using Akka.Actor;
using Akka.Cluster.Tools.PublishSubscribe;
using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Commons.Messages.Logging;
using ZB.MOM.WW.OtOpcUa.Runtime.Scripting;
using ZB.MOM.WW.OtOpcUa.Runtime.Telemetry;
using ZB.MOM.WW.OtOpcUa.Runtime.Tests.Harness;
using ZB.MOM.WW.OtOpcUa.Runtime.VirtualTags;

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

/// <summary>
///     Verifies <see cref="DpsScriptLogPublisher"/> routes a <see cref="ScriptLogEntry"/>
///     onto the Akka DistributedPubSub <c>script-logs</c> topic and never throws back into
///     the calling logging pipeline.
/// </summary>
public sealed class DpsScriptLogPublisherTests : RuntimeActorTestBase
{
    /// <summary>Builds a representative entry for assertions.</summary>
    private static ScriptLogEntry SampleEntry() => new(
        ScriptId: "S1",
        Level: "Information",
        Message: "hello from script",
        TimestampUtc: DateTime.UtcNow,
        VirtualTagId: "V1",
        AlarmId: null,
        EquipmentId: "EQ1");

    /// <summary>
    ///     A published entry is delivered verbatim to a probe subscribed to the
    ///     <see cref="VirtualTagActor.ScriptLogsTopic"/> topic via the DPS mediator.
    /// </summary>
    [Fact]
    public void Publish_routes_entry_to_subscribers_of_the_script_logs_topic()
    {
        var probe = CreateTestProbe();
        var mediator = DistributedPubSub.Get(Sys).Mediator;
        // Send the Subscribe FROM the probe so the SubscribeAck returns to the probe's mailbox
        // (a bare mediator.Tell would route the ack to the implicit TestActor instead).
        probe.Send(mediator, new Subscribe(VirtualTagActor.ScriptLogsTopic, probe.Ref));
        probe.ExpectMsg<SubscribeAck>(TimeSpan.FromSeconds(10));

        var publisher = new DpsScriptLogPublisher(() => Sys, new NoopHub());
        var entry = SampleEntry();

        // The SubscribeAck confirms the subscribe was registered, but DPS topic membership is
        // eventually-consistent — publish in a short retry loop until the probe sees the entry
        // (mirrors the Host.IntegrationTests DPS round-trip pattern), then assert the payload.
        AwaitAssert(() =>
        {
            publisher.Publish(entry);
            probe.ExpectMsg<ScriptLogEntry>(TimeSpan.FromMilliseconds(200)).ShouldBe(entry);
        }, duration: TimeSpan.FromSeconds(5), interval: TimeSpan.FromMilliseconds(250));
    }

    /// <summary>
    ///     A logging sink must never throw into the logging pipeline: if the system
    ///     accessor throws, <see cref="DpsScriptLogPublisher.Publish"/> swallows it.
    /// </summary>
    [Fact]
    public void Publish_does_not_throw_when_the_system_accessor_throws()
    {
        var publisher = new DpsScriptLogPublisher(
            () => throw new InvalidOperationException("system not ready"), new NoopHub());

        Should.NotThrow(() => publisher.Publish(SampleEntry()));
    }

    /// <summary>The constructor rejects a null system accessor.</summary>
    [Fact]
    public void Null_system_accessor_throws_ArgumentNullException()
    {
        Should.Throw<ArgumentNullException>(() => new DpsScriptLogPublisher(null!, new NoopHub()));
    }

    /// <summary>No-op telemetry hub for the publisher tests (the hub tap is asserted in
    /// <c>PublishSeamEmitsToHubTests</c>; here it must simply not interfere).</summary>
    private sealed class NoopHub : ITelemetryLocalHub
    {
        public void Emit(TelemetryItem item) { }

        public ITelemetrySubscription Subscribe(int boundedCapacity) => throw new NotSupportedException();
    }
}
