it.niedermann.owncloud.notes.persistence.entity.Note;
 import it.niedermann.owncloud.notes.persistence.entity.NotesListWidgetData;
@@ -37,7 +37,7 @@ public class NoteListWidgetFactory implements RemoteViewsService.RemoteViewsFact
 
     private final Context context;
     private final int appWidgetId;
-    private final NotesDatabase db;
+    private final NotesRepository repo;
     @NonNull
     private final List<Note> dbNotes = new ArrayList<>();
     private NotesListWidgetData data;
@@ -45,7 +45,7 @@ public class NoteListWidgetFactory implements RemoteViewsService.RemoteViewsFact
     NoteListWidgetFactory(Context context, Intent intent) {
         this.context = context;
         this.appWidgetId = intent.getIntExtra(AppWidgetManager.EXTRA_APPWIDGET_ID, AppWidgetManager.INVALID_APPWIDGET_ID);
-        db = NotesDatabase.getInstance(context);
+        repo = NotesRepository.getInstance(context);
     }
 
     @Override
@@ -57,21 +57,21 @@ public class NoteListWidgetFactory implements RemoteViewsService.RemoteViewsFact
     public void onDataSetChanged() {
         dbNotes.clear();
         try {
-            data = db.getWidgetNotesListDao().getNoteListWidgetData(appWidgetId);
+            data = repo.getNoteListWidgetData(appWidgetId);
             Log.v(TAG, "--- data - " + data);
             switch (data.getMode()) {
                 case MODE_DISPLAY_ALL:
-                    dbNotes.addAll(db.getNoteDao().searchRecentByModified(data.getAccountId(), "%"));
+                    dbNotes.addAll(repo.searchRecentByModified(data.getAccountId(), "%"));
                     break;
                 case MODE_DISPLAY_STARRED:
-                    dbNotes.addAll(db.getNoteDao().searchFavoritesByModified(data.getAccountId(), "%"));
+                    dbNotes.addAll(repo.searchFavoritesByModified(data.getAccountId(), "%"));
                     break;
                 case MODE_DISPLAY_CATEGORY:
                 default:
                     if (data.getCategory() != null) {
-                        dbNotes.addAll(db.getNoteDao().searchCategoryByModified(data.getAccountId(), "%", data.getCategory()));
+                        dbNotes.addAll(repo.searchCategoryByModified(data.getAccountId(), "%", data.getCategory()));
                     } else {
-                        dbNotes.addAll(db.getNoteDao().searchUncategorizedByModified(data.getAccountId(), "%"));
+                        dbNotes.addAll(repo.searchUncategorizedByModified(data.getAccountId(), "%"));
                     }
                     break;
             }
@@ -95,7 +95,7 @@ public class NoteListWidgetFactory implements RemoteViewsService.RemoteViewsFact
         final RemoteViews note_content;
 
         if (position == 0) {
-            final Account localAccount = db.getAccountDao().getAccountById(data.getAccountId());
+            final Account localAccount = repo.getAccountById(data.getAccountId());
             final Intent openIntent = new Intent(Intent.ACTION_MAIN).setComponent(new ComponentName(context.getPackageName(), MainActivity.class.getName()));
             final Intent createIntent = new Intent(context, EditNoteActivity.class);
             final Bundle extras = new Bundle();
diff --git a/app/src/main/java/it/niedermann/owncloud/notes/widget/singlenote/SingleNoteWidget.java b/app/src/main/java/it/niedermann/owncloud/notes/widget/singlenote/SingleNoteWidget.java
index 3ad56c76..e208603a 100644
--- a/app/src/main/java/it/niedermann/owncloud/notes/widget/singlenote/SingleNoteWidget.java
+++ b/app/src/main/java/it/niedermann/owncloud/notes/widget/singlenote/SingleNoteWidget.java
@@ -11,9 +11,9 @@ import android.util.Log;
 import android.widget.RemoteViews;
 
 import it.niedermann.owncloud.notes.R;
-import it.niedermann.owncloud.notes.edit.EditNoteActivity;
 import it.niedermann.owncloud.notes.edit.BaseNoteFragment;
-import it.niedermann.owncloud.notes.persistence.NotesDatabase;
+import it.niedermann.owncloud.notes.edit.EditNoteActivity;
+import it.niedermann.owncloud.notes.persistence.NotesRepository;
 import it.niedermann.owncloud.notes.persistence.entity.SingleNoteWidgetData;
 
 public class SingleNoteWidget extends AppWidgetProvider {
@@ -22,11 +22,11 @@ public class SingleNoteWidget extends AppWidgetProvider {
 
     static void updateAppWidget(Context context, AppWidgetManager awm, int[] appWidgetIds) {
         final Intent templateIntent = new Intent(context, EditNoteActivity.class);
-        final NotesDatabase db = NotesDatabase.getInstance(context);
+        final NotesRepository repo = NotesRepository.getInstance(context);
 
         for (int appWidgetId : appWidgetIds) {
-            final SingleNoteWidgetData data = db.getWidgetSingleNoteDao().getSingleNoteWidgetData(appWidgetId);
-            if(data != null) {
+            final SingleNoteWidgetData data = repo.getSingleNoteWidgetData(appWidgetId);
+            if (data != null) {
                 templateIntent.putExtra(BaseNoteFragment.PARAM_ACCOUNT_ID, data.getAccountId());
 
                 final PendingIntent templatePendingIntent = PendingIntent.getActivity(context, appWidgetId, templateIntent,
@@ -66,10 +66,10 @@ public class SingleNoteWidget extends AppWidgetProvider {
 
     @Override
     public void onDeleted(Context context, int[] appWidgetIds) {
-        final NotesDatabase db = NotesDatabase.getInstance(context);
+        final NotesRepository repo = NotesRepository.getInstance(context);
 
         for (int appWidgetId : appWidgetIds) {
-            new Thread(() -> db.getWidgetSingleNoteDao().removeSingleNoteWidget(appWidgetId)).start();
+            new Thread(() -> repo.removeSingleNoteWidget(appWidgetId)).start();
         }
         super.onDeleted(context, appWidgetIds);
     }
diff --git a/app/src/main/java/it/niedermann/owncloud/notes/widget/singlenote/SingleNoteWidgetFactory.java b/app/src/main/java/it/niedermann/owncloud/notes/widget/singlenote/SingleNoteWidgetFactory.java
index db26da24..f6ca4a24 100644
--- a/app/src/main/java/it/niedermann/owncloud/notes/widget/singlenote/SingleNoteWidgetFactory.java
+++ b/app/src/main/java/it/niedermann/owncloud/notes/widget/singlenote/SingleNoteWidgetFactory.java
@@ -13,7 +13,7 @@ import androidx.annotation.Nullable;
 import it.niedermann.android.markdown.MarkdownUtil;
 import it.niedermann.owncloud.notes.R;
 import it.niedermann.owncloud.notes.edit.EditNoteActivity;
-import it.niedermann.owncloud.notes.persistence.NotesDatabase;
+import it.niedermann.owncloud.notes.persistence.NotesRepository;
 import it.niedermann.owncloud.notes.persistence.entity.Note;
 import it.niedermann.owncloud.notes.persistence.entity.SingleNoteWidgetData;
 
@@ -22,7 +22,7 @@ public class SingleNoteWidgetFactory implements RemoteViewsService.RemoteViewsFa
     private final Context context;
     private final int appWidgetId;
 
-    private final NotesDatabase db;
+    private final NotesRepository repo;
     @Nullable
     private Note note;
 
@@ -31,7 +31,7 @@ public class SingleNoteWidgetFactory implements RemoteViewsService.RemoteViewsFa
     SingleNoteWidgetFactory(Context context, Intent intent) {
         this.context = context;
         this.appWidgetId = intent.getIntExtra(AppWidgetManager.EXTRA_APPWIDGET_ID, AppWidgetManager.INVALID_APPWIDGET_ID);
-        this.db = NotesDatabase.getInstance(context);
+        this.repo = NotesRepository.getInstance(context);
     }
 
     @Override
@@ -41,11 +41,11 @@ public class SingleNoteWidgetFactory implements RemoteViewsService.RemoteViewsFa
 
     @Override
     public void onDataSetChanged() {
-        final SingleNoteWidgetData data = db.getWidgetSingleNoteDao().getSingleNoteWidgetData(appWidgetId);
-        if(data != null) {
+        final SingleNoteWidgetData data = repo.getSingleNoteWidgetData(appWidgetId);
+        if (data != null) {
             final long noteId = data.getNoteId();
             Log.v(TAG, "Fetch note with id " + noteId);
-            note = db.getNoteDao().getNoteById(noteId);
+            note = repo.getNoteById(noteId);
 
             if (note == null) {
                 Log.e(TAG, "Error: note not found");
diff --git a/app/src/test/java/it/niedermann/owncloud/notes/persistence/NotesRepositoryTest.java b/app/src/test/java/it/niedermann/owncloud/notes/persistence/NotesRepositoryTest.java
new file mode 100644
index 00000000..7859b2eb
--- /dev/null
+++ b/app/src/test/java/it/niedermann/owncloud/notes/persistence/NotesRepositoryTest.java
@@ -0,0 +1,151 @@
+package it.niedermann.owncloud.notes.persistence;
+
+import android.content.Context;
+import android.os.Build;
+
+import androidx.annotation.NonNull;
+import androidx.arch.core.executor.testing.InstantTaskExecutorRule;
+import androidx.room.Room;
+import androidx.test.core.app.ApplicationProvider;
+
+import com.nextcloud.android.sso.exceptions.NextcloudHttpRequestFailedException;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Ignore;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mockito;
+import org.robolectric.RobolectricTestRunner;
+import org.robolectric.annotation.Config;
+
+import java.util.Arrays;
+import java.util.Calendar;
+import java.util.Map;
+
+import it.niedermann.owncloud.notes.persistence.entity.Account;
+import it.niedermann.owncloud.notes.persistence.entity.Note;
+import it.niedermann.owncloud.notes.shared.model.Capabilities;
+
+import static it.niedermann.owncloud.notes.persistence.NotesDatabaseTestUtil.getOrAwaitValue;
+import static it.niedermann.owncloud.notes.shared.model.DBStatus.LOCAL_DELETED;
+import static it.niedermann.owncloud.notes.shared.model.DBStatus.LOCAL_EDITED;
+import static it.niedermann.owncloud.notes.shared.model.DBStatus.VOID;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertThrows;
+
+@RunWith(RobolectricTestRunner.class)
+@Config(sdk = {Build.VERSION_CODES.P})
+public class NotesRepositoryTest {
+
+    @Rule
+    public InstantTaskExecutorRule instantTaskExecutorRule = new InstantTaskExecutorRule();
+
+    @NonNull
+    private Context context;
+    private NotesRepository repoMock = null;
+    private Account account = null;
+    private Account secondAccount = null;
+
+    @Before
+    public void setupDB() throws NextcloudHttpRequestFailedException {
+        context = ApplicationProvider.getApplicationContext();
+        repoMock = Mockito.mock(NotesRepository.class);
+        final NotesDatabase db = Room
+                .inMemoryDatabaseBuilder(ApplicationProvider.getApplicationContext(), NotesDatabase.class)
+                .allowMainThreadQueries()
+                .build();
+        Mockito.when(repoMock.db.getNoteDao()).thenReturn(db.getNoteDao());
+
+        repoMock.addAccount("https://äöüß.example.com", "彼得", "彼得@äöüß.example.com", new Capabilities("{\"ocs\":{\"meta\":{\"status\":\"ok\",\"statuscode\":200,\"message\":\"OK\"},\"data\":{\"version\":{\"major\":18,\"minor\":0,\"micro\":4,\"string\":\"18.0.4\",\"edition\":\"\",\"extendedSupport\":false},\"capabilities\":{\"core\":{\"pollinterval\":60,\"webdav-root\":\"remote.php\\/webdav\"},\"bruteforce\":{\"delay\":0},\"files\":{\"bigfilechunking\":true,\"blacklisted_files\":[\".htaccess\"],\"directEditing\":{\"url\":\"https:\\/\\/efss.qloud.my\\/ocs\\/v2.php\\/apps\\/files\\/api\\/v1\\/directEditing\",\"etag\":\"ed2b141af2a39b0e42666952ba60988d\"},\"versioning\":true,\"undelete\":true},\"activity\":{\"apiv2\":[\"filters\",\"filters-api\",\"previews\",\"rich-strings\"]},\"ocm\":{\"enabled\":true,\"apiVersion\":\"1.0-proposal1\",\"endPoint\":\"https:\\/\\/efss.qloud.my\\/index.php\\/ocm\",\"resourceTypes\":[{\"name\":\"file\",\"shareTypes\":[\"user\",\"group\"],\"protocols\":{\"webdav\":\"\\/public.php\\/webdav\\/\"}}]},\"deck\":{\"version\":\"0.8.2\"},\"richdocuments\":{\"mimetypes\":[\"application\\/vnd.oasis.opendocument.text\",\"application\\/vnd.oasis.opendocument.spreadsheet\",\"application\\/vnd.oasis.opendocument.graphics\",\"application\\/vnd.oasis.opendocument.presentation\",\"application\\/vnd.lotus-wordpro\",\"application\\/vnd.visio\",\"application\\/vnd.wordperfect\",\"application\\/msonenote\",\"application\\/msword\",\"application\\/rtf\",\"text\\/rtf\",\"application\\/vnd.openxmlformats-officedocument.wordprocessingml.document\",\"application\\/vnd.openxmlformats-officedocument.wordprocessingml.template\",\"application\\/vnd.ms-word.document.macroEnabled.12\",\"application\\/vnd.ms-word.template.macroEnabled.12\",\"application\\/vnd.ms-excel\",\"application\\/vnd.openxmlformats-officedocument.spreadsheetml.sheet\",\"application\\/vnd.openxmlformats-officedocument.spreadsheetml.template\",\"application\\/vnd.ms-excel.sheet.macroEnabled.12\",\"application\\/vnd.ms-excel.template.macroEnabled.12\",\"application\\/vnd.ms-excel.addin.macroEnabled.12\",\"application\\/vnd.ms-excel.sheet.binary.macroEnabled.12\",\"application\\/vnd.ms-powerpoint\",\"application\\/vnd.openxmlformats-officedocument.presentationml.presentation\",\"application\\/vnd.openxmlformats-officedocument.presentationml.template\",\"application\\/vnd.openxmlformats-officedocument.presentationml.slideshow\",\"application\\/vnd.ms-powerpoint.addin.macroEnabled.12\",\"application\\/vnd.ms-powerpoint.presentation.macroEnabled.12\",\"application\\/vnd.ms-powerpoint.template.macroEnabled.12\",\"application\\/vnd.ms-powerpoint.slideshow.macroEnabled.12\",\"text\\/csv\"],\"mimetypesNoDefaultOpen\":[\"image\\/svg+xml\",\"application\\/pdf\",\"text\\/plain\",\"text\\/spreadsheet\"],\"collabora\":[],\"direct_editing\":false,\"templates\":false,\"productName\":\"\\u5728\\u7ebf\\u534f\\u4f5c\"},\"dav\":{\"chunking\":\"1.0\"},\"files_sharing\":{\"api_enabled\":true,\"public\":{\"enabled\":true,\"password\":{\"enforced\":true,\"askForOptionalPassword\":false},\"expire_date\":{\"enabled\":true,\"days\":\"7\",\"enforced\":false},\"multiple_links\":true,\"expire_date_internal\":{\"enabled\":false},\"send_mail\":false,\"upload\":true,\"upload_files_drop\":true},\"resharing\":true,\"user\":{\"send_mail\":false,\"expire_date\":{\"enabled\":true}},\"group_sharing\":true,\"group\":{\"enabled\":true,\"expire_date\":{\"enabled\":true}},\"default_permissions\":31,\"federation\":{\"outgoing\":false,\"incoming\":false,\"expire_date\":{\"enabled\":true}},\"sharee\":{\"query_lookup_default\":false},\"sharebymail\":{\"enabled\":true,\"upload_files_drop\":{\"enabled\":true},\"password\":{\"enabled\":true},\"expire_date\":{\"enabled\":true}}},\"external\":{\"v1\":[\"sites\",\"device\",\"groups\",\"redirect\"]},\"notifications\":{\"ocs-endpoints\":[\"list\",\"get\",\"delete\",\"delete-all\",\"icons\",\"rich-strings\",\"action-web\"],\"push\":[\"devices\",\"object-data\",\"delete\"],\"admin-notifications\":[\"ocs\",\"cli\"]},\"password_policy\":{\"minLength\":8,\"enforceNonCommonPassword\":true,\"enforceNumericCharacters\":false,\"enforceSpecialCharacters\":false,\"enforceUpperLowerCase\":false,\"api\":{\"generate\":\"https:\\/\\/efss.qloud.my\\/ocs\\/v2.php\\/apps\\/password_policy\\/api\\/v1\\/generate\",\"validate\":\"https:\\/\\/efss.qloud.my\\/ocs\\/v2.php\\/apps\\/password_policy\\/api\\/v1\\/validate\"}},\"theming\":{\"name\":\"QloudData\",\"url\":\"https:\\/\\/www.qloud.my\\/qloud-data\\/\",\"slogan\":\"Powered by NextCloud\",\"color\":\"#1E4164\",\"color-text\":\"#ffffff\",\"color-element\":\"#1E4164\",\"logo\":\"https:\\/\\/efss.qloud.my\\/index.php\\/apps\\/theming\\/image\\/logo?useSvg=1&v=47\",\"background\":\"https:\\/\\/efss.qloud.my\\/core\\/img\\/background.png?v=47\",\"background-plain\":false,\"background-default\":true,\"logoheader\":\"https:\\/\\/efss.qloud.my\\/index.php\\/apps\\/theming\\/image\\/logo?useSvg=1&v=47\",\"favicon\":\"https:\\/\\/efss.qloud.my\\/index.php\\/apps\\/theming\\/image\\/logo?useSvg=1&v=47\"},\"registration\":{\"enabled\":true,\"apiRoot\":\"\\/ocs\\/v2.php\\/apps\\/registration\\/api\\/v1\\/\",\"apiLevel\":\"v1\"}}}}}", null));
+        account = repoMock.getAccountDao().getAccountByName("彼得@äöüß.example.com");
+
+        repoMock.addAccount("https://example.org", "test", "test@example.org", new Capabilities("{ocs: {}}", null));
+        secondAccount = repoMock.getAccountDao().getAccountByName("test@example.org");
+
+        Arrays.stream(new Note[]{
+                new Note(1, 1001L, Calendar.getInstance(), "美好的一天", "C", "Movies", false, null, VOID, account.getId(), "", 0),
+                new Note(2, null, Calendar.getInstance(), "T", "C", "Movies", false, null, LOCAL_EDITED, account.getId(), "", 0),
+                new Note(3, 1003L, Calendar.getInstance(), "美好的一天", "C", "Movies", false, null, LOCAL_EDITED, account.getId(), "", 0),
+                new Note(4, null, Calendar.getInstance(), "T", "C", "Music", false, null, VOID, account.getId(), "", 0),
+                new Note(5, 1005L, Calendar.getInstance(), "美好的一天", "C", " 兄弟，这真是美好的一天。", false, null, LOCAL_EDITED, account.getId(), "", 0),
+                new Note(6, 1006L, Calendar.getInstance(), "美好的一天", "C", " 兄弟，这真是美好的一天。", false, null, LOCAL_DELETED, account.getId(), "", 0),
+                new Note(7, null, Calendar.getInstance(), "T", "C", "Music", true, null, LOCAL_EDITED, secondAccount.getId(), "", 0),
+                new Note(8, 1008L, Calendar.getInstance(), "美好的一天", "C", "ToDo", true, null, LOCAL_EDITED, secondAccount.getId(), "", 0),
+                new Note(9, 1009L, Calendar.getInstance(), "美好的一天", "C", "ToDo", true, null, LOCAL_DELETED, secondAccount.getId(), "", 0)
+        }).forEach(note -> repoMock.getNoteDao().addNote(note));
+    }
+
+    @After
+    public void closeDb() {
+        repoMock.close();
+    }
+
+    @Test
+    public void testGetIdMap() {
+        final Map<Long, Long> idMapOfFirstAccount = repoMock.getIdMap(account.getId());
+        assertEquals(3, idMapOfFirstAccount.size());
+        assertEquals(Long.valueOf(1L), idMapOfFirstAccount.get(1001L));
+        assertEquals(Long.valueOf(3L), idMapOfFirstAccount.get(1003L));
+        assertEquals(Long.valueOf(5L), idMapOfFirstAccount.get(1005L));
+
+        final Map<Long, Long> idMapOfSecondAccount = repoMock.getIdMap(secondAccount.getId());
+        assertEquals(1, idMapOfSecondAccount.size());
+        assertEquals(Long.valueOf(8L), idMapOfSecondAccount.get(1008L));
+    }
+
+    @Test
+    public void testAddAccount() throws NextcloudHttpRequestFailedException, InterruptedException {
+        final Account createdAccount = getOrAwaitValue(repoMock.addAccount("https://äöüß.example.com", "彼得", "彼得@äöüß.example.com", new Capabilities("{ocs: {}}", null)));
+        assertEquals("https://äöüß.example.com", createdAccount.getUrl());
+        assertEquals("彼得", createdAccount.getUserName());
+        assertEquals("彼得@äöüß.example.com", createdAccount.getAccountName());
+    }
+
+    @Test
+    public void testAddNote() {
+        final Note localNote = new Note(null, Calendar.getInstance(), "Fancy Title", "MyContent", "Samples", false, "123");
+        localNote.setId(99);
+        final Note createdNoteFromLocal = repoMock.addNote(account.getId(), localNote);
+        assertEquals(LOCAL_EDITED, createdNoteFromLocal.getStatus());
+        assertEquals("MyContent", createdNoteFromLocal.getExcerpt());
+
+        final Note createdNoteFromRemote = repoMock.addNote(account.getId(), new Note(null, Calendar.getInstance(), "Fancy Title", "MyContent", "Samples", false, "123"));
+        assertEquals(VOID, createdNoteFromRemote.getStatus());
+        assertEquals("MyContent", createdNoteFromRemote.getExcerpt());
+    }
+
+    @Test
+    public void updateApiVersion() {
+        assertThrows(IllegalArgumentException.class, () -> repoMock.updateApiVersion(account.getId(), ""));
+        assertThrows(IllegalArgumentException.class, () -> repoMock.updateApiVersion(account.getId(), "asdf"));
+        assertThrows(IllegalArgumentException.class, () -> repoMock.updateApiVersion(account.getId(), "{}"));
+
+        repoMock.updateApiVersion(account.getId(), null);
+        assertNull(repoMock.getAccountDao().getAccountById(account.getId()).getApiVersion());
+        repoMock.updateApiVersion(account.getId(), "[]");
+        assertNull(repoMock.getAccountDao().getAccountById(account.getId()).getApiVersion());
+
+        repoMock.updateApiVersion(account.getId(), "[1.0]");
+        assertEquals("[1.0]", repoMock.getAccountDao().getAccountById(account.getId()).getApiVersion());
+        repoMock.updateApiVersion(account.getId(), "[0.2, 1.0]");
+        assertEquals("[0.2, 1.0]", repoMock.getAccountDao().getAccountById(account.getId()).getApiVersion());
+
+        // TODO is this really indented?
+        repoMock.updateApiVersion(account.getId(), "[0.2, abc]");
+        assertEquals("[0.2, abc]", repoMock.getAccountDao().getAccountById(account.getId()).getApiVersion());
+    }
+
+    @Test
+    @Ignore("Need to find a way to stub deleteAndSync method")
+    public void moveNoteToAnotherAccount() throws InterruptedException {
+        final Note noteToMove = repoMock.getNoteDao().getNoteById(1);
+        assertEquals(3, repoMock.getNoteDao().getLocalModifiedNotes(secondAccount.getId()).size());
+        final Note movedNote = getOrAwaitValue(repoMock.moveNoteToAnotherAccount(secondAccount, noteToMove));
+        assertEquals(4, repoMock.getNoteDao().getLocalModifiedNotes(secondAccount.getId()).size());
+        assertEquals(LOCAL_EDITED, movedNote.getStatus());
+        // TODO assert deleteAndSync has been called
+    }
+}
\ No newline at end of file