using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
using ZB.MOM.WW.OtOpcUa.Driver.AbCip;

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

/// <summary>
///     PR abcip-1.4 — multi-tag write packing. Validates that <see cref="AbCipDriver.WriteAsync"/>
///     groups writes by device, dispatches packable writes for request-packing-capable
///     families concurrently, falls back to sequential writes on Micro800, keeps BOOL-RMW
///     writes on the per-parent semaphore path, and fans per-tag StatusCodes out to the
///     correct positions on partial failures.
/// </summary>
[Trait("Category", "Unit")]
public sealed class AbCipMultiWritePackingTests
{
    [Fact]
    public async Task Writes_get_grouped_by_device()
    {
        var factory = new FakeAbCipTagFactory();
        var drv = new AbCipDriver(new AbCipDriverOptions
        {
            Devices =
            [
                new AbCipDeviceOptions("ab://10.0.0.5/1,0"),
                new AbCipDeviceOptions("ab://10.0.0.6/1,0"),
            ],
            Tags =
            [
                new AbCipTagDefinition("A1", "ab://10.0.0.5/1,0", "A1", AbCipDataType.DInt),
                new AbCipTagDefinition("A2", "ab://10.0.0.5/1,0", "A2", AbCipDataType.DInt),
                new AbCipTagDefinition("B1", "ab://10.0.0.6/1,0", "B1", AbCipDataType.DInt),
            ],
        }, "drv-1", factory);
        await drv.InitializeAsync("{}", CancellationToken.None);

        var results = await drv.WriteAsync(
        [
            new WriteRequest("A1", 1),
            new WriteRequest("B1", 100),
            new WriteRequest("A2", 2),
        ], CancellationToken.None);

        results.Count.ShouldBe(3);
        results[0].StatusCode.ShouldBe(AbCipStatusMapper.Good);
        results[1].StatusCode.ShouldBe(AbCipStatusMapper.Good);
        results[2].StatusCode.ShouldBe(AbCipStatusMapper.Good);
        // Per-device handles materialised — A1/A2 share device A, B1 lives on device B.
        factory.Tags["A1"].CreationParams.Gateway.ShouldBe("10.0.0.5");
        factory.Tags["A2"].CreationParams.Gateway.ShouldBe("10.0.0.5");
        factory.Tags["B1"].CreationParams.Gateway.ShouldBe("10.0.0.6");
        factory.Tags["A1"].WriteCount.ShouldBe(1);
        factory.Tags["A2"].WriteCount.ShouldBe(1);
        factory.Tags["B1"].WriteCount.ShouldBe(1);
    }

    [Fact]
    public async Task ControlLogix_packs_concurrently_within_a_device()
    {
        // ControlLogix has SupportsRequestPacking=true → a multi-write batch is dispatched in
        // parallel. The fake's WriteAsync gates on a TaskCompletionSource so we can prove that
        // both writes are in flight at the same time before either completes.
        var gate = new TaskCompletionSource<int>(TaskCreationOptions.RunContinuationsAsynchronously);
        var inFlight = 0;
        var maxInFlight = 0;
        var factory = new FakeAbCipTagFactory
        {
            Customise = p => new GatedWriteFake(p, gate, () =>
            {
                var current = Interlocked.Increment(ref inFlight);
                var observed = maxInFlight;
                while (current > observed
                    && Interlocked.CompareExchange(ref maxInFlight, current, observed) != observed)
                    observed = maxInFlight;
            }, () => Interlocked.Decrement(ref inFlight)),
        };
        var drv = new AbCipDriver(new AbCipDriverOptions
        {
            Devices = [new AbCipDeviceOptions("ab://10.0.0.5/1,0", AbCipPlcFamily.ControlLogix)],
            Tags =
            [
                new AbCipTagDefinition("A", "ab://10.0.0.5/1,0", "A", AbCipDataType.DInt),
                new AbCipTagDefinition("B", "ab://10.0.0.5/1,0", "B", AbCipDataType.DInt),
                new AbCipTagDefinition("C", "ab://10.0.0.5/1,0", "C", AbCipDataType.DInt),
            ],
        }, "drv-1", factory);
        await drv.InitializeAsync("{}", CancellationToken.None);

        var writeTask = drv.WriteAsync(
        [
            new WriteRequest("A", 1),
            new WriteRequest("B", 2),
            new WriteRequest("C", 3),
        ], CancellationToken.None);

        // Wait until all three writes have entered WriteAsync simultaneously, then release.
        await WaitForAsync(() => Volatile.Read(ref inFlight) >= 3, TimeSpan.FromSeconds(2));
        gate.SetResult(0);

        var results = await writeTask;
        results.Count.ShouldBe(3);
        results[0].StatusCode.ShouldBe(AbCipStatusMapper.Good);
        results[1].StatusCode.ShouldBe(AbCipStatusMapper.Good);
        results[2].StatusCode.ShouldBe(AbCipStatusMapper.Good);
        maxInFlight.ShouldBeGreaterThanOrEqualTo(2,
            "ControlLogix supports request packing — packable writes should run concurrently within the device.");
    }

    [Fact]
    public async Task Micro800_falls_back_to_sequential_writes()
    {
        // Micro800 has SupportsRequestPacking=false → writes go one-at-a-time; the gated fake
        // never sees more than one in-flight at a time.
        var gate = new TaskCompletionSource<int>(TaskCreationOptions.RunContinuationsAsynchronously);
        gate.SetResult(0); // No need to gate — we just observe concurrency.
        var inFlight = 0;
        var maxInFlight = 0;
        var factory = new FakeAbCipTagFactory
        {
            Customise = p => new GatedWriteFake(p, gate, () =>
            {
                var current = Interlocked.Increment(ref inFlight);
                var observed = maxInFlight;
                while (current > observed
                    && Interlocked.CompareExchange(ref maxInFlight, current, observed) != observed)
                    observed = maxInFlight;
            }, () => Interlocked.Decrement(ref inFlight)),
        };
        var drv = new AbCipDriver(new AbCipDriverOptions
        {
            Devices = [new AbCipDeviceOptions("ab://10.0.0.5/", AbCipPlcFamily.Micro800)],
            Tags =
            [
                new AbCipTagDefinition("A", "ab://10.0.0.5/", "A", AbCipDataType.DInt),
                new AbCipTagDefinition("B", "ab://10.0.0.5/", "B", AbCipDataType.DInt),
                new AbCipTagDefinition("C", "ab://10.0.0.5/", "C", AbCipDataType.DInt),
            ],
        }, "drv-1", factory);
        await drv.InitializeAsync("{}", CancellationToken.None);

        var results = await drv.WriteAsync(
        [
            new WriteRequest("A", 1),
            new WriteRequest("B", 2),
            new WriteRequest("C", 3),
        ], CancellationToken.None);

        results.Count.ShouldBe(3);
        results.ShouldAllBe(r => r.StatusCode == AbCipStatusMapper.Good);
        maxInFlight.ShouldBe(1,
            "Micro800 disables request packing — writes must execute sequentially.");
    }

    [Fact]
    public async Task Bit_in_dint_writes_still_route_through_RMW_path()
    {
        // BOOL-with-bitIndex must hit the per-parent RMW semaphore — it must NOT go through
        // the packable per-tag runtime path. We prove this by checking that:
        //   (a) the per-tag "bit-selector" runtime is never created (it would throw via
        //       LibplctagTagRuntime's NotSupportedException had the bypass happened);
        //   (b) the parent-DINT runtime got both a Read and a Write.
        var factory = new FakeAbCipTagFactory();
        var drv = new AbCipDriver(new AbCipDriverOptions
        {
            Devices = [new AbCipDeviceOptions("ab://10.0.0.5/1,0")],
            Tags =
            [
                new AbCipTagDefinition("Flag3", "ab://10.0.0.5/1,0", "Flags.3", AbCipDataType.Bool),
                new AbCipTagDefinition("Speed", "ab://10.0.0.5/1,0", "Speed", AbCipDataType.DInt),
            ],
        }, "drv-1", factory);
        await drv.InitializeAsync("{}", CancellationToken.None);

        var results = await drv.WriteAsync(
        [
            new WriteRequest("Flag3", true),
            new WriteRequest("Speed", 99),
        ], CancellationToken.None);

        results.Count.ShouldBe(2);
        results[0].StatusCode.ShouldBe(AbCipStatusMapper.Good);
        results[1].StatusCode.ShouldBe(AbCipStatusMapper.Good);

        // Parent runtime created lazily for Flags (no .3 suffix) — drove the RMW.
        factory.Tags.ShouldContainKey("Flags");
        factory.Tags["Flags"].ReadCount.ShouldBe(1);
        factory.Tags["Flags"].WriteCount.ShouldBe(1);
        // Speed went through the packable path.
        factory.Tags["Speed"].WriteCount.ShouldBe(1);
    }

    [Fact]
    public async Task Per_tag_status_code_fan_out_works_on_partial_failure()
    {
        // Mix Good + BadTimeout + BadNotWritable + BadNodeIdUnknown across two devices to
        // exercise the original-index preservation through the per-device plan + concurrent
        // dispatch.
        var factory = new FakeAbCipTagFactory
        {
            Customise = p => p.TagName == "B"
                ? new FakeAbCipTag(p) { Status = -5 /* timeout */ }
                : new FakeAbCipTag(p),
        };
        var drv = new AbCipDriver(new AbCipDriverOptions
        {
            Devices =
            [
                new AbCipDeviceOptions("ab://10.0.0.5/1,0"),
                new AbCipDeviceOptions("ab://10.0.0.6/1,0"),
            ],
            Tags =
            [
                new AbCipTagDefinition("A", "ab://10.0.0.5/1,0", "A", AbCipDataType.DInt),
                new AbCipTagDefinition("B", "ab://10.0.0.5/1,0", "B", AbCipDataType.DInt),
                new AbCipTagDefinition("RO", "ab://10.0.0.5/1,0", "RO", AbCipDataType.DInt, Writable: false),
                new AbCipTagDefinition("C", "ab://10.0.0.6/1,0", "C", AbCipDataType.DInt),
            ],
        }, "drv-1", factory);
        await drv.InitializeAsync("{}", CancellationToken.None);

        var results = await drv.WriteAsync(
        [
            new WriteRequest("A", 1),
            new WriteRequest("B", 2),
            new WriteRequest("RO", 3),
            new WriteRequest("UnknownTag", 4),
            new WriteRequest("C", 5),
        ], CancellationToken.None);

        results.Count.ShouldBe(5);
        results[0].StatusCode.ShouldBe(AbCipStatusMapper.Good);
        results[1].StatusCode.ShouldBe(AbCipStatusMapper.BadTimeout);
        results[2].StatusCode.ShouldBe(AbCipStatusMapper.BadNotWritable);
        results[3].StatusCode.ShouldBe(AbCipStatusMapper.BadNodeIdUnknown);
        results[4].StatusCode.ShouldBe(AbCipStatusMapper.Good);
    }

    private static async Task WaitForAsync(Func<bool> predicate, TimeSpan timeout)
    {
        var deadline = DateTime.UtcNow + timeout;
        while (!predicate())
        {
            if (DateTime.UtcNow >= deadline)
                throw new TimeoutException("predicate did not become true within timeout");
            await Task.Delay(10).ConfigureAwait(false);
        }
    }

    /// <summary>
    ///     Test fake whose <see cref="WriteAsync"/> blocks on a shared
    ///     <see cref="TaskCompletionSource"/> so the test can observe how many writes are
    ///     simultaneously in flight inside the driver.
    /// </summary>
    private sealed class GatedWriteFake : FakeAbCipTag
    {
        private readonly TaskCompletionSource<int> _gate;
        private readonly Action _onEnter;
        private readonly Action _onExit;

        public GatedWriteFake(AbCipTagCreateParams p, TaskCompletionSource<int> gate,
            Action onEnter, Action onExit) : base(p)
        {
            _gate = gate;
            _onEnter = onEnter;
            _onExit = onExit;
        }

        public override async Task WriteAsync(CancellationToken ct)
        {
            _onEnter();
            try
            {
                await _gate.Task.ConfigureAwait(false);
                await base.WriteAsync(ct).ConfigureAwait(false);
            }
            finally
            {
                _onExit();
            }
        }
    }
}