fcs/lib/helpers/network_connectivity.dart

import 'dart:async';
import 'dart:io';

import 'package:fcs/config.dart';
import 'package:flutter/foundation.dart';
import 'package:logging/logging.dart';
import 'package:connectivity_plus/connectivity_plus.dart';

import 'api_helper.dart';

enum ConnectivityStatus { none, online }

class NetworkConnectivity {
  final log = Logger('NetworkConnectivity');

  static final NetworkConnectivity instance = NetworkConnectivity._internal();
  static String _hostName = "";
  static ConnectivityStatus? _currentResult;

  NetworkConnectivity._internal() {
    _initialise();
    var uri = Uri.parse(Config.instance.apiURL);
    _hostName = uri.host;
    log.info("host name:$_hostName");
  }

  Connectivity connectivity = Connectivity();

  final StreamController<ConnectivityStatus> _controller =
      StreamController.broadcast();

  Stream<ConnectivityStatus> get statusStream => _controller.stream;

  Timer? _checkTimer;
  void _initialise() async {
    await _checkStatus(await connectivity.checkConnectivity());

    connectivity.onConnectivityChanged.listen((result) {
      if (_currentResult == null) {
        _checkStatus(result);
      } else {
        _checkTimer?.cancel();
        _checkTimer = Timer(const Duration(seconds: 7), () {
          _checkTimer?.cancel();
          _checkStatus(result);
        });
      }
    });
  }

  Future<void> _checkStatus(List<ConnectivityResult> result) async {
    bool isOnline = false;
    if (!result.contains(ConnectivityResult.none) && !kIsWeb) {
      try {
        final hostNameLookup = await InternetAddress.lookup(_hostName);
        if (hostNameLookup.isNotEmpty &&
            hostNameLookup[0].rawAddress.isNotEmpty) {
          if (await checkHeartbeat()) {
            isOnline = true;
          }
        } else {
          isOnline = false;
        }
        isOnline = true;
      } on Exception catch (_) {
        isOnline = false;
      }
    }
    _addStream(isOnline || kIsWeb
        ? ConnectivityStatus.online
        : ConnectivityStatus.none);
  }

  Future<bool> checkHeartbeat() async {
    try {
      var result = await requestAPI("/hb", "GET");
      var status = result["status"];
      if (status != null && status != "") {
        return true;
      }
    } catch (e) {
      return false;
    }
    return false;
  }

  void disposeStream() => _controller.close();

  _addStream(ConnectivityStatus? updateResult) async {
    if (updateResult == null) return;
    if (updateResult == _currentResult) return;
    _currentResult = updateResult;

    if (!_controller.isClosed) {
      log.info("sink: $_currentResult");
      _controller.sink.add(_currentResult!);
    }
  }
}