fix(imap): remap local id to new UID after MOVE so caches survive

IMAP UIDs are mailbox-scoped, so MOVE assigns a fresh UID in the
destination folder. The flush previously discarded the response
from `client.uidMove(...)`, so the local row kept the *source*
UID while its `mailbox_path` already pointed at the destination.
Two things broke:

- Deletion reconciliation, which runs per mailbox and compares
  local UIDs to the server's `ALL` search result, would not find
  the source UID in the destination mailbox and wipe the row —
  taking the cached body and queued undo with it.
- `UndoLog` rows kept referencing the old `accountId:mailbox:uid`
  id, so undo had to fall back to a Message-ID lookup just to
  rediscover the moved message.

The fix captures the RFC 4315 `COPYUID` response code that
modern `UIDPLUS` servers attach to `MOVE`/`COPY` (already exposed
as `GenericImapResult.responseCodeCopyUid` in `enough_mail`).
When that's missing — i.e. the server doesn't support UIDPLUS —
we fall back to `UID SEARCH HEADER Message-ID …` in the
destination mailbox. Either way the local id is rewritten in
place to `accountId:destMailbox:newUid` and the cascading
`email_bodies`, `threads`, `pending_changes`, and `undo_actions`
references are updated in the same transaction.

`_reconcileDeletedImap` now also skips rows whose
`move`/`snooze`/`unsnooze` is still queued in `pending_changes`,
so the optimistic local move can't be wiped between the
optimistic write and the server flush.

Closes #539

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

DB-SYNC.md

@@ -54,6 +54,13 @@ This document covers the mail-to-database sync layer only, not the UI.
   optimistic local update; `flushPendingChanges` drains the queue over a single
   IMAP connection at the start of each sync cycle.
 - Sent messages are appended to the Sent folder after SMTP delivery.
+- IMAP move remap: after a `MOVE` is flushed, the local row id is rewritten in
+  place using the RFC 4315 `COPYUID` response code (UIDPLUS); if the server
+  doesn't support UIDPLUS, the new UID is looked up via `UID SEARCH HEADER
+  Message-ID …` in the destination mailbox. Cached bodies (`email_bodies`),
+  threads, queued pending changes, and undo entries follow the new id.
+  Deletion reconciliation skips rows whose `move`/`snooze`/`unsnooze` is still
+  in `pending_changes` so the optimistic local move isn't wiped mid-flight.
 - Sync retries use exponential backoff after failures.
 
 ### Cross-protocol

SYNC.md

@@ -81,6 +81,17 @@ start()
 On each run, only UIDs greater than `lastUid` are fetched. If `uidValidity` changes the full
 folder is re-scanned and the checkpoint is reset.
 
+**IMAP move remap** — IMAP UIDs are mailbox-scoped, so a moved message gets a new UID in
+its destination folder. When a `move`/`snooze`/`unsnooze` change is flushed, the local row
+id (`accountId:mailboxPath:uid`) is rewritten in place to point at the new UID. The new
+UID is taken from the RFC 4315 `COPYUID` response code returned by `MOVE`; if the server
+does not advertise `UIDPLUS`, a `UID SEARCH HEADER Message-ID …` in the destination
+mailbox is used as a fallback. `email_bodies`, `threads`, `pending_changes`, and
+`undo_actions` rows that reference the old id are updated atomically so cached bodies and
+pending undo operations keep tracking the same physical message. Deletion reconciliation
+also skips rows whose move is still queued, so the optimistic local move never gets
+wiped mid-flight.
+
 **IDLE cap** — IDLE sessions are limited to 25 minutes per the RFC. The loop also wakes
 immediately if `syncNow()` is called (e.g. user pulls-to-refresh).
 

lib/data/repositories/email_repository_impl.dart

@@ -6,6 +6,7 @@ import 'dart:math' as math;
 import 'package:drift/drift.dart';
 import 'package:enough_mail/enough_mail.dart' as imap;
 import 'package:http/http.dart' as http;
+import 'package:meta/meta.dart';
 import 'package:path/path.dart' as p;
 import 'package:path_provider/path_provider.dart';
 
@@ -728,6 +729,14 @@ class EmailRepositoryImpl implements EmailRepository {
     await _saveSyncState(accountId, resourceType, jsonEncode(data));
   }
 
+  @visibleForTesting
+  Future<void> reconcileDeletedImapForTest(
+    String accountId,
+    String mailboxPath,
+    List<int> serverUids,
+  ) =>
+      _reconcileDeletedImap(accountId, mailboxPath, serverUids);
+
   Future<void> _reconcileDeletedImap(
     String accountId,
     String mailboxPath,
@@ -752,10 +761,28 @@ class EmailRepositoryImpl implements EmailRepository {
       return;
     }
 
+    // Email IDs that still have a queued move/snooze/unsnooze waiting to be
+    // flushed. The optimistic local move has already updated mailbox_path, so
+    // these rows look orphaned from both the old and new mailbox until the
+    // server applies the change and we remap to the destination UID. Skipping
+    // them here avoids wiping the row mid-flight.
+    final inFlightIds = await (_db.selectOnly(_db.pendingChanges)
+          ..addColumns([_db.pendingChanges.resourceId])
+          ..where(
+            _db.pendingChanges.accountId.equals(accountId) &
+                _db.pendingChanges.changeType.isIn(
+                  const ['move', 'snooze', 'unsnooze'],
+                ),
+          ))
+        .map((row) => row.read(_db.pendingChanges.resourceId)!)
+        .get();
+    final inFlightSet = inFlightIds.toSet();
+
     final serverUidSet = serverUids.toSet();
     final affectedThreads = <String>{};
     for (final row in localRows) {
       if (!serverUidSet.contains(row.uid)) {
+        if (inFlightSet.contains(row.id)) continue;
         affectedThreads.add(row.threadId ?? row.id);
         await (_db.delete(_db.emails)..where((t) => t.id.equals(row.id))).go();
       }
@@ -2317,7 +2344,15 @@ class EmailRepositoryImpl implements EmailRepository {
             ? await client.uidMarkFlagged(seq)
             : await client.uidMarkUnflagged(seq);
       case 'move':
-        await client.uidMove(seq, targetMailboxPath: payload['dest'] as String);
+        final dest = payload['dest'] as String;
+        final result = await client.uidMove(seq, targetMailboxPath: dest);
+        await _remapEmailAfterImapMove(
+          client,
+          oldId: row.resourceId,
+          sourceUid: uid,
+          destMailboxPath: dest,
+          moveResult: result,
+        );
       case 'delete':
         await client.uidMarkDeleted(seq);
         await client.uidExpunge(seq);
@@ -2332,7 +2367,14 @@ class EmailRepositoryImpl implements EmailRepository {
           await client.createMailbox(dest);
         } catch (_) {}
         await client.uidStore(seq, [keyword], action: imap.StoreAction.add);
-        await client.uidMove(seq, targetMailboxPath: dest);
+        final snoozeResult = await client.uidMove(seq, targetMailboxPath: dest);
+        await _remapEmailAfterImapMove(
+          client,
+          oldId: row.resourceId,
+          sourceUid: uid,
+          destMailboxPath: dest,
+          moveResult: snoozeResult,
+        );
       case 'unsnooze':
         final dest = payload['dest'] as String;
         try {
@@ -2351,7 +2393,151 @@ class EmailRepositoryImpl implements EmailRepository {
             );
           }
         }
+        final unsnoozeResult =
             await client.uidMove(seq, targetMailboxPath: dest);
+        await _remapEmailAfterImapMove(
+          client,
+          oldId: row.resourceId,
+          sourceUid: uid,
+          destMailboxPath: dest,
+          moveResult: unsnoozeResult,
+        );
+    }
+  }
+
+  /// Rewrites the local row identity after an IMAP MOVE so the cache keeps
+  /// tracking the same physical message under its new (mailbox, UID).
+  ///
+  /// The new UID is taken from the RFC 4315 `COPYUID` response code first
+  /// (every modern server advertises `UIDPLUS`). If that's missing we fall
+  /// back to `UID SEARCH HEADER Message-ID …` in the destination mailbox.
+  /// When neither yields a UID we leave the row in place; the next sync
+  /// cycle will re-fetch it as a new message and reconciliation will drop
+  /// the stale source-side row.
+  Future<void> _remapEmailAfterImapMove(
+    imap.ImapClient client, {
+    required String oldId,
+    required int sourceUid,
+    required String destMailboxPath,
+    required imap.GenericImapResult moveResult,
+  }) async {
+    final row = await (_db.select(_db.emails)..where((t) => t.id.equals(oldId)))
+        .getSingleOrNull();
+    if (row == null) return;
+
+    final newUid = _resolveCopyUid(moveResult, sourceUid) ??
+        await _searchUidByMessageId(
+          client,
+          destMailboxPath,
+          row.messageId,
+        );
+    if (newUid == null) {
+      log(
+        '_remapEmailAfterImapMove: could not resolve new UID for $oldId '
+        'after move to $destMailboxPath (no COPYUID, '
+        'messageId=${row.messageId}); row will be re-fetched on next sync',
+      );
+      return;
+    }
+
+    final newId = '${row.accountId}:$destMailboxPath:$newUid';
+    if (newId == oldId) return;
+
+    await _db.transaction(() async {
+      await _db.customStatement('PRAGMA defer_foreign_keys = ON');
+
+      await _db.customStatement(
+        'UPDATE email_bodies SET email_id = ?1 WHERE email_id = ?2',
+        [newId, oldId],
+      );
+
+      await (_db.update(_db.emails)..where((t) => t.id.equals(oldId))).write(
+        EmailsCompanion(
+          id: Value(newId),
+          uid: Value(newUid),
+          mailboxPath: Value(destMailboxPath),
+        ),
+      );
+
+      await (_db.update(_db.pendingChanges)
+            ..where((t) => t.resourceId.equals(oldId)))
+          .write(PendingChangesCompanion(resourceId: Value(newId)));
+
+      // threads.latest_email_id is a plain equality match; threads.email_ids_json
+      // is a JSON array of email IDs — both are safe to update via REPLACE()
+      // because email IDs are unique opaque strings.
+      await _db.customStatement(
+        'UPDATE threads SET latest_email_id = ?1 '
+        'WHERE latest_email_id = ?2',
+        [newId, oldId],
+      );
+      await _db.customStatement(
+        'UPDATE threads SET email_ids_json = '
+        'REPLACE(email_ids_json, ?1, ?2) '
+        'WHERE email_ids_json LIKE ?3',
+        ['"$oldId"', '"$newId"', '%"$oldId"%'],
+      );
+
+      // UndoAction.toJson() embeds email IDs as quoted JSON strings in both
+      // emailIds and originalEmails[].id, so the same REPLACE() works.
+      await _db.customStatement(
+        'UPDATE undo_actions SET data_json = '
+        'REPLACE(data_json, ?1, ?2) '
+        'WHERE data_json LIKE ?3',
+        ['"$oldId"', '"$newId"', '%"$oldId"%'],
+      );
+    });
+
+    // Rebuild thread aggregates in both mailboxes from the now-updated emails.
+    final threadId = row.threadId ?? newId;
+    await _updateThread(row.accountId, row.mailboxPath, threadId);
+    await _updateThread(row.accountId, destMailboxPath, threadId);
+  }
+
+  /// Extracts the destination UID for [sourceUid] from a MOVE/COPY result's
+  /// `COPYUID` response code (RFC 4315). Returns null when the server did not
+  /// advertise UIDPLUS or the response code is malformed.
+  int? _resolveCopyUid(imap.GenericImapResult result, int sourceUid) {
+    final code = result.responseCodeCopyUid;
+    if (code == null) return null;
+    try {
+      final sources = code.originalSequence?.toList();
+      final targets = code.targetSequence.toList();
+      if (sources == null) {
+        // Some servers omit the source set when only one message moved.
+        return targets.length == 1 ? targets.first : null;
+      }
+      final idx = sources.indexOf(sourceUid);
+      if (idx < 0 || idx >= targets.length) return null;
+      return targets[idx];
+    } catch (_) {
+      return null;
+    }
+  }
+
+  /// Looks up the UID of a message in [mailboxPath] by its RFC 2822
+  /// `Message-ID` header. Used as a fallback when the server doesn't
+  /// support UIDPLUS so we can still relink the local row after a move.
+  Future<int?> _searchUidByMessageId(
+    imap.ImapClient client,
+    String mailboxPath,
+    String? messageId,
+  ) async {
+    if (messageId == null || messageId.isEmpty) return null;
+    try {
+      await client.selectMailboxByPath(mailboxPath);
+      // RFC 3501 SEARCH HEADER uses an astring for the value; quoting is safe
+      // for typical Message-ID syntax (no embedded quotes or backslashes).
+      final escaped = messageId.replaceAll(r'\', r'\\').replaceAll('"', r'\"');
+      final result = await client.uidSearchMessages(
+        searchCriteria: 'HEADER Message-ID "$escaped"',
+      );
+      final uids = result.matchingSequence?.toList() ?? const <int>[];
+      if (uids.isEmpty) return null;
+      return uids.reduce((a, b) => a > b ? a : b);
+    } catch (e) {
+      log('_searchUidByMessageId failed for $messageId in $mailboxPath: $e');
+      return null;
     }
   }
 

pubspec.lock

@@ -680,7 +680,7 @@ packages:
     source: hosted
     version: "0.13.0"
   meta:
-    dependency: transitive
+    dependency: "direct main"
     description:
       name: meta
       sha256: "1741988757a65eb6b36abe716829688cf01910bbf91c34354ff7ec1c3de2b349"

pubspec.yaml

@@ -67,6 +67,9 @@ dependencies:
   share_plus: ^13.1.0
   device_info_plus: ^13.1.0
 
+  # @visibleForTesting annotation used in lib/data/repositories.
+  meta: ^1.16.0
+
 dev_dependencies:
   flutter_test:
     sdk: flutter

test/unit/email_repository_impl_test.dart

@@ -1109,6 +1109,242 @@ void main() {
         expect(spy.movedToMailbox, 'Snoozed');
       },
     );
+
+    test(
+      'move flush remaps local id/uid from COPYUID and rewrites cached bodies',
+      () async {
+        final spy = SnoozeSpyImapClient(
+          copyUidValidity: 1,
+          copyUidSourceToTarget: const {5: 42},
+        );
+        final r = _makeRepos(imapConnect: (_, __, ___) async => spy);
+        await r.accounts.addAccount(_account, 'pw');
+
+        const oldId = 'acc-1:INBOX:5';
+        await r.db.into(r.db.emails).insert(
+              EmailsCompanion.insert(
+                id: oldId,
+                accountId: 'acc-1',
+                mailboxPath: 'Archive', // already optimistically moved
+                uid: 5,
+                receivedAt: DateTime(2024),
+                messageId: const Value('<msg-1@example.com>'),
+                threadId: const Value('thr-1'),
+              ),
+            );
+        await r.db.into(r.db.emailBodies).insert(
+              EmailBodiesCompanion.insert(
+                emailId: oldId,
+                textBody: const Value('cached body'),
+              ),
+            );
+        await r.db.into(r.db.pendingChanges).insert(
+              PendingChangesCompanion.insert(
+                accountId: 'acc-1',
+                resourceType: 'Email',
+                resourceId: oldId,
+                changeType: 'move',
+                payload: jsonEncode({
+                  'uid': 5,
+                  'mailboxPath': 'INBOX',
+                  'dest': 'Archive',
+                }),
+                createdAt: DateTime.now(),
+              ),
+            );
+
+        await r.emails.flushPendingChanges('acc-1', 'pw');
+
+        // Pending change drained.
+        expect(await r.db.select(r.db.pendingChanges).get(), isEmpty);
+
+        // Old id is gone; new id reflects destination mailbox + new UID.
+        expect(await r.emails.getEmail(oldId), isNull);
+        const newId = 'acc-1:Archive:42';
+        final moved = await r.emails.getEmail(newId);
+        expect(moved, isNotNull);
+        expect(moved!.uid, 42);
+        expect(moved.mailboxPath, 'Archive');
+
+        // Body cache follows the new id.
+        final bodies = await r.db.select(r.db.emailBodies).get();
+        expect(bodies, hasLength(1));
+        expect(bodies.first.emailId, newId);
+        expect(bodies.first.textBody, 'cached body');
+      },
+    );
+
+    test(
+      'move flush falls back to UID SEARCH HEADER Message-ID without UIDPLUS',
+      () async {
+        const messageId = '<msg-1@example.com>';
+        const criteria = 'HEADER Message-ID "$messageId"';
+        final spy = SnoozeSpyImapClient(
+          // No copyUidValidity → no COPYUID in the MOVE response.
+          searchResults: {
+            criteria: const [99]
+          },
+        );
+        final r = _makeRepos(imapConnect: (_, __, ___) async => spy);
+        await r.accounts.addAccount(_account, 'pw');
+
+        const oldId = 'acc-1:INBOX:5';
+        await r.db.into(r.db.emails).insert(
+              EmailsCompanion.insert(
+                id: oldId,
+                accountId: 'acc-1',
+                mailboxPath: 'Archive',
+                uid: 5,
+                receivedAt: DateTime(2024),
+                messageId: const Value(messageId),
+              ),
+            );
+        await r.db.into(r.db.pendingChanges).insert(
+              PendingChangesCompanion.insert(
+                accountId: 'acc-1',
+                resourceType: 'Email',
+                resourceId: oldId,
+                changeType: 'move',
+                payload: jsonEncode({
+                  'uid': 5,
+                  'mailboxPath': 'INBOX',
+                  'dest': 'Archive',
+                }),
+                createdAt: DateTime.now(),
+              ),
+            );
+
+        await r.emails.flushPendingChanges('acc-1', 'pw');
+
+        expect(spy.lastSearchCriteria, criteria);
+        const newId = 'acc-1:Archive:99';
+        final moved = await r.emails.getEmail(newId);
+        expect(moved, isNotNull);
+        expect(moved!.uid, 99);
+      },
+    );
+
+    test(
+      'move flush rewrites pending undo_actions referencing the old id',
+      () async {
+        final spy = SnoozeSpyImapClient(
+          copyUidValidity: 1,
+          copyUidSourceToTarget: const {5: 42},
+        );
+        final r = _makeRepos(imapConnect: (_, __, ___) async => spy);
+        await r.accounts.addAccount(_account, 'pw');
+
+        const oldId = 'acc-1:INBOX:5';
+        await r.db.into(r.db.emails).insert(
+              EmailsCompanion.insert(
+                id: oldId,
+                accountId: 'acc-1',
+                mailboxPath: 'Archive',
+                uid: 5,
+                receivedAt: DateTime(2024),
+              ),
+            );
+        await r.db.into(r.db.pendingChanges).insert(
+              PendingChangesCompanion.insert(
+                accountId: 'acc-1',
+                resourceType: 'Email',
+                resourceId: oldId,
+                changeType: 'move',
+                payload: jsonEncode({
+                  'uid': 5,
+                  'mailboxPath': 'INBOX',
+                  'dest': 'Archive',
+                }),
+                createdAt: DateTime.now(),
+              ),
+            );
+        // An undo entry created when the user did the move, referencing oldId
+        // in both emailIds and originalEmails[].id.
+        await r.db.into(r.db.undoActions).insert(
+              UndoActionsCompanion.insert(
+                id: 'undo-1',
+                accountId: 'acc-1',
+                dataJson: jsonEncode({
+                  'id': 'undo-1',
+                  'accountId': 'acc-1',
+                  'type': 'move',
+                  'emailIds': [oldId],
+                  'sourceMailboxPath': 'INBOX',
+                  'destinationMailboxPath': 'Archive',
+                  'timestamp': DateTime(2024).toIso8601String(),
+                  'originalEmails': [
+                    {
+                      'id': oldId,
+                      'accountId': 'acc-1',
+                      'mailboxPath': 'INBOX',
+                      'uid': 5,
+                      'receivedAt': DateTime(2024).toIso8601String(),
+                      'from': [],
+                      'to': [],
+                      'cc': [],
+                      'isSeen': false,
+                      'isFlagged': false,
+                      'hasAttachment': false,
+                    },
+                  ],
+                }),
+                createdAt: DateTime(2024),
+              ),
+            );
+
+        await r.emails.flushPendingChanges('acc-1', 'pw');
+
+        const newId = 'acc-1:Archive:42';
+        final stored = await r.db.select(r.db.undoActions).getSingle();
+        final json = jsonDecode(stored.dataJson) as Map<String, dynamic>;
+        expect(json['emailIds'], [newId]);
+        expect(
+          (json['originalEmails'] as List).first as Map<String, dynamic>,
+          containsPair('id', newId),
+        );
+      },
+    );
+
+    test(
+      'reconciliation skips rows with a pending move so they are not wiped',
+      () async {
+        final r = _makeRepos();
+        await r.accounts.addAccount(_account, 'pw');
+
+        const oldId = 'acc-1:INBOX:5';
+        await r.db.into(r.db.emails).insert(
+              EmailsCompanion.insert(
+                id: oldId,
+                accountId: 'acc-1',
+                mailboxPath: 'Archive', // optimistically moved
+                uid: 5,
+                receivedAt: DateTime(2024),
+              ),
+            );
+        await r.db.into(r.db.pendingChanges).insert(
+              PendingChangesCompanion.insert(
+                accountId: 'acc-1',
+                resourceType: 'Email',
+                resourceId: oldId,
+                changeType: 'move',
+                payload: jsonEncode({
+                  'uid': 5,
+                  'mailboxPath': 'INBOX',
+                  'dest': 'Archive',
+                }),
+                createdAt: DateTime.now(),
+              ),
+            );
+
+        // Run the deletion-reconciliation pass with a destination snapshot
+        // that does NOT contain UID 5 — the row would be wiped without the
+        // in-flight guard.
+        await r.emails
+            .reconcileDeletedImapForTest('acc-1', 'Archive', const []);
+
+        expect(await r.emails.getEmail(oldId), isNotNull);
+      },
+    );
   });
 
   group('Snooze', () {

test/unit/fake_imap.dart

@@ -19,9 +19,25 @@ class FakeImapClient extends imap.ImapClient {
 
 /// Spy IMAP client that records snooze-related operations and succeeds silently.
 class SnoozeSpyImapClient extends FakeImapClient {
+  SnoozeSpyImapClient({
+    this.copyUidValidity,
+    this.copyUidSourceToTarget = const {},
+    this.searchResults = const {},
+  });
+
   String? selectedMailbox;
   String? createdMailbox;
   String? movedToMailbox;
+  String? lastSearchCriteria;
+
+  /// When non-null, `uidMove` returns a `COPYUID` response code built from
+  /// these mappings (sourceUid → destinationUid) for the moved sequence.
+  final int? copyUidValidity;
+  final Map<int, int> copyUidSourceToTarget;
+
+  /// Maps a `UID SEARCH HEADER Message-ID …` search criteria (the literal
+  /// IMAP atom incl. quotes) to the UIDs the fake should return.
+  final Map<String, List<int>> searchResults;
 
   imap.Mailbox _fakeMailbox(String path) => imap.Mailbox(
         encodedName: path,
@@ -63,7 +79,33 @@ class SnoozeSpyImapClient extends FakeImapClient {
     String? targetMailboxPath,
   }) async {
     movedToMailbox = targetMailboxPath;
-    return imap.GenericImapResult();
+    final result = imap.GenericImapResult();
+    if (copyUidValidity != null && copyUidSourceToTarget.isNotEmpty) {
+      final sources = sequence.toList();
+      final mapped = sources
+          .where(copyUidSourceToTarget.containsKey)
+          .map((uid) => copyUidSourceToTarget[uid]!)
+          .toList();
+      if (mapped.isNotEmpty) {
+        final src = sources.join(',');
+        final dst = mapped.join(',');
+        result.responseCode = 'COPYUID $copyUidValidity $src $dst';
+      }
+    }
+    return result;
+  }
+
+  @override
+  Future<imap.SearchImapResult> uidSearchMessages({
+    String searchCriteria = 'UNSEEN',
+    List<imap.ReturnOption>? returnOptions,
+    Duration? responseTimeout,
+  }) async {
+    lastSearchCriteria = searchCriteria;
+    final hits = searchResults[searchCriteria] ?? const <int>[];
+    final result = imap.SearchImapResult()
+      ..matchingSequence = imap.MessageSequence.fromIds(hits, isUid: true);
+    return result;
   }
 
   @override