using Akka.Actor;
using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Commons.OpcUa;
using ZB.MOM.WW.OtOpcUa.Runtime.OpcUa;
using ZB.MOM.WW.OtOpcUa.Runtime.Tests.Harness;

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

/// <summary>
///     <see cref="OpcUaPublishActor.AttributeStatusBatchUpdate"/> — the status-only route to the sink
///     that the comms-loss fan-out uses (archreview 03/S15). It must reach
///     <see cref="IOpcUaAddressSpaceSink.WriteStatuses"/> as exactly one call, never decompose into
///     value writes (which would null every node's value), and survive a throwing sink.
/// </summary>
public sealed class OpcUaPublishActorStatusBatchTests : RuntimeActorTestBase
{
    /// <summary>
    ///     One message, one <c>WriteStatuses</c> call carrying every item verbatim — and <b>zero</b> value
    ///     writes. The second half is load-bearing: a handler that fell through to <c>WriteValues</c> (or
    ///     to the interface's default, which loops <c>WriteValue</c> with a null value) would satisfy "the
    ///     status arrived" while erasing the last known value the annotation exists to keep.
    /// </summary>
    [Fact]
    public void Status_batch_reaches_sink_as_one_WriteStatuses_call()
    {
        var sink = new RecordingSink();
        var actor = Sys.ActorOf(OpcUaPublishActor.PropsForTests(sink: sink));

        var t0 = new DateTime(2026, 8, 20, 10, 0, 0, DateTimeKind.Utc);
        var items = new[]
        {
            new StatusWrite("Plant/Modbus/dev1/Speed", OpcUaStatus.BadNoCommunication, t0, AddressSpaceRealm.Raw),
            new StatusWrite("AreaA/Line1/Eq1/Speed", OpcUaStatus.BadNoCommunication, t0, AddressSpaceRealm.Uns),
        };

        actor.Tell(new OpcUaPublishActor.AttributeStatusBatchUpdate(items));

        AwaitAssert(() => sink.StatusBatches.Count.ShouldBe(1), PresenceBudget);
        var batch = sink.StatusBatches[0];
        batch.Count.ShouldBe(2);
        batch[0].ShouldBe(items[0]);
        batch[1].ShouldBe(items[1]);

        sink.ValueBatches.Count.ShouldBe(0, "a status annotation must never be routed as a value write");
        sink.SingleWrites.Count.ShouldBe(0);
    }

    /// <summary>
    ///     A partial failure is metered honestly, exactly as the value batch is: the tally advances by the
    ///     items the sink DID apply, not by zero and not by the whole batch.
    /// </summary>
    [Fact]
    public void Partial_failure_still_counts_the_items_that_landed()
    {
        var sink = new PartialFailureSink();
        var actor = ActorOfAsTestActorRef<OpcUaPublishActor>(OpcUaPublishActor.PropsForTests(sink: sink));

        var t0 = new DateTime(2026, 8, 20, 10, 0, 0, DateTimeKind.Utc);
        actor.Tell(new OpcUaPublishActor.AttributeStatusBatchUpdate(new[]
        {
            new StatusWrite("Plant/Modbus/dev1/Speed", OpcUaStatus.BadNoCommunication, t0, AddressSpaceRealm.Raw),
            new StatusWrite("", OpcUaStatus.BadNoCommunication, t0, AddressSpaceRealm.Raw),
            new StatusWrite("Plant/Modbus/dev1/Temp", OpcUaStatus.BadNoCommunication, t0, AddressSpaceRealm.Raw),
        }));

        sink.Threw.ShouldBeTrue();
        actor.UnderlyingActor.WriteCount.ShouldBe(2,
            "the two items the sink DID apply must still be counted — not 0 (the general catch) and not 3");
    }

    /// <summary>
    ///     A throwing sink is swallowed and logged, so a node manager fault cannot restart the publish
    ///     actor and drop live traffic. As in the value-batch suite, survival alone proves nothing (Akka's
    ///     restart preserves the mailbox) — the load-bearing assertions are that no exception reaches
    ///     supervision and that the handler logs its own Warning.
    /// </summary>
    [Fact]
    public void Sink_throw_is_swallowed_and_logged()
    {
        var sink = new ThrowOnWriteStatusesSink();
        var actor = Sys.ActorOf(OpcUaPublishActor.PropsForTests(sink: sink));

        var t0 = new DateTime(2026, 8, 20, 10, 0, 0, DateTimeKind.Utc);

        EventFilter.Exception<InvalidOperationException>().Expect(0, () =>
        {
            EventFilter.Warning(contains: "sink.WriteStatuses threw").ExpectOne(() =>
                actor.Tell(new OpcUaPublishActor.AttributeStatusBatchUpdate(new[]
                {
                    new StatusWrite("Plant/Modbus/dev1/Speed", OpcUaStatus.BadNoCommunication, t0, AddressSpaceRealm.Raw),
                })));

            // Survival: a follow-up on the untouched per-item value path lands only if the actor is pumping.
            actor.Tell(new OpcUaPublishActor.AttributeValueUpdate(
                "Plant/Modbus/dev1/Temp", 2, OpcUaStatus.Good, t0, AddressSpaceRealm.Raw));

            AwaitAssert(() => sink.SingleWrites.Count.ShouldBe(1), PresenceBudget);
        });

        sink.Threw.ShouldBeTrue();
    }

    private void AwaitAssert(Action assertion, TimeSpan duration)
    {
        var deadline = DateTime.UtcNow + duration;
        Exception? last = null;
        while (DateTime.UtcNow < deadline)
        {
            try { assertion(); return; }
            catch (Exception ex) { last = ex; Thread.Sleep(25); }
        }
        if (last is not null) throw last;
    }

    /// <summary>Records status batches, value batches and per-item value writes separately, so a handler
    /// that routed a status annotation down the value path is distinguishable from one that did not.</summary>
    private class RecordingSink : IOpcUaAddressSpaceSink
    {
        private readonly object _gate = new();
        private readonly List<IReadOnlyList<StatusWrite>> _statusBatches = new();
        private readonly List<IReadOnlyList<ValueWrite>> _valueBatches = new();
        private readonly List<ValueWrite> _singles = new();

        public IReadOnlyList<IReadOnlyList<StatusWrite>> StatusBatches { get { lock (_gate) return _statusBatches.ToArray(); } }
        public IReadOnlyList<IReadOnlyList<ValueWrite>> ValueBatches { get { lock (_gate) return _valueBatches.ToArray(); } }
        public IReadOnlyList<ValueWrite> SingleWrites { get { lock (_gate) return _singles.ToArray(); } }

        public void WriteValue(string nodeId, object? value, uint statusCode, DateTime sourceTimestampUtc, AddressSpaceRealm realm = AddressSpaceRealm.Uns)
        {
            lock (_gate) _singles.Add(new ValueWrite(nodeId, value, statusCode, sourceTimestampUtc, realm));
        }

        public void WriteValues(IReadOnlyList<ValueWrite> values)
        {
            lock (_gate) _valueBatches.Add(values.ToArray());
        }

        // Overrides the interface's default (which loops WriteValue with a NULL value).
        public virtual void WriteStatuses(IReadOnlyList<StatusWrite> statuses)
        {
            lock (_gate) _statusBatches.Add(statuses.ToArray());
        }

        public void WriteAlarmQuality(string alarmNodeId, uint statusCode, DateTime sourceTimestampUtc, AddressSpaceRealm realm) { }
        public void WriteAlarmCondition(string alarmNodeId, AlarmConditionSnapshot state, DateTime occurredUtc, AddressSpaceRealm realm = AddressSpaceRealm.Uns) { }
        public void MaterialiseAlarmCondition(string alarmNodeId, string equipmentNodeId, string displayName, string alarmType, int severity, AddressSpaceRealm realm, bool isNative = false) { }
        public void EnsureFolder(string folderNodeId, string? parentNodeId, string displayName, AddressSpaceRealm realm = AddressSpaceRealm.Uns) { }
        public void EnsureVariable(string variableNodeId, string? parentFolderNodeId, string displayName, string dataType, bool writable, AddressSpaceRealm realm, string? historianTagname = null, bool isArray = false, uint? arrayLength = null, bool refuseArrayOnScalar = false) { }
        public void RebuildAddressSpace() { }
        public void RaiseNodesAddedModelChange(string affectedNodeId, AddressSpaceRealm realm = AddressSpaceRealm.Uns) { }
        public void WireAlarmNotifiers(string alarmNodeId, AddressSpaceRealm alarmRealm, IReadOnlyList<string> notifierFolderNodeIds, AddressSpaceRealm notifierFolderRealm) { }
        public void AddReference(string sourceNodeId, AddressSpaceRealm sourceRealm, string targetNodeId, AddressSpaceRealm targetRealm, string referenceType = "Organizes") { }
    }

    /// <summary>Throws a PLAIN exception out of the status batch — drives the handler's general catch.</summary>
    private sealed class ThrowOnWriteStatusesSink : RecordingSink
    {
        private int _threw;

        public bool Threw => Volatile.Read(ref _threw) != 0;

        public override void WriteStatuses(IReadOnlyList<StatusWrite> statuses)
        {
            Interlocked.Exchange(ref _threw, 1);
            throw new InvalidOperationException("simulated status-write fault");
        }
    }

    /// <summary>Models the real sink's PARTIAL failure: applies every item with a non-empty NodeId, then
    /// reports the aggregate as a <see cref="ValueWriteBatchException"/>.</summary>
    private sealed class PartialFailureSink : RecordingSink
    {
        private int _threw;

        public bool Threw => Volatile.Read(ref _threw) != 0;

        public override void WriteStatuses(IReadOnlyList<StatusWrite> statuses)
        {
            var applied = statuses.Where(s => !string.IsNullOrEmpty(s.NodeId)).ToArray();
            var failedCount = statuses.Count - applied.Length;
            if (failedCount == 0)
            {
                base.WriteStatuses(statuses);
                return;
            }

            base.WriteStatuses(applied);
            Interlocked.Exchange(ref _threw, 1);
            throw new ValueWriteBatchException(
                firstFailedNodeId: statuses.First(s => string.IsNullOrEmpty(s.NodeId)).NodeId,
                failedCount: failedCount,
                succeededCount: applied.Length,
                firstFailure: new ArgumentException("empty NodeId"));
        }
    }
}