Chat Clearing on Login Fix

Problem

Lobby chat was not being cleared when users logged back in, causing old messages to persist across login sessions.

Root Cause Analysis

Issue 1: Display-Only Clearing

The original implementation only cleared the UI display variables:

_chatInText = "";
_chatOutText = "";
_lastChatCount = 0;

However, when RefreshChat() was called after data loading, it would repopulate the display with existing messages from the LobbyChatService, effectively undoing the clear.

Issue 2: Wrong Clearing Method

The code was using display-level clearing instead of service-level clearing:

  • Display clearing: Clears only what the user sees
  • Service clearing: Clears the user’s personal chat view permanently

Solution Implemented

Fixed LoadUserData Method

private async Task LoadUserData()
{
    // Clear chat display when loading user data (login/refresh)
    _chatInText = "";
    _chatOutText = "";
    _lastChatCount = 0;
    _scrollPending = false;
    _dataLoaded = false;
    
    // Get current user ID and admin status
    var user = HttpContextAccessor.HttpContext?.User;
    var rawUid = user?.FindFirst("uid")?.Value;
    _isAdmin = user?.IsInRole("Admin") ?? false;
    
    if (int.TryParse(rawUid, out var userId))
    {
        _currentUserId = userId;
        
        // Clear user's personal chat view to ensure fresh start on login
        LobbyChatSvc.ClearChatForUser(userId);
        
        // Load user groups
        try
        {
            _userGroups = await Auth.GetUserGroupsAsync(userId);
        }
        catch
        {
            _userGroups = new List<Drafts.Data.Group>();
        }
    }
    
    _dataLoaded = true;
    
    // Refresh chat after data is loaded to apply proper filtering
    RefreshChat();
    await InvokeAsync(StateHasChanged);
}

Key Changes

1. Proper Service-Level Clearing

  • Before: Only cleared display variables
  • After: Uses LobbyChatSvc.ClearChatForUser(userId) to clear the user’s personal chat view

2. Correct Execution Order

  • Step 1: Get user ID
  • Step 2: Clear user’s chat view in service
  • Step 3: Load user groups
  • Step 4: Refresh chat with proper filtering

3. Persistent Clearing

The ClearChatForUser method adds all current message indexes to the user’s deleted messages set, ensuring they won’t appear in future RefreshChat() calls.

How ClearChatForUser Works

public void ClearChatForUser(int userId)
{
    lock (_lock)
    {
        var allMessageIndexes = _messages.Select(m => m.MessageIndex).ToHashSet();
        _userDeletedMessages[userId] = allMessageIndexes;
    }

    ChatUpdated?.Invoke();
}

This method:

  1. Gets all current message indexes from the chat service
  2. Adds them to user’s deleted set to hide all messages
  3. Triggers chat update to refresh UI

Expected Behavior After Fix

Login Process:

  1. User logs in → LoadUserData() called
  2. Display cleared → _chatInText, _chatOutText reset
  3. User ID obtained → Current user identified
  4. Service chat cleared → ClearChatForUser() hides all messages
  5. Groups loaded → User’s group memberships retrieved
  6. Chat refreshed → Only new messages after login appear

User Experience:

  • Fresh chat start on every login ✅
  • No old message persistence ✅
  • Proper group filtering maintained ✅
  • Loading state prevents flicker ✅

Testing Verification

Test Scenario:

  1. User logs in → Chat should be empty
  2. Messages sent → Appear in chat
  3. User logs out → Messages persist in service
  4. User logs back in → Chat should be empty again
  5. New messages → Only new messages appear

Expected Results:

  • ✅ Chat cleared on login
  • ✅ No old messages visible after login
  • ✅ New messages appear correctly
  • ✅ Group filtering still works

Technical Benefits

1. Proper State Management

  • Service-level clearing ensures persistence
  • User-specific clearing doesn’t affect other users
  • Message index tracking prevents message re-appearance

2. Improved User Experience

  • Clean login experience - no confusing old messages
  • Predictable behavior - same result every time
  • Privacy maintained - users don’t see previous session messages

3. System Stability

  • Thread-safe operations with proper locking
  • Memory efficient - doesn’t delete actual messages
  • Scalable - works with multiple concurrent users

Files Modified

  1. Components/LobbyChat.razor
    • Fixed LoadUserData() method
    • Added proper service-level chat clearing
    • Maintained correct execution order

Status: ✅ COMPLETE

The chat clearing issue has been resolved. Users will now see a clean, empty chat interface when they log back in, with only new messages appearing after login.