Refactor data handling of contacts (#267)

* Refactor data handling in MeshCoreConnector and BufferReader for improved readability and efficiency

* Update lib/connector/meshcore_connector.dart

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* Fix pointer tracking in BufferReader's readCString method

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

lib/connector/meshcore_connector.dart

@@ -3820,40 +3820,40 @@ class MeshCoreConnector extends ChangeNotifier {
 
   void _handleRxData(Uint8List frame) {
     final packet = BufferReader(frame);
-    double snr = 0.0;
-    int routeType = 0;
-    int payloadType = 0;
-    Uint8List pathBytes = Uint8List(0);
-    Uint8List payload = Uint8List(0);
     try {
       packet.skipBytes(1); // Skip frame type byte
-      snr = packet.readInt8() / 4.0;
+      final snr = packet.readInt8() / 4.0;
       packet.skipBytes(1); // Skip RSSI byte
       //final rssi = packet.readByte();
       final header = packet.readByte();
-      routeType = header & 0x03;
-      payloadType = (header >> 2) & 0x0F;
+      final routeType = header & 0x03;
+      final payloadType = (header >> 2) & 0x0F;
+      if (routeType == _routeTransportFlood ||
+          routeType == _routeTransportDirect) {
+        packet.skipBytes(4); // Skip transport-specific bytes
+      }
       //final payloadVer = (header >> 6) & 0x03;
       final pathLen = packet.readByte();
-      pathBytes = packet.readBytes(pathLen);
-      payload = packet.readBytes(packet.remaining);
+      final pathBytes = packet.readBytes(pathLen);
+      final payload = packet.readBytes(packet.remaining);
+
+      final rawPacket = frame.sublist(3);
+      switch (payloadType) {
+        case payloadTypeADVERT:
+          _handlePayloadAdvertReceived(
+            rawPacket,
+            payload,
+            pathBytes,
+            routeType,
+            snr,
+          );
+          break;
+        default:
+      }
     } catch (e) {
       appLogger.warn('Malformed RX frame: $e', tag: 'Connector');
       return;
     }
-    final rawPacket = frame.sublist(3);
-    switch (payloadType) {
-      case payloadTypeADVERT:
-        _handlePayloadAdvertReceived(
-          rawPacket,
-          payload,
-          pathBytes,
-          routeType,
-          snr,
-        );
-        break;
-      default:
-    }
   }
 
   void importContact(Uint8List frame) {
@@ -3865,7 +3865,12 @@ class MeshCoreConnector extends ChangeNotifier {
       packet.skipBytes(1); // Skip SNR byte
       packet.skipBytes(1); // Skip RSSI byte
       final header = packet.readByte();
+      final routeType = header & 0x03;
       payloadType = (header >> 2) & 0x0F;
+      if (routeType == _routeTransportFlood ||
+          routeType == _routeTransportDirect) {
+        packet.skipBytes(4); // Skip transport-specific bytes
+      }
       //final payloadVer = (header >> 6) & 0x03;
       final pathLen = packet.readByte();
       pathBytes = packet.readBytes(pathLen);
@@ -3915,7 +3920,7 @@ class MeshCoreConnector extends ChangeNotifier {
         publicKey: publicKey,
         name: name,
         type: type,
-        pathLength: pathBytes.length,
+        pathLength: pathBytes.isEmpty ? -1 : pathBytes.length,
         path: Uint8List.fromList(
           pathBytes.reversed.toList(),
         ), // Store path in reverse for easier use in outgoing messages

lib/connector/meshcore_protocol.dart

@@ -4,6 +4,7 @@ import 'dart:typed_data';
 // Buffer Reader - sequential binary data reader with pointer tracking
 class BufferReader {
   int _pointer = 0;
+  int _lastPointer = 0;
   final Uint8List _buffer;
 
   BufferReader(Uint8List data) : _buffer = Uint8List.fromList(data);
@@ -13,6 +14,7 @@ class BufferReader {
   int readByte() => readBytes(1)[0];
 
   Uint8List readBytes(int count) {
+    _lastPointer = _pointer;
     if (_pointer + count > _buffer.length) {
       throw RangeError(
         'Attempted to read $count bytes at offset $_pointer, but only $remaining bytes remaining in buffer of length ${_buffer.length}',
@@ -24,6 +26,7 @@ class BufferReader {
   }
 
   void skipBytes(int count) {
+    _lastPointer = _pointer;
     if (_pointer + count > _buffer.length) {
       throw RangeError(
         'Attempted to skip $count bytes at offset $_pointer, but only $remaining bytes remaining in buffer of length ${_buffer.length}',
@@ -35,6 +38,7 @@ class BufferReader {
   Uint8List readRemainingBytes() => readBytes(remaining);
 
   String readString() {
+    _lastPointer = _pointer;
     final value = readRemainingBytes();
     try {
       return utf8.decode(Uint8List.fromList(value), allowMalformed: true);
@@ -43,7 +47,8 @@ class BufferReader {
     }
   }
 
-  String readCString(int maxLength) {
+  String readCStringGreedy(int maxLength) {
+    _lastPointer = _pointer;
     final value = <int>[];
     final bytes = readBytes(maxLength);
     for (final byte in bytes) {
@@ -57,6 +62,24 @@ class BufferReader {
     }
   }
 
+  String readCString(int maxLength) {
+    final backupPointer = _pointer;
+    final value = <int>[];
+    int counter = 0;
+    while (counter < maxLength) {
+      final byte = readByte();
+      if (byte == 0) break;
+      value.add(byte);
+      counter++;
+    }
+    _lastPointer = backupPointer;
+    try {
+      return utf8.decode(Uint8List.fromList(value), allowMalformed: true);
+    } catch (e) {
+      return String.fromCharCodes(value); // Latin-1 fallback
+    }
+  }
+
   int readUInt8() => readBytes(1).buffer.asByteData().getUint8(0);
   int readInt8() => readBytes(1).buffer.asByteData().getInt8(0);
   int readUInt16LE() =>
@@ -78,6 +101,9 @@ class BufferReader {
     if ((value & 0x800000) != 0) value -= 0x1000000;
     return value;
   }
+
+  void resetPointer() => _pointer = 0;
+  void rewind() => _pointer = _lastPointer;
 }
 
 // Buffer Writer - accumulating binary data builder

lib/models/contact.dart

@@ -1,4 +1,6 @@
 import 'dart:typed_data';
+import 'package:meshcore_open/utils/app_logger.dart';
+
 import '../connector/meshcore_protocol.dart';
 
 class Contact {
@@ -166,28 +168,27 @@ class Contact {
 
   static Contact? fromFrame(Uint8List data) {
     if (data.isEmpty) return null;
-    if (data[0] != respCodeContact) return null;
+    final reader = BufferReader(data);
     try {
-      final pubKey = Uint8List.fromList(
-        data.sublist(contactPubKeyOffset, contactPubKeyOffset + pubKeySize),
-      );
-      final type = data[contactTypeOffset];
-      final flags = data[contactFlagsOffset];
-      final pathLen = data[contactPathLenOffset].toSigned(8);
+      final respCode = reader.readByte();
+      if (respCode != respCodeContact && respCode != pushCodeNewAdvert) {
+        return null;
+      }
+      final pubKey = reader.readBytes(pubKeySize);
+      final type = reader.readByte();
+      final flags = reader.readByte();
+      final pathLen = reader.readByte();
       final safePathLen = pathLen > 0
           ? (pathLen > maxPathSize ? maxPathSize : pathLen)
           : 0;
-      final pathBytes = safePathLen > 0
-          ? Uint8List.fromList(
-              data.sublist(contactPathOffset, contactPathOffset + safePathLen),
-            )
-          : Uint8List(0);
-      final name = readCString(data, contactNameOffset, maxNameSize);
-      final lastmod = readUint32LE(data, contactLastModOffset);
+      final pathBytes = reader.readBytes(maxPathSize).sublist(0, safePathLen);
+      final name = reader.readCStringGreedy(maxNameSize);
+
+      final lastMod = reader.readUInt32LE();
 
       double? lat, lon;
-      final latRaw = readInt32LE(data, contactLatOffset);
-      final lonRaw = readInt32LE(data, contactLonOffset);
+      final latRaw = reader.readInt32LE();
+      final lonRaw = reader.readInt32LE();
       if (latRaw != 0 || lonRaw != 0) {
         lat = latRaw / 1e6;
         lon = lonRaw / 1e6;
@@ -198,14 +199,14 @@ class Contact {
         name: name.isEmpty ? 'Unknown' : name,
         type: type,
         flags: flags,
-        pathLength: pathLen,
+        pathLength: pathLen > 0 ? (pathLen > maxPathSize ? -1 : pathLen) : -1,
         path: pathBytes,
         latitude: lat,
         longitude: lon,
-        lastSeen: DateTime.fromMillisecondsSinceEpoch(lastmod * 1000),
+        lastSeen: DateTime.fromMillisecondsSinceEpoch(lastMod * 1000),
       );
     } catch (e) {
-      // If parsing fails, return null
+      appLogger.error('Failed to parse contact frame: $e');
       return null;
     }
   }