using System.Collections.Concurrent;
using System.Diagnostics.Metrics;
using System.Text.Json;
using Akka.Actor;
using Akka.Cluster.Tools.PublishSubscribe;
using Akka.TestKit;
using Microsoft.EntityFrameworkCore;
using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Commons.Engines;
using ZB.MOM.WW.OtOpcUa.Commons.Messages.Alerts;
using ZB.MOM.WW.OtOpcUa.Commons.Messages.Deploy;
using ZB.MOM.WW.OtOpcUa.Commons.Messages.Fleet;
using ZB.MOM.WW.OtOpcUa.Commons.Messages.Redundancy;
using ZB.MOM.WW.OtOpcUa.Commons.Observability;
using ZB.MOM.WW.OtOpcUa.Commons.Types;
using ZB.MOM.WW.OtOpcUa.Configuration;
using ZB.MOM.WW.OtOpcUa.Configuration.Entities;
using ZB.MOM.WW.OtOpcUa.Configuration.Enums;
using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
using ZB.MOM.WW.OtOpcUa.Runtime.Drivers;
using ZB.MOM.WW.OtOpcUa.Runtime.OpcUa;
using ZB.MOM.WW.OtOpcUa.Runtime.ScriptedAlarms;
using ZB.MOM.WW.OtOpcUa.Runtime.Tests.Harness;

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

/// <summary>
///     archreview 03/S4 — the boot-window primary-gate guard. On a MULTI-driver cluster (member count &gt; 1)
///     while the role is UNKNOWN, the Primary data-plane gates (inbound write, native ack, native alerts emit)
///     default-DENY; on a SINGLE-driver cluster (count &lt;= 1) they default-ALLOW (boot-window / single-node
///     posture). Driver member count is injected via the <c>driverMemberCountProvider</c> Props seam.
/// </summary>
public sealed class DriverHostActorPrimaryGateTests : RuntimeActorTestBase
{
    private static readonly NodeId TestNode = NodeId.Parse("driver-pgate-test");
    private static readonly RevisionHash RevA = RevisionHash.Parse(new string('a', 64));
    private static readonly DateTime Ts = new(2026, 7, 13, 10, 0, 0, DateTimeKind.Utc);
    private static readonly TimeSpan Timeout = TimeSpan.FromSeconds(5);

    // ---------------- write gate ----------------

    /// <summary>Role unknown + a real driver peer (count 2) ⇒ RouteNodeWrite is DENIED with the
    /// boot-window reason and the driver sees no write.</summary>
    [Fact]
    public void Unknown_role_multi_driver_denies_write_with_role_unknown_reason()
    {
        var db = NewInMemoryDbFactory();
        var recorder = new RecordingDriverFactory("Modbus");
        var dep = SeedWriteTagDeployment(db);
        var actor = SpawnWriteHost(db, dep, recorder, driverMemberCount: 2);

        var asker = CreateTestProbe();
        actor.Tell(new DriverHostActor.RouteNodeWrite("eq-1/speed", 123.0), asker.Ref);

        var result = asker.ExpectMsg<DriverHostActor.NodeWriteResult>(Timeout);
        result.Success.ShouldBeFalse();
        result.Reason.ShouldBe("not primary (role unknown)");
        recorder.Writes.ShouldBeEmpty();
    }

    /// <summary>Role unknown + no driver peer (count 1) ⇒ the write is SERVICED (single-node / boot-window
    /// posture preserved).</summary>
    [Fact]
    public void Unknown_role_single_driver_services_write()
    {
        var db = NewInMemoryDbFactory();
        var recorder = new RecordingDriverFactory("Modbus");
        var dep = SeedWriteTagDeployment(db);
        var actor = SpawnWriteHost(db, dep, recorder, driverMemberCount: 1);

        // The gate must ALLOW (count 1, role unknown). The driver child's async connect can lag the ApplyAck,
        // so a first write may transiently report "driver not connected" — retry until connected (a real
        // client retries too). The point under test is that the gate never denies (never "not primary").
        AwaitAssert(() =>
        {
            var asker = CreateTestProbe();
            actor.Tell(new DriverHostActor.RouteNodeWrite("eq-1/speed", 123.0), asker.Ref);
            var res = asker.ExpectMsg<DriverHostActor.NodeWriteResult>(Timeout);
            res.Reason.ShouldNotBe("not primary");
            res.Reason.ShouldNotBe("not primary (role unknown)");
            res.Success.ShouldBeTrue(res.Reason);
        }, duration: TimeSpan.FromSeconds(10));
        recorder.Writes.ShouldNotBeEmpty();
    }

    /// <summary>A Primary snapshot services even at count 2; a Secondary snapshot denies with the steady-state
    /// reason (distinct from the boot-window reason).</summary>
    [Fact]
    public void Known_role_wins_over_member_count()
    {
        var db = NewInMemoryDbFactory();
        var recorder = new RecordingDriverFactory("Modbus");
        var dep = SeedWriteTagDeployment(db);
        var actor = SpawnWriteHost(db, dep, recorder, driverMemberCount: 2);

        // Primary snapshot ⇒ serviced even with a driver peer. Retry through the transient driver-connect
        // window; the invariant under test is that the gate never denies a Primary.
        TellRole(actor, RedundancyRole.Primary);
        AwaitAssert(() =>
        {
            var asker1 = CreateTestProbe();
            actor.Tell(new DriverHostActor.RouteNodeWrite("eq-1/speed", 1.0), asker1.Ref);
            var res = asker1.ExpectMsg<DriverHostActor.NodeWriteResult>(Timeout);
            res.Reason.ShouldNotBe("not primary");
            res.Success.ShouldBeTrue(res.Reason);
        }, duration: TimeSpan.FromSeconds(10));

        // Secondary snapshot ⇒ denied with the steady-state reason.
        TellRole(actor, RedundancyRole.Secondary);
        var asker2 = CreateTestProbe();
        actor.Tell(new DriverHostActor.RouteNodeWrite("eq-1/speed", 2.0), asker2.Ref);
        var denied = asker2.ExpectMsg<DriverHostActor.NodeWriteResult>(Timeout);
        denied.Success.ShouldBeFalse();
        denied.Reason.ShouldBe("not primary");
    }

    /// <summary>The denial meter carries the site + reason tags.</summary>
    [Fact]
    public void Denied_write_increments_primary_gate_denied_meter_with_tags()
    {
        using var recorder = new MeterRecorder("otopcua.redundancy.primary_gate_denied");
        var db = NewInMemoryDbFactory();
        var factory = new RecordingDriverFactory("Modbus");
        var dep = SeedWriteTagDeployment(db);
        var actor = SpawnWriteHost(db, dep, factory, driverMemberCount: 2);

        var asker = CreateTestProbe();
        actor.Tell(new DriverHostActor.RouteNodeWrite("eq-1/speed", 9.0), asker.Ref);
        asker.ExpectMsg<DriverHostActor.NodeWriteResult>(Timeout).Success.ShouldBeFalse();

        AwaitAssert(() =>
        {
            recorder.Total.ShouldBeGreaterThanOrEqualTo(1);
            recorder.WithTag("site", "write").ShouldBeGreaterThanOrEqualTo(1);
            recorder.WithTag("reason", "role-unknown").ShouldBeGreaterThanOrEqualTo(1);
        }, duration: Timeout);
    }

    // ---------------- ack gate ----------------

    /// <summary>Role unknown + count 2 ⇒ a native-alarm ack is dropped at Warning and the denial meter
    /// increments with site=ack.</summary>
    [Fact]
    public void Unknown_role_multi_driver_drops_native_ack_with_warning_and_meter()
    {
        using var meter = new MeterRecorder("otopcua.redundancy.primary_gate_denied");
        var db = NewInMemoryDbFactory();
        var dep = SeedAlarmTagDeployment(db);
        var (actor, _) = SpawnAlarmHost(db, dep, driverMemberCount: 2);

        EventFilter.Warning(contains: "role unknown").ExpectOne(() =>
            actor.Tell(new DriverHostActor.RouteNativeAlarmAck("eq-1/temp_hi", Comment: null, OperatorUser: "op")));

        AwaitAssert(() =>
        {
            meter.WithTag("site", "ack").ShouldBeGreaterThanOrEqualTo(1);
        }, duration: Timeout);
    }

    // ---------------- alarm-emit gate ----------------

    /// <summary>Role unknown + count 2 ⇒ ForwardNativeAlarm still writes the (ungated) OPC UA condition update
    /// but publishes NO cluster-wide alerts transition.</summary>
    [Fact]
    public void Unknown_role_multi_driver_suppresses_alerts_emit_but_updates_condition()
    {
        var db = NewInMemoryDbFactory();
        var dep = SeedAlarmTagDeployment(db);
        var alerts = CreateTestProbe();
        SubscribeToAlerts(alerts);
        var (actor, publish) = SpawnAlarmHost(db, dep, driverMemberCount: 2);

        actor.Tell(RaiseAlarm());

        // The ungated OPC UA condition write still arrives.
        publish.ExpectMsg<OpcUaPublishActor.AlarmStateUpdate>(Timeout).AlarmNodeId.ShouldBe("eq-1/temp_hi");
        // The cluster-wide alerts publish is suppressed (a real Primary peer publishes the single copy).
        alerts.ExpectNoMsg(TimeSpan.FromMilliseconds(500));
    }

    /// <summary>Role unknown + count 1 ⇒ ForwardNativeAlarm publishes the alerts transition (single-node
    /// posture preserved).</summary>
    [Fact]
    public void Unknown_role_single_driver_publishes_alerts_emit()
    {
        var db = NewInMemoryDbFactory();
        var dep = SeedAlarmTagDeployment(db);
        var alerts = CreateTestProbe();
        SubscribeToAlerts(alerts);
        var (actor, publish) = SpawnAlarmHost(db, dep, driverMemberCount: 1);

        actor.Tell(RaiseAlarm());

        publish.ExpectMsg<OpcUaPublishActor.AlarmStateUpdate>(Timeout);
        alerts.ExpectMsg<AlarmTransitionEvent>(Timeout).AlarmId.ShouldBe("eq-1/temp_hi");
    }

    // ---------------- helpers ----------------

    private static DriverInstanceActor.AttributeAlarmPublished RaiseAlarm() =>
        new("drv-1", new AlarmEventArgs(
            new StubAlarmHandle(),
            SourceNodeId: "Temp",
            ConditionId: "Temp.HiHi",
            AlarmType: "OffNormalAlarm",
            Message: "temperature high",
            Severity: AlarmSeverity.High,
            SourceTimestampUtc: Ts,
            Kind: AlarmTransitionKind.Raise));

    private static void TellRole(IActorRef host, RedundancyRole role) =>
        host.Tell(new RedundancyStateChanged(
            new[]
            {
                new NodeRedundancyState(TestNode, role,
                    IsClusterLeader: role == RedundancyRole.Primary,
                    IsRoleLeaderForDriver: role == RedundancyRole.Primary,
                    AsOfUtc: DateTime.UtcNow),
            },
            CorrelationId.NewId()));

    private IActorRef SpawnWriteHost(
        IDbContextFactory<OtOpcUaConfigDbContext> db, DeploymentId dep, IDriverFactory factory, int driverMemberCount)
    {
        var coordinator = CreateTestProbe();
        var actor = Sys.ActorOf(DriverHostActor.Props(
            db, TestNode, coordinator.Ref,
            driverFactory: factory,
            localRoles: new HashSet<string> { "driver" },
            driverMemberCountProvider: () => driverMemberCount));

        actor.Tell(new DispatchDeployment(dep, RevA, CorrelationId.NewId()));
        coordinator.ExpectMsg<ApplyAck>(Timeout).Outcome.ShouldBe(ApplyAckOutcome.Applied);
        return actor;
    }

    private (IActorRef Actor, TestProbe Publish) SpawnAlarmHost(
        IDbContextFactory<OtOpcUaConfigDbContext> db, DeploymentId dep, int driverMemberCount)
    {
        var coordinator = CreateTestProbe();
        var publish = CreateTestProbe();
        var mux = CreateTestProbe();
        var vtHost = CreateTestProbe();

        var actor = Sys.ActorOf(DriverHostActor.Props(
            db, TestNode, coordinator.Ref,
            localRoles: new HashSet<string> { "driver" },
            dependencyMux: mux.Ref,
            opcUaPublishActor: publish.Ref,
            virtualTagEvaluator: NullVirtualTagEvaluator.Instance,
            virtualTagHostOverride: vtHost.Ref,
            driverMemberCountProvider: () => driverMemberCount));

        actor.Tell(new DispatchDeployment(dep, RevA, CorrelationId.NewId()));
        coordinator.ExpectMsg<ApplyAck>(Timeout).Outcome.ShouldBe(ApplyAckOutcome.Applied);
        publish.ExpectMsg<OpcUaPublishActor.RebuildAddressSpace>(Timeout);
        return (actor, publish);
    }

    private void SubscribeToAlerts(TestProbe probe)
    {
        DistributedPubSub.Get(Sys).Mediator.Tell(
            new Subscribe(ScriptedAlarmHostActor.AlertsTopic, probe.Ref), probe.Ref);
        probe.ExpectMsg<SubscribeAck>(Timeout);
    }

    private static DeploymentId SeedWriteTagDeployment(IDbContextFactory<OtOpcUaConfigDbContext> db)
    {
        var artifact = JsonSerializer.SerializeToUtf8Bytes(new
        {
            Namespaces = new[] { new { NamespaceId = "ns-eq", Kind = 0 } },
            DriverInstances = new[]
            {
                new
                {
                    DriverInstanceRowId = Guid.NewGuid(),
                    DriverInstanceId = "drv-1",
                    Name = "drv-1",
                    DriverType = "Modbus",
                    Enabled = true,
                    DriverConfig = "{}",
                    NamespaceId = "ns-eq",
                },
            },
            Tags = new[]
            {
                new
                {
                    TagId = "tag-0",
                    EquipmentId = "eq-1",
                    DriverInstanceId = "drv-1",
                    Name = "speed",
                    FolderPath = (string?)null,
                    DataType = "Double",
                    TagConfig = JsonSerializer.Serialize(new { FullName = "40001" }),
                },
            },
        });
        return SealArtifact(db, artifact);
    }

    private static DeploymentId SeedAlarmTagDeployment(IDbContextFactory<OtOpcUaConfigDbContext> db)
    {
        var artifact = JsonSerializer.SerializeToUtf8Bytes(new
        {
            Namespaces = new[] { new { NamespaceId = "ns-eq", Kind = 0 } },
            DriverInstances = new[] { new { DriverInstanceId = "drv-1", NamespaceId = "ns-eq" } },
            Tags = new[]
            {
                new
                {
                    TagId = "tag-0",
                    EquipmentId = "eq-1",
                    DriverInstanceId = "drv-1",
                    Name = "temp_hi",
                    FolderPath = (string?)null,
                    DataType = "Boolean",
                    TagConfig = JsonSerializer.Serialize(new
                    {
                        FullName = "Temp.HiHi",
                        alarm = new { alarmType = "OffNormalAlarm", severity = 700 },
                    }),
                },
            },
        });
        return SealArtifact(db, artifact);
    }

    private static DeploymentId SealArtifact(IDbContextFactory<OtOpcUaConfigDbContext> db, byte[] artifact)
    {
        var id = DeploymentId.NewId();
        using var ctx = db.CreateDbContext();
        ctx.Deployments.Add(new Deployment
        {
            DeploymentId = id.Value,
            RevisionHash = RevA.Value,
            Status = DeploymentStatus.Sealed,
            CreatedBy = "test",
            SealedAtUtc = DateTime.UtcNow,
            ArtifactBlob = artifact,
        });
        ctx.SaveChanges();
        return id;
    }

    private sealed class StubAlarmHandle : IAlarmSubscriptionHandle
    {
        public string DiagnosticId => "stub-alarm-sub";
    }

    private sealed class RecordingDriverFactory : IDriverFactory
    {
        private readonly string _supportedType;
        private readonly RecordingDriver _driver = new();
        public RecordingDriverFactory(string supportedType) { _supportedType = supportedType; }
        public IReadOnlyList<WriteRequest> Writes => _driver.Writes;

        public IDriver? TryCreate(string driverType, string driverInstanceId, string driverConfigJson)
        {
            if (!string.Equals(driverType, _supportedType, StringComparison.Ordinal)) return null;
            _driver.Bind(driverInstanceId, driverType);
            return _driver;
        }

        public IReadOnlyCollection<string> SupportedTypes => new[] { _supportedType };
    }

    private sealed class RecordingDriver : IDriver, IWritable
    {
        private readonly ConcurrentQueue<WriteRequest> _writes = new();
        public string DriverInstanceId { get; private set; } = string.Empty;
        public string DriverType { get; private set; } = string.Empty;
        public IReadOnlyList<WriteRequest> Writes => _writes.ToArray();
        public void Bind(string id, string type) { DriverInstanceId = id; DriverType = type; }
        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, DateTime.UtcNow, LastError: null);
        public long GetMemoryFootprint() => 0;
        public Task FlushOptionalCachesAsync(CancellationToken cancellationToken) => Task.CompletedTask;
        public Task<IReadOnlyList<WriteResult>> WriteAsync(
            IReadOnlyList<WriteRequest> writes, CancellationToken cancellationToken)
        {
            foreach (var w in writes) _writes.Enqueue(w);
            return Task.FromResult<IReadOnlyList<WriteResult>>(writes.Select(_ => new WriteResult(0u)).ToArray());
        }
    }

    private sealed class MeterRecorder : IDisposable
    {
        private readonly string _name;
        private readonly MeterListener _listener;
        private long _total;
        private readonly List<KeyValuePair<string, object?>[]> _tagSets = new();
        private readonly object _gate = new();

        public MeterRecorder(string instrumentName)
        {
            _name = instrumentName;
            _listener = new MeterListener
            {
                InstrumentPublished = (instrument, listener) =>
                {
                    if (instrument.Meter.Name == OtOpcUaTelemetry.MeterName && instrument.Name == _name)
                        listener.EnableMeasurementEvents(instrument);
                }
            };
            _listener.SetMeasurementEventCallback<long>((_, value, tags, _) =>
            {
                lock (_gate) { _total += value; _tagSets.Add(tags.ToArray()); }
            });
            _listener.Start();
        }

        public long Total { get { lock (_gate) return _total; } }

        public int WithTag(string key, string value)
        {
            lock (_gate) return _tagSets.Count(set => set.Any(t => t.Key == key && Equals(t.Value, value)));
        }

        public void Dispose() => _listener.Dispose();
    }
}