using System;
using System.IO;
using System.IO.Pipes;
using Xunit;
using ytLive.Helpers;
using ytLive.Services.Audio;

namespace ytLive.Tests;

/// <summary>
/// 2026-11-06 crash: two LlamaCasty instances on one machine, the second one died on the Go Live click with
/// <c>IOException: All pipe instances are busy</c>. The audio pipe server allows exactly ONE instance and the
/// name was a shared constant, so this pins both halves of the fix — the collision is real, and each dev
/// instance now gets its own name.
/// </summary>
public sealed class AudioPipeInstanceTests : IDisposable
{
    private readonly string? _original = Environment.GetEnvironmentVariable(InstanceProfile.InstanceVariable);

    public void Dispose() => Environment.SetEnvironmentVariable(InstanceProfile.InstanceVariable, _original);

    [Fact]
    public void ASecondServerOnTheSameName_CannotStart_WhichIsWhatKilledTheSecondInstance()
    {
        var name = $"ytllive_test_{Guid.NewGuid():N}";
        using var first = new NamedPipeServerStream(name, PipeDirection.Out, 1, PipeTransmissionMode.Byte, PipeOptions.Asynchronous);

        var error = Record.Exception(() =>
            new NamedPipeServerStream(name, PipeDirection.Out, 1, PipeTransmissionMode.Byte, PipeOptions.Asynchronous));

        Assert.NotNull(error);
        Assert.IsType<IOException>(error);
    }

    [Fact]
    public void ADevInstanceServesItsOwnPipeName()
    {
        Environment.SetEnvironmentVariable(InstanceProfile.InstanceVariable, null);
#if DEBUG
        // No claimed id (launched from the IDE) must still never collide with the Release build's pipe.
        var unnamed = InstanceProfile.AudioPipeName("ytllive_audio");
        Assert.StartsWith("ytllive_audio_pid", unnamed);
        Assert.Equal(unnamed, InstanceProfile.AudioPipeName("ytllive_audio"));
#else
        Assert.Equal("ytllive_audio", InstanceProfile.AudioPipeName("ytllive_audio"));
#endif

        Environment.SetEnvironmentVariable(InstanceProfile.InstanceVariable, "2");
        Assert.Equal("ytllive_audio_2", InstanceProfile.AudioPipeName("ytllive_audio"));

        Environment.SetEnvironmentVariable(InstanceProfile.InstanceVariable, "qa");
        Assert.Equal("ytllive_audio_qa", InstanceProfile.AudioPipeName("ytllive_audio"));
        Assert.NotEqual(InstanceProfile.AudioPipeName("ytllive_audio"),
            WithInstance("3", () => InstanceProfile.AudioPipeName("ytllive_audio")));
    }

    private static string WithInstance(string id, Func<string> read)
    {
        var original = Environment.GetEnvironmentVariable(InstanceProfile.InstanceVariable);
        try
        {
            Environment.SetEnvironmentVariable(InstanceProfile.InstanceVariable, id);
            return read();
        }
        finally
        {
            Environment.SetEnvironmentVariable(InstanceProfile.InstanceVariable, original);
        }
    }

    [Fact]
    public void TheMixerRefusesAStartedSecondTime_ButAWriterOnATakenNameThrows()
    {
        // The mixer's own guard is idempotent (StartLive twice is a no-op); the exception came from the
        // pipe itself, which the VM now catches and reports instead of letting it end the process.
        var name = $"ytllive_test_{Guid.NewGuid():N}";
        var writer = new NamedPipeAudioWriter();
        writer.Start(name);
        try
        {
            var second = Record.Exception(() => new NamedPipeAudioWriter().Start(name));
            Assert.IsType<IOException>(second);
        }
        finally
        {
            writer.Stop();
        }
    }
}