brass-and-sigil/server/Services/RconManager.cs

namespace BrassAndSigil.Server.Services;

/// <summary>
/// Thin reconnecting wrapper around <see cref="RconClient"/>. The original
/// single-connection-with-no-retry pattern caches a dead client whenever the
/// initial connect happens before MC has opened the RCON port (which is normal --
/// boot takes ~30 s). This manager lazily connects on first use, retries on
/// failure, and drops the client when a send throws so the next call reconnects.
/// </summary>
public sealed class RconManager : IDisposable
{
    private readonly string _host;
    private readonly int _port;
    private readonly string _password;
    private readonly SemaphoreSlim _lock = new(1, 1);
    private RconClient? _client;

    public RconManager(string host, int port, string password)
    {
        _host = host;
        _port = port;
        _password = password;
    }

    public async Task<string> SendCommandAsync(string command, CancellationToken ct = default)
    {
        var client = await EnsureConnectedAsync(ct);
        try
        {
            return await client.SendCommandAsync(command, ct);
        }
        catch
        {
            await DropAsync();
            throw;
        }
    }

    private async Task<RconClient> EnsureConnectedAsync(CancellationToken ct)
    {
        await _lock.WaitAsync(ct);
        try
        {
            if (_client is { Connected: true }) return _client;
            _client?.Dispose();
            _client = new RconClient();
            await _client.ConnectAsync(_host, _port, _password, ct);
            return _client;
        }
        finally
        {
            _lock.Release();
        }
    }

    private async Task DropAsync()
    {
        await _lock.WaitAsync();
        try { _client?.Dispose(); _client = null; }
        finally { _lock.Release(); }
    }

    public void Dispose()
    {
        _client?.Dispose();
        _lock.Dispose();
    }
}