feat: Help with serializing and deserializing the BTVT manager

lib/src/omemo/ratchet_map_key.dart

@@ -4,9 +4,24 @@ import 'package:meta/meta.dart';
 class RatchetMapKey {
 
   const RatchetMapKey(this.jid, this.deviceId);
+
+  factory RatchetMapKey.fromJsonKey(String key) {
+    final parts = key.split(':');
+    final deviceId = int.parse(parts.first);
+
+    return RatchetMapKey(
+      parts.sublist(1).join(':'),
+      deviceId,
+    );
+  }
+
   final String jid;
   final int deviceId;
 
+  String toJsonKey() {
+    return '$deviceId:$jid';
+  }
+  
   @override
   bool operator ==(Object other) {
     return other is RatchetMapKey && jid == other.jid && deviceId == other.deviceId;

lib/src/trust/always.dart

@@ -17,4 +17,7 @@ class AlwaysTrustingTrustManager extends TrustManager {
 
   @override
   Future<void> setEnabled(String jid, int deviceId, bool enabled) async {}
+
+  @override
+  Future<Map<String, dynamic>> toJson() async => <String, dynamic>{};
 }

lib/src/trust/base.dart

@@ -16,4 +16,7 @@ abstract class TrustManager {
   /// Mark the device with id [deviceId] of Jid [jid] as enabled if [enabled] is true or as disabled
   /// if [enabled] is false.
   Future<void> setEnabled(String jid, int deviceId, bool enabled);
+
+  /// Serialize the trust manager to JSON.
+  Future<Map<String, dynamic>> toJson();
 }

lib/src/trust/btbv.dart

@@ -8,9 +8,26 @@ import 'package:synchronized/synchronized.dart';
 /// - blindTrust: The fingerprint is not verified using OOB means
 /// - verified: The fingerprint has been verified using OOB means
 enum BTBVTrustState {
-  notTrusted,
-  blindTrust,
-  verified,
+  notTrusted, // = 1
+  blindTrust, // = 2
+  verified,   // = 3
+}
+
+int _trustToInt(BTBVTrustState state) {
+  switch (state) {
+    case BTBVTrustState.notTrusted: return 1;
+    case BTBVTrustState.blindTrust: return 2;
+    case BTBVTrustState.verified:   return 3;
+  }
+}
+
+BTBVTrustState _trustFromInt(int i) {
+  switch (i) {
+    case 1: return BTBVTrustState.notTrusted;
+    case 2: return BTBVTrustState.blindTrust;
+    case 3: return BTBVTrustState.verified;
+    default: return BTBVTrustState.notTrusted;
+  }
 }
 
 /// A TrustManager that implements the idea of Blind Trust Before Verification.
@@ -23,14 +40,17 @@ abstract class BlindTrustBeforeVerificationTrustManager extends TrustManager {
       _lock = Lock();
 
   /// The cache for mapping a RatchetMapKey to its trust state
+  @visibleForTesting
   @protected
   final Map<RatchetMapKey, BTBVTrustState> trustCache;
 
   /// The cache for mapping a RatchetMapKey to whether it is enabled or not
+  @visibleForTesting
   @protected
   final Map<RatchetMapKey, bool> enablementCache;
   
   /// Mapping of Jids to their device identifiers
+  @visibleForTesting
   @protected
   final Map<String, List<int>> devices;
 
@@ -142,6 +162,50 @@ abstract class BlindTrustBeforeVerificationTrustManager extends TrustManager {
     await commitState();
   }
 
+  @override
+  Future<Map<String, dynamic>> toJson() async {
+    return {
+      'devices': devices,
+      'trust': trustCache.map((key, value) => MapEntry(
+        key.toJsonKey(), _trustToInt(value),
+      ),),
+      'enable': enablementCache.map((key, value) => MapEntry(key.toJsonKey(), value)),
+    };
+  }
+
+  /// From a serialized version of a BTBV trust manager, extract the device list.
+  /// NOTE: This is needed as Dart cannot just cast a List<dynamic> to List<int> and so on.
+  static Map<String, List<int>> deviceListFromJson(Map<String, dynamic> json) {
+    return (json['devices']! as Map<String, dynamic>).map<String, List<int>>(
+      (key, value) => MapEntry(
+        key,
+        (value as List<dynamic>).map<int>((i) => i as int).toList(),
+      ),
+    );
+  }
+
+  /// From a serialized version of a BTBV trust manager, extract the trust cache.
+  /// NOTE: This is needed as Dart cannot just cast a List<dynamic> to List<int> and so on.
+  static Map<RatchetMapKey, BTBVTrustState> trustCacheFromJson(Map<String, dynamic> json) {
+    return (json['trust']! as Map<String, dynamic>).map<RatchetMapKey, BTBVTrustState>(
+      (key, value) => MapEntry(
+        RatchetMapKey.fromJsonKey(key),
+        _trustFromInt(value as int),
+      ),
+    );
+  }
+
+  /// From a serialized version of a BTBV trust manager, extract the enable cache.
+  /// NOTE: This is needed as Dart cannot just cast a List<dynamic> to List<int> and so on.
+  static Map<RatchetMapKey, bool> enableCacheFromJson(Map<String, dynamic> json) {
+    return (json['enable']! as Map<String, dynamic>).map<RatchetMapKey, bool>(
+      (key, value) => MapEntry(
+        RatchetMapKey.fromJsonKey(key),
+        value as bool,
+      ),
+    );
+  }
+  
   /// Called when the state of the trust manager has been changed. Allows the user to
   /// commit the trust state to persistent storage.
   @visibleForOverriding

lib/src/trust/never.dart

@@ -17,4 +17,7 @@ class NeverTrustingTrustManager extends TrustManager {
 
   @override
   Future<void> setEnabled(String jid, int deviceId, bool enabled) async {}
+
+  @override
+  Future<Map<String, dynamic>> toJson() async => <String, dynamic>{};
 }

test/serialisation_test.dart

@@ -1,3 +1,4 @@
+import 'dart:convert';
 import 'package:omemo_dart/omemo_dart.dart';
 import 'package:omemo_dart/src/trust/always.dart';
 import 'package:test/test.dart';
@@ -104,4 +105,84 @@ void main() {
       expect(await oldRatchet.equals(newRatchet), true);
     }
   });
+
+  test('Test serialising and deserialising the BlindTrustBeforeVerificationTrustManager', () async {
+    // Caroline's BTBV manager
+    final btbv = MemoryBTBVTrustManager();
+    // Example data
+    const aliceJid = 'alice@some.server';
+    const bobJid = 'bob@other.server';
+    
+    // Caroline starts a chat a device from Alice
+    await btbv.onNewSession(aliceJid, 1);
+    expect(await btbv.isTrusted(aliceJid, 1), true);
+    expect(await btbv.isEnabled(aliceJid, 1), true);
+
+    // Caroline meets with Alice and verifies her fingerprint
+    await btbv.setDeviceTrust(aliceJid, 1, BTBVTrustState.verified);
+    expect(await btbv.isTrusted(aliceJid, 1), true);
+
+    // Alice adds a new device
+    await btbv.onNewSession(aliceJid, 2);
+    expect(await btbv.isTrusted(aliceJid, 2), false);
+    expect(btbv.getDeviceTrust(aliceJid, 2), BTBVTrustState.notTrusted);
+    expect(await btbv.isEnabled(aliceJid, 2), false);
+
+    // Caronline starts a chat with Bob but since they live far apart, Caroline cannot
+    // verify his fingerprint.
+    await btbv.onNewSession(bobJid, 3);
+
+    // Bob adds a new device
+    await btbv.onNewSession(bobJid, 4);
+    expect(await btbv.isTrusted(bobJid, 3), true);
+    expect(await btbv.isTrusted(bobJid, 4), true);
+    expect(btbv.getDeviceTrust(bobJid, 3), BTBVTrustState.blindTrust);
+    expect(btbv.getDeviceTrust(bobJid, 4), BTBVTrustState.blindTrust);
+    expect(await btbv.isEnabled(bobJid, 3), true);
+    expect(await btbv.isEnabled(bobJid, 4), true);
+  });
+
+  test('Test serializing and deserializing RatchetMapKey', () {
+    const test1 = RatchetMapKey('user@example.org', 1234);
+    final result1 = RatchetMapKey.fromJsonKey(test1.toJsonKey());
+    expect(result1.jid, test1.jid);
+    expect(result1.deviceId, test1.deviceId);
+
+    const test2 = RatchetMapKey('user@example.org/hallo:welt', 3333);
+    final result2 = RatchetMapKey.fromJsonKey(test2.toJsonKey());
+    expect(result2.jid, test2.jid);
+    expect(result2.deviceId, test2.deviceId);
+  });
+
+  test('Test serializing and deserializing the components of the BTBV manager', () async {
+    // Caroline's BTBV manager
+    final btbv = MemoryBTBVTrustManager();
+    // Example data
+    const aliceJid = 'alice@some.server';
+    const bobJid = 'bob@other.server';
+    
+    await btbv.onNewSession(aliceJid, 1);
+    await btbv.setDeviceTrust(aliceJid, 1, BTBVTrustState.verified);
+    await btbv.onNewSession(aliceJid, 2);
+    await btbv.onNewSession(bobJid, 3);
+    await btbv.onNewSession(bobJid, 4);
+
+    final managerJson = await btbv.toJson();
+    final managerString = jsonEncode(managerJson);
+    final managerPostJson = jsonDecode(managerString) as Map<String, dynamic>;
+    final deviceList = BlindTrustBeforeVerificationTrustManager.deviceListFromJson(
+      managerPostJson,
+    );
+    expect(btbv.devices, deviceList);
+
+    final trustCache = BlindTrustBeforeVerificationTrustManager.trustCacheFromJson(
+      managerPostJson,
+    );
+    expect(btbv.trustCache, trustCache);
+
+    final enableCache = BlindTrustBeforeVerificationTrustManager.enableCacheFromJson(
+      managerPostJson,
+    );
+    expect(btbv.enablementCache, enableCache);
+  });
 }