// ignore_for_file: prefer_final_fields

import 'dart:async';
import 'package:meta/meta.dart';
import 'package:protobuf/protobuf.dart';
import 'packets/message_common.pb.dart';
import 'transport.dart';

abstract class Communicator {
  static const int maxNonce = 2147483647;

  Map<String, IDataHandler> _handlerDic = {};
  Map<String, Future<void> Function(List<int>, int)> _requestHandlerDic = {};
  Map<int, _PendingRequest> _pendingRequests = {};
  late Map<String, GeneratedMessage Function(List<int>)> _instanceGenerator;
  Future<void> _outboundWrite = Future.value();
  Transport? _transport;

  /// Monotonically increasing nonce. Shared by send / sendRequest / response.
  int _nonce = 0;
  int get nonce => _nonce;

  @protected
  set nonce(int value) => _nonce = value;

  @protected
  int nextNonce() {
    if (_nonce >= maxNonce) {
      _nonce = 0;
    }
    _nonce += 1;
    return _nonce;
  }

  /// Whether the connection is alive. Set by each transport implementation.
  bool _isAlive = false;
  bool get isAlive => _isAlive;

  @protected
  set isAlive(bool value) => _isAlive = value;

  Communicator();

  void initialize(
      Map<String, GeneratedMessage Function(List<int>)> instanceGenerator,
      {required Transport transport}) {
    _instanceGenerator = instanceGenerator;
    _transport = transport;
  }

  T Function(List<int>) getGenerator<T extends GeneratedMessage>(String type) {
    if (!_instanceGenerator.containsKey(type)) {
      throw Exception(
          'Must set protobuf packet creator before use it. Type: ${(T).toString()}');
    }
    return _instanceGenerator[type] as T Function(List<int>);
  }

  /// Serializes writes so stream transports do not interleave packets.
  Future<void> queuePacket(PacketBase base) {
    final write = _outboundWrite.then((_) => _transport!.writePacket(base));
    _outboundWrite = write.catchError((_) {});
    return write;
  }

  Future<void> send<T extends GeneratedMessage>(T data) async {
    if (isAlive) {
      await queuePacket(PacketBase()
        ..typeName = data.info_.qualifiedMessageName
        ..nonce = nextNonce()
        ..data = data.writeToBuffer());
    }
  }

  @protected
  void cancelPendingRequests() {
    final snapshot = Map<int, _PendingRequest>.from(_pendingRequests);
    _pendingRequests.clear();
    for (final pending in snapshot.values) {
      pending.completeError(
          StateError('connection closed'), StackTrace.current);
    }
  }

  /// Sends [data] as a request and waits for a typed response.
  ///
  /// The remote side must have registered an [addRequestListener] for [Req].
  /// [Res] must be registered in the parser map.
  ///
  /// ```dart
  /// final res = await client.sendRequest<GetUser, UserData>(GetUser()..id = 1);
  /// ```
  Future<Res>
      sendRequest<Req extends GeneratedMessage, Res extends GeneratedMessage>(
          Req data,
          {Duration timeout = const Duration(seconds: 30)}) async {
    if (!isAlive) return Future.error(StateError('not connected'));
    final requestNonce = nextNonce();
    final completer = Completer<Res>();
    final expectedResponseType = Res.toString();
    _pendingRequests[requestNonce] = _PendingRequest(
      expectedTypeName: expectedResponseType,
      complete: (bytes) {
        completer.complete(getGenerator<Res>(expectedResponseType)(bytes));
      },
      completeError: (error, stackTrace) {
        completer.completeError(error, stackTrace);
      },
    );
    await queuePacket(PacketBase()
          ..typeName = data.info_.qualifiedMessageName
          ..nonce = requestNonce
          ..data = data.writeToBuffer())
        .catchError((error, stackTrace) {
      _pendingRequests.remove(requestNonce);
      completer.completeError(error, stackTrace);
    });
    return completer.future.timeout(timeout, onTimeout: () {
      _pendingRequests.remove(requestNonce);
      throw TimeoutException(
          'sendRequest timeout for nonce $requestNonce', timeout);
    });
  }

  /// Registers a request handler for [Req] that returns [Res].
  ///
  /// When a [Req] packet arrives the handler is called and the returned [Res]
  /// is automatically sent back to the caller.
  ///
  /// ```dart
  /// server.addRequestListener<GetUser, UserData>((req) async {
  ///   return UserData()..name = db.getUser(req.id).name;
  /// });
  /// ```
  void addRequestListener<Req extends GeneratedMessage,
      Res extends GeneratedMessage>(Future<Res> Function(Req) handler) {
    final reqType = Req.toString();
    if (_handlerDic.containsKey(reqType)) {
      throw StateError(
          'Type $reqType is already registered with addListener and cannot also use addRequestListener.');
    }
    _requestHandlerDic[reqType] = (List<int> bytes, int requestNonce) async {
      final req = getGenerator<Req>(reqType)(bytes);
      final res = await handler(req);
      if (isAlive) {
        await queuePacket(PacketBase()
          ..typeName = res.info_.qualifiedMessageName
          ..nonce = nextNonce()
          ..responseNonce = requestNonce
          ..data = res.writeToBuffer());
      }
    };
  }

  void onReceivedData(String typeName, List<int> data,
      {int incomingNonce = 0, int responseNonce = 0}) {
    if (responseNonce > 0) {
      final pending = _pendingRequests.remove(responseNonce);
      if (pending == null) return;
      if (typeName != pending.expectedTypeName) {
        pending.completeError(
          StateError(
              'Response type mismatch for nonce $responseNonce: expected ${pending.expectedTypeName}, got $typeName'),
          StackTrace.current,
        );
        return;
      }
      pending.complete(data);
      return;
    }
    if (_requestHandlerDic.containsKey(typeName)) {
      _requestHandlerDic[typeName]!(data, incomingNonce);
      return;
    }
    if (_handlerDic.containsKey(typeName)) {
      _handlerDic[typeName]?.onMessage(data);
    }
  }

  void addListener<T extends GeneratedMessage>(void Function(T) listener) {
    var type = T.toString();
    if (_requestHandlerDic.containsKey(type)) {
      throw StateError(
          'Type $type is already registered with addRequestListener and cannot also use addListener.');
    }
    if (!_handlerDic.containsKey(type)) {
      _handlerDic[type] = DataHandler<T>(getGenerator(type));
    }
    var handler = _handlerDic[type] as DataHandler<T>;
    handler.addListener(listener);
  }

  void removeListener<T extends GeneratedMessage>(void Function(T) listener) {
    var type = T.toString();
    if (_handlerDic.containsKey(type)) {
      var handler = _handlerDic[type] as DataHandler<T>;
      handler.removeListener(listener);
    }
  }
}

abstract class IDataHandler {
  void onMessage(List<int> data);
}

class DataHandler<T extends GeneratedMessage> implements IDataHandler {
  T Function(List<int>) _generator;
  List<void Function(T)> _listeners = [];

  DataHandler(this._generator);

  @override
  void onMessage(List<int> data) {
    for (var listener in _listeners) {
      listener.call(_generator(data));
    }
  }

  void addListener(void Function(T) handler) {
    removeListener(handler); // 중복 리스너 불허
    _listeners.add(handler);
  }

  void removeListener(void Function(T) handler) {
    _listeners.remove(handler);
  }
}

class _PendingRequest {
  final String expectedTypeName;
  final void Function(List<int>) complete;
  final void Function(Object, StackTrace) completeError;

  _PendingRequest({
    required this.expectedTypeName,
    required this.complete,
    required this.completeError,
  });
}