natsdotnet/tests/NATS.Server.Tests/Routes/RouteInfoBroadcastParityBatch4Tests.cs

using System.Net;
using System.Net.Sockets;
using System.Text;
using Microsoft.Extensions.Logging.Abstractions;
using NATS.Server;

namespace NATS.Server.Tests.Routes;

public class RouteInfoBroadcastParityBatch4Tests
{
    [Fact]
    public async Task UpdateServerINFOAndSendINFOToClients_broadcasts_INFO_to_connected_clients()
    {
        var port = GetFreePort();
        using var server = new NatsServer(new NatsOptions { Host = "127.0.0.1", Port = port }, NullLoggerFactory.Instance);
        using var cts = new CancellationTokenSource();
        _ = server.StartAsync(cts.Token);
        await server.WaitForReadyAsync();

        using var socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
        await socket.ConnectAsync(IPAddress.Loopback, port);

        _ = await ReadLineAsync(socket, CancellationToken.None); // initial INFO
        await socket.SendAsync(Encoding.ASCII.GetBytes("CONNECT {}\r\nPING\r\n"), SocketFlags.None);
        _ = await ReadUntilContainsAsync(socket, "PONG", CancellationToken.None);

        server.UpdateServerINFOAndSendINFOToClients();

        var info = await ReadLineAsync(socket, CancellationToken.None);
        info.ShouldStartWith("INFO ");

        await server.ShutdownAsync();
    }

    private static async Task<string> ReadUntilContainsAsync(Socket socket, string token, CancellationToken ct)
    {
        var end = DateTime.UtcNow.AddSeconds(3);
        var builder = new StringBuilder();
        while (DateTime.UtcNow < end)
        {
            var line = await ReadLineAsync(socket, ct);
            if (line.Length == 0)
                continue;

            builder.AppendLine(line);
            if (builder.ToString().Contains(token, StringComparison.Ordinal))
                return builder.ToString();
        }

        return builder.ToString();
    }

    private static async Task<string> ReadLineAsync(Socket socket, CancellationToken ct)
    {
        var buffer = new List<byte>(256);
        var one = new byte[1];
        while (true)
        {
            var n = await socket.ReceiveAsync(one.AsMemory(0, 1), SocketFlags.None, ct);
            if (n == 0)
                break;
            if (one[0] == '\n')
                break;
            if (one[0] != '\r')
                buffer.Add(one[0]);
        }

        return Encoding.ASCII.GetString([.. buffer]);
    }

    private static int GetFreePort()
    {
        var listener = new TcpListener(IPAddress.Loopback, 0);
        listener.Start();
        try
        {
            return ((IPEndPoint)listener.LocalEndpoint).Port;
        }
        finally
        {
            listener.Stop();
        }
    }
}