using System.Collections.Concurrent;
using Akka.Actor;
using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
using ZB.MOM.WW.OtOpcUa.Runtime.Drivers;
using ZB.MOM.WW.OtOpcUa.Runtime.Tests.Harness;

namespace ZB.MOM.WW.OtOpcUa.Runtime.Tests.Drivers;

/// <summary>
///     lmxopcua#869 — <see cref="DriverInstanceActor"/> asks an <see cref="IAlarmAcknowledgeConfirmation"/> driver to
///     confirm an ack AFTER <see cref="IAlarmSource.AcknowledgeAsync"/> returned, off its mailbox, and reports
///     <see cref="DriverInstanceActor.AlarmAckFailed"/> to the router when the confirmation fails — including one that
///     fails long after the ack handler returned, and one abandoned because the actor stopped.
/// </summary>
public sealed class DriverInstanceActorAckConfirmationTests : RuntimeActorTestBase
{
    private static readonly TimeSpan Timeout = PresenceBudget;

    /// <summary>A confirmation that faults asynchronously, after the ack handler returned, is reported failed.</summary>
    [Fact]
    public void A_confirmation_that_fails_later_is_reported_as_a_failed_ack()
    {
        var driver = new ConfirmingDriver();
        var actor = SpawnConnected(driver);
        var gate = new TaskCompletionSource();
        driver.Confirmation = () => gate.Task;
        var router = CreateTestProbe();

        actor.Tell(Ack("n1"), router.Ref);
        AwaitCondition(() => driver.ConfirmCalls == 1, Timeout, TestContext.Current.CancellationToken);
        gate.SetException(new DriverOperationRefusedException("not confirmed within 10 s (BadTimeout)"));

        var failed = router.ExpectMsg<DriverInstanceActor.AlarmAckFailed>(Timeout, cancellationToken: TestContext.Current.CancellationToken);
        failed.ConditionNodeId.ShouldBe("n1");
        failed.Reason.ShouldContain("BadTimeout");
        driver.ForeignConfirmations.ShouldBe(0, "the confirmation must get the SAME request instance the ack was sent with");
    }

    /// <summary>
    ///     A confirmation still pending when the actor stops is abandoned AND reported failed, so the host reverts the
    ///     ack this incarnation can no longer confirm. (A confirmation continuation posted back to the stopped actor
    ///     would dead-letter and never report.)
    /// </summary>
    [Fact]
    public void A_confirmation_pending_when_the_actor_stops_is_reported_as_a_failed_ack()
    {
        var driver = new ConfirmingDriver();
        var actor = SpawnConnected(driver);
        driver.Confirmation = () => new TaskCompletionSource().Task; // never completes on its own
        var router = CreateTestProbe();

        actor.Tell(Ack("n-stop"), router.Ref);
        AwaitCondition(() => driver.ConfirmCalls == 1, Timeout, TestContext.Current.CancellationToken);
        Sys.Stop(actor);

        var failed = router.ExpectMsg<DriverInstanceActor.AlarmAckFailed>(Timeout, cancellationToken: TestContext.Current.CancellationToken);
        failed.ConditionNodeId.ShouldBe("n-stop");
        failed.Reason.ShouldContain("stopped");
    }

    /// <summary>
    ///     A confirmation that succeeds reports nothing. Positive control: a later ack whose confirmation fails is
    ///     reported, and it is the FIRST report the router receives — so none came for the confirmed one.
    /// </summary>
    [Fact]
    public void A_confirmed_ack_reports_nothing()
    {
        var driver = new ConfirmingDriver();
        var actor = SpawnConnected(driver);
        var router = CreateTestProbe();

        // Already complete: the actor's confirmation task finishes (and would report) right after the call that
        // bumps ConfirmCalls, long before the second ack below makes its actor round trip.
        driver.Confirmation = () => Task.CompletedTask;
        actor.Tell(Ack("n-ok"), router.Ref);
        AwaitCondition(() => driver.ConfirmCalls == 1, Timeout, TestContext.Current.CancellationToken);

        driver.Confirmation = () => Task.FromException(new DriverOperationRefusedException("unconfirmed"));
        actor.Tell(Ack("n-bad"), router.Ref);

        router.ExpectMsg<DriverInstanceActor.AlarmAckFailed>(Timeout, cancellationToken: TestContext.Current.CancellationToken).ConditionNodeId.ShouldBe("n-bad");
    }

    /// <summary>
    ///     lmxopcua#869 review — the failure echoes the routed ack's <see cref="DriverInstanceActor.RouteAlarmAck.AckSequence"/>,
    ///     which is what lets the host revert only the acknowledge that failed (keyed in
    ///     <c>NativeAlarmProjector.TryRevertAcknowledge(nodeId, ackSequence, …)</c>).
    /// </summary>
    [Fact]
    public void A_failed_confirmation_echoes_the_ack_sequence()
    {
        var driver = new ConfirmingDriver();
        var actor = SpawnConnected(driver);
        driver.Confirmation = () => Task.FromException(new DriverOperationRefusedException("unconfirmed"));
        var router = CreateTestProbe();

        actor.Tell(Ack("n-seq") with { AckSequence = 42 }, router.Ref);

        router.ExpectMsg<DriverInstanceActor.AlarmAckFailed>(Timeout, cancellationToken: TestContext.Current.CancellationToken)
            .AckSequence.ShouldBe(42L);
    }

    private static DriverInstanceActor.RouteAlarmAck Ack(string conditionNodeId) =>
        new("Tank.Hi", "c", "alice", ConditionNodeId: conditionNodeId);

    /// <summary>Spawns the actor as a child of the test actor and waits for its Connected announcement.</summary>
    private IActorRef SpawnConnected(ConfirmingDriver driver)
    {
        var actor = ChildActorOf(DriverInstanceActor.Props(driver));
        actor.Tell(new DriverInstanceActor.InitializeRequested("{}"));
        FishForMessage<DriverInstanceActor.ConnectivityChanged>(c => c.Connected, Timeout);
        return actor;
    }

    private sealed class ConfirmingDriver : IDriver, IAlarmSource, IAlarmAcknowledgeConfirmation
    {
        private int _ackCalls;
        private int _confirmCalls;
        private readonly ConcurrentQueue<IReadOnlyList<AlarmAcknowledgeRequest>> _ackedLists = new();
        private int _foreignConfirmations;

        /// <summary>Confirmations asked for a request list that was NOT the instance passed to AcknowledgeAsync —
        /// the contract a driver matching by instance (Galaxy) relies on.</summary>
        public int ForeignConfirmations => Volatile.Read(ref _foreignConfirmations);

        public Func<Task>? Confirmation { get; set; }

        public int AckCalls => Volatile.Read(ref _ackCalls);

        public int ConfirmCalls => Volatile.Read(ref _confirmCalls);

        public string DriverInstanceId => "drv-confirm";

        public string DriverType => "Test";

        public Task InitializeAsync(string driverConfigJson, CancellationToken cancellationToken) => Task.CompletedTask;

        public Task ReinitializeAsync(string driverConfigJson, CancellationToken cancellationToken) => Task.CompletedTask;

        public Task ShutdownAsync(CancellationToken cancellationToken) => Task.CompletedTask;

        public DriverHealth GetHealth() => new(DriverState.Healthy, null, null);

        public Task<IAlarmSubscriptionHandle> SubscribeAlarmsAsync(
            IReadOnlyList<string> sourceNodeIds, CancellationToken cancellationToken) =>
            Task.FromResult<IAlarmSubscriptionHandle>(new Handle());

        public Task UnsubscribeAlarmsAsync(IAlarmSubscriptionHandle handle, CancellationToken cancellationToken) =>
            Task.CompletedTask;

        public Task AcknowledgeAsync(
            IReadOnlyList<AlarmAcknowledgeRequest> acknowledgements, CancellationToken cancellationToken)
        {
            _ackedLists.Enqueue(acknowledgements);
            Interlocked.Increment(ref _ackCalls);
            return Task.CompletedTask;
        }

        public Task ConfirmAcknowledgedAsync(
            IReadOnlyList<AlarmAcknowledgeRequest> acknowledgements, CancellationToken cancellationToken)
        {
            if (!_ackedLists.Any(l => ReferenceEquals(l, acknowledgements))) Interlocked.Increment(ref _foreignConfirmations);
            Interlocked.Increment(ref _confirmCalls);
            return (Confirmation?.Invoke() ?? Task.CompletedTask).WaitAsync(cancellationToken);
        }

        public event EventHandler<AlarmEventArgs>? OnAlarmEvent
        {
            add { }
            remove { }
        }

        private sealed class Handle : IAlarmSubscriptionHandle
        {
            public string DiagnosticId => "h";
        }
    }
}