using System.Diagnostics;
using System.Net.Sockets;
using System.Text;

namespace BSO.Launcher;

/// <summary>
/// Fragt einen BSO-Server direkt ab wie die Mod (wie ServerBrowser.cs bei MSCO): Info senden, InfoReply lesen. Liefert die
/// Laufzeit (Ping) und den aktuellen Stand (Spieler) - die Liste der Website ist bis zu einer Minute alt.
/// Paketaufbau: [int Laenge][byte Typ][Daten], Info = 9, InfoReply = 10 (string Name, string Version, int Spieler, int max).
/// </summary>
public static class ServerPing
{
    public sealed record Info(int Ping, string Name, string Version, int Players, int MaxPlayers);

    public static async Task<Info?> Query(string host, int port, int timeoutMs = 2500)
    {
        try
        {
            using var tcp = new TcpClient { NoDelay = true };
            using var cts = new CancellationTokenSource(timeoutMs);
            var clock = Stopwatch.StartNew();
            await tcp.ConnectAsync(host, port, cts.Token);
            var stream = tcp.GetStream();
            await stream.WriteAsync(new byte[] { 1, 0, 0, 0, 9 }, cts.Token);
            var head = new byte[5];
            await stream.ReadExactlyAsync(head, cts.Token);
            int ping = (int)clock.ElapsedMilliseconds;
            int length = BitConverter.ToInt32(head, 0);
            if (head[4] != 10 || length < 1 || length > 4096) return null;
            var payload = new byte[length - 1];
            await stream.ReadExactlyAsync(payload, cts.Token);
            using var r = new BinaryReader(new MemoryStream(payload), Encoding.UTF8);
            return new Info(ping, r.ReadString(), r.ReadString(), r.ReadInt32(), r.ReadInt32());
        }
        catch { return null; }
    }
}