using System.Diagnostics;
using Xunit;
using Xunit.Sdk;

namespace ZB.MOM.WW.OtOpcUa.Driver.AbCip.IntegrationTests;

/// <summary>
///     Shared fixture that starts libplctag's <c>ab_server</c> simulator in the background for
///     the duration of an integration test collection. Binary is expected on PATH; the per-test
///     JSON profile is passed via <c>--config</c>.
/// </summary>
/// <remarks>
///     <para><c>ab_server</c> is a C binary shipped in the same repo as libplctag (see
///     <c>test-data-sources.md</c> §2 and plan decision #99). On a developer workstation it's
///     built once from source and placed on PATH; in CI we intend to publish a prebuilt Windows
///     x64 binary as a GitHub release asset in a follow-up PR so the fixture can download +
///     extract it at setup time. Until then every test in this project is skipped when
///     <c>ab_server</c> is not locatable.</para>
///
///     <para>Per-family JSON profiles (ControlLogix / CompactLogix / Micro800 / GuardLogix)
///     ship under <c>Profiles/</c> and drive the simulator's tag shape — this is where the
///     UDT + Program-scope coverage gap will be filled by the hand-rolled stub in PR 6.</para>
/// </remarks>
public sealed class AbServerFixture : IAsyncLifetime
{
    private Process? _proc;
    public int Port { get; } = 44818;

    public bool IsAvailable { get; private set; }

    public ValueTask InitializeAsync() => InitializeAsync(default);
    public ValueTask DisposeAsync() => DisposeAsync(default);

    public async ValueTask InitializeAsync(CancellationToken cancellationToken)
    {
        if (LocateBinary() is not string binary)
        {
            IsAvailable = false;
            return;
        }
        IsAvailable = true;

        _proc = new Process
        {
            StartInfo = new ProcessStartInfo
            {
                FileName = binary,
                Arguments = $"--port {Port} --plc controllogix",
                RedirectStandardOutput = true,
                RedirectStandardError = true,
                UseShellExecute = false,
                CreateNoWindow = true,
            },
        };
        _proc.Start();

        // Give the server a moment to accept its listen socket before tests try to connect.
        await Task.Delay(500, cancellationToken).ConfigureAwait(false);
    }

    public ValueTask DisposeAsync(CancellationToken cancellationToken)
    {
        try
        {
            if (_proc is { HasExited: false })
            {
                _proc.Kill(entireProcessTree: true);
                _proc.WaitForExit(5_000);
            }
        }
        catch { /* best-effort cleanup */ }
        _proc?.Dispose();
        return ValueTask.CompletedTask;
    }

    /// <summary>
    ///     Locate <c>ab_server</c> on PATH. Returns <c>null</c> when missing — tests that
    ///     depend on it should use <see cref="AbServerFact"/> so CI runs without the binary
    ///     simply skip rather than fail.
    /// </summary>
    public static string? LocateBinary()
    {
        var names = new[] { "ab_server.exe", "ab_server" };
        var path = Environment.GetEnvironmentVariable("PATH") ?? "";
        foreach (var dir in path.Split(Path.PathSeparator))
        {
            foreach (var name in names)
            {
                var candidate = Path.Combine(dir, name);
                if (File.Exists(candidate)) return candidate;
            }
        }
        return null;
    }
}

/// <summary>
///     <c>[Fact]</c>-equivalent that skips when <c>ab_server</c> is not available on PATH.
///     Integration tests use this instead of <c>[Fact]</c> so a developer box without
///     <c>ab_server</c> installed still gets a green run.
/// </summary>
public sealed class AbServerFactAttribute : FactAttribute
{
    public AbServerFactAttribute()
    {
        if (AbServerFixture.LocateBinary() is null)
            Skip = "ab_server not on PATH; install libplctag test binaries to run.";
    }
}