using Shouldly;
using Xunit;

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

[Trait("Category", "Unit")]
public sealed class FocasHandleRecycleTests
{
    /// <summary>Verifies that the recycle loop disposes clients on interval and reopens fresh ones.</summary>
    [Fact]
    public async Task Recycle_loop_disposes_client_on_interval_reads_reopen_fresh_one()
    {
        var factory = new FakeFocasClientFactory();
        var drv = new FocasDriver(new FocasDriverOptions
        {
            Devices = [new FocasDeviceOptions("focas://10.0.0.5:8193")],
            RawTags = [FocasRawTags.Entry(new FocasTagDefinition("R", "focas://10.0.0.5:8193", "R100", FocasDataType.Byte))],
            Probe = new FocasProbeOptions { Enabled = false },
            HandleRecycle = new FocasHandleRecycleOptions
            {
                Enabled = true,
                Interval = TimeSpan.FromMilliseconds(80),
            },
        }, "drv-1", factory);

        await drv.InitializeAsync("{}", CancellationToken.None);

        // First read forces the initial connect.
        await drv.ReadAsync(["R"], CancellationToken.None);
        var initialClients = factory.Clients.Count;
        initialClients.ShouldBe(1);

        // Wait for a recycle tick, then read again — a new client must have been created.
        await WaitFor(() => factory.Clients[0].DisposeCount > 0, TimeSpan.FromSeconds(3));
        await drv.ReadAsync(["R"], CancellationToken.None);

        factory.Clients.Count.ShouldBeGreaterThan(initialClients);

        await drv.ShutdownAsync(CancellationToken.None);
    }

    /// <summary>Verifies that the recycle loop stays off when not enabled.</summary>
    [Fact]
    public async Task Recycle_loop_stays_off_when_not_enabled()
    {
        var factory = new FakeFocasClientFactory();
        var drv = new FocasDriver(new FocasDriverOptions
        {
            Devices = [new FocasDeviceOptions("focas://10.0.0.5:8193")],
            RawTags = [FocasRawTags.Entry(new FocasTagDefinition("R", "focas://10.0.0.5:8193", "R100", FocasDataType.Byte))],
            Probe = new FocasProbeOptions { Enabled = false },
        }, "drv-1", factory);

        await drv.InitializeAsync("{}", CancellationToken.None);
        await drv.ReadAsync(["R"], CancellationToken.None);
        await Task.Delay(150);

        // With recycle off the same client stays live — no Dispose during the window.
        factory.Clients.Count.ShouldBe(1);
        factory.Clients[0].DisposeCount.ShouldBe(0);

        await drv.ShutdownAsync(CancellationToken.None);
    }

    /// <summary>A client whose reads take a while — long enough for a recycle tick to land mid-read.</summary>
    private sealed class SlowReadClient : FakeFocasClient
    {
        public override async Task<(object? value, uint status)> ReadAsync(
            FocasAddress address, FocasDataType type, CancellationToken ct)
        {
            await Task.Delay(200, ct).ConfigureAwait(false);
            if (!IsConnected) throw new ObjectDisposedException(nameof(SlowReadClient), "disposed mid-read");
            return ((sbyte)5, FocasStatusMapper.Good);
        }
    }

    /// <summary>
    ///     #740 / R07:L6 — the recycle loop disposed the device client with no gate, so a recycle tick landing
    ///     mid-read killed that read (BadCommunicationError + Degraded, every interval). The recycle now takes the
    ///     device's connect gate and lets the in-flight read finish before disposing the client it detached.
    /// </summary>
    [Fact]
    public async Task Recycle_tick_landing_mid_read_lets_the_read_finish()
    {
        var factory = new FakeFocasClientFactory { Customise = () => new SlowReadClient() };
        var drv = new FocasDriver(new FocasDriverOptions
        {
            Devices = [new FocasDeviceOptions("focas://10.0.0.5:8193")],
            RawTags = [FocasRawTags.Entry(new FocasTagDefinition("R", "focas://10.0.0.5:8193", "R100", FocasDataType.Byte))],
            Probe = new FocasProbeOptions { Enabled = false },
            HandleRecycle = new FocasHandleRecycleOptions { Enabled = true, Interval = TimeSpan.FromMilliseconds(50) },
        }, "drv-1", factory);
        await drv.InitializeAsync("{}", CancellationToken.None);

        // Each 200 ms read spans at least three recycle ticks.
        for (var i = 0; i < 3; i++)
        {
            var snap = (await drv.ReadAsync(["R"], CancellationToken.None))[0];
            snap.StatusCode.ShouldBe(FocasStatusMapper.Good, $"read {i} was killed by a recycle tick");
            snap.Value.ShouldBe((sbyte)5);
        }
        drv.GetHealth().State.ShouldBe(Core.Abstractions.DriverState.Healthy);

        // Positive control: the recycle really ran — the first client was disposed and a fresh one opened.
        await WaitFor(() => factory.Clients[0].DisposeCount > 0, TimeSpan.FromSeconds(3));
        factory.Clients[0].DisposeCount.ShouldBeGreaterThan(0);
        factory.Clients.Count.ShouldBeGreaterThan(1);
        await drv.ShutdownAsync(CancellationToken.None);
        factory.Clients.ShouldAllBe(c => !c.IsConnected, "no client opened around a recycle may be orphaned");
    }

    /// <summary>DisposeWhenIdleAsync drains the in-flight op, then disposes; a later op is refused, not run on a dead socket.</summary>
    [Fact]
    public async Task DisposeWhenIdle_drains_the_in_flight_op_then_refuses_new_ones()
    {
        var inner = new SlowReadClient();
        await inner.ConnectAsync(new FocasHostAddress("10.0.0.5", 8193), TimeSpan.FromSeconds(1), CancellationToken.None);
        var sync = new SynchronizedFocasClient(inner, TimeSpan.FromSeconds(5));
        var addr = FocasAddress.TryParse("R100")!;

        var read = sync.ReadAsync(addr, FocasDataType.Byte, CancellationToken.None);
        await Task.Delay(20);
        sync.PendingOperations.ShouldBe(1);
        var dispose = sync.DisposeWhenIdleAsync(TimeSpan.FromSeconds(5));

        (await read).status.ShouldBe(FocasStatusMapper.Good);
        await dispose;
        inner.DisposeCount.ShouldBe(1);
        await Should.ThrowAsync<ObjectDisposedException>(() => sync.ReadAsync(addr, FocasDataType.Byte, CancellationToken.None));
    }

    private static async Task WaitFor(Func<bool> pred, TimeSpan timeout)
    {
        var deadline = DateTime.UtcNow + timeout;
        while (DateTime.UtcNow < deadline)
        {
            if (pred()) return;
            await Task.Delay(20);
        }
    }
}