using System.Net;
using System.Net.Sockets;
using System.Text;
using NATS.Server.LeafNodes;
using NATS.Server.Subscriptions;

namespace NATS.Server.Tests;

public class LeafAdvancedSemanticsTests
{
    [Fact]
    public async Task Leaf_loop_marker_blocks_reinjected_message_and_account_mapping_routes_to_expected_account()
    {
        const string serverId = "S1";
        var marked = LeafLoopDetector.Mark("orders.created", serverId);
        LeafLoopDetector.IsLooped(marked, serverId).ShouldBeTrue();
        LeafLoopDetector.IsLooped(marked, "S2").ShouldBeFalse();
        LeafLoopDetector.TryUnmark(marked, out var unmarked).ShouldBeTrue();
        unmarked.ShouldBe("orders.created");

        using var listener = new TcpListener(IPAddress.Loopback, 0);
        listener.Start();
        var port = ((IPEndPoint)listener.LocalEndpoint).Port;

        using var remoteSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
        await remoteSocket.ConnectAsync(IPAddress.Loopback, port);
        using var leafSocket = await listener.AcceptSocketAsync();
        await using var leaf = new LeafConnection(leafSocket);

        using var timeout = new CancellationTokenSource(TimeSpan.FromSeconds(5));
        var handshakeTask = leaf.PerformOutboundHandshakeAsync("LOCAL", timeout.Token);
        (await ReadLineAsync(remoteSocket, timeout.Token)).ShouldBe("LEAF LOCAL");
        await WriteLineAsync(remoteSocket, "LEAF REMOTE", timeout.Token);
        await handshakeTask;

        var received = new TaskCompletionSource<RemoteSubscription>(TaskCreationOptions.RunContinuationsAsynchronously);
        leaf.RemoteSubscriptionReceived = sub =>
        {
            received.TrySetResult(sub);
            return Task.CompletedTask;
        };
        leaf.StartLoop(timeout.Token);

        await WriteLineAsync(remoteSocket, "LS+ ACC_A leaf.>", timeout.Token);
        var lsPlus = await received.Task.WaitAsync(timeout.Token);
        lsPlus.Account.ShouldBe("ACC_A");
        lsPlus.Subject.ShouldBe("leaf.>");
    }

    private static async Task<string> ReadLineAsync(Socket socket, CancellationToken ct)
    {
        var bytes = new List<byte>(64);
        var single = new byte[1];
        while (true)
        {
            var read = await socket.ReceiveAsync(single, SocketFlags.None, ct);
            if (read == 0)
                break;
            if (single[0] == (byte)'\n')
                break;
            if (single[0] != (byte)'\r')
                bytes.Add(single[0]);
        }

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

    private static Task WriteLineAsync(Socket socket, string line, CancellationToken ct)
        => socket.SendAsync(Encoding.ASCII.GetBytes($"{line}\r\n"), SocketFlags.None, ct).AsTask();
}
