ScadaBridge/tests/ZB.MOM.WW.ScadaBridge.Host.Tests/CentralCacheInvalidationBusTests.cs

using Akka.Actor;
using Akka.Cluster.Tools.PublishSubscribe;
using Akka.TestKit.Xunit2;
using Microsoft.Extensions.Logging.Abstractions;
using ZB.MOM.WW.ScadaBridge.Commons.Interfaces.Services;
using ZB.MOM.WW.ScadaBridge.Commons.Messages.Communication;

namespace ZB.MOM.WW.ScadaBridge.Host.Tests;

/// <summary>
/// ScadaBridge#100 item 3: the central cache-invalidation bus publishes typed invalidations on
/// one topic, and the subscriber hands the peer's (never its own) to every handler.
/// </summary>
public class CentralCacheInvalidationBusTests : TestKit
{
    private sealed class RecordingHandler : ICentralCacheInvalidationHandler
    {
        public List<ICentralCacheInvalidation> Applied { get; } = new();

        public void Apply(ICentralCacheInvalidation invalidation)
        {
            lock (Applied) Applied.Add(invalidation);
        }
    }

    private sealed class ThrowingHandler : ICentralCacheInvalidationHandler
    {
        public void Apply(ICentralCacheInvalidation invalidation) => throw new InvalidOperationException("boom");
    }

    private readonly CentralCacheInvalidationBus _bus = new(NullLogger<CentralCacheInvalidationBus>.Instance);

    /// <summary>Publishing wraps the invalidation with this node's origin id on the shared topic.</summary>
    [Fact]
    public void Publish_SendsAnEnvelopeOnTheSharedTopic()
    {
        var mediator = CreateTestProbe();
        _bus.SetMediator(mediator.Ref);

        _bus.Publish(new RoleMappingsInvalidated());

        var publish = mediator.ExpectMsg<Publish>();
        Assert.Equal("central-cache-invalidation", publish.Topic);
        var envelope = Assert.IsType<CentralCacheInvalidationEnvelope>(publish.Message);
        Assert.Equal(_bus.OriginId, envelope.OriginId);
        Assert.IsType<RoleMappingsInvalidated>(envelope.Invalidation);
        mediator.ExpectNoMsg(TimeSpan.FromMilliseconds(100)); // one topic, one publish (#105)
    }

    /// <summary>Before the mediator exists publishing is a silent no-op.</summary>
    [Fact]
    public void Publish_WithoutAMediator_DoesNotThrow()
    {
        _bus.Publish(new ExternalDefinitionsInvalidated());
    }

    /// <summary>The peer's invalidation reaches every handler; this node's own broadcast is skipped.</summary>
    [Fact]
    public void Subscriber_AppliesPeerInvalidations_AndSkipsItsOwn()
    {
        var handler = new RecordingHandler();
        var subscriber = Sys.ActorOf(Props.Create(() => new CentralCacheInvalidationSubscriber(
            _bus, new ICentralCacheInvalidationHandler[] { new ThrowingHandler(), handler })));

        subscriber.Tell(new CentralCacheInvalidationEnvelope(_bus.OriginId, new RoleMappingsInvalidated()));
        subscriber.Tell(new CentralCacheInvalidationEnvelope("peer", new ExternalDefinitionsInvalidated()));
        subscriber.Tell(new CentralCacheInvalidationEnvelope("peer", new InboundApiMethodInvalidated("M")));

        AwaitAssert(() =>
        {
            lock (handler.Applied)
            {
                // A throwing handler ahead of it does not stop delivery.
                Assert.Equal(
                    new ICentralCacheInvalidation[] { new ExternalDefinitionsInvalidated(), new InboundApiMethodInvalidated("M") },
                    handler.Applied);
            }
        });
    }
}