Register to conversation updates

lib/helpers/conversations_helper.dart

@@ -1,6 +1,7 @@
 import 'package:comunic/helpers/database/conversation_messages_database_helper.dart';
 import 'package:comunic/helpers/database/conversations_database_helper.dart';
 import 'package:comunic/helpers/users_helper.dart';
+import 'package:comunic/helpers/websocket_helper.dart';
 import 'package:comunic/lists/conversation_messages_list.dart';
 import 'package:comunic/lists/conversations_list.dart';
 import 'package:comunic/lists/users_list.dart';
@@ -20,6 +21,8 @@ import 'package:meta/meta.dart';
 enum SendMessageResult { SUCCESS, MESSAGE_REJECTED, FAILED }
 
 class ConversationsHelper {
+  static final _registeredConversations = Map<int, int>();
+
   final ConversationsDatabaseHelper _conversationsDatabaseHelper =
       ConversationsDatabaseHelper();
   final ConversationMessagesDatabaseHelper _conversationMessagesDatabaseHelper =
@@ -356,6 +359,29 @@ class ConversationsHelper {
     return await _conversationMessagesDatabaseHelper.delete(id);
   }
 
+  /// Register a conversation : ask the server to notify about updates to the
+  /// conversation through WebSocket
+  Future<void> registerConversationEvents(int id) async {
+    if (_registeredConversations.containsKey(id))
+      _registeredConversations[id]++;
+    else {
+      _registeredConversations[id] = 1;
+      await ws("\$main/register_conv", {"convID": id});
+    }
+  }
+
+  /// Un-register to conversation update events
+  Future<void> unregisterConversationEvents(int id) async {
+    if (!_registeredConversations.containsKey(id)) return;
+
+    _registeredConversations[id]--;
+
+    if (_registeredConversations[id] <= 0) {
+      _registeredConversations.remove(id);
+      await ws("\$main/unregister_conv", {"convID": id});
+    }
+  }
+
   /// Turn an API response into a ConversationMessage object
   ConversationMessage _apiToConversationMessage({
     @required int conversationID,

lib/ui/screens/conversation_screen.dart

@@ -7,6 +7,7 @@ import 'package:comunic/lists/users_list.dart';
 import 'package:comunic/models/conversation_message.dart';
 import 'package:comunic/models/new_conversation_message.dart';
 import 'package:comunic/ui/tiles/conversation_message_tile.dart';
+import 'package:comunic/ui/widgets/safe_state.dart';
 import 'package:comunic/ui/widgets/scroll_watcher.dart';
 import 'package:comunic/utils/files_utils.dart';
 import 'package:comunic/utils/intl_utils.dart';
@@ -32,7 +33,7 @@ class ConversationScreen extends StatefulWidget {
   State<StatefulWidget> createState() => _ConversationScreenState();
 }
 
-class _ConversationScreenState extends State<ConversationScreen> {
+class _ConversationScreenState extends SafeState<ConversationScreen> {
   //Helpers
   final ConversationsHelper _conversationsHelper = ConversationsHelper();
   final UsersHelper _usersHelper = UsersHelper();
@@ -44,27 +45,19 @@ class _ConversationScreenState extends State<ConversationScreen> {
   bool _isMessageValid = false;
   bool _isSendingMessage = false;
   TextEditingController _textEditingController = TextEditingController();
-  Timer _refreshTime;
   ScrollWatcher _scrollController;
   _OlderMessagesLevel _loadingOlderMessages = _OlderMessagesLevel.NONE;
 
   @override
   void initState() {
     super.initState();
-    _scrollController = ScrollWatcher(onReachBottom: _loadOlderMessages);
+    _init();
   }
 
   @override
-  void didChangeDependencies() {
+  void dispose() {
-    super.didChangeDependencies();
+    super.dispose();
-    _initializeLoading();
+    _deallocate();
-  }
-
-  @override
-  void deactivate() {
-    super.deactivate();
-
-    if (_refreshTime != null) _refreshTime.cancel();
   }
 
   void _setError(ErrorLevel err) => setState(() => _error = err);
@@ -81,14 +74,20 @@ class _ConversationScreenState extends State<ConversationScreen> {
   }
 
   /// Load the first conversations
-  Future<void> _initializeLoading() async {
+  Future<void> _init() async {
+    _scrollController = ScrollWatcher(onReachBottom: _loadOlderMessages);
+
+    // Fetch latest messages
     await _loadMessages(false);
     await _loadMessages(true);
 
-    // Set a timer to regularly update conversation messages
+    await _conversationsHelper
-    if (_refreshTime == null || !_refreshTime.isActive)
+        .registerConversationEvents(widget.conversationID);
-      _refreshTime = Timer.periodic(
+  }
-          Duration(milliseconds: 1500), (t) => _loadMessages(true));
+
+  /// Free resources when this conversation widget is no longer required
+  void _deallocate() {
+    _conversationsHelper.unregisterConversationEvents(widget.conversationID);
   }
 
   /// Load a list of messages