lmxopcua/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.AbCip.Tests/AbCipLifecycleConcurrencyTests.cs

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

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

/// <summary>
///     Lifecycle overlap the runtime can produce (review 07 H13/F10, Lane A): the final stop runs
///     <c>ShutdownAsync</c> then <c>DisposeAsync</c> under one bounded budget, so a slow shutdown is abandoned and
///     the dispose runs CONCURRENTLY with it; an abandoned <c>InitializeAsync</c> can overlap the next attempt's
///     shutdown. Device tables are build-and-swapped, so each teardown owns a disjoint set of device states.
/// </summary>
[Trait("Category", "Unit")]
public sealed class AbCipLifecycleConcurrencyTests
{
    private const string Host = "ab://10.0.0.5/1,0";

    /// <summary>A fake whose reads ignore cancellation for a while, so a teardown waits on the probe loop.</summary>
    private sealed class SlowTag(AbCipTagCreateParams p, TimeSpan readDelay) : FakeAbCipTag(p)
    {
        private int _disposeCount;

        public int DisposeCount => Volatile.Read(ref _disposeCount);

        public override async Task ReadAsync(CancellationToken cancellationToken)
        {
            await base.ReadAsync(cancellationToken);
            if (readDelay > TimeSpan.Zero) await Task.Delay(readDelay, CancellationToken.None);
        }

        public override void Dispose()
        {
            Interlocked.Increment(ref _disposeCount);
            base.Dispose();
        }
    }

    private static (AbCipDriver Driver, FakeAbCipTagFactory Factory) Build(TimeSpan probeReadDelay)
    {
        var factory = new FakeAbCipTagFactory
        {
            Customise = p => new SlowTag(p, p.TagName == "ProbeTag" ? probeReadDelay : TimeSpan.Zero) { Value = 1 },
        };
        var drv = new AbCipDriver(new AbCipDriverOptions
        {
            Devices = [new AbCipDeviceOptions(Host)],
            RawTags = AbCipRawTags.From(new AbCipTagDefinition("Speed", Host, "Motor1.Speed", AbCipDataType.DInt)),
            Probe = new AbCipProbeOptions
            {
                Enabled = true,
                ProbeTagPath = "ProbeTag",
                Interval = TimeSpan.FromMilliseconds(10),
                Timeout = TimeSpan.FromMilliseconds(200),
            },
        }, "abcip-lifecycle", factory);
        return (drv, factory);
    }

    private static async Task WaitUntilAsync(Func<bool> condition, string what)
    {
        var deadline = DateTime.UtcNow.AddSeconds(5);
        while (!condition())
        {
            if (DateTime.UtcNow > deadline) throw new TimeoutException(what);
            await Task.Delay(5);
        }
    }

    /// <summary>
    ///     Shutdown and Dispose racing each other tear the device down exactly once: the data runtime is
    ///     disposed once (not once per teardown), neither call throws, and the probe loop has exited.
    /// </summary>
    [Fact]
    public async Task Dispose_concurrent_with_a_running_Shutdown_tears_each_state_down_exactly_once()
    {
        var (drv, factory) = Build(probeReadDelay: TimeSpan.FromMilliseconds(300));
        await drv.InitializeAsync("{}", CancellationToken.None);
        (await drv.ReadAsync(["Speed"], CancellationToken.None))[0].StatusCode.ShouldBe(AbCipStatusMapper.Good);
        await WaitUntilAsync(() => factory.Tags.ContainsKey("ProbeTag"), "probe never started");
        var state = drv.GetDeviceState(Host)!;
        var probeLoop = state.ProbeTask!;
        var data = (SlowTag)factory.Tags["Motor1.Speed"];

        var shutdown = drv.ShutdownAsync(CancellationToken.None);
        var dispose = drv.DisposeAsync().AsTask();
        await Task.WhenAll(shutdown, dispose);

        data.DisposeCount.ShouldBe(1);
        probeLoop.IsCompleted.ShouldBeTrue();
        drv.GetDeviceState(Host).ShouldBeNull();
    }

    /// <summary>
    ///     An InitializeAsync that a ShutdownAsync overtakes publishes nothing: no device state and no probe
    ///     loop survive the shutdown. Positive control: an init that nothing overtakes still publishes.
    /// </summary>
    [Fact]
    public async Task An_init_overtaken_by_Shutdown_publishes_no_device_and_starts_no_probe()
    {
        var (drv, factory) = Build(probeReadDelay: TimeSpan.FromMilliseconds(300));
        await drv.InitializeAsync("{}", CancellationToken.None);
        await WaitUntilAsync(() => factory.Tags.ContainsKey("ProbeTag"), "probe never started");
        var firstProbe = factory.Tags["ProbeTag"];

        // The second init's own release waits on the slow first probe loop; the shutdown overtakes it there.
        var init = drv.InitializeAsync("{}", CancellationToken.None);
        await Task.Delay(50);
        await drv.ShutdownAsync(CancellationToken.None);
        await Should.ThrowAsync<OperationCanceledException>(() => init);

        drv.GetDeviceState(Host).ShouldBeNull();
        drv.GetHostStatuses().ShouldBeEmpty();
        await Task.Delay(100);
        factory.Tags["ProbeTag"].ShouldBeSameAs(firstProbe); // no second probe loop ever created a runtime
        drv.GetHealth().State.ShouldNotBe(DriverState.Healthy);

        // Positive control: a later init that nothing overtakes publishes the device again.
        await drv.InitializeAsync("{}", CancellationToken.None);
        drv.GetDeviceState(Host).ShouldNotBeNull();
        drv.GetHealth().State.ShouldBe(DriverState.Healthy);
        await drv.DisposeAsync();
    }

    /// <summary>
    ///     Readers of the device/routing tables (the retained poll engine, the actor's host-status pull) never
    ///     see a table mid-mutation while the driver re-initialises underneath them, never trip over a per-tag lock a
    ///     retire disposed, and never leak a runtime they cold-created into a device state a retire already tore down.
    /// </summary>
    [Fact]
    public async Task Readers_survive_repeated_reinitialisation_and_leak_no_runtime()
    {
        var created = new System.Collections.Concurrent.ConcurrentBag<FakeAbCipTag>();
        var factory = new FakeAbCipTagFactory
        {
            Customise = p =>
            {
                var t = new FakeAbCipTag(p) { Value = 1 };
                created.Add(t);
                return t;
            },
        };
        var drv = new AbCipDriver(new AbCipDriverOptions
        {
            Devices = [new AbCipDeviceOptions(Host)],
            RawTags = AbCipRawTags.From(new AbCipTagDefinition("Speed", Host, "Motor1.Speed", AbCipDataType.DInt)),
            Probe = new AbCipProbeOptions { Enabled = false },
        }, "abcip-lifecycle", factory);
        await drv.InitializeAsync("{}", CancellationToken.None);
        using var stop = new CancellationTokenSource();
        var started = new TaskCompletionSource(TaskCreationOptions.RunContinuationsAsynchronously);
        var badHealth = 0;
        var reader = Task.Run(async () =>
        {
            var reads = 0;
            while (!stop.IsCancellationRequested)
            {
                _ = drv.GetHostStatuses();
                _ = drv.ResolveHost("Speed");
                await drv.ReadAsync(["Speed"], CancellationToken.None);
                if (drv.GetHealth().State == DriverState.Degraded) Interlocked.Increment(ref badHealth);
                reads++;
                started.TrySetResult();
            }
            return reads;
        });
        await started.Task.WaitAsync(TimeSpan.FromSeconds(5));

        for (var i = 0; i < 200; i++)
            await drv.InitializeAsync("{}", CancellationToken.None);
        stop.Cancel();

        (await reader).ShouldBeGreaterThan(0); // positive control: the reader actually ran
        Volatile.Read(ref badHealth).ShouldBe(0, "a re-init is not a comms fault");
        await drv.DisposeAsync();
        created.Where(t => !t.Disposed).ShouldBeEmpty("every runtime a reader created must be disposed by some teardown");
    }

    /// <summary>F10: DisposeAsync is the complete, idempotent teardown (the runtime prefers it).</summary>
    [Fact]
    public async Task DisposeAsync_is_a_complete_idempotent_teardown()
    {
        var (drv, factory) = Build(probeReadDelay: TimeSpan.Zero);
        await drv.InitializeAsync("{}", CancellationToken.None);
        await WaitUntilAsync(() => factory.Tags.ContainsKey("ProbeTag"), "probe never started");
        var loop = drv.GetDeviceState(Host)!.ProbeTask!;

        await drv.DisposeAsync();
        await drv.DisposeAsync(); // idempotent

        loop.IsCompleted.ShouldBeTrue();
        factory.Tags["ProbeTag"].Disposed.ShouldBeTrue();
    }

    /// <summary>
    ///     F10: the sync <c>Dispose()</c> no longer blocks the caller's thread on the async teardown (sync-over-async —
    ///     a dispatcher thread for up to the probe join). It starts the same teardown and returns; the teardown still
    ///     completes.
    /// </summary>
    [Fact]
    public async Task Sync_Dispose_does_not_block_on_the_teardown_but_still_completes_it()
    {
        var (drv, factory) = Build(probeReadDelay: TimeSpan.FromMilliseconds(500));
        await drv.InitializeAsync("{}", CancellationToken.None);
        await WaitUntilAsync(() => factory.Tags.ContainsKey("ProbeTag"), "probe never started");
        var loop = drv.GetDeviceState(Host)!.ProbeTask!;
        await Task.Delay(20); // the probe is inside its slow, cancellation-deaf read

        var sw = System.Diagnostics.Stopwatch.StartNew();
        ((IDisposable)drv).Dispose();
        sw.Stop();

        sw.Elapsed.ShouldBeLessThan(TimeSpan.FromMilliseconds(250)); // did not wait out the 500 ms probe read
        await WaitUntilAsync(() => loop.IsCompleted && factory.Tags["ProbeTag"].Disposed, "teardown never completed");
        drv.GetDeviceState(Host).ShouldBeNull();
    }
}