comunicmobile/lib/helpers/websocket_helper.dart

import 'dart:convert';

import 'package:comunic/helpers/events_helper.dart';
import 'package:comunic/models/api_request.dart';
import 'package:comunic/models/config.dart';
import 'package:comunic/models/ws_message.dart';
import 'package:web_socket_channel/web_socket_channel.dart';

/// User web socket helper
///
/// @author Pierre Hubert

class WebSocketHelper {
  static WebSocketChannel _ws;

  /// Check out whether we are currently connected to WebSocket or not
  static bool isConnected() {
    return _ws != null && _ws.closeCode == null;
  }

  /// Get WebSocket access token
  //TODO : Handles the case user tokens were destroyed (auto sign-out user)
  static Future<String> _getWsToken() async =>
      (await APIRequest(uri: "ws/token", needLogin: true).exec())
          .assertOk()
          .getObject()["token"];

  /// Connect to WebSocket
  static connect() async {
    if (isConnected()) return;

    // First, get an access token
    final token = await _getWsToken();

    // Determine WebSocket URI
    final wsURL =
        "${(config().apiServerSecure ? "wss" : "ws")}://${config()
        .apiServerName}${config().apiServerUri}ws?token=$token";
    final wsURI = Uri.parse(wsURL);

    // Connect
    _ws = WebSocketChannel.connect(wsURI);

    _ws.stream.listen(
      // When we got data
          (data) {
        print("WS New data: $data");
        _processMessage(data.toString());
      },

      // Print errors on console
      onError: (e, stack) {
        print("WS error! $e");
        print(stack);
      },

      // Notify when the channel is closed
      onDone: () {
        print("WS Channel closed");
        EventsHelper.emit(WSClosedEvent());
      },
    );
  }

  /// Process incoming message
  static _processMessage(String msgStr) {
    try {
      final msg = WsMessage.fromJSON(jsonDecode(msgStr));

      if (!msg.hasId)
        _processUnattendedMessage(msg);
      else
        throw Exception("Do not know how to process attended message!");
    } catch (e, stack) {
      print("WS could not process message: $e");
      print(stack);
    }
  }

  /// Process an unattended message
  static _processUnattendedMessage(WsMessage msg) {
    switch (msg.title) {
      case "number_notifs":
        EventsHelper.emit(NewNumberNotifsEvent(msg.data));
        break;

      default:
        throw Exception("Unknown message type: ${msg.title}");
    }
  }
}