Add swarm mode transport doc

test/models/contact_route_codec_test.dart

@@ -0,0 +1,110 @@
+import 'dart:typed_data';
+
+import 'package:flutter_test/flutter_test.dart';
+import 'package:meshcore_sar_app/models/contact.dart';
+
+void main() {
+  Contact buildContact({
+    required int signedPathLen,
+    required Uint8List outPath,
+  }) {
+    return Contact(
+      publicKey: Uint8List.fromList(List<int>.generate(32, (index) => index)),
+      type: ContactType.chat,
+      flags: 0,
+      outPathLen: signedPathLen,
+      outPath: outPath,
+      advName: 'Route Contact',
+      lastAdvert: 0,
+      advLat: 0,
+      advLon: 0,
+      lastMod: 0,
+    );
+  }
+
+  group('ContactRouteCodec.parse', () {
+    test('parses 1-byte hop routes', () {
+      final route = ContactRouteCodec.parse('AA,BB,CC');
+
+      expect(route.hashSize, 1);
+      expect(route.hopCount, 3);
+      expect(route.encodedPathLen, 0x03);
+      expect(route.canonicalText, 'AA,BB,CC');
+      expect(route.pathBytes, [0xAA, 0xBB, 0xCC]);
+    });
+
+    test('parses 2-byte hop routes', () {
+      final route = ContactRouteCodec.parse('AABB,CCDD');
+
+      expect(route.hashSize, 2);
+      expect(route.hopCount, 2);
+      expect(route.encodedPathLen, 0x42);
+      expect(route.canonicalText, 'AABB,CCDD');
+      expect(route.pathBytes, [0xAA, 0xBB, 0xCC, 0xDD]);
+    });
+
+    test('parses 3-byte hop routes', () {
+      final route = ContactRouteCodec.parse('AABBCC,DDEEFF');
+
+      expect(route.hashSize, 3);
+      expect(route.hopCount, 2);
+      expect(route.encodedPathLen, 0x82);
+      expect(route.signedEncodedPathLen, -126);
+      expect(route.pathBytes, [0xAA, 0xBB, 0xCC, 0xDD, 0xEE, 0xFF]);
+    });
+
+    test('accepts colon-separated hops and normalizes output', () {
+      final route = ContactRouteCodec.parse('AA:BB,CC:DD');
+
+      expect(route.hashSize, 2);
+      expect(route.canonicalText, 'AABB,CCDD');
+    });
+
+    test('rejects mixed hop widths', () {
+      expect(
+        () => ContactRouteCodec.parse('AA,AABB'),
+        throwsA(isA<ContactRouteFormatException>()),
+      );
+    });
+
+    test('rejects invalid tokens', () {
+      expect(
+        () => ContactRouteCodec.parse('AA,XYZ'),
+        throwsA(isA<ContactRouteFormatException>()),
+      );
+      expect(
+        () => ContactRouteCodec.parse('AAA'),
+        throwsA(isA<ContactRouteFormatException>()),
+      );
+    });
+
+    test('rejects routes over 64 bytes', () {
+      final tooLong = List.filled(22, 'AABBCC').join(',');
+      expect(
+        () => ContactRouteCodec.parse(tooLong),
+        throwsA(isA<ContactRouteFormatException>()),
+      );
+    });
+  });
+
+  group('Contact route helpers', () {
+    test('interprets signed 3-byte descriptors as valid routes', () {
+      final outPath = Uint8List(64)
+        ..setRange(0, 6, [0xAA, 0xBB, 0xCC, 0xDD, 0xEE, 0xFF]);
+      final contact = buildContact(signedPathLen: -126, outPath: outPath);
+
+      expect(contact.routeHasPath, isTrue);
+      expect(contact.routeHashSize, 3);
+      expect(contact.routeHopCount, 2);
+      expect(contact.routeCanonicalText, 'AABBCC,DDEEFF');
+      expect(contact.routeSupportsLegacyRawTransport, isFalse);
+    });
+
+    test('treats -1 as unknown route', () {
+      final contact = buildContact(signedPathLen: -1, outPath: Uint8List(0));
+
+      expect(contact.routeHasPath, isFalse);
+      expect(contact.routeSummary, 'Flood/Unknown');
+    });
+  });
+}