using System.Runtime.CompilerServices;
using System.Threading.Channels;
using Opc.Ua;
using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Commons.OpcUa;
using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
using ZB.MOM.WW.OtOpcUa.Driver.MTConnect;
using ZB.MOM.WW.OtOpcUa.Runtime.Drivers;
using static ZB.MOM.WW.OtOpcUa.OpcUaServer.IntegrationTests.ServerEventRig;

namespace ZB.MOM.WW.OtOpcUa.OpcUaServer.IntegrationTests;

/// <summary>
///     Gitea #626 over the wire — an MTConnect CONDITION transition, streamed by a scripted Agent through the real
///     <see cref="MTConnectDriver"/>, projected by the production <see cref="NativeAlarmProjector"/> and written
///     through the production sink, reaches a client's event subscription on the RAW DEVICE FOLDER as a Part 9
///     condition event carrying the driver's message — then its return to normal does too.
/// </summary>
/// <remarks>
///     The one seam not exercised is <c>DriverHostActor</c>'s routing (ConditionId → condition NodeId), which
///     <c>DriverHostActorNativeAlarmTests</c> covers; here the driver's ConditionId is asserted to BE the
///     materialised condition's RawPath, which is the whole contract that routing relies on.
/// </remarks>
public sealed class MTConnectConditionAlarmWireTests
{
    private const string DataItemId = "dev1_system_cond";

    [Fact]
    public async Task A_condition_fault_and_its_clear_reach_the_raw_device_folder_as_part9_events()
    {
        var ct = TestContext.Current.CancellationToken;
        var rig = await StartAsync("MTConnectConditionWire", encrypted: false, ct);
        try
        {
            rig.MaterialiseNative();

            using var session = await rig.ConnectAsync(anonymous: true, ct);
            var events = new RecordedEvents();
            var subscription = await RecordedEvents.SubscribeAsync(session, events, ct);
            var rawNs = (ushort)session.NamespaceUris.GetIndex(V3NodeIds.RawNamespaceUri);
            var folderItem = RecordedEvents.AddEventItem(subscription, new NodeId(RawDeviceFolder, rawNs));
            await subscription.ApplyChangesAsync(ct);
            folderItem.Status.Error.ShouldBeNull();

            var agent = new ScriptedAgent();
            var driver = new MTConnectDriver(
                new ZB.MOM.WW.OtOpcUa.Driver.MTConnect.MTConnectDriverOptions
                {
                    AgentUri = "http://scripted-agent:5000",
                    RawTags = [new RawTagEntry(RawAlarmPath, $$"""{"address":"{{DataItemId}}"}""", false, "dev1")],
                },
                "mt-wire",
                _ => agent);

            // What DriverHostActor.ForwardNativeAlarm does for a routed transition, minus the routing.
            var projector = new NativeAlarmProjector();
            var routed = new List<string>();
            driver.OnAlarmEvent += (_, e) =>
            {
                lock (routed) routed.Add(e.ConditionId);
                rig.Sink.WriteAlarmCondition(e.ConditionId, projector.Project(e.ConditionId, e), e.SourceTimestampUtc, AddressSpaceRealm.Raw);
            };

            await driver.InitializeAsync("{}", ct);
            await driver.SubscribeAlarmsAsync([RawAlarmPath], ct);

            agent.Push(Condition("Fault", "E17", "Spindle overtemperature", 108));
            const string FaultMessage = "Spindle overtemperature [nativeCode=E17]";
            await RecordedEvents.WaitUntilAsync(() => events.Has(folderItem, FaultMessage));

            agent.Push(Condition("Normal", null, null, 109));
            await RecordedEvents.WaitUntilAsync(() => events.Has(folderItem, "SYSTEM Normal"));

            lock (routed) routed.ShouldAllBe(id => id == RawAlarmPath, "ConditionId must be the alarm tag's RawPath");

            var fault = events.ConditionEvents(folderItem, FaultMessage).ShouldHaveSingleItem();
            fault[RecordedEvents.AckedField].Value.ShouldBe(false, "a fresh fault is unacknowledged");

            await driver.ShutdownAsync(ct);
        }
        finally
        {
            await rig.DisposeAsync();
        }
    }

    private static MTConnectStreamsResult Condition(string state, string? nativeCode, string? text, long sequence) =>
        new(1, sequence + 1, sequence,
        [
            new MTConnectObservation(DataItemId, state, DateTime.UtcNow,
                Condition: new MTConnectConditionDetail(text, nativeCode, null, null, "SYSTEM")),
        ]);

    /// <summary>An Agent whose <c>/current</c> reports the condition Normal and whose <c>/sample</c> a test drives.</summary>
    private sealed class ScriptedAgent : IMTConnectAgentClient
    {
        private readonly Channel<MTConnectStreamsResult> _chunks = Channel.CreateUnbounded<MTConnectStreamsResult>();

        public void Push(MTConnectStreamsResult chunk) => _chunks.Writer.TryWrite(chunk);

        public Task<MTConnectProbeModel> ProbeAsync(CancellationToken ct) =>
            Task.FromResult(new MTConnectProbeModel(
            [
                new MTConnectDevice("dev1", "dev1", [],
                    [new MTConnectDataItem(DataItemId, "system", "CONDITION", "SYSTEM", null, null, null, null)]),
            ]));

        public Task<MTConnectStreamsResult> CurrentAsync(CancellationToken ct) =>
            Task.FromResult(new MTConnectStreamsResult(1, 108, 1,
            [
                new MTConnectObservation(DataItemId, "Normal", DateTime.UtcNow,
                    Condition: new MTConnectConditionDetail(null, null, null, null, "SYSTEM")),
            ]));

        public async IAsyncEnumerable<MTConnectStreamsResult> SampleAsync(
            long from, [EnumeratorCancellation] CancellationToken ct)
        {
            while (true)
            {
                yield return await _chunks.Reader.ReadAsync(ct);
            }
        }

        public Task<MTConnectWriteOutcome> WriteObservationAsync(
            string deviceName, string dataItemId, string value, CancellationToken cancellationToken) =>
            throw new NotSupportedException();

        public void Dispose() => _chunks.Writer.TryComplete();
    }
}