LibAC-dart/lib/packets/packets.dart

import 'dart:convert';
import 'dart:io';

import 'package:libac_flutter/nbt/NbtIo.dart';
import 'package:libac_flutter/nbt/Tag.dart';
import 'package:libac_flutter/nbt/impl/CompoundTag.dart';
import 'package:libac_flutter/nbt/impl/StringTag.dart';

class PacketServer {
  static ServerSocket? socket;
  static Future<void> start() async {
    socket = await ServerSocket.bind(InternetAddress.anyIPv4, 25306);
    print("Server now listening on port 25306");

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

      sock.listen((data) async {
        S2CStatusResponse response = S2CStatusResponse();
        try {
          CompoundTag tag = await NbtIo.readFromStream(data);
          C2SRequestPacket request = C2SRequestPacket();
          request.decodeTag(tag);

          PacketResponse reply = await request.handlePacket();
          // Server uses NBT to communicate
          sock.add(await NbtIo.writeToStream(reply.replyDataTag));
        } catch (E) {
          response.reason = "Malformed request packet";

          sock.add(
              await NbtIo.writeToStream(response.encodeTag() as CompoundTag));
        }
      }, onDone: () {
        sock.close();
      }, onError: () {
        sock.close();
      });
    }
  }
}

class PacketClient {
  Socket? socket;
  bool connected = false;

  PacketClient(String IPAddress) {
    startConnect(IPAddress);
  }

  Future<void> startConnect(String IPAddress) async {
    try {
      socket = await Socket.connect(IPAddress, 25306);
      connected = true;
    } catch (E) {
      connected = false;
      socket = null;
    }
  }

  Future<CompoundTag> send(IPacket packet) async {
    if (!connected) {
      return CompoundTag();
    }
    socket!.add(await NbtIo.writeToStream(packet.encodeTag().asCompoundTag()));
    CompoundTag ct = CompoundTag();
    socket!.listen((data) async {
      ct = await NbtIo.readFromStream(data);
    });

    return ct;
  }

  void close() {
    socket!.close();
    connected = false;
  }
}

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

  // This function handles the packet
  Future<PacketResponse> handlePacket();
  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> handlePacket() async {
    PacketServer.socket!.close();

    return PacketResponse(replyDataTag: CompoundTag());
  }

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

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._();

  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(S2CStatusResponse(), () {
      return S2CStatusResponse();
    });
    register(C2SRequestPacket(), () {
      return C2SRequestPacket();
    });
    register(StopServerPacket(), () {
      return StopServerPacket();
    });
  }
}

enum NetworkDirection { ClientToServer, ServerToClient }

enum PacketOperation { Encode, Decode }

class S2CStatusResponse implements IPacket {
  String reason = "";

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

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

  @override
  Future<PacketResponse> handlePacket() async {
    // No handling is required for this packet type
    return PacketResponse.nil;
  }

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

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

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

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

    return tag;
  }

  @override
  void fromJson(Map<String, dynamic> params) {
    reason = params["reason"] as String;
  }

  @override
  Map<String, dynamic> toJson() {
    Map<String, dynamic> map = {
      "reason": reason,
    };

    return map;
  }
}

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> handlePacket() async {
    // This has no internal handling
    return payload.handlePacket();
  }

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

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);
}