using Akka.Actor;
using Akka.TestKit.Xunit2;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging.Abstractions;
using Microsoft.Extensions.Options;
using NSubstitute;
using ZB.MOM.WW.ScadaBridge.Commons.Entities.Instances;
using ZB.MOM.WW.ScadaBridge.Commons.Entities.Sites;
using ZB.MOM.WW.ScadaBridge.Commons.Interfaces.Repositories;
using ZB.MOM.WW.ScadaBridge.Communication;
using ZB.MOM.WW.ScadaBridge.Communication.Actors;
using ZB.MOM.WW.ScadaBridge.Communication.Grpc;

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

/// <summary>
/// Tests for DebugStreamService session lifecycle.
/// </summary>
/// <remarks>
/// Shares the <c>DebugStreamStatics</c> xUnit collection with <c>DebugStreamBridgeActorTests</c>
/// so the two classes never race on the actor's static test seams (see that class).
/// </remarks>
[Collection("DebugStreamStatics")]
public class DebugStreamServiceTests : TestKit
{
    [Fact]
    public async Task StartStreamAsync_StreamTerminatesBeforeSnapshot_ThrowsMeaningfulException()
    {
        // Regression test for Communication-001. When the debug stream terminates before
        // the initial snapshot arrives, StartStreamAsync used to let the raw
        // InvalidOperationException from onTerminatedWrapper escape its
        // OperationCanceledException-only catch — the caller saw an untranslated exception
        // and the failure path did not deterministically tear the bridge actor down.
        // The fix catches any failure, tells the bridge actor StopDebugStream, and throws
        // a descriptive exception that names the instance and wraps the underlying cause.
        var instance = new Instance("Site1.Pump01") { Id = 7, SiteId = 3 };
        var site = new Site("Site One", "site-1")
        {
            Id = 3,
            GrpcNodeAAddress = "http://localhost:5100",
            GrpcNodeBAddress = "http://localhost:5200"
        };

        var instanceRepo = Substitute.For<ITemplateEngineRepository>();
        instanceRepo.GetInstanceByIdAsync(7, Arg.Any<CancellationToken>()).Returns(instance);
        var siteRepo = Substitute.For<ISiteRepository>();
        siteRepo.GetSiteByIdAsync(3, Arg.Any<CancellationToken>()).Returns(site);

        var services = new ServiceCollection();
        services.AddScoped(_ => instanceRepo);
        services.AddScoped(_ => siteRepo);
        using var provider = services.BuildServiceProvider();

        var commProbe = CreateTestProbe();
        var commService = new CommunicationService(
            Options.Create(new CommunicationOptions()),
            NullLogger<CommunicationService>.Instance);
        commService.SetCommunicationActor(commProbe.Ref);

        using var grpcFactory = new SiteStreamGrpcClientFactory(NullLoggerFactory.Instance);
        var service = new DebugStreamService(
            commService, provider, grpcFactory, NullLogger<DebugStreamService>.Instance);
        service.SetActorSystem(Sys);

        // Act — start the stream; it blocks awaiting the initial snapshot.
        var startTask = service.StartStreamAsync(instanceId: 7, onEvent: _ => { }, onTerminated: () => { });

        // The bridge actor's PreStart sends SubscribeDebugViewRequest to the comm actor;
        // the envelope's sender is the bridge actor itself.
        commProbe.ExpectMsg<SiteEnvelope>(TimeSpan.FromSeconds(5));
        var bridgeActor = commProbe.LastSender;

        // Simulate the site terminating the stream before any snapshot is delivered.
        bridgeActor.Tell(new DebugStreamTerminated("site-1", "corr"));

        // Assert — a descriptive exception that names the instance and wraps the cause,
        // not the raw "terminated before snapshot received" InvalidOperationException.
        var ex = await Assert.ThrowsAsync<InvalidOperationException>(() => startTask);
        Assert.Contains("Site1.Pump01", ex.Message);
        Assert.NotNull(ex.InnerException);
    }

    [Fact]
    public async Task AttachedSession_IsKeptAliveByTheServiceKeepalive_AndDiesOnceDetached()
    {
        // The consumer half of the orphan net: holding a session in DebugStreamService IS
        // "a consumer is attached", and the service's shared timer is what renews the bridge
        // actor's window. Without this wiring every healthy session self-terminated one
        // window after its snapshot (the old mailbox-based ReceiveTimeout had nothing
        // recurring to reset it) and the consumer was told "Site disconnected".
        var previousKeepalive = DebugStreamService.KeepaliveInterval;
        var previousIdle = DebugStreamBridgeActor.ConsumerIdleTimeout;
        var previousCheck = DebugStreamBridgeActor.ConsumerLivenessCheckInterval;
        DebugStreamService.KeepaliveInterval = TimeSpan.FromMilliseconds(50);
        DebugStreamBridgeActor.ConsumerIdleTimeout = TimeSpan.FromMilliseconds(400);
        DebugStreamBridgeActor.ConsumerLivenessCheckInterval = TimeSpan.FromMilliseconds(50);
        try
        {
            var instance = new Instance("Site1.Pump01") { Id = 7, SiteId = 3 };
            var site = new Site("Site One", "site-1")
            {
                Id = 3,
                GrpcNodeAAddress = "http://localhost:5100",
                GrpcNodeBAddress = "http://localhost:5200"
            };

            var instanceRepo = Substitute.For<ITemplateEngineRepository>();
            instanceRepo.GetInstanceByIdAsync(7, Arg.Any<CancellationToken>()).Returns(instance);
            var siteRepo = Substitute.For<ISiteRepository>();
            siteRepo.GetSiteByIdAsync(3, Arg.Any<CancellationToken>()).Returns(site);

            var services = new ServiceCollection();
            services.AddScoped(_ => instanceRepo);
            services.AddScoped(_ => siteRepo);
            using var provider = services.BuildServiceProvider();

            var commProbe = CreateTestProbe();
            var commService = new CommunicationService(
                Options.Create(new CommunicationOptions()),
                NullLogger<CommunicationService>.Instance);
            commService.SetCommunicationActor(commProbe.Ref);

            // Mock gRPC factory: the real one would dial localhost:5100, fail, and trip the
            // bridge actor's retry budget — a termination unrelated to the orphan net under
            // test. The mock keeps the stream "up" so the only thing that can end this
            // session is the consumer-liveness decision.
            using var grpcFactory = new Grpc.MockSiteStreamGrpcClientFactory(
                new Grpc.MockSiteStreamGrpcClient());
            using var service = new DebugStreamService(
                commService, provider, grpcFactory, NullLogger<DebugStreamService>.Instance);
            service.SetActorSystem(Sys);

            var startTask = service.StartStreamAsync(
                instanceId: 7, onEvent: _ => { }, onTerminated: () => { });

            commProbe.ExpectMsg<SiteEnvelope>(TimeSpan.FromSeconds(5));
            var bridgeActor = commProbe.LastSender;
            Watch(bridgeActor);

            // Resolve the snapshot so the session is fully established.
            bridgeActor.Tell(new ZB.MOM.WW.ScadaBridge.Commons.Messages.DebugView.DebugViewSnapshot(
                "Site1.Pump01",
                new List<ZB.MOM.WW.ScadaBridge.Commons.Messages.Streaming.AttributeValueChanged>(),
                new List<ZB.MOM.WW.ScadaBridge.Commons.Messages.Streaming.AlarmStateChanged>(),
                DateTimeOffset.UtcNow));
            var session = await startTask;

            // Several orphan windows with NO traffic of any kind — only the service's
            // keepalive timer. The session must survive.
            await Task.Delay(TimeSpan.FromMilliseconds(1500));
            ExpectNoMsg(TimeSpan.FromMilliseconds(100));
            Assert.False(bridgeActor.IsNobody());

            // Detach the consumer: the session leaves the registry, keepalives stop, and the
            // actor is stopped (StopStream) — the orphan net is the backstop for the case
            // where that explicit stop never happens.
            service.StopStream(session.SessionId);
            ExpectTerminated(bridgeActor, TimeSpan.FromSeconds(3));
        }
        finally
        {
            DebugStreamService.KeepaliveInterval = previousKeepalive;
            DebugStreamBridgeActor.ConsumerIdleTimeout = previousIdle;
            DebugStreamBridgeActor.ConsumerLivenessCheckInterval = previousCheck;
        }
    }
}