the-cycle/src/Prospect.Server.Api/Hubs/SignalRConnectionRegistry.cs

using System.Collections.Concurrent;

namespace Prospect.Server.Api.Hubs;

// Maps players to their live SignalR connection so server-initiated messages (e.g. the
// matchmaking-success "travel to match" signal) can target a single player instead of being
// broadcast to everyone. The client's SignalR URL carries a `uid` query param (added by
// GetSignalRConnection); CycleHub records it on connect.
public class SignalRConnectionRegistry
{
    private readonly ConcurrentDictionary<string, string> _userToConn = new();
    private readonly ConcurrentDictionary<string, string> _connToUser = new();

    public void Add(string userId, string connectionId)
    {
        if (string.IsNullOrEmpty(userId)) return;
        _userToConn[userId] = connectionId;
        _connToUser[connectionId] = userId;
    }

    public void Remove(string connectionId)
    {
        if (_connToUser.TryRemove(connectionId, out var userId))
            _userToConn.TryRemove(userId, out _);
    }

    public string? GetConnection(string userId)
        => _userToConn.TryGetValue(userId, out var c) ? c : null;
}