import 'dart:io';
import 'dart:typed_data';

import 'package:flutter_test/flutter_test.dart';

import 'package:dmc_app/transport/link_transport.dart';
import 'package:dmc_app/transport/udp/udp_transport.dart';

void main() {
  // Port 0 laesst das Betriebssystem einen freien Port waehlen, damit die
  // Tests nicht mit einer echten mLRS-Bruecke oder parallelen Testlaeufen
  // um Port 14550 konkurrieren.
  Future<UdpTransport> openTransport({String? host}) async {
    final transport = UdpTransport(
      getHost: () async => host,
      getPort: () async => 0,
    );
    await transport.connect();
    return transport;
  }

  test('connect() bindet einen lokalen Port und meldet connected', () async {
    final transport = await openTransport();
    final states = <LinkState>[];
    transport.state.listen(states.add);

    expect(transport.currentState, LinkState.connected);
    expect(transport.boundPort, isNotNull);
    expect(transport.boundPort, greaterThan(0));

    transport.dispose();
  });

  test('eingehende Pakete kommen ueber incoming an und lernen die Gegenstelle',
      () async {
    final transport = await openTransport();
    final sender = await RawDatagramSocket.bind(InternetAddress.loopbackIPv4, 0);

    final received = <Uint8List>[];
    transport.incoming.listen(received.add);

    sender.send(
      Uint8List.fromList([1, 2, 3]),
      InternetAddress.loopbackIPv4,
      transport.boundPort!,
    );
    await Future<void>.delayed(const Duration(milliseconds: 50));

    expect(received, [
      Uint8List.fromList([1, 2, 3]),
    ]);
    expect(transport.peerDescription, contains(sender.port.toString()));

    sender.close();
    transport.dispose();
  });

  test('send() ohne bekannte Gegenstelle wirft LinkConnectException', () async {
    final transport = await openTransport();

    expect(
      () => transport.send(Uint8List.fromList([1])),
      throwsA(isA<LinkConnectException>()),
    );

    transport.dispose();
  });

  test('send() schickt Bytes an die gelernte Gegenstelle', () async {
    final transport = await openTransport();
    final peer = await RawDatagramSocket.bind(InternetAddress.loopbackIPv4, 0);

    // Erst "sprechen" lassen, damit der Transport die Gegenstelle lernt
    // (Doku Kommunikationsschicht Abschnitt 3: "Gegenstelle aus dem Verkehr
    // lernen").
    peer.send(
      Uint8List.fromList([9]),
      InternetAddress.loopbackIPv4,
      transport.boundPort!,
    );
    await Future<void>.delayed(const Duration(milliseconds: 50));

    final receivedByPeer = <Uint8List>[];
    peer.listen((event) {
      if (event == RawSocketEvent.read) {
        final datagram = peer.receive();
        if (datagram != null) receivedByPeer.add(datagram.data);
      }
    });

    await transport.send(Uint8List.fromList([7, 7, 7]));
    await Future<void>.delayed(const Duration(milliseconds: 50));

    expect(receivedByPeer, [
      Uint8List.fromList([7, 7, 7]),
    ]);

    peer.close();
    transport.dispose();
  });

  test('disconnect() setzt LinkState.disconnected', () async {
    final transport = await openTransport();

    await transport.disconnect();

    expect(transport.currentState, LinkState.disconnected);
    expect(transport.boundPort, isNull);

    transport.dispose();
  });

  test('weicht auf einen fluechtigen Port aus, wenn der konfigurierte belegt ist',
      () async {
    final occupied = await RawDatagramSocket.bind(InternetAddress.anyIPv4, 0);
    final transport = UdpTransport(
      getHost: () async => null,
      getPort: () async => occupied.port,
    );

    await transport.connect();

    expect(transport.currentState, LinkState.connected);
    expect(transport.boundPort, isNot(occupied.port));
    expect(transport.lastErrorMessage, contains('belegt'));

    occupied.close();
    transport.dispose();
  });

  test('konfigurierte Host-Vorgabe wird als initiale Gegenstelle uebernommen',
      () async {
    final transport = UdpTransport(
      getHost: () async => '127.0.0.1',
      getPort: () async => 0,
    );
    await transport.connect();

    expect(transport.peerDescription, isNotNull);
    expect(transport.peerDescription, startsWith('127.0.0.1'));

    transport.dispose();
  });
}