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. The fixture takes an
///     <see cref="AbServerProfile"/> (see <see cref="KnownProfiles"/>) so each AB family — ControlLogix,
///     CompactLogix, Micro800, GuardLogix — starts the simulator with the right <c>--plc</c>
///     mode + preseed tag set. Binary is expected on PATH; CI resolves that via a job step
///     that downloads the pinned Windows build from libplctag GitHub Releases before
///     <c>dotnet test</c> — see <c>docs/v2/test-data-sources.md §2.CI</c> for the exact step.
/// </summary>
/// <remarks>
///     <para><c>ab_server</c> is a C binary shipped in libplctag's repo (MIT). On developer
///     workstations it's built once from source and placed on PATH; on CI the workflow file
///     fetches a version-pinned prebuilt + stages it. Tests skip (via
///     <see cref="AbServerFactAttribute"/>) when the binary is not on PATH so a fresh clone
///     without the simulator still gets a green unit-test run.</para>
///
///     <para>Per-family profiles live in <see cref="KnownProfiles"/>. When a test wants a
///     specific family, instantiate the fixture with that profile — either via a
///     <see cref="IClassFixture{TFixture}"/> derived type or by constructing directly in a
///     parametric test (the latter is used below for the smoke suite).</para>
/// </remarks>
public sealed class AbServerFixture : IAsyncLifetime
{
    private Process? _proc;

    /// <summary>The profile the simulator was started with. Same instance the driver-side options should use.</summary>
    public AbServerProfile Profile { get; }
    public int Port { get; }
    public bool IsAvailable { get; private set; }

    public AbServerFixture() : this(KnownProfiles.ControlLogix, AbServerProfile.DefaultPort) { }

    public AbServerFixture(AbServerProfile profile) : this(profile, AbServerProfile.DefaultPort) { }

    public AbServerFixture(AbServerProfile profile, int port)
    {
        Profile = profile ?? throw new ArgumentNullException(nameof(profile));
        Port = port;
    }

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

    public async ValueTask InitializeAsync(CancellationToken cancellationToken)
    {
        // Docker-first path: if the operator has the container running (or pointed us at a
        // real PLC via AB_SERVER_ENDPOINT), TCP-probe + skip the spawn. Matches the probe
        // patterns in ModbusSimulatorFixture / Snap7ServerFixture / OpcPlcFixture.
        var endpointOverride = Environment.GetEnvironmentVariable("AB_SERVER_ENDPOINT");
        if (endpointOverride is not null || TcpProbe("127.0.0.1", Port))
        {
            IsAvailable = true;
            await Task.Delay(0, cancellationToken).ConfigureAwait(false);
            return;
        }

        // Fallback: no container + no override — spawn ab_server from PATH (the original
        // native-binary path the existing profile CLI args target).
        if (LocateBinary() is not string binary)
        {
            IsAvailable = false;
            return;
        }
        IsAvailable = true;

        _proc = new Process
        {
            StartInfo = new ProcessStartInfo
            {
                FileName = binary,
                Arguments = Profile.BuildCliArgs(Port),
                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);
    }

    /// <summary>One-shot TCP probe; 500 ms budget so a missing server fails the probe fast.</summary>
    private static bool TcpProbe(string host, int port)
    {
        try
        {
            using var client = new System.Net.Sockets.TcpClient();
            var task = client.ConnectAsync(host, port);
            return task.Wait(TimeSpan.FromMilliseconds(500)) && client.Connected;
        }
        catch { return 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>
    ///     <c>true</c> when the AB CIP integration path has a live target: a Docker-run
    ///     container bound to <c>127.0.0.1:44818</c>, an <c>AB_SERVER_ENDPOINT</c> env
    ///     override, or <c>ab_server</c> on <c>PATH</c> (native spawn fallback).
    /// </summary>
    public static bool IsServerAvailable()
    {
        if (Environment.GetEnvironmentVariable("AB_SERVER_ENDPOINT") is not null) return true;
        if (TcpProbe("127.0.0.1", AbServerProfile.DefaultPort)) return true;
        return LocateBinary() is not null;
    }

    /// <summary>
    ///     Locate <c>ab_server</c> on PATH. Returns <c>null</c> when missing — tests that
    ///     depend on it should use <see cref="AbServerFactAttribute"/> 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 neither the Docker container nor the
///     native binary is available. Accepts: (a) a running listener on
///     <c>localhost:44818</c> (the Dockerized fixture's bind), or (b) <c>ab_server</c> on
///     <c>PATH</c> for the native-spawn fallback, or (c) an explicit
///     <c>AB_SERVER_ENDPOINT</c> env var pointing at a real PLC.
/// </summary>
public sealed class AbServerFactAttribute : FactAttribute
{
    public AbServerFactAttribute()
    {
        if (!AbServerFixture.IsServerAvailable())
            Skip = "ab_server not reachable. Start the Docker container " +
                   "(docker compose -f Docker/docker-compose.yml --profile controllogix up) " +
                   "or install libplctag test binaries.";
    }
}

/// <summary>
///     <c>[Theory]</c>-equivalent with the same availability rules as
///     <see cref="AbServerFactAttribute"/>. Pair with
///     <c>[MemberData(nameof(KnownProfiles.All))]</c>-style providers to run one theory row
///     per family.
/// </summary>
public sealed class AbServerTheoryAttribute : TheoryAttribute
{
    public AbServerTheoryAttribute()
    {
        if (!AbServerFixture.IsServerAvailable())
            Skip = "ab_server not reachable. Start the Docker container " +
                   "(docker compose -f Docker/docker-compose.yml --profile controllogix up) " +
                   "or install libplctag test binaries.";
    }
}