#2 Support to receive chat messages

lib/src/connect/meeting/main_websocket/chat/chat.dart

@@ -1,3 +1,6 @@
+import 'dart:async';
+
+import 'package:bbb_app/src/connect/meeting/main_websocket/chat/message.dart';
 import 'package:bbb_app/src/connect/meeting/main_websocket/module.dart';
 import 'package:flutter/widgets.dart';
 
@@ -6,27 +9,71 @@ class ChatModule extends Module {
   /// The default chat ID of the main public group chat.
   static const String defaultChatID = "MAIN-PUBLIC-GROUP-CHAT";
 
+  /// Topic of chat messages to subscribe to.
+  static const String _groupChatMessageTopic = "group-chat-msg";
+
+  /// Controller publishing chat messages.
+  StreamController<ChatMessage> _chatMessageController =
+      StreamController.broadcast();
+
+  /// Messages already received.
+  List<ChatMessage> _messages = [];
+
   ChatModule(messageSender) : super(messageSender);
 
   /// Send a chat message.
   Future<void> sendGroupChatMsg({
     String chatID = defaultChatID,
     @required String internUserID,
     @required String message,
-  }) async {}
+  }) async {
+    // TODO
+  }
 
   @override
   void processMessage(Map<String, dynamic> msg) {
-    // TODO: implement processMessage
+    final String method = msg["msg"];
+
+    if (method == "added") {
+      String collectionName = msg["collection"];
+
+      if (collectionName == "group-chat-msg") {
+        Map<String, dynamic> fields = msg["fields"];
+
+        String chatID = fields["chatId"];
+        int timestamp = fields["timestamp"];
+        String senderID = fields["sender"];
+        String content = fields["message"];
+
+        ChatMessage message = ChatMessage(
+          chatID: chatID,
+          senderID: senderID,
+          content: content,
+          timestamp: new DateTime.fromMillisecondsSinceEpoch(timestamp),
+        );
+
+        print(
+            "Incoming message: ${message.content} (From ${message.timestamp.toString()}");
+
+        _messages.add(message);
+        _chatMessageController.add(message);
+      }
+    }
   }
 
   @override
   void onConnected() {
-    // TODO: Subscribe to the chat topic
+    subscribe(_groupChatMessageTopic);
   }
 
   @override
   Future<void> onDisconnect() async {
     // Do nothing
   }
+
+  /// Get a stream of incoming messages.
+  Stream<ChatMessage> get messageStream => _chatMessageController.stream;
+
+  /// Get already received messages.
+  List<ChatMessage> get messages => _messages;
 }

lib/src/connect/meeting/main_websocket/chat/message.dart

@@ -0,0 +1,32 @@
+/// A chat message representation.
+class ChatMessage {
+  /// ID of the chat.
+  String _chatID;
+
+  /// Intern user ID of the sender.
+  String _senderID;
+
+  /// Content of the message.
+  String _content;
+
+  /// Timestamp of the message.
+  DateTime _timestamp;
+
+  ChatMessage({
+    String chatID,
+    String senderID,
+    String content,
+    DateTime timestamp,
+  })  : this._chatID = chatID,
+        this._senderID = senderID,
+        this._content = content,
+        this._timestamp = timestamp;
+
+  String get content => _content;
+
+  String get senderID => _senderID;
+
+  String get chatID => _chatID;
+
+  DateTime get timestamp => _timestamp;
+}