fix issues with contact sync

this adds the actual last modified timestamp when present, before we used
last advert time as last modified in error

also sets _pendingInitialContactsSync to true on first connect over BLE

lib/connector/meshcore_connector.dart

@@ -2140,6 +2140,7 @@ class MeshCoreConnector extends ChangeNotifier {
       return;
     }
     _bleInitialSyncStarted = true;
+    _pendingInitialContactsSync = true;
 
     await _requestDeviceInfo();
     _startBatteryPolling();
@@ -4117,7 +4118,9 @@ class MeshCoreConnector extends ChangeNotifier {
     if (_contacts.isEmpty) return 0;
     var latest = 0;
     for (final contact in _contacts) {
-      final seconds = contact.lastSeen.millisecondsSinceEpoch ~/ 1000;
+      // prefer lastmod per spec, fallback to lastseen
+      final source = contact.lastModified ?? contact.lastSeen;
+      final seconds = source.millisecondsSinceEpoch ~/ 1000;
       if (seconds > latest) {
         latest = seconds;
       }

lib/connector/meshcore_protocol.dart

@@ -735,10 +735,15 @@ Uint8List buildUpdateContactPathFrame(
     writer.writeInt32LE((longitude * 1e6).round());
   }
 
-  if (lastModified != null) {
+  final hasLocation = lat != null && lon != null;
-    // Last modified
+  if (hasLocation || lastModified != null) {
-    final lastModifiedTimestamp = lastModified.millisecondsSinceEpoch ~/ 1000;
+    writer.writeInt32LE(hasLocation ? (lat * 1e6).round() : 0);
-    writer.writeUInt32LE(lastModifiedTimestamp);
+    writer.writeInt32LE(hasLocation ? (lon * 1e6).round() : 0);
+    if (lastModified != null) {
+      // Last modified
+      final lastModifiedTimestamp = lastModified.millisecondsSinceEpoch ~/ 1000;
+      writer.writeUInt32LE(lastModifiedTimestamp);
+    }
   }
 
   return writer.toBytes();

lib/models/contact.dart

@@ -17,6 +17,7 @@ class Contact {
   final double? longitude;
   final DateTime lastSeen;
   final DateTime lastMessageAt;
+  final DateTime? lastModified;
   final bool isActive;
   final bool wasPulled;
   final Uint8List? rawPacket;
@@ -33,6 +34,7 @@ class Contact {
     this.latitude,
     this.longitude,
     required this.lastSeen,
+    this.lastModified,
     DateTime? lastMessageAt,
     this.isActive = true,
     this.wasPulled = false,
@@ -94,6 +96,7 @@ class Contact {
     double? longitude,
     DateTime? lastSeen,
     DateTime? lastMessageAt,
+    DateTime? lastModified,
     bool? isActive,
     Uint8List? rawPacket,
   }) {
@@ -114,6 +117,7 @@ class Contact {
       longitude: longitude ?? this.longitude,
       lastSeen: lastSeen ?? this.lastSeen,
       lastMessageAt: lastMessageAt ?? this.lastMessageAt,
+      lastModified: lastModified ?? this.lastModified,
       isActive: isActive ?? this.isActive,
       rawPacket: rawPacket ?? this.rawPacket,
     );
@@ -182,16 +186,34 @@ class Contact {
         return null;
       }
 
-      final lastMod = reader.readUInt32LE();
+      // mandatory last_advert_timestamp
+      final lastAdvertTimestamp = reader.readUInt32LE();
 
       double? lat, lon;
-      if (reader.remaining >= 8) {
+      DateTime? lastModified;
+      if (reader.remaining >= 12) {
         final latRaw = reader.readInt32LE();
         final lonRaw = reader.readInt32LE();
+        final lastModRaw = reader.readUInt32LE();
+        // TODO: should this be &&?
         if (latRaw != 0 || lonRaw != 0) {
           lat = latRaw / 1e6;
           lon = lonRaw / 1e6;
         }
+        if (lastModRaw != 0) {
+          lastModified = DateTime.fromMillisecondsSinceEpoch(lastModRaw * 1000);
+        }
+      } else if (reader.remaining >= 8) {
+        // Old layout: gps without lastmod
+        final latRaw = reader.readInt32LE();
+        final lonRaw = reader.readInt32LE();
+        if (latRaw != 0 || lonRaw != 0) {
+          lat = latRaw / 1e6;
+          lon = lonRaw / 1e6;
+        }
+        appLogger.info(
+          'Contact ${pubKeyToHex(pubKey).substring(0, 8)} has gps but no lastmod (legacy firmware layout)',
+        );
       }
 
       return Contact(
@@ -203,7 +225,10 @@ class Contact {
         path: pathBytes,
         latitude: lat,
         longitude: lon,
-        lastSeen: DateTime.fromMillisecondsSinceEpoch(lastMod * 1000),
+        lastSeen: DateTime.fromMillisecondsSinceEpoch(
+          lastAdvertTimestamp * 1000,
+        ),
+        lastModified: lastModified,
         isActive: true,
         rawPacket: null,
       );

lib/storage/contact_discovery_store.dart

@@ -43,6 +43,7 @@ class ContactDiscoveryStore {
       'latitude': contact.latitude,
       'longitude': contact.longitude,
       'lastSeen': contact.lastSeen.millisecondsSinceEpoch,
+      'lastModified': contact.lastModified?.millisecondsSinceEpoch,
       'lastMessageAt': contact.lastMessageAt.millisecondsSinceEpoch,
       'rawPacket': contact.rawPacket != null
           ? base64Encode(contact.rawPacket!)
@@ -53,6 +54,7 @@ class ContactDiscoveryStore {
   Contact _fromJson(Map<String, dynamic> json) {
     final lastSeenMs = json['lastSeen'] as int? ?? 0;
     final lastMessageMs = json['lastMessageAt'] as int?;
+    final lastModifiedMs = json['lastModified'] as int?;
     return Contact(
       publicKey: Uint8List.fromList(base64Decode(json['publicKey'] as String)),
       name: json['name'] as String? ?? 'Unknown',
@@ -71,6 +73,9 @@ class ContactDiscoveryStore {
       latitude: (json['latitude'] as num?)?.toDouble(),
       longitude: (json['longitude'] as num?)?.toDouble(),
       lastSeen: DateTime.fromMillisecondsSinceEpoch(lastSeenMs),
+      lastModified: lastModifiedMs == null
+          ? null
+          : DateTime.fromMillisecondsSinceEpoch(lastModifiedMs),
       lastMessageAt: DateTime.fromMillisecondsSinceEpoch(
         lastMessageMs ?? lastSeenMs,
       ),

lib/storage/contact_store.dart

@@ -75,6 +75,7 @@ class ContactStore {
       'latitude': contact.latitude,
       'longitude': contact.longitude,
       'lastSeen': contact.lastSeen.millisecondsSinceEpoch,
+      'lastModified': contact.lastModified?.millisecondsSinceEpoch,
       'lastMessageAt': contact.lastMessageAt.millisecondsSinceEpoch,
       'isActive': contact.isActive,
       'rawPacket': contact.rawPacket != null
@@ -86,6 +87,7 @@ class ContactStore {
   Contact _fromJson(Map<String, dynamic> json) {
     final lastSeenMs = json['lastSeen'] as int? ?? 0;
     final lastMessageMs = json['lastMessageAt'] as int?;
+    final lastModifiedMs = json['lastModified'] as int?;
     return Contact(
       publicKey: Uint8List.fromList(base64Decode(json['publicKey'] as String)),
       name: json['name'] as String? ?? 'Unknown',
@@ -104,6 +106,9 @@ class ContactStore {
       latitude: (json['latitude'] as num?)?.toDouble(),
       longitude: (json['longitude'] as num?)?.toDouble(),
       lastSeen: DateTime.fromMillisecondsSinceEpoch(lastSeenMs),
+      lastModified: lastModifiedMs == null
+          ? null
+          : DateTime.fromMillisecondsSinceEpoch(lastModifiedMs),
       lastMessageAt: DateTime.fromMillisecondsSinceEpoch(
         lastMessageMs ?? lastSeenMs,
       ),