Add a network packet system

lib/packets/packets.dart

@@ -0,0 +1,238 @@
+import 'dart:convert';
+import 'dart:io';
+
+import 'package:libac_flutter/nbt/NbtIo.dart';
+import 'package:libac_flutter/nbt/NbtUtils.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 Future<void> start() async {
+    final ServerSocket 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);
+        } catch (E) {
+          response.status = false;
+          response.reason = "Malformed request packet";
+
+          sock.write(
+              await NbtIo.writeToStream(response.encodeTag() as CompoundTag));
+        }
+      }, onDone: () {
+        sock.close();
+      }, onError: () {
+        sock.close();
+      });
+    }
+  }
+}
+
+abstract class IPacket with NbtEncodable, JsonEncodable {
+  String getChannelID();
+
+  // This function handles the packet
+  Future<void> handlePacket();
+  NetworkDirection direction();
+}
+
+class PacketRegistry {
+  Map<String, IPacket Function()> _registry = {};
+  static PacketRegistry _inst = PacketRegistry._();
+
+  PacketRegistry._();
+
+  factory PacketRegistry() {
+    return _inst;
+  }
+
+  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();
+    });
+  }
+}
+
+enum NetworkDirection { ClientToServer, ServerToClient }
+
+enum PacketOperation { Encode, Decode }
+
+class S2CStatusResponse implements IPacket {
+  bool status = false;
+  String reason = "";
+  late IPacket payload;
+
+  @override
+  NetworkDirection direction() {
+    return NetworkDirection.ServerToClient;
+  }
+
+  @override
+  String getChannelID() {
+    return "StatusResponse";
+  }
+
+  @override
+  Future<void> handlePacket() async {
+    // No handling is required for this packet type
+    if (status) {
+      payload.handlePacket();
+    }
+  }
+
+  @override
+  void decodeJson(String encoded) {
+    fromJson(json.decode(encoded));
+  }
+
+  @override
+  void decodeTag(Tag encoded) {
+    CompoundTag ct = encoded as CompoundTag;
+    status = NbtUtils.readBoolean(ct, "status");
+    reason = ct.get("reason")!.asString();
+
+    if (ct.contains("payload")) {
+      String channel = ct.get("pc")!.asString();
+      payload = PacketRegistry().getPacket(channel);
+
+      payload.decodeTag(ct.get("payload")!);
+    }
+  }
+
+  @override
+  String encodeJson() {
+    return json.encode(toJson());
+  }
+
+  @override
+  Tag encodeTag() {
+    CompoundTag tag = CompoundTag();
+    NbtUtils.writeBoolean(tag, "status", status);
+    tag.put("reason", StringTag.valueOf(reason));
+    if (status) {
+      tag.put("pc", StringTag.valueOf(payload.getChannelID()));
+      tag.put("payload", payload.encodeTag());
+    }
+
+    return tag;
+  }
+
+  @override
+  void fromJson(Map<String, dynamic> params) {
+    status = params["status"] as bool;
+    reason = params["reason"] as String;
+
+    if (status) {
+      String channel = params['pc'] as String;
+      payload = PacketRegistry().getPacket(channel);
+      payload.fromJson(params['payload']);
+    }
+  }
+
+  @override
+  Map<String, dynamic> toJson() {
+    Map<String, dynamic> map = {
+      "status": status,
+      "reason": reason,
+    };
+
+    if (status) {
+      map.addAll({"pc": payload.getChannelID(), "payload": payload.toJson()});
+    }
+
+    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<void> handlePacket() async {
+    // This has no internal handling
+  }
+
+  @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);
+}