using System.IO.Pipes;
using System.Text;
using RioJoy.Core.Feedback;
using Xunit;

namespace RioJoy.Core.Tests.Feedback;

public class FeedbackPipeServerTests
{
    private static string UniqueName() => $"riojoy-fb-test-{Guid.NewGuid():N}";

    private static byte[] Latin1(string s) => Encoding.GetEncoding(28591).GetBytes(s);

    /// <summary>Collector whose Count/Snapshot are safe against the reader threads.</summary>
    private sealed class Lines
    {
        private readonly List<string> _lines = new();

        public void Add(string line)
        {
            lock (_lines) _lines.Add(line);
        }

        public int Count
        {
            get { lock (_lines) return _lines.Count; }
        }

        public string[] Snapshot()
        {
            lock (_lines) return _lines.ToArray();
        }
    }

    // The accept loop arms asynchronously after Start; retry until it listens.
    private static NamedPipeClientStream Connect(string name, int timeoutMs = 5000)
    {
        var deadline = DateTime.UtcNow.AddMilliseconds(timeoutMs);
        while (true)
        {
            var client = new NamedPipeClientStream(".", name, PipeDirection.Out);
            try
            {
                client.Connect(200);
                return client;
            }
            catch (Exception ex) when (ex is IOException or TimeoutException)
            {
                client.Dispose();
                Assert.True(DateTime.UtcNow < deadline, $"could not connect to {name}: {ex.Message}");
                Thread.Sleep(20);
            }
        }
    }

    private static void Send(NamedPipeClientStream client, string text)
    {
        byte[] data = Latin1(text);
        client.Write(data, 0, data.Length);
        client.Flush();
    }

    [Fact]
    public async Task Lines_AreDeliveredInOrder()
    {
        string name = UniqueName();
        var lines = new Lines();
        using var server = new FeedbackPipeServer(name, lines.Add);
        server.Start();

        using NamedPipeClientStream client = Connect(name);
        Send(client, "lamp 1 dim\r\nplasma clear\n");

        await FeedbackWait.For(() => lines.Count >= 2);
        Assert.Equal(new[] { "lamp 1 dim", "plasma clear" }, lines.Snapshot());
    }

    [Fact]
    public async Task Line_SplitAcrossWrites_Reassembles()
    {
        string name = UniqueName();
        var lines = new Lines();
        using var server = new FeedbackPipeServer(name, lines.Add);
        server.Start();

        using NamedPipeClientStream client = Connect(name);
        Send(client, "lamp 0x12 fa");
        Send(client, "st bright\n");

        await FeedbackWait.For(() => lines.Count >= 1);
        Assert.Equal("lamp 0x12 fast bright", Assert.Single(lines.Snapshot()));
    }

    [Fact]
    public async Task TwoConcurrentClients_BothDeliver()
    {
        string name = UniqueName();
        var lines = new Lines();
        using var server = new FeedbackPipeServer(name, lines.Add);
        server.Start();

        using NamedPipeClientStream a = Connect(name);
        using NamedPipeClientStream b = Connect(name); // second instance while A stays connected
        Send(a, "lamp 1 dim\n");
        Send(b, "lamp 2 off\n");

        await FeedbackWait.For(() => lines.Count >= 2);
        Assert.Equal(new[] { "lamp 1 dim", "lamp 2 off" }, lines.Snapshot().OrderBy(l => l));
    }

    [Fact]
    public async Task ClientDisconnect_ThenReconnect_Works()
    {
        string name = UniqueName();
        var lines = new Lines();
        using var server = new FeedbackPipeServer(name, lines.Add);
        server.Start();

        using (NamedPipeClientStream first = Connect(name))
            Send(first, "lamp 1 dim\n");
        await FeedbackWait.For(() => lines.Count >= 1);

        using NamedPipeClientStream second = Connect(name); // server re-arms after the EOF
        Send(second, "lamp 2 off\n");
        await FeedbackWait.For(() => lines.Count >= 2);
    }

    [Fact]
    public async Task ThrowingLineHandler_DoesNotKillTheConnection()
    {
        string name = UniqueName();
        var lines = new Lines();
        using var server = new FeedbackPipeServer(name, line =>
        {
            if (line.Contains("boom"))
                throw new InvalidOperationException("handler bug");
            lines.Add(line);
        });
        server.Start();

        using NamedPipeClientStream client = Connect(name);
        Send(client, "boom\nlamp 1 dim\n");

        await FeedbackWait.For(() => lines.Count >= 1); // the good line still lands
        Assert.Equal("lamp 1 dim", Assert.Single(lines.Snapshot()));
    }

    [Fact]
    public void Dispose_UnblocksThePendingAccept()
    {
        var server = new FeedbackPipeServer(UniqueName(), _ => { });
        server.Start();
        Thread.Sleep(100);   // let the accept loop park in WaitForConnection
        server.Dispose();    // must not hang on the pending accept (poke-connect)
    }
}