fix: a store that cannot brick itself on its own history

Matthias Nott

yesterday e6eb093cc63ba020799844905439f1cabfddcd3c

fix: a store that cannot brick itself on its own history

Startup built its index by jsonDecode-ing every line of the message log to read
one short field. Each line carries its attachment inline as base64, so building
the index cost the size of the entire history — and once that history was large
enough, launch exceeded the iOS watchdog and the app could never be opened
again. 9.5 seconds of CPU, killed at 0x8BADF00D, on a store that had grown a
few megabytes at a time for weeks.

The index needs only the session id, which is a scan rather than a parse.
Compaction now also triggers on bytes: 200 messages per session bounds the
count and nothing else when a message can carry a screenshot.

Also: a saved file is no longer named by appending an extension to a caption
that already ends in one, which produced names with two dots and, when the type
was unknown, a .bin no player would open. The type table gained the video,
audio and image types it never had, and falls back to a self-naming subtype
instead of bin.

 lib/services/message_store.dart
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@@ -88,19 +88,32 @@
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     }
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   }
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+  /// Session id, without decoding the message it belongs to.
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+  ///
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+  /// The index needs ONE short field per line. jsonDecode gave it by parsing
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+  /// the whole record — including an inline base64 attachment that can be tens
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+  /// of megabytes — so building the index cost the size of the entire history.
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+  /// With enough of it, startup exceeded the iOS watchdog and the app could
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+  /// never open again: 9.5 seconds of CPU, killed at 0x8BADF00D, on a store
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+  /// that had grown a few megabytes at a time for weeks.
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+  ///
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+  /// A line is written by us and always carries "sessionId":"…", so reading it
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+  /// is a scan, not a parse.
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+  static final RegExp _sessionIdPattern = RegExp(r'"sessionId"\s*:\s*"([^"]+)"');
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+
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+  static String? _sessionIdOf(String line) =>
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+      _sessionIdPattern.firstMatch(line)?.group(1);
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+
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   static Future<void> _rebuildIndex(File logFile) async {
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     _index.clear();
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     final lines = logFile.readAsLinesSync();
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     for (var i = 0; i < lines.length; i++) {
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       final line = lines[i].trim();
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       if (line.isEmpty) continue;
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-      try {
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-        final map = jsonDecode(line) as Map<String, dynamic>;
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-        final sessionId = map['sessionId'] as String?;
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-        if (sessionId != null) {
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-          _index.putIfAbsent(sessionId, () => []).add(i);
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-        }
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-      } catch (_) {}
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+      final sessionId = _sessionIdOf(line);
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+      if (sessionId != null) {
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+        _index.putIfAbsent(sessionId, () => []).add(i);
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+      }
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     }
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   }
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..
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@@ -189,6 +202,9 @@
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   // ------------------------------------------------------------- compact --
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+  /// Above this, compact regardless of how few lines there are.
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+  static const int _compactAboveBytes = 8 * 1024 * 1024;
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+
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   /// Rewrite the log keeping at most [keepPerSession] messages per session.
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   /// Called once on startup after initialize(). NOT called during normal use.
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   static Future<void> compact({int keepPerSession = 200}) async {
..
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@@ -198,7 +214,12 @@
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       if (!logFile.existsSync()) return;
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       final allLines = logFile.readAsLinesSync();
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-      if (allLines.length < 500) return; // nothing worth compacting
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+      // Compact on SIZE as well as line count. A store is bounded at 200
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+      // messages per session, which bounds nothing when a message carries an
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+      // inline attachment: 200 screenshots is tens of megabytes, and the count
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+      // never trips the threshold. Bytes are what startup has to read.
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+      final bytes = logFile.lengthSync();
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+      if (allLines.length < 500 && bytes < _compactAboveBytes) return;
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       // Build a set of line numbers to keep: last keepPerSession per session.
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       final keepLines = <int>{};
..
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@@ -224,14 +245,13 @@
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         final line = allLines[i].trim();
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         if (line.isEmpty) continue;
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         buffer.write('$line\n');
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-        // Extract sessionId for new index.
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-        try {
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-          final map = jsonDecode(line) as Map<String, dynamic>;
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-          final sid = map['sessionId'] as String?;
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-          if (sid != null) {
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-            newIndex.putIfAbsent(sid, () => []).add(newLine);
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-          }
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-        } catch (_) {}
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+        // Same scan as the index build, for the same reason: the only field
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+        // needed here is short, and decoding the record to reach it makes
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+        // compaction cost the size of the history it exists to bound.
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+        final sid = _sessionIdOf(line);
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+        if (sid != null) {
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+          newIndex.putIfAbsent(sid, () => []).add(newLine);
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+        }
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         newLine++;
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       }
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 lib/widgets/message_bubble.dart
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@@ -468,8 +468,7 @@
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       // Other files: save to temp and share
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       final ext = _mimeToExt(mime);
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       final dir = await getTemporaryDirectory();
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-      final fileName =
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-          '${message.content.isNotEmpty ? message.content.replaceAll(RegExp(r'[^\w\s.-]'), '').trim() : 'file'}.$ext';
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+      final fileName = _fileNameFor(message.content, ext);
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       final file = File('${dir.path}/$fileName');
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       await file.writeAsBytes(bytes);
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..
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@@ -483,6 +482,23 @@
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         ).showSnackBar(SnackBar(content: Text('Could not open file: $e')));
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       }
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     }
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+  }
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+
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+  /// The name to save an incoming file under.
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+  ///
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+  /// The caption is normally the sender's own filename, so it already carries
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+  /// an extension. Appending another unconditionally produced `clip.mp4.mp4` —
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+  /// and where the caption had been reduced to a trailing dot, `clip..bin`,
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+  /// which no player would open until it was renamed by hand.
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+  ///
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+  /// So: sanitise, drop trailing dots, and add the extension only when the name
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+  /// does not already end in it.
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+  String _fileNameFor(String caption, String ext) {
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+    var base = caption.replaceAll(RegExp(r'[^\w\s.-]'), '').trim();
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+    base = base.replaceAll(RegExp(r'\.+$'), '').trim();
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+    if (base.isEmpty) base = 'file';
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+    if (base.toLowerCase().endsWith('.${ext.toLowerCase()}')) return base;
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+    return '$base.$ext';
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   }
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   String _mimeToExt(String mime) {
..
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@@ -503,8 +519,33 @@
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       'application/xml': 'xml',
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       'application/zip': 'zip',
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       'application/gzip': 'gz',
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+      // Video and audio were absent, which is how an mp4 became a `.bin` even
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+      // once the sender labelled it correctly. The hub's table is the source
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+      // this mirrors.
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+      'video/mp4': 'mp4',
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+      'video/quicktime': 'mov',
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+      'video/x-msvideo': 'avi',
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+      'video/x-matroska': 'mkv',
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+      'audio/mpeg': 'mp3',
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+      'audio/wav': 'wav',
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+      'audio/ogg': 'ogg',
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+      'audio/mp4': 'm4a',
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+      'image/jpeg': 'jpg',
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+      'image/png': 'png',
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+      'image/gif': 'gif',
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+      'image/webp': 'webp',
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+      'image/svg+xml': 'svg',
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     };
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-    return map[mime] ?? 'bin';
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+    final normalised = mime.toLowerCase().split(';').first.trim();
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+    final known = map[normalised];
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+    if (known != null) return known;
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+    // A type this table does not carry but whose subtype names itself:
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+    // image/heic -> heic. Better than calling it `bin`.
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+    final subtype = normalised.split('/').length > 1
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+        ? normalised.split('/')[1]
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+        : '';
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+    if (RegExp(r'^[a-z0-9]{2,5}$').hasMatch(subtype)) return subtype;
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+    return 'bin';
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   }
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   Widget _buildFooter(BuildContext context) {
 pubspec.yaml
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@@ -1,7 +1,7 @@
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 name: pailot
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 description: "Voice-first AI communicator"
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 publish_to: 'none'
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-version: 1.1.0+2
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+version: 1.1.2+4
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 environment:
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   sdk: ^3.11.1