using Akka.Actor;
using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Commons.Messages.Redundancy;
using ZB.MOM.WW.OtOpcUa.ControlPlane.Redundancy;
using ZB.MOM.WW.OtOpcUa.ControlPlane.Tests.Harness;

namespace ZB.MOM.WW.OtOpcUa.ControlPlane.Tests;

/// <summary>
/// Verifies <see cref="RedundancyStateActor"/> publishes a <see cref="RedundancyStateChanged"/>
/// snapshot in response to cluster events, and that the 250ms debounce coalesces bursts.
/// The actor accepts an <c>Action&lt;object&gt;</c> broadcast override so tests can use a
/// TestProbe sink instead of bootstrapping DistributedPubSub (which is flaky single-node).
/// </summary>
public sealed class RedundancyStateActorTests : ControlPlaneActorTestBase
{
    /// <summary>Verifies that a self-join event triggers RedundancyStateChanged through the broadcast override.</summary>
    [Fact]
    public void Self_join_triggers_RedundancyStateChanged_via_broadcast_override()
    {
        var probe = CreateTestProbe("redundancy-listener");
        Sys.ActorOf(RedundancyStateActor.Props(broadcast: msg => probe.Ref.Tell(msg)),
            "redundancy-actor");

        var msg = probe.ExpectMsg<RedundancyStateChanged>(TimeSpan.FromSeconds(3));
        msg.Nodes.ShouldNotBeNull();
        msg.CorrelationId.Value.ShouldNotBe(Guid.Empty);
    }

    /// <summary>Verifies that multiple back-to-back events debounce to a single RedundancyStateChanged publication.</summary>
    [Fact]
    public void Multiple_back_to_back_events_debounce_to_single_publish()
    {
        var probe = CreateTestProbe("dedup-listener");
        Sys.ActorOf(RedundancyStateActor.Props(broadcast: msg => probe.Ref.Tell(msg)),
            "redundancy-debounce");

        // First publish should arrive within the debounce window.
        probe.ExpectMsg<RedundancyStateChanged>(TimeSpan.FromSeconds(3));

        // After debounce settles, no more events are fired by a quiescent cluster.
        probe.ExpectNoMsg(TimeSpan.FromMilliseconds(500));
    }
}
