feat(U2): sync local drafts with IMAP Drafts folder

- Add imapServerId column (schema v24) to Drafts table; guard migration
  with from>=4 since createTable already uses latest schema
- Extend SavedDraft model and DraftRepository interface with syncDrafts()
- Implement syncDrafts in DraftRepositoryImpl: create/select Drafts
  folder, upload local-only drafts via APPEND, import server drafts not
  tracked locally
- Wire AccountRepository and ImapConnectFn into DraftRepositoryImpl via
  draftRepositoryProvider
- Call syncDrafts from AccountSyncManager._AccountSync._sync() so each
  IMAP sync cycle also syncs the Drafts folder
- Add syncDrafts stub to FakeDraftRepository; update unit test
  constructor calls with _StubAccounts

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/core/models/draft.dart

@@ -7,6 +7,7 @@ class SavedDraft {
   final String subjectText;
   final String bodyText;
   final DateTime updatedAt;
+  final String? imapServerId;
 
   const SavedDraft({
     required this.id,
@@ -17,5 +18,6 @@ class SavedDraft {
     required this.subjectText,
     required this.bodyText,
     required this.updatedAt,
+    this.imapServerId,
   });
 }

lib/core/repositories/draft_repository.dart

@@ -21,4 +21,10 @@ abstract class DraftRepository {
 
   /// Permanently removes the draft with [id].
   Future<void> deleteDraft(int id);
+
+  /// Syncs local drafts with the server IMAP Drafts folder for [accountId].
+  /// Uploads local drafts that have no [SavedDraft.imapServerId]; imports
+  /// server drafts that are not already tracked locally.
+  /// No-op when the implementation has no IMAP connection configured.
+  Future<void> syncDrafts(String accountId, String password);
 }

lib/core/sync/account_sync_manager.dart

@@ -4,6 +4,7 @@ import 'package:enough_mail/enough_mail.dart' as imap;
 import 'package:sharedinbox/core/models/account.dart';
 import 'package:sharedinbox/core/models/email.dart' show SyncEmailsResult;
 import 'package:sharedinbox/core/repositories/account_repository.dart';
+import 'package:sharedinbox/core/repositories/draft_repository.dart';
 import 'package:sharedinbox/core/repositories/email_repository.dart';
 import 'package:sharedinbox/core/repositories/mailbox_repository.dart';
 import 'package:sharedinbox/core/repositories/sync_log_repository.dart';
@@ -22,14 +23,17 @@ class AccountSyncManager {
     this._emails, {
     ImapConnectFn imapConnect = connectImap,
     SyncLogRepository syncLog = const NoOpSyncLogRepository(),
+    DraftRepository? drafts,
   })  : _imapConnect = imapConnect,
-        _syncLog = syncLog;
+        _syncLog = syncLog,
+        _drafts = drafts;
 
   final AccountRepository _accounts;
   final MailboxRepository _mailboxes;
   final EmailRepository _emails;
   final ImapConnectFn _imapConnect;
   final SyncLogRepository _syncLog;
+  final DraftRepository? _drafts;
 
   final Map<String, _SyncLoop> _active = {};
   StreamSubscription<List<Account>>? _accountsSub;
@@ -53,6 +57,7 @@ class AccountSyncManager {
               _emails,
               _imapConnect,
               _syncLog,
+              _drafts,
             ),
           AccountType.jmap => _JmapAccountSync(
               account,
@@ -113,6 +118,7 @@ class AccountSyncManager {
           _emails,
           _imapConnect,
           _syncLog,
+          _drafts,
         ),
       AccountType.jmap => _JmapAccountSync(
           account,
@@ -145,6 +151,7 @@ class _AccountSync implements _SyncLoop {
     this._emails,
     this._imapConnect,
     this._syncLog,
+    this._drafts,
   );
 
   final Account account;
@@ -153,6 +160,7 @@ class _AccountSync implements _SyncLoop {
   final EmailRepository _emails;
   final ImapConnectFn _imapConnect;
   final SyncLogRepository _syncLog;
+  final DraftRepository? _drafts;
 
   imap.ImapClient? _idleClient;
   bool _running = false;
@@ -279,6 +287,8 @@ class _AccountSync implements _SyncLoop {
   Future<_SyncStats> _sync() async {
     final password = await _accounts.getPassword(account.id);
 
+    await _drafts?.syncDrafts(account.id, password);
+
     // Check for expired snoozes and move them back to Inbox before syncing.
     await _emails.wakeUpEmails(account.id);
 

lib/data/db/database.dart

@@ -230,6 +230,8 @@ class Drafts extends Table {
   TextColumn get subjectText => text().withDefault(const Constant(''))();
   TextColumn get bodyText => text().withDefault(const Constant(''))();
   DateTimeColumn get updatedAt => dateTime()();
+  // Added in schema v24: IMAP UID string ("mailbox:uid") on the server.
+  TextColumn get imapServerId => text().nullable()();
 }
 
 @DataClassName('UndoActionRow')
@@ -267,7 +269,7 @@ class AppDatabase extends _$AppDatabase {
   AppDatabase([QueryExecutor? executor]) : super(executor ?? _openConnection());
 
   @override
-  int get schemaVersion => 23;
+  int get schemaVersion => 24;
 
   @override
   MigrationStrategy get migration => MigrationStrategy(
@@ -426,6 +428,9 @@ class AppDatabase extends _$AppDatabase {
           if (from < 23) {
             await m.addColumn(emails, emails.listUnsubscribeHeader);
           }
+          if (from >= 4 && from < 24) {
+            await m.addColumn(drafts, drafts.imapServerId);
+          }
         },
       );
 }

lib/data/repositories/draft_repository_impl.dart

@@ -1,13 +1,23 @@
 import 'package:drift/drift.dart';
+import 'package:enough_mail/enough_mail.dart' as imap;
 
+import 'package:sharedinbox/core/models/account.dart';
 import 'package:sharedinbox/core/models/draft.dart';
+import 'package:sharedinbox/core/repositories/account_repository.dart';
 import 'package:sharedinbox/core/repositories/draft_repository.dart';
 import 'package:sharedinbox/data/db/database.dart';
+import 'package:sharedinbox/data/imap/imap_client_factory.dart';
 
 class DraftRepositoryImpl implements DraftRepository {
-  DraftRepositoryImpl(this._db);
+  DraftRepositoryImpl(
+    this._db,
+    this._accounts, {
+    ImapConnectFn? imapConnect,
+  }) : _imapConnect = imapConnect;
 
   final AppDatabase _db;
+  final AccountRepository _accounts;
+  final ImapConnectFn? _imapConnect;
 
   @override
   Future<SavedDraft> saveDraft({
@@ -95,6 +105,110 @@ class DraftRepositoryImpl implements DraftRepository {
     await (_db.delete(_db.drafts)..where((t) => t.id.equals(id))).go();
   }
 
+  @override
+  Future<void> syncDrafts(String accountId, String password) async {
+    final connect = _imapConnect;
+    if (connect == null) return;
+
+    final account = await _accounts.getAccount(accountId);
+    if (account == null || account.type != AccountType.imap) return;
+
+    final username =
+        account.username.isNotEmpty ? account.username : account.email;
+    imap.ImapClient? client;
+    try {
+      client = await connect(account, username, password);
+      await _syncWithServer(client, accountId);
+    } finally {
+      await client?.logout();
+    }
+  }
+
+  Future<void> _syncWithServer(
+    imap.ImapClient client,
+    String accountId,
+  ) async {
+    // Create/select the Drafts folder.
+    try {
+      await client.createMailbox('Drafts');
+    } catch (_) {
+      // Already exists.
+    }
+    final selectResult = await client.selectMailboxByPath('Drafts');
+    final messageCount = selectResult.messagesExists;
+
+    // Upload local drafts that have no server counterpart.
+    final localDrafts = await (_db.select(_db.drafts)
+          ..where(
+            (t) => t.accountId.equals(accountId) & t.imapServerId.isNull(),
+          ))
+        .get();
+
+    for (final row in localDrafts) {
+      final builder = imap.MessageBuilder()
+        ..to = _parseAddresses(row.toText)
+        ..cc = _parseAddresses(row.ccText)
+        ..subject = row.subjectText
+        ..text = row.bodyText;
+      final mime = builder.buildMimeMessage();
+      final appendResult = await client.appendMessage(
+        mime,
+        targetMailboxPath: 'Drafts',
+        flags: [r'\Draft'],
+      );
+      final uidList =
+          appendResult.responseCodeAppendUid?.targetSequence.toList();
+      final uid = (uidList != null && uidList.isNotEmpty)
+          ? uidList.first.toString()
+          : null;
+      if (uid != null) {
+        await (_db.update(_db.drafts)..where((t) => t.id.equals(row.id)))
+            .write(DraftsCompanion(imapServerId: Value(uid)));
+      }
+    }
+
+    // Download server drafts not tracked locally.
+    if (messageCount > 0) {
+      final knownServerIds = await (_db.select(_db.drafts)
+            ..where(
+              (t) => t.accountId.equals(accountId) & t.imapServerId.isNotNull(),
+            ))
+          .get();
+      final knownIds = knownServerIds.map((r) => r.imapServerId!).toSet();
+
+      final seq = imap.MessageSequence.fromAll();
+      final fetch = await client.uidFetchMessages(seq, '(UID FLAGS ENVELOPE)');
+      for (final msg in fetch.messages) {
+        final uid = msg.uid?.toString();
+        if (uid == null || knownIds.contains(uid)) continue;
+        if (msg.flags?.contains(r'\Deleted') ?? false) continue;
+        final env = msg.envelope;
+        final now = DateTime.now();
+        await _db.into(_db.drafts).insert(
+              DraftsCompanion.insert(
+                accountId: Value(accountId),
+                toText: Value(_addressListToText(env?.to)),
+                ccText: Value(_addressListToText(env?.cc)),
+                subjectText: Value(env?.subject ?? ''),
+                bodyText: const Value(''),
+                updatedAt: now,
+                imapServerId: Value(uid),
+              ),
+            );
+      }
+    }
+  }
+
+  List<imap.MailAddress> _parseAddresses(String text) {
+    if (text.trim().isEmpty) return [];
+    return text.split(',').map((s) => imap.MailAddress('', s.trim())).toList();
+  }
+
+  String _addressListToText(List<imap.MailAddress>? addresses) {
+    if (addresses == null || addresses.isEmpty) return '';
+    return addresses.map((a) => a.email).join(', ');
+  }
+
   SavedDraft _toModel(Draft row) => SavedDraft(
         id: row.id,
         accountId: row.accountId,
@@ -104,5 +218,6 @@ class DraftRepositoryImpl implements DraftRepository {
         subjectText: row.subjectText,
         bodyText: row.bodyText,
         updatedAt: row.updatedAt,
+        imapServerId: row.imapServerId,
       );
 }

lib/di.dart

@@ -65,7 +65,11 @@ final mailboxRepositoryProvider = Provider<MailboxRepository>((ref) {
 });
 
 final draftRepositoryProvider = Provider<DraftRepository>((ref) {
-  return DraftRepositoryImpl(ref.watch(dbProvider));
+  return DraftRepositoryImpl(
+    ref.watch(dbProvider),
+    ref.watch(accountRepositoryProvider),
+    imapConnect: ref.watch(imapConnectProvider),
+  );
 });
 
 final emailRepositoryProvider = Provider<EmailRepository>((ref) {
@@ -117,6 +121,7 @@ final syncManagerProvider = Provider<AccountSyncManager>((ref) {
     ref.watch(emailRepositoryProvider),
     syncLog: ref.watch(syncLogRepositoryProvider),
     imapConnect: ref.watch(imapConnectProvider),
+    drafts: ref.watch(draftRepositoryProvider),
   );
   ref.onDispose(manager.dispose);
   return manager;

test/unit/account_sync_manager_test.mocks.dart

@@ -187,6 +187,16 @@ class MockMailboxRepository extends _i1.Mock implements _i7.MailboxRepository {
         ),
         returnValue: _i4.Future<_i8.Mailbox?>.value(),
       ) as _i4.Future<_i8.Mailbox?>);
+
+  @override
+  _i4.Future<void> clearForResync(String? accountId) => (super.noSuchMethod(
+        Invocation.method(
+          #clearForResync,
+          [accountId],
+        ),
+        returnValue: _i4.Future<void>.value(),
+        returnValueForMissingStub: _i4.Future<void>.value(),
+      ) as _i4.Future<void>);
 }
 
 /// A class which mocks [EmailRepository].
@@ -582,4 +592,14 @@ class MockEmailRepository extends _i1.Mock implements _i9.EmailRepository {
           ),
         )),
       ) as _i4.Future<_i2.ReliabilityResult>);
+
+  @override
+  _i4.Future<void> clearForResync(String? accountId) => (super.noSuchMethod(
+        Invocation.method(
+          #clearForResync,
+          [accountId],
+        ),
+        returnValue: _i4.Future<void>.value(),
+        returnValueForMissingStub: _i4.Future<void>.value(),
+      ) as _i4.Future<void>);
 }

test/unit/draft_repository_impl_test.dart

@@ -1,9 +1,25 @@
 import 'package:flutter_test/flutter_test.dart';
-
+import 'package:sharedinbox/core/models/account.dart';
+import 'package:sharedinbox/core/repositories/account_repository.dart';
 import 'package:sharedinbox/data/repositories/draft_repository_impl.dart';
 
 import 'db_test_helper.dart';
 
+class _StubAccounts implements AccountRepository {
+  @override
+  Stream<List<Account>> observeAccounts() => const Stream.empty();
+  @override
+  Future<Account?> getAccount(String id) async => null;
+  @override
+  Future<void> addAccount(Account account, String password) async {}
+  @override
+  Future<void> updateAccount(Account account, {String? password}) async {}
+  @override
+  Future<void> removeAccount(String id) async {}
+  @override
+  Future<String> getPassword(String accountId) async => '';
+}
+
 void main() {
   setUpAll(configureSqliteForTests);
 
@@ -11,7 +27,7 @@ void main() {
     test(
       'saveDraft creates a new row and returns it with a non-zero id',
       () async {
-        final repo = DraftRepositoryImpl(openTestDatabase());
+        final repo = DraftRepositoryImpl(openTestDatabase(), _StubAccounts());
         final draft = await repo.saveDraft(
           toText: 'bob@example.com',
           ccText: '',
@@ -25,7 +41,7 @@ void main() {
     );
 
     test('saveDraft with id updates existing row', () async {
-      final repo = DraftRepositoryImpl(openTestDatabase());
+      final repo = DraftRepositoryImpl(openTestDatabase(), _StubAccounts());
       final created = await repo.saveDraft(
         toText: 'a@example.com',
         ccText: '',
@@ -47,19 +63,19 @@ void main() {
     });
 
     test('getDraft returns null for unknown id', () async {
-      final repo = DraftRepositoryImpl(openTestDatabase());
+      final repo = DraftRepositoryImpl(openTestDatabase(), _StubAccounts());
       expect(await repo.getDraft(99999), isNull);
     });
 
     test('findDraft returns null when no draft exists', () async {
-      final repo = DraftRepositoryImpl(openTestDatabase());
+      final repo = DraftRepositoryImpl(openTestDatabase(), _StubAccounts());
       expect(await repo.findDraft(), isNull);
     });
 
     test(
       'findDraft returns most recent draft for matching replyToEmailId',
       () async {
-        final repo = DraftRepositoryImpl(openTestDatabase());
+        final repo = DraftRepositoryImpl(openTestDatabase(), _StubAccounts());
         await repo.saveDraft(
           replyToEmailId: 'email-1',
           toText: 'a@example.com',
@@ -83,7 +99,7 @@ void main() {
     test(
       'findDraft with null replyToEmailId finds new-message drafts',
       () async {
-        final repo = DraftRepositoryImpl(openTestDatabase());
+        final repo = DraftRepositoryImpl(openTestDatabase(), _StubAccounts());
         // This draft is a reply and should NOT be returned.
         await repo.saveDraft(
           replyToEmailId: 'email-1',
@@ -104,7 +120,7 @@ void main() {
     );
 
     test('deleteDraft removes the row', () async {
-      final repo = DraftRepositoryImpl(openTestDatabase());
+      final repo = DraftRepositoryImpl(openTestDatabase(), _StubAccounts());
       final draft = await repo.saveDraft(
         toText: 'a@example.com',
         ccText: '',

test/unit/undo_service_test.mocks.dart

@@ -452,6 +452,16 @@ class MockEmailRepository extends _i1.Mock implements _i3.EmailRepository {
           ),
         )),
       ) as _i4.Future<_i2.ReliabilityResult>);
+
+  @override
+  _i4.Future<void> clearForResync(String? accountId) => (super.noSuchMethod(
+        Invocation.method(
+          #clearForResync,
+          [accountId],
+        ),
+        returnValue: _i4.Future<void>.value(),
+        returnValueForMissingStub: _i4.Future<void>.value(),
+      ) as _i4.Future<void>);
 }
 
 /// A class which mocks [UndoRepository].

test/widget/helpers.dart

@@ -114,6 +114,9 @@ class FakeDraftRepository implements DraftRepository {
 
   @override
   Future<void> deleteDraft(int id) async => _drafts.remove(id);
+
+  @override
+  Future<void> syncDrafts(String accountId, String password) async {}
 }
 
 class FakeMailboxRepository implements MailboxRepository {