feat: Introduce logging for logging purposes

lib/src/omemo/sessionmanager.dart

@@ -3,6 +3,7 @@ import 'dart:convert';
 import 'package:collection/collection.dart';
 import 'package:cryptography/cryptography.dart';
 import 'package:hex/hex.dart';
+import 'package:logging/logging.dart';
 import 'package:meta/meta.dart';
 import 'package:omemo_dart/src/crypto.dart';
 import 'package:omemo_dart/src/double_ratchet/double_ratchet.dart';
@@ -31,7 +32,8 @@ class OmemoSessionManager {
   OmemoSessionManager(this._device, this._deviceMap, this._ratchetMap, this._trustManager)
     : _lock = Lock(),
       _deviceLock = Lock(),
-      _eventStreamController = StreamController<OmemoEvent>.broadcast();
+      _eventStreamController = StreamController<OmemoEvent>.broadcast(),
+      _log = Logger('OmemoSessionManager');
 
   /// Deserialise the OmemoSessionManager from JSON data [data].
   factory OmemoSessionManager.fromJson(Map<String, dynamic> data, TrustManager trustManager) {
@@ -69,6 +71,9 @@ class OmemoSessionManager {
     return OmemoSessionManager(device, {}, {}, trustManager);
   }
 
+  /// Logging
+  Logger _log;
+  
   /// Lock for _ratchetMap and _bundleMap
   final Lock _lock;
 
@@ -304,7 +309,7 @@ class OmemoSessionManager {
   /// [mapKey] with [oldRatchet].
   Future<void> _restoreRatchet(RatchetMapKey mapKey, OmemoDoubleRatchet oldRatchet) async {
     await _lock.synchronized(() {
-      print('RESTORING RATCHETS');
+      _log.finest('Restoring ratchet ${mapKey.jid}:${mapKey.deviceId}');
       _ratchetMap[mapKey] = oldRatchet;
 
       // Commit the ratchet

pubspec.yaml

@@ -11,6 +11,7 @@ dependencies:
   collection: ^1.16.0
   cryptography: ^2.0.5
   hex: ^0.2.0
+  logging: ^1.0.2
   meta: ^1.7.0
   pinenacl: ^0.5.1
   synchronized: ^3.0.0+2

test/omemo_test.dart

@@ -1,9 +1,17 @@
+import 'package:logging/logging.dart';
 import 'package:omemo_dart/omemo_dart.dart';
 import 'package:omemo_dart/src/trust/always.dart';
 import 'package:omemo_dart/src/trust/never.dart';
 import 'package:test/test.dart';
 
 void main() {
+  Logger.root
+    ..level = Level.ALL
+    ..onRecord.listen((record) {
+      // ignore: avoid_print
+      print('${record.level.name}: ${record.message}');
+    });
+
   test('Test using OMEMO sessions with only one device per user', () async {
     const aliceJid = 'alice@server.example';
     const bobJid = 'bob@other.server.example';