fix: single pailot/out topic, per-session file locks, merge protection, res...

Matthias Nott

10 days ago 6cbbea9b96db551e5c0ac26f0ace3d4c3d82a276

 lib/services/message_store.dart
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@@ -15,6 +15,8 @@
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   static Directory? _baseDir;
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   static Timer? _debounceTimer;
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   static final Map<String, List<Message>> _pendingSaves = {};
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+  // Per-session lock to prevent concurrent read/write on the same file
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+  static final Map<String, Completer<void>> _locks = {};
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   static const _backupChannel =
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       MethodChannel('com.mnsoft.pailot/backup');
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@@ -60,10 +62,25 @@
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   /// Write directly to disk, bypassing debounce. For critical saves.
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   static Future<void> writeDirect(String sessionId, List<Message> messages) async {
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-    // Cancel ALL pending debounce to prevent race with frozen iOS timers
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     _debounceTimer?.cancel();
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     _pendingSaves.remove(sessionId);
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-    await _writeSession(sessionId, messages);
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+    await _withLock(sessionId, () => _writeSession(sessionId, messages));
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+  }
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+
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+  /// Acquire a per-session lock, run the operation, release.
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+  static Future<T> _withLock<T>(String sessionId, Future<T> Function() fn) async {
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+    // Wait for any existing operation on this session to finish
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+    while (_locks.containsKey(sessionId)) {
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+      await _locks[sessionId]!.future;
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+    }
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+    final completer = Completer<void>();
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+    _locks[sessionId] = completer;
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+    try {
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+      return await fn();
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+    } finally {
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+      _locks.remove(sessionId);
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+      completer.complete();
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+    }
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   }
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   /// Immediately flush all pending saves.
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@@ -77,7 +94,7 @@
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     _pendingSaves.clear();
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     for (final entry in entries.entries) {
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-      await _writeSession(entry.key, entry.value);
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+      await _withLock(entry.key, () => _writeSession(entry.key, entry.value));
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     }
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   }
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@@ -128,6 +145,10 @@
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   /// Load all messages for a session (no pagination).
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   static Future<List<Message>> loadAll(String sessionId) async {
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+    return _withLock(sessionId, () => _loadAllImpl(sessionId));
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+  }
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+
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+  static Future<List<Message>> _loadAllImpl(String sessionId) async {
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     try {
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       final dir = await _getBaseDir();
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       final file = File('${dir.path}/${_fileForSession(sessionId)}');