using System;
using System.Collections.Generic;
using MxGateway.Contracts.Proto;
using MxGateway.Worker.MxAccess;

namespace MxGateway.Worker.Tests.MxAccess;

/// <summary>
///     Unit tests for the in-process A.3 dispatcher: prove that
///     <see cref="IMxAccessAlarmConsumer.AlarmTransitionEmitted"/> events
///     fan out to the worker's <see cref="MxAccessEventQueue"/> as proto
///     <see cref="OnAlarmTransitionEvent"/> messages with correctly mapped
///     fields. The fake consumer below stands in for the wnwrap-backed
///     production implementation so this exercise needs no AVEVA install.
/// </summary>
public sealed class AlarmDispatcherTests
{
    private const string SessionId = "session-001";

    [Fact]
    public void OnTransition_WhenAlarmTransitionRaised_LandsInQueueWithMappedFields()
    {
        FakeAlarmConsumer consumer = new FakeAlarmConsumer();
        MxAccessEventQueue queue = new MxAccessEventQueue();
        MxAccessAlarmEventSink sink = new MxAccessAlarmEventSink(queue, new MxAccessEventMapper());
        using AlarmDispatcher dispatcher = new AlarmDispatcher(consumer, sink, SessionId);

        DateTime ts = new DateTime(2026, 5, 1, 17, 26, 14, 709, DateTimeKind.Utc);
        consumer.RaiseTransition(new MxAlarmTransitionEvent
        {
            PreviousState = MxAlarmStateKind.Unspecified,
            Record = new MxAlarmSnapshotRecord
            {
                AlarmGuid = Guid.NewGuid(),
                ProviderName = "Galaxy",
                Group = "TestArea",
                TagName = "TestMachine_001.TestAlarm001",
                Type = "DSC",
                Priority = 500,
                State = MxAlarmStateKind.UnackAlm,
                TransitionTimestampUtc = ts,
                AlarmComment = "Test alarm #1",
            },
        });

        Assert.Equal(1, queue.Count);
        Assert.True(queue.TryDequeue(out WorkerEvent? workerEvent));
        Assert.NotNull(workerEvent);
        MxEvent mxEvent = workerEvent!.Event;
        Assert.Equal(MxEventFamily.OnAlarmTransition, mxEvent.Family);
        Assert.Equal(SessionId, mxEvent.SessionId);

        OnAlarmTransitionEvent body = mxEvent.OnAlarmTransition;
        Assert.NotNull(body);
        Assert.Equal("Galaxy!TestArea.TestMachine_001.TestAlarm001", body.AlarmFullReference);
        Assert.Equal("TestMachine_001.TestAlarm001", body.SourceObjectReference);
        Assert.Equal("DSC", body.AlarmTypeName);
        Assert.Equal(AlarmTransitionKind.Raise, body.TransitionKind);
        Assert.Equal(500, body.Severity);
        Assert.Equal("Test alarm #1", body.OperatorComment);
        Assert.Equal("TestArea", body.Category);
        Assert.NotNull(body.TransitionTimestamp);
        Assert.Equal(ts, body.TransitionTimestamp.ToDateTime());
    }

    [Fact]
    public void OnTransition_WithConsecutiveUnchangedState_DoesNotEmitTransition()
    {
        // Mapper.MapTransition returns Unspecified when the state didn't
        // change; the dispatcher should drop the event before queueing.
        FakeAlarmConsumer consumer = new FakeAlarmConsumer();
        MxAccessEventQueue queue = new MxAccessEventQueue();
        MxAccessAlarmEventSink sink = new MxAccessAlarmEventSink(queue, new MxAccessEventMapper());
        using AlarmDispatcher dispatcher = new AlarmDispatcher(consumer, sink, SessionId);

        consumer.RaiseTransition(new MxAlarmTransitionEvent
        {
            PreviousState = MxAlarmStateKind.UnackAlm,
            Record = new MxAlarmSnapshotRecord
            {
                AlarmGuid = Guid.NewGuid(),
                ProviderName = "Galaxy",
                Group = "X",
                TagName = "Y",
                State = MxAlarmStateKind.UnackAlm,
            },
        });

        Assert.Equal(0, queue.Count);
    }

    [Theory]
    [InlineData(MxAlarmStateKind.Unspecified, MxAlarmStateKind.UnackAlm, AlarmTransitionKind.Raise)]
    [InlineData(MxAlarmStateKind.UnackAlm, MxAlarmStateKind.AckAlm, AlarmTransitionKind.Acknowledge)]
    [InlineData(MxAlarmStateKind.UnackAlm, MxAlarmStateKind.UnackRtn, AlarmTransitionKind.Clear)]
    [InlineData(MxAlarmStateKind.UnackRtn, MxAlarmStateKind.UnackAlm, AlarmTransitionKind.Raise)]
    public void MapTransition_ForEachStatePair_FollowsStateTable(
        MxAlarmStateKind previous,
        MxAlarmStateKind current,
        AlarmTransitionKind expected)
    {
        FakeAlarmConsumer consumer = new FakeAlarmConsumer();
        MxAccessEventQueue queue = new MxAccessEventQueue();
        MxAccessAlarmEventSink sink = new MxAccessAlarmEventSink(queue, new MxAccessEventMapper());
        using AlarmDispatcher dispatcher = new AlarmDispatcher(consumer, sink, SessionId);

        consumer.RaiseTransition(new MxAlarmTransitionEvent
        {
            PreviousState = previous,
            Record = new MxAlarmSnapshotRecord
            {
                AlarmGuid = Guid.NewGuid(),
                ProviderName = "Galaxy",
                Group = "G",
                TagName = "T",
                State = current,
            },
        });

        Assert.Equal(1, queue.Count);
        queue.TryDequeue(out WorkerEvent? evt);
        Assert.Equal(expected, evt!.Event.OnAlarmTransition.TransitionKind);
    }

    [Fact]
    public void Subscribe_WhenInvoked_ForwardsToConsumer()
    {
        FakeAlarmConsumer consumer = new FakeAlarmConsumer();
        using AlarmDispatcher dispatcher = new AlarmDispatcher(
            consumer,
            new MxAccessAlarmEventSink(new MxAccessEventQueue(), new MxAccessEventMapper()),
            SessionId);

        dispatcher.Subscribe(@"\\HOST\Galaxy!Area1");
        Assert.Equal(@"\\HOST\Galaxy!Area1", consumer.LastSubscription);
    }

    [Fact]
    public void Acknowledge_WhenInvoked_ForwardsToConsumerWithFullOperatorIdentity()
    {
        FakeAlarmConsumer consumer = new FakeAlarmConsumer();
        consumer.AcknowledgeReturn = 0;
        using AlarmDispatcher dispatcher = new AlarmDispatcher(
            consumer,
            new MxAccessAlarmEventSink(new MxAccessEventQueue(), new MxAccessEventMapper()),
            SessionId);

        Guid guid = Guid.NewGuid();
        int rc = dispatcher.Acknowledge(
            guid, "Acked", "alice", "WS01", "CORP", "Alice Smith");

        Assert.Equal(0, rc);
        Assert.Equal(guid, consumer.LastAckGuid);
        Assert.Equal("Acked", consumer.LastAckComment);
        Assert.Equal("alice", consumer.LastAckOperatorName);
        Assert.Equal("WS01", consumer.LastAckOperatorNode);
        Assert.Equal("CORP", consumer.LastAckOperatorDomain);
        Assert.Equal("Alice Smith", consumer.LastAckOperatorFullName);
    }

    [Fact]
    public void AcknowledgeByName_WhenInvoked_ForwardsToConsumerWithFullTuple()
    {
        FakeAlarmConsumer consumer = new FakeAlarmConsumer { AcknowledgeReturn = 0 };
        using AlarmDispatcher dispatcher = new AlarmDispatcher(
            consumer,
            new MxAccessAlarmEventSink(new MxAccessEventQueue(), new MxAccessEventMapper()),
            SessionId);

        int rc = dispatcher.AcknowledgeByName(
            alarmName: "TestMachine_001.TestAlarm001",
            providerName: "Galaxy",
            groupName: "TestArea",
            ackComment: "ack",
            ackOperatorName: "alice",
            ackOperatorNode: "WS",
            ackOperatorDomain: "CORP",
            ackOperatorFullName: "Alice Smith");

        Assert.Equal(0, rc);
        Assert.NotNull(consumer.LastAckByNameTuple);
        Assert.Equal("TestMachine_001.TestAlarm001", consumer.LastAckByNameTuple!.Value.Name);
        Assert.Equal("Galaxy", consumer.LastAckByNameTuple!.Value.Provider);
        Assert.Equal("TestArea", consumer.LastAckByNameTuple!.Value.Group);
    }

    [Fact]
    public void SnapshotActiveAlarms_WhenConsumerHasRecords_MapsRecordsToProtos()
    {
        FakeAlarmConsumer consumer = new FakeAlarmConsumer();
        DateTime ts = new DateTime(2026, 5, 1, 17, 26, 14, 709, DateTimeKind.Utc);
        consumer.SnapshotResult = new[]
        {
            new MxAlarmSnapshotRecord
            {
                AlarmGuid = Guid.NewGuid(),
                ProviderName = "Galaxy",
                Group = "TestArea",
                TagName = "Tag1",
                Type = "DSC",
                Priority = 500,
                State = MxAlarmStateKind.UnackAlm,
                TransitionTimestampUtc = ts,
                AlarmComment = "x",
            },
            new MxAlarmSnapshotRecord
            {
                AlarmGuid = Guid.NewGuid(),
                ProviderName = "Galaxy",
                Group = "TestArea",
                TagName = "Tag2",
                Type = "ANL",
                Priority = 100,
                State = MxAlarmStateKind.AckAlm,
                TransitionTimestampUtc = ts,
            },
        };
        using AlarmDispatcher dispatcher = new AlarmDispatcher(
            consumer,
            new MxAccessAlarmEventSink(new MxAccessEventQueue(), new MxAccessEventMapper()),
            SessionId);

        IReadOnlyList<ActiveAlarmSnapshot> snapshots = dispatcher.SnapshotActiveAlarms();
        Assert.Equal(2, snapshots.Count);

        Assert.Equal("Galaxy!TestArea.Tag1", snapshots[0].AlarmFullReference);
        Assert.Equal(AlarmConditionState.Active, snapshots[0].CurrentState);
        Assert.Equal(500, snapshots[0].Severity);
        Assert.Equal(ts, snapshots[0].LastTransitionTimestamp.ToDateTime());

        Assert.Equal("Galaxy!TestArea.Tag2", snapshots[1].AlarmFullReference);
        Assert.Equal(AlarmConditionState.ActiveAcked, snapshots[1].CurrentState);
    }

    [Fact]
    public void Dispose_WhenSubscribed_UnsubscribesHandlerAndDisposesConsumer()
    {
        FakeAlarmConsumer consumer = new FakeAlarmConsumer();
        MxAccessEventQueue queue = new MxAccessEventQueue();
        MxAccessAlarmEventSink sink = new MxAccessAlarmEventSink(queue, new MxAccessEventMapper());
        AlarmDispatcher dispatcher = new AlarmDispatcher(consumer, sink, SessionId);

        dispatcher.Dispose();

        Assert.True(consumer.Disposed);
        consumer.RaiseTransition(new MxAlarmTransitionEvent
        {
            PreviousState = MxAlarmStateKind.Unspecified,
            Record = new MxAlarmSnapshotRecord
            {
                AlarmGuid = Guid.NewGuid(),
                ProviderName = "Galaxy",
                Group = "G",
                TagName = "T",
                State = MxAlarmStateKind.UnackAlm,
            },
        });
        Assert.Equal(0, queue.Count);
    }

    private sealed class FakeAlarmConsumer : IMxAccessAlarmConsumer
    {
        public event EventHandler<MxAlarmTransitionEvent>? AlarmTransitionEmitted;

        public string? LastSubscription { get; private set; }
        public Guid LastAckGuid { get; private set; }
        public string? LastAckComment { get; private set; }
        public string? LastAckOperatorName { get; private set; }
        public string? LastAckOperatorNode { get; private set; }
        public string? LastAckOperatorDomain { get; private set; }
        public string? LastAckOperatorFullName { get; private set; }
        public int AcknowledgeReturn { get; set; }
        public IReadOnlyList<MxAlarmSnapshotRecord> SnapshotResult { get; set; } =
            Array.Empty<MxAlarmSnapshotRecord>();
        public bool Disposed { get; private set; }

        public void RaiseTransition(MxAlarmTransitionEvent transition)
        {
            AlarmTransitionEmitted?.Invoke(this, transition);
        }

        public void Subscribe(string subscription)
        {
            LastSubscription = subscription;
        }

        public int AcknowledgeByGuid(
            Guid alarmGuid,
            string ackComment,
            string ackOperatorName,
            string ackOperatorNode,
            string ackOperatorDomain,
            string ackOperatorFullName)
        {
            LastAckGuid = alarmGuid;
            LastAckComment = ackComment;
            LastAckOperatorName = ackOperatorName;
            LastAckOperatorNode = ackOperatorNode;
            LastAckOperatorDomain = ackOperatorDomain;
            LastAckOperatorFullName = ackOperatorFullName;
            return AcknowledgeReturn;
        }

        public int AcknowledgeByName(
            string alarmName, string providerName, string groupName,
            string ackComment, string ackOperatorName, string ackOperatorNode,
            string ackOperatorDomain, string ackOperatorFullName)
        {
            LastAckByNameTuple = (alarmName, providerName, groupName);
            LastAckOperatorName = ackOperatorName;
            return AcknowledgeReturn;
        }

        public (string Name, string Provider, string Group)? LastAckByNameTuple { get; private set; }

        public IReadOnlyList<MxAlarmSnapshotRecord> SnapshotActiveAlarms()
        {
            return SnapshotResult;
        }

        public int PollCount { get; private set; }

        public void PollOnce()
        {
            PollCount++;
        }

        public void Dispose()
        {
            Disposed = true;
        }
    }
}