LibAC-dart/lib/packets/packets.dart

import 'dart:async';
import 'dart:convert';
import 'dart:io';
import 'dart:typed_data';

import 'package:libac_dart/utils/Hashing.dart';

import '../nbt/NbtIo.dart';
import '../nbt/Stream.dart';
import '../nbt/Tag.dart';
import '../nbt/impl/CompoundTag.dart';
import '../nbt/impl/StringTag.dart';

class PacketServer {
  static ServerSocket? socket;
  static bool shouldRestart = true;
  static Future<void> start(int port) async {
    socket = await ServerSocket.bind(InternetAddress.anyIPv4, port);
    print("Server now listening on port ${port}");

    await for (var sock in socket!) {
      S2CResponse response = S2CResponse();
      print(
          "New connection from ${sock.remoteAddress.address}:${sock.remotePort}");

      ByteLayer layer = ByteLayer();

      try {
        sock.listen((data) {
          layer.writeBytes(data);
        }, onDone: () async {
          layer.resetPosition();
          try {
            List<int> dataHash = layer.readBytes(256);
            int sequenceID = layer.readLong();
            print("Sequence ID in request: $sequenceID");

            int numBytes = layer.readLong();

            List<int> remainingBytes = layer.readBytes(numBytes);

            String sha256OriginalHash = Hashing.bytes2Hash(dataHash);
            String sha256Hash =
                Hashing.bytes2Hash(Hashing.sha1Sum(remainingBytes));
            if (sha256OriginalHash == sha256Hash) {
              CompoundTag tag = await NbtIo.readFromStream(
                  Uint8List.fromList(remainingBytes));
              StringBuilder builder = StringBuilder();
              Tag.writeStringifiedNamedTag(tag, builder, 0);

              print("Request from client: \n${builder}");

              C2SRequestPacket request = C2SRequestPacket();
              request.decodeTag(tag);

              PacketResponse reply = await request.handleServerPacket();

              // Server uses NBT to communicate
              builder = StringBuilder();
              Tag.writeStringifiedNamedTag(reply.replyDataTag, builder, 0);

              print("Response to client: \n${builder}");
              Uint8List nbtData = await NbtIo.writeToStream(reply.replyDataTag);

              layer.clear();
              layer.writeLong(sequenceID);
              layer.writeByte(0xFF); // Successful receipt
              layer.writeBytes(Hashing.sha256Sum(nbtData));
              layer.writeLong(nbtData.lengthInBytes);
              layer.writeBytes(nbtData);

              sock.add(layer.bytes);
            } else {
              // Return a failure packet
              layer.clear();
              layer.writeLong(sequenceID);
              layer.writeByte(0x00);

              sock.add(layer.bytes); // Failure code.
              print(
                  "ERROR: The inbound hash did not match real hash: $sha256OriginalHash != $sha256Hash\n> REFUSING TO PROCESS PACKET. SENDING ERROR CODE TO CLIENT");
            }
          } catch (E, stack) {
            response.contents
                .put("error", StringTag.valueOf("Malformed request packet"));

            print(
                "Something went wrong. Malformed request? \n\n${E}\n\n${stack}\n\n\n\n");
          } finally {
            await sock.flush();
            sock.close();
          }
          layer.clear();
        }, onError: (E) {
          print("ERROR: ${E}");
          sock.close();
          layer.clear();
        });
      } catch (E) {
        sock.close();
      }
    }
  }
}

class PacketClient {
  Socket? socket;
  bool connected = false;
  String lastIP = "";
  int port = 25306;
  int packetSequence = 0;

  PacketClient();

  Future<void> startConnect(String IPAddress, int port) async {
    try {
      socket = await Socket.connect(IPAddress, port);
      connected = true;
      lastIP = IPAddress;
      this.port = port;
    } catch (E) {
      connected = false;
      socket = null;
    }
  }

  /// Tries to send a packet to the connected server
  ///
  /// On success, returns either, the decoded [S2CResponse], or on error a S2CResponse containing an error and a stacktrace as [StringTag]
  Future<S2CResponse> send(IPacket packet, bool shouldReconnect) async {
    if (!connected) {
      return S2CResponse();
    }
    C2SRequestPacket request = C2SRequestPacket();
    request.payload = packet;
    request.cap = packet.getChannelID();
    bool success = false;

    ByteLayer layer = ByteLayer();

    Uint8List nbtData =
        await NbtIo.writeToStream(request.encodeTag().asCompoundTag());
    List<int> nbtDataHash = Hashing.sha256Sum(nbtData);

    ByteLayer reply = ByteLayer();
    CompoundTag NBTTag = CompoundTag();

    while (!success) {
      layer.clear();
      layer.writeBytes(nbtDataHash);
      layer.writeLong(packetSequence);
      layer.writeLong(nbtData.lengthInBytes);
      layer.writeBytes(nbtData);

      Completer responseWait = Completer();

      socket!.add(layer.bytes);

      socket!.listen((data) {
        reply.writeBytes(data);
      }, onDone: () async {
        // Validate response validity
        reply.resetPosition();
        int sequence = reply.readLong();
        int successReceipt = reply.readByte();
        List<int> serverHash = reply.readBytes(256);
        String srvHashStr = Hashing.bytes2Hash(serverHash);
        int numBytes = reply.readLong();
        List<int> pktBytes = reply.readBytes(numBytes);
        String pktHash = Hashing.bytes2Hash(Hashing.sha256Sum(pktBytes));

        if (successReceipt == 0xFF &&
            packetSequence == sequence &&
            srvHashStr == pktHash) success = true;

        if (success) {
          NBTTag = await NbtIo.readFromStream(Uint8List.fromList(pktBytes));
        }

        responseWait.complete();
      }, onError: () {
        if (!responseWait.isCompleted) responseWait.complete();
      });

      await responseWait.future;

      packetSequence++;
      if (!success) await Future.delayed(Duration(seconds: 5));
    }

    CompoundTag ct = CompoundTag();
    StringBuilder builder = StringBuilder();
    Tag.writeStringifiedNamedTag(NBTTag, builder, 0);

    print("Response from server: \n${builder}");
    ct.put("result", NBTTag);

    await close();

    if (shouldReconnect) await startConnect(lastIP, port);

    S2CResponse replyPkt = S2CResponse();
    try {
      replyPkt.decodeTag(ct.get("result")!.asCompoundTag());
    } catch (E, stack) {
      replyPkt.contents = CompoundTag(); // This is essentially a null response
      replyPkt.contents.put("error", StringTag.valueOf(E.toString()));
      replyPkt.contents.put("stacktrace", StringTag.valueOf(stack.toString()));
    }

    return replyPkt;
  }

  Future<void> close() async {
    await socket!.close();
    connected = false;
  }
}

abstract class IPacket with NbtEncodable, JsonEncodable {
  String getChannelID();

  // This function handles the packet
  Future<PacketResponse> handleServerPacket();
  Future<void> handleClientPacket();
  NetworkDirection direction();
}

class StopServerPacket extends IPacket {
  @override
  void decodeJson(String params) {}

  @override
  void decodeTag(Tag tag) {}

  @override
  NetworkDirection direction() {
    return NetworkDirection.ClientToServer;
  }

  @override
  String encodeJson() {
    return json.encode({});
  }

  @override
  Tag encodeTag() {
    return CompoundTag();
  }

  @override
  void fromJson(Map<String, dynamic> js) {}

  @override
  String getChannelID() {
    return "StopServer";
  }

  @override
  Future<PacketResponse> handleServerPacket() async {
    // We're now on the server. Handle the packet with a response to the client
    PacketServer.shouldRestart = false;

    S2CResponse response = S2CResponse();

    return PacketResponse(replyDataTag: response.encodeTag().asCompoundTag());
  }

  @override
  Map<String, dynamic> toJson() {
    return {};
  }

  @override
  Future<void> handleClientPacket() {
    throw UnimplementedError();
  }
}

class PacketResponse {
  static final nil = PacketResponse(replyDataTag: CompoundTag());

  PacketResponse({required this.replyDataTag});

  CompoundTag replyDataTag = CompoundTag();
}

class PacketRegistry {
  Map<String, IPacket Function()> _registry = {};
  static PacketRegistry _inst = PacketRegistry._();

  PacketRegistry._() {
    registerDefaults();
  }

  factory PacketRegistry() {
    return _inst;
  }

  int get count => _registry.length;

  void register(IPacket packet, IPacket Function() packetResolver) {
    _registry[packet.getChannelID()] = packetResolver;
  }

  IPacket getPacket(String channel) {
    if (_registry.containsKey(channel)) {
      IPacket Function() callback = _registry[channel]!;
      return callback();
    } else
      throw Exception("No such channel has been registered");
  }

  void registerDefaults() {
    register(S2CResponse(), () {
      return S2CResponse();
    });
    register(C2SRequestPacket(), () {
      return C2SRequestPacket();
    });
    register(StopServerPacket(), () {
      return StopServerPacket();
    });
    register(C2SPing(), () {
      return C2SPing();
    });
  }
}

enum NetworkDirection { ClientToServer, ServerToClient }

enum PacketOperation { Encode, Decode }

class S2CResponse implements IPacket {
  CompoundTag contents = CompoundTag();

  @override
  NetworkDirection direction() {
    return NetworkDirection.ServerToClient;
  }

  @override
  String getChannelID() {
    return "Response";
  }

  @override
  Future<PacketResponse> handleServerPacket() async {
    // We can't predict handling for this type, it is a data packet response with no pre-defined structure.
    return PacketResponse.nil;
  }

  @override
  void decodeJson(String encoded) {
    fromJson(json.decode(encoded));
  }

  @override
  void decodeTag(Tag encoded) {
    CompoundTag ct = encoded as CompoundTag;
    contents = ct.get("contents")!.asCompoundTag();
  }

  @override
  String encodeJson() {
    return json.encode(toJson());
  }

  @override
  Tag encodeTag() {
    CompoundTag tag = CompoundTag();
    tag.put("contents", contents);

    return tag;
  }

  @override
  void fromJson(Map<String, dynamic> params) {}

  @override
  Map<String, dynamic> toJson() {
    return {}; // Operation is not supported at this time.
  }

  @override
  Future<void> handleClientPacket() async {
    // We haven't got anything to process. This is structured data
  }
}

class C2SRequestPacket implements IPacket {
  String cap = ""; // Packet channel
  late IPacket payload;

  @override
  void decodeJson(String encoded) {
    fromJson(json.decode(encoded));
  }

  @override
  void decodeTag(Tag encoded) {
    CompoundTag tag = encoded.asCompoundTag();
    String cap = tag.get("cap")!.asString();
    payload = PacketRegistry().getPacket(cap);
    payload.decodeTag(tag.get("payload")!.asCompoundTag());
  }

  @override
  NetworkDirection direction() {
    return NetworkDirection.ClientToServer;
  }

  @override
  String encodeJson() {
    return json.encode(toJson());
  }

  @override
  Tag encodeTag() {
    CompoundTag tag = CompoundTag();
    tag.put("cap", StringTag.valueOf(payload.getChannelID()));
    tag.put("payload", payload.encodeTag());

    return tag;
  }

  @override
  void fromJson(Map<String, dynamic> params) {
    String cap = params['cap'] as String;
    payload = PacketRegistry().getPacket(cap);
    payload.fromJson(params['payload']);
  }

  @override
  String getChannelID() {
    return "C2SRequest";
  }

  @override
  Future<PacketResponse> handleServerPacket() async {
    // This has no internal handling
    return payload.handleServerPacket();
  }

  @override
  Map<String, dynamic> toJson() {
    return {"cap": payload.getChannelID(), "payload": payload.toJson()};
  }

  @override
  Future<void> handleClientPacket() {
    throw UnimplementedError();
  }
}

class C2SPing implements IPacket {
  String clientVersion = "";

  @override
  void decodeJson(String params) {
    fromJson(json.decode(params));
  }

  @override
  void decodeTag(Tag tag) {
    clientVersion = tag.asCompoundTag().get("version")!.asString();
  }

  @override
  NetworkDirection direction() {
    return NetworkDirection.ClientToServer;
  }

  @override
  String encodeJson() {
    return json.encode(toJson());
  }

  @override
  Tag encodeTag() {
    CompoundTag tag = CompoundTag();
    tag.put("version", StringTag.valueOf(clientVersion));

    return tag;
  }

  @override
  void fromJson(Map<String, dynamic> js) {
    clientVersion = js['version'] as String;
  }

  @override
  String getChannelID() {
    return "Ping";
  }

  @override
  Future<PacketResponse> handleServerPacket() async {
    CompoundTag tag = CompoundTag();
    tag.put("pong", StringTag.valueOf(Platform.version));

    S2CResponse response = S2CResponse();
    response.contents = tag;

    PacketResponse reply =
        PacketResponse(replyDataTag: response.encodeTag().asCompoundTag());
    return reply;
  }

  @override
  Map<String, dynamic> toJson() {
    return {"version": clientVersion};
  }

  @override
  Future<void> handleClientPacket() {
    throw UnimplementedError();
  }
}

mixin JsonEncodable {
  String encodeJson();
  void decodeJson(String params);

  Map<String, dynamic> toJson();
  void fromJson(Map<String, dynamic> js);
}

mixin NbtEncodable {
  Tag encodeTag();
  void decodeTag(Tag tag);
}