using System.Collections.Concurrent;
using System.Reflection;
using Opc.Ua;
using ZB.MOM.WW.ScadaBridge.Commons.Types.Alarms;
using ZB.MOM.WW.ScadaBridge.Commons.Types.Enums;
using ZB.MOM.WW.ScadaBridge.DataConnectionLayer.Adapters;

namespace ZB.MOM.WW.ScadaBridge.DataConnectionLayer.Tests.Adapters;

/// <summary>
/// ScadaBridge#138 / OtOpcUa Warm design §4.5 + §5 "Alarms are compatible": when a Warm standby
/// is promoted, OtOpcUa runs a ConditionRefresh on every live event item ON ITS OWN — the client
/// never asked. The existing items therefore receive an unsolicited RefreshStart, the retained
/// conditions, RefreshEnd, then new events. ScadaBridge must treat that exactly like the refresh it
/// triggers itself on subscribe: one framed snapshot with its own epoch, and live derivation
/// before and after it.
/// </summary>
public class RealOpcUaPromotionRefreshTests
{
    private const string Handle = "h1";
    private const string Source = "ns=2;s=Tank01";

    private static readonly MethodInfo Handler =
        typeof(RealOpcUaClient).GetMethod("HandleAlarmEvent", BindingFlags.Instance | BindingFlags.NonPublic)!;

    /// <summary>What <c>CreateAlarmSubscriptionAsync</c> sets up for a live handle: its per-condition state map.</summary>
    private static void SeedSubscribedHandle(RealOpcUaClient client)
    {
        var field = typeof(RealOpcUaClient).GetField("_alarmLastState", BindingFlags.Instance | BindingFlags.NonPublic)!;
        var map = (ConcurrentDictionary<string, Dictionary<string, (bool Active, bool Acked)>>)field.GetValue(client)!;
        map[Handle] = new Dictionary<string, (bool Active, bool Acked)>(StringComparer.Ordinal);
    }

    private static void Boundary(RealOpcUaClient client, NodeId type, List<NativeAlarmTransition> sink) =>
        Handler.Invoke(client, [Handle, Source,
            new EventFieldList { EventFields = new Variant[] { Variant.From(type), Variant.Null, Variant.Null, Variant.Null, Variant.Null, Variant.Null } },
            (Action<NativeAlarmTransition>)sink.Add]);

    private static void Condition(RealOpcUaClient client, string condition, bool active, bool acked, List<NativeAlarmTransition> sink)
    {
        var fields = new Variant[]
        {
            Variant.From(ObjectTypeIds.AlarmConditionType), // 0 EventType
            Variant.From(new NodeId("Tank01", 2)),          // 1 SourceNode
            Variant.From("Tank01"),                         // 2 SourceName
            Variant.From(DateTime.UtcNow),                  // 3 Time
            Variant.From(new LocalizedText("msg")),         // 4 Message
            Variant.From((ushort)500),                      // 5 Severity
            Variant.From(active),                           // 6 ActiveState/Id
            Variant.From(acked),                            // 7 AckedState/Id
            Variant.Null,                                   // 8 ConfirmedState/Id
            Variant.From(false),                            // 9 SuppressedOrShelved
            Variant.Null,                                   // 10 ShelvingState
            Variant.From(condition),                        // 11 ConditionName
        };
        Handler.Invoke(client, [Handle, Source, new EventFieldList { EventFields = fields },
            (Action<NativeAlarmTransition>)sink.Add]);
    }

    /// <summary>
    /// Subscribe-time refresh, live traffic, then the UNSOLICITED promotion refresh on the same
    /// item, then live traffic again. The promotion replay is framed SnapshotStart → Snapshot… →
    /// SnapshotComplete under a fresh epoch (distinct from the subscribe-time one), and live events
    /// after it are derived live again — the replay does not leave the item stuck in Snapshot mode.
    /// </summary>
    [Fact]
    public void UnsolicitedPromotionRefresh_IsFramedAsItsOwnSnapshot_AndLiveDerivationResumes()
    {
        var client = new RealOpcUaClient();
        SeedSubscribedHandle(client);
        var sink = new List<NativeAlarmTransition>();

        // Subscribe-time refresh (the one ScadaBridge triggers): Hi is active.
        Boundary(client, ObjectTypeIds.RefreshStartEventType, sink);
        Condition(client, "Hi", active: true, acked: false, sink);
        Boundary(client, ObjectTypeIds.RefreshEndEventType, sink);

        // Live while the old Active serves: Lo raises.
        Condition(client, "Lo", active: true, acked: false, sink);
        var liveBefore = sink[^1];

        // Promotion on the other node: an unsolicited refresh on the existing item.
        Boundary(client, ObjectTypeIds.RefreshStartEventType, sink);
        Condition(client, "Hi", active: true, acked: false, sink);
        Condition(client, "Lo", active: true, acked: false, sink);
        Boundary(client, ObjectTypeIds.RefreshEndEventType, sink);

        // Live after promotion: Lo is acknowledged.
        Condition(client, "Lo", active: true, acked: true, sink);
        var liveAfter = sink[^1];

        Assert.Equal(
            ["SnapshotStart", "Snapshot", "SnapshotComplete", liveBefore.Kind.ToString(),
             "SnapshotStart", "Snapshot", "Snapshot", "SnapshotComplete", liveAfter.Kind.ToString()],
            sink.Select(t => t.Kind.ToString()));

        // Live kinds really are live (not Snapshot) on both sides of the promotion refresh.
        Assert.Equal(AlarmTransitionKind.Raise, liveBefore.Kind);
        Assert.Equal(AlarmTransitionKind.Acknowledge, liveAfter.Kind);
        Assert.Null(liveBefore.SnapshotId);
        Assert.Null(liveAfter.SnapshotId);

        // The promotion replay has its own epoch, shared by its boundaries and its conditions.
        var subscribeEpoch = sink[0].SnapshotId;
        var promotionEpoch = sink[4].SnapshotId;
        Assert.NotNull(subscribeEpoch);
        Assert.NotNull(promotionEpoch);
        Assert.NotEqual(subscribeEpoch, promotionEpoch);
        Assert.All(sink.Skip(4).Take(4), t => Assert.Equal(promotionEpoch, t.SnapshotId));
        Assert.All(sink.Skip(4).Take(4), t => Assert.Equal(Source, t.SnapshotSourceReference));
    }
}