import 'dart:async';

import 'package:connectivity_plus/connectivity_plus.dart';
import 'package:flutter/widgets.dart';

import '../session/session.dart';

/// 监听网络切换与应用恢复，触发 IM 极速重连。
class ImLifecycle with WidgetsBindingObserver {
  ImLifecycle(this.session);
  final SessionStore session;
  StreamSubscription<List<ConnectivityResult>>? _netSub;
  List<ConnectivityResult> _lastNet = const [];

  void start() {
    WidgetsBinding.instance.addObserver(this);
    _netSub = Connectivity().onConnectivityChanged.listen(_onNet);
    Connectivity().checkConnectivity().then((r) => _lastNet = r);
  }

  void stop() {
    WidgetsBinding.instance.removeObserver(this);
    _netSub?.cancel();
    _netSub = null;
  }

  void _onNet(List<ConnectivityResult> next) {
    final wasOffline = _lastNet.every((e) => e == ConnectivityResult.none);
    final nowOnline = next.any((e) => e != ConnectivityResult.none);
    _lastNet = next;
    if (wasOffline && nowOnline && session.signedIn) {
      unawaited(session.connectIm(force: true));
    }
  }

  @override
  void didChangeAppLifecycleState(AppLifecycleState state) {
    if (state == AppLifecycleState.resumed && session.signedIn) {
      unawaited(session.connectIm(force: true));
    }
  }
}