Serialize User to Json inside session file to prevent future breaking changes

src/Client.cs

@@ -43,6 +43,7 @@ namespace WTelegram
 		private readonly Dictionary<long, (Type type, TaskCompletionSource<object> tcs)> _pendingRequests = new();
 		private SemaphoreSlim _sendSemaphore = new(0);
 		private CancellationTokenSource _cts;
+		private int _reactorReconnects = 0;
 
 		/// <summary>Welcome to WTelegramClient! 😀</summary>
 		/// <param name="configProvider">Config callback, is queried for: api_id, api_hash, session_pathname</param>
@@ -164,7 +165,7 @@ namespace WTelegram
 				var authorization = await this.Auth_ImportAuthorization(exported.id, exported.bytes);
 				if (authorization is not Auth_Authorization { user: User user })
 					throw new ApplicationException("Failed to get Authorization: " + authorization.GetType().Name);
-				_session.User = user.Serialize();
+				_session.User = user;
 			}
 		}
 
@@ -180,7 +181,6 @@ namespace WTelegram
 
 		private async Task Reactor(NetworkStream stream, CancellationTokenSource cts)
 		{
-			int reconnects = 0;
 			while (!cts.IsCancellationRequested)
 			{
 				ITLObject obj = null;
@@ -203,8 +203,8 @@ namespace WTelegram
 							_pendingRequests.Clear();
 							_bareRequest = 0;
 						}
-						reconnects = (reconnects + 1) % MaxAutoReconnects;
+						_reactorReconnects = (_reactorReconnects + 1) % MaxAutoReconnects;
-						if (reconnects != 0)
+						if (_reactorReconnects != 0)
 						{
 							Reset(false);
 							await ConnectAsync(); // start a new reactor
@@ -696,7 +696,7 @@ namespace WTelegram
 			{ 
 				try
 				{
-					var prevUser = Serialization.Deserialize<User>(_session.User);
+					var prevUser = _session.User;
 					if (prevUser?.id == int.Parse(botToken.Split(':')[0]))
 						return prevUser;
 				}
@@ -709,7 +709,7 @@ namespace WTelegram
 			var authorization = await this.Auth_ImportBotAuthorization(0, _apiId, _apiHash, botToken);
 			if (authorization is not Auth_Authorization { user: User user })
 				throw new ApplicationException("Failed to get Authorization: " + authorization.GetType().Name);
-			_session.User = user.Serialize();
+			_session.User = user;
 			_session.Save();
 			return user;
 		}
@@ -728,7 +728,7 @@ namespace WTelegram
 			{
 				try
 				{
-					var prevUser = Serialization.Deserialize<User>(_session.User);
+					var prevUser = _session.User;
 					var userId = _config("user_id"); // if config prefers to validate current user by its id, use it
 					if (userId == null || !int.TryParse(userId, out int id) || id != -1 && prevUser.id != id)
 					{
@@ -780,7 +780,7 @@ namespace WTelegram
 			if (authorization is not Auth_Authorization { user: User user })
 				throw new ApplicationException("Failed to get Authorization: " + authorization.GetType().Name);
 			//TODO: find better serialization for User not subject to TL changes?
-			_session.User = user.Serialize();
+			_session.User = user;
 			_session.Save();
 			return user;
 		}

src/Helpers.cs

@@ -1,6 +1,8 @@
 using System;
 using System.Collections.Generic;
 using System.Numerics;
+using System.Text.Json;
+using System.Text.Json.Serialization;
 
 namespace WTelegram
 {
@@ -9,7 +11,7 @@ namespace WTelegram
 		// int argument is the LogLevel: https://docs.microsoft.com/en-us/dotnet/api/microsoft.extensions.logging.loglevel
 		public static Action<int, string> Log { get; set; } = DefaultLogger;
 
-		public static readonly System.Text.Json.JsonSerializerOptions JsonOptions = new(System.Text.Json.JsonSerializerDefaults.Web) { IncludeFields = true, WriteIndented = true };
+		public static readonly JsonSerializerOptions JsonOptions = new() { IncludeFields = true, WriteIndented = true };
 
 		public static V GetOrCreate<K, V>(this Dictionary<K, V> dictionary, K key) where V : new()
 			=> dictionary.TryGetValue(key, out V value) ? value : dictionary[key] = new V();
@@ -23,6 +25,41 @@ namespace WTelegram
 			Console.ResetColor();
 		}
 
+		internal class PolymorphicConverter<T> : JsonConverter<T> where T : class
+		{
+			public override bool HandleNull => true;
+
+			public override void Write(Utf8JsonWriter writer, T value, JsonSerializerOptions options)
+			{
+				if (value == null)
+					writer.WriteNullValue();
+				else
+				{
+					writer.WriteStartObject();
+					writer.WritePropertyName(value.GetType().FullName);
+					JsonSerializer.Serialize(writer, value, value.GetType(), JsonOptions);
+					writer.WriteEndObject();
+				}
+			}
+
+			public override T Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+			{
+				if (reader.TokenType == JsonTokenType.Null)
+					return null;
+				else if (reader.TokenType == JsonTokenType.StartObject)
+				{
+					if (!reader.Read() || reader.TokenType != JsonTokenType.PropertyName) throw new JsonException();
+					var returnType = typeToConvert.Assembly.GetType(reader.GetString());
+					if (!typeToConvert.IsAssignableFrom(returnType)) throw new JsonException();
+					var result = (T)JsonSerializer.Deserialize(ref reader, returnType, JsonOptions);
+					if (!reader.Read() || reader.TokenType != JsonTokenType.EndObject) throw new JsonException();
+					return result;
+				}
+				else
+					throw new JsonException();
+			}
+		}
+
 		public static long RandomLong()
 		{
 #if NETCOREAPP2_1_OR_GREATER

src/Session.cs

@@ -16,13 +16,21 @@ namespace WTelegram
 		public long ServerTicksOffset;
 		public long LastSentMsgId;
 		public TL.DcOption DataCenter;
-		public byte[] User;     // serialization of TL.User
+		public TL.User User;
 
 		public DateTime SessionStart => _sessionStart;
 		private readonly DateTime _sessionStart = DateTime.UtcNow;
 		private string _pathname;
 		private byte[] _apiHash;	// used as AES key for encryption of session file
 
+		private static readonly JsonSerializerOptions JsonOptions = new(Helpers.JsonOptions)
+		{
+			Converters = {
+				new Helpers.PolymorphicConverter<TL.UserProfilePhotoBase>(),
+				new Helpers.PolymorphicConverter<TL.UserStatus>()
+			}
+		};
+
 		internal static Session LoadOrCreate(string pathname, byte[] apiHash)
 		{
 			if (File.Exists(pathname))
@@ -51,12 +59,12 @@ namespace WTelegram
 			var utf8Json = decryptor.TransformFinalBlock(input, 16, input.Length - 16);
 			if (!Encryption.Sha256.ComputeHash(utf8Json, 32, utf8Json.Length - 32).SequenceEqual(utf8Json[0..32]))
 				throw new ApplicationException("Integrity check failed in session loading");
-			return JsonSerializer.Deserialize<Session>(utf8Json.AsSpan(32), Helpers.JsonOptions);
+			return JsonSerializer.Deserialize<Session>(utf8Json.AsSpan(32), JsonOptions);
 		}
 
 		internal void Save()
 		{
-			var utf8Json = JsonSerializer.SerializeToUtf8Bytes(this, Helpers.JsonOptions);
+			var utf8Json = JsonSerializer.SerializeToUtf8Bytes(this, JsonOptions);
 			var finalBlock = new byte[16];
 			var output = new byte[(16 + 32 + utf8Json.Length + 16) & ~15];
 			Encryption.RNG.GetBytes(output, 0, 16);
@@ -91,7 +99,8 @@ namespace WTelegram
 		{
 			DataCenter = newDC;
 			AuthKeyID = Salt = Seqno = 0;
-			AuthKey = User = null;
+			AuthKey = null;
+			User = null;
 		}
 	}
 }