comunicmobile/lib/helpers/websocket_helper.dart

import 'dart:async';
import 'dart:convert';

import 'package:comunic/helpers/comments_helper.dart';
import 'package:comunic/helpers/conversations_helper.dart';
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;

  static int _counter = 0;

  static final _requests = Map<String, Completer<dynamic>>();

  /// 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");

        // Clear Futures queue
        _requests.clear();

        EventsHelper.emit(WSClosedEvent());
      },
    );
  }

  /// Send a new message
  ///
  /// This method might throw an [Exception] in case of failure
  static Future<dynamic> sendMessage(String title, dynamic data) {
    if (!isConnected())
      throw Exception("WS: Trying to send message but websocket is closed!");

    final completer = Completer();

    final id = "freq-${_counter++}";

    final msg = WsMessage(id: id, title: title, data: data).toJSON();

    print("WS Send message: $msg");

    _ws.sink.add(msg);

    _requests[id] = completer;
    return completer.future;
  }

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

      if (!msg.hasId)
        _processUnattendedMessage(msg);
      else
        _respondRequests(msg);
    } catch (e, stack) {
      print("WS could not process message: $e");
      print(stack);
    }
  }

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

      // New number of unread conversations
      case "number_unread_conversations":
        EventsHelper.emit(NewNumberUnreadConversations(msg.data));
        break;

      // New comment
      case "new_comment":
        EventsHelper.emit(
            NewCommentEvent(CommentsHelper.apiToComment(msg.data)));
        break;

      // Updated comment
      case "comment_updated":
        EventsHelper.emit(
            UpdatedCommentEvent(CommentsHelper.apiToComment(msg.data)));
        break;

      // Deleted comment
      case "comment_deleted":
        EventsHelper.emit(DeletedCommentEvent(msg.data));
        break;

      // Created new conversation message
      case "new_conv_message":
        EventsHelper.emit(NewConversationMessageEvent(
            ConversationsHelper.apiToConversationMessage(msg.data)));
        break;

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

  /// Process responses to requests
  static _respondRequests(WsMessage msg) {
    if (!_requests.containsKey(msg.id))
      throw Exception(
          "Could not find request ${msg.id} in the requests queue!");

    final completer = _requests.remove(msg.id);

    // Handles errors
    if (msg.title != "success") {
      completer.completeError(Exception("Could not process request!"));
      return;
    }

    completer.complete(msg.data);
  }
}

/// Helper function
Future<dynamic> ws(String title, dynamic data) =>
    WebSocketHelper.sendMessage(title, data);