using Microsoft.Extensions.Logging.Abstractions;
using Opc.Ua;
using Opc.Ua.Client;
using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Commons.OpcUa;

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

/// <summary>
///     Review 01 L2, over the wire against the real SDK: a rebuild (or a surgical remove + re-add) that
///     recreates a NodeId must not leave the SDK's per-NodeId <c>MonitoredNode2</c> — and its component-cache
///     entry — pointing at the DEAD <c>NodeState</c>. Before the fix, ANY new item on that NodeId, from any
///     session, bound to the dead node while an older item on it still existed: created <c>Good</c>, fed its
///     stale initial value, then never again.
///     <para>
///         Each test keeps the OLD item alive while creating the NEW one — that is exactly the trap — and
///         proves the positive path (the new item receives a value written AFTER its creation) before asserting
///         the old item's <c>BadNodeIdUnknown</c>. Deleting the old item afterwards must succeed too.
///     </para>
/// </summary>
public sealed class StaleMonitoredNodeWireTests
{
    private const string ServerUri = "urn:OtOpcUa.StaleMonitoredNode";
    private const string Device = "Plant/Modbus/dev1";
    private const string Tag = "Plant/Modbus/dev1/Speed";

    /// <summary>Rebuild + re-create the same NodeId: the old item is told, a new item on the same NodeId receives values.</summary>
    [Fact]
    public async Task A_new_item_after_a_rebuild_binds_to_the_recreated_node()
    {
        await RunAsync("rebuild", nm =>
        {
            nm.RebuildAddressSpace();
            nm.CompleteAddressSpaceApply();
            Materialise(nm);
        });
    }

    /// <summary>Surgical remove + re-add of the same NodeId: same contract as the rebuild.</summary>
    [Fact]
    public async Task A_new_item_after_a_surgical_remove_and_readd_binds_to_the_recreated_node()
    {
        await RunAsync("surgical", nm =>
        {
            nm.RemoveVariableNode(Tag, AddressSpaceRealm.Raw).ShouldBeTrue();
            nm.EnsureVariable(Tag, Device, "Speed", "Int32", writable: false, realm: AddressSpaceRealm.Raw);
        });
    }

    /// <summary>
    ///     The same trap from a SECOND session: a UaExpert operator connecting after a deploy while ScadaBridge's
    ///     original item is still alive.
    /// </summary>
    [Fact]
    public async Task A_second_session_binds_to_the_recreated_node_while_the_first_sessions_item_lives()
    {
        var pkiRoot = Path.Combine(Path.GetTempPath(), $"otopcua-stale-2s-{Guid.NewGuid():N}");
        var ct = TestContext.Current.CancellationToken;
        try
        {
            var (server, host, port) = await BootServerAsync(pkiRoot, ServerUri + ".TwoSessions", ct);
            await using var _ = host;
            var nm = server.NodeManager!;
            Materialise(nm);
            nm.WriteValue(Tag, 1, OpcUaStatus.Good, DateTime.UtcNow, AddressSpaceRealm.Raw);

            using var sessionA = await OpenSessionAsync($"opc.tcp://127.0.0.1:{port}/OtOpcUa", ct);
            var nodeId = new NodeId(Tag, (ushort)sessionA.NamespaceUris.GetIndex(V3NodeIds.RawNamespaceUri));
            var (subA, oldItem, oldValues, gate) = await SubscribeAsync(sessionA, nodeId, ct);
            await WaitUntilAsync(() => { lock (gate) return oldValues.Count >= 1; }, TimeSpan.FromSeconds(5));

            nm.RebuildAddressSpace();
            nm.CompleteAddressSpaceApply();
            Materialise(nm);
            nm.WriteValue(Tag, 2, OpcUaStatus.Good, DateTime.UtcNow, AddressSpaceRealm.Raw);

            // Session B arrives AFTER the rebuild, while A's item is still in A's subscription.
            using var sessionB = await OpenSessionAsync($"opc.tcp://127.0.0.1:{port}/OtOpcUa", ct);
            var (subB, newItem, newValues, gateB) = await SubscribeAsync(sessionB, nodeId, ct);
            await WaitUntilAsync(() => { lock (gateB) return newValues.Count >= 1; }, TimeSpan.FromSeconds(5));

            nm.WriteValue(Tag, 3, OpcUaStatus.Good, DateTime.UtcNow, AddressSpaceRealm.Raw);
            await WaitUntilAsync(() => { lock (gateB) return newValues.Any(v => Equals(v.Value, 3)); }, TimeSpan.FromSeconds(5),
                "the second session's item must receive a value written after its creation");

            lock (gate) oldValues.ShouldContain(v => v.StatusCode == StatusCodes.BadNodeIdUnknown, "the first session's item was told its node went away");
            lock (gateB) newValues.ShouldNotContain(v => v.StatusCode == StatusCodes.BadNodeIdUnknown);

            subA.RemoveItem(oldItem);
            await subA.ApplyChangesAsync(ct);
            subB.RemoveItem(newItem);
            await subB.ApplyChangesAsync(ct);
        }
        finally
        {
            SafeDelete(pkiRoot);
        }
    }

    private static async Task RunAsync(string name, Action<OtOpcUaNodeManager> recreate)
    {
        var pkiRoot = Path.Combine(Path.GetTempPath(), $"otopcua-stale-{name}-{Guid.NewGuid():N}");
        var ct = TestContext.Current.CancellationToken;
        try
        {
            var (server, host, port) = await BootServerAsync(pkiRoot, $"{ServerUri}.{name}", ct);
            await using var _ = host;
            var nm = server.NodeManager!;
            Materialise(nm);
            nm.WriteValue(Tag, 41, OpcUaStatus.Good, DateTime.UtcNow, AddressSpaceRealm.Raw);

            using var session = await OpenSessionAsync($"opc.tcp://127.0.0.1:{port}/OtOpcUa", ct);
            var nodeId = new NodeId(Tag, (ushort)session.NamespaceUris.GetIndex(V3NodeIds.RawNamespaceUri));
            var (subscription, oldItem, oldValues, gate) = await SubscribeAsync(session, nodeId, ct);
            await WaitUntilAsync(() => { lock (gate) return oldValues.Any(v => Equals(v.Value, 41)); }, TimeSpan.FromSeconds(5));
            nm.IsNodeMonitored(nodeId).ShouldBeTrue("non-vacuity: the SDK really holds a fan-out for the node");

            // The node goes away and comes back under the same NodeId; a fresh value lands on the NEW node.
            recreate(nm);
            nm.WriteValue(Tag, 42, OpcUaStatus.Good, DateTime.UtcNow, AddressSpaceRealm.Raw);

            // A NEW item on the same NodeId, in the same subscription, with the old one still present.
            var newValues = new List<DataValue>();
            var newItem = new MonitoredItem(subscription.DefaultItem)
            {
                StartNodeId = nodeId, AttributeId = Attributes.Value, SamplingInterval = 50, QueueSize = 10,
            };
            newItem.Notification += (item, _) => { foreach (var v in item.DequeueValues()) lock (gate) newValues.Add(v); };
            subscription.AddItem(newItem);
            await subscription.ApplyChangesAsync(ct);
            newItem.Status.Error.ShouldBeNull();

            // Positive control: the initial value is the NEW node's, and a value written afterwards arrives.
            await WaitUntilAsync(() => { lock (gate) return newValues.Any(v => Equals(v.Value, 42)); }, TimeSpan.FromSeconds(5),
                "the new item's initial read must come from the re-created node");
            nm.WriteValue(Tag, 43, OpcUaStatus.Good, DateTime.UtcNow, AddressSpaceRealm.Raw);
            await WaitUntilAsync(() => { lock (gate) return newValues.Any(v => Equals(v.Value, 43)); }, TimeSpan.FromSeconds(5),
                "the new item must receive a value written after its creation");
            lock (gate) newValues.ShouldNotContain(v => v.StatusCode == StatusCodes.BadNodeIdUnknown);

            // Review fix I3: the cache entry the new item holds is ITS reference alone — the old item's was released
            // by the removal.
            CacheRefCount(nm, nodeId).ShouldBe(1, "one live item, one component-cache reference");

            // The old item was told, and the dead node's fan-out is gone.
            await WaitUntilAsync(() => { lock (gate) return oldValues.Any(v => v.StatusCode == StatusCodes.BadNodeIdUnknown); }, TimeSpan.FromSeconds(5),
                "the item on the removed node must be told BadNodeIdUnknown");
            nm.IsNodeMonitored(nodeId).ShouldBeTrue("the NEW item's fan-out exists for the re-created node");

            // The old item's delete completes — its node is gone, not its right to be deleted.
            subscription.RemoveItem(oldItem);
            await subscription.ApplyChangesAsync(ct);
            (oldItem.Status.Error is null || ServiceResult.IsGood(oldItem.Status.Error)).ShouldBeTrue(
                $"deleting the orphaned item must succeed, got {oldItem.Status.Error}");

            // The SDK releases a deleted item's cache reference on a Good delete; the old item's was released by the
            // removal already, so a second release would evict the NEW item's live entry (review fix I3).
            CacheRefCount(nm, nodeId).ShouldBe(1, "deleting the orphaned item must not take the new item's reference");

            // And the new item is unaffected by that delete.
            nm.WriteValue(Tag, 44, OpcUaStatus.Good, DateTime.UtcNow, AddressSpaceRealm.Raw);
            await WaitUntilAsync(() => { lock (gate) return newValues.Any(v => Equals(v.Value, 44)); }, TimeSpan.FromSeconds(5));

            // Positive control: deleting the live item gives its reference back.
            subscription.RemoveItem(newItem);
            await subscription.ApplyChangesAsync(ct);
            CacheRefCount(nm, nodeId).ShouldBe(0);
        }
        finally
        {
            SafeDelete(pkiRoot);
        }
    }

    /// <summary>The SDK's component-cache reference count for <paramref name="nodeId"/> (private SDK state, read by
    /// reflection: <c>CustomNodeManager2.m_componentCache</c> → <c>CacheEntry.RefCount</c>); 0 when no entry.</summary>
    private static int CacheRefCount(OtOpcUaNodeManager nm, NodeId nodeId)
    {
        const System.Reflection.BindingFlags Any =
            System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.NonPublic;
        var field = typeof(Opc.Ua.Server.CustomNodeManager2).GetField("m_componentCache", Any)
            .ShouldNotBeNull("the SDK's component cache field (SDK internals moved?)");
        lock (nm.Lock)
        {
            if (field.GetValue(nm) is not System.Collections.IDictionary cache || !cache.Contains(nodeId)) return 0;
            var entry = cache[nodeId]!;
            var member = (object?)entry.GetType().GetField("RefCount", Any) ?? entry.GetType().GetProperty("RefCount", Any);
            return member switch
            {
                System.Reflection.FieldInfo f => (int)f.GetValue(entry)!,
                System.Reflection.PropertyInfo p => (int)p.GetValue(entry)!,
                _ => throw new InvalidOperationException("CacheEntry.RefCount not found"),
            };
        }
    }

    private static void Materialise(OtOpcUaNodeManager nm)
    {
        nm.EnsureFolder(Device, null, "dev1", AddressSpaceRealm.Raw);
        nm.EnsureVariable(Tag, Device, "Speed", "Int32", writable: false, realm: AddressSpaceRealm.Raw);
    }

    private static async Task<(Subscription Subscription, MonitoredItem Item, List<DataValue> Values, object Gate)> SubscribeAsync(
        ISession session, NodeId nodeId, CancellationToken ct)
    {
        var values = new List<DataValue>();
        var gate = new object();
        var subscription = new Subscription(session.DefaultSubscription) { PublishingInterval = 100 };
        session.AddSubscription(subscription);
        await subscription.CreateAsync(ct);
        var item = new MonitoredItem(subscription.DefaultItem)
        {
            StartNodeId = nodeId, AttributeId = Attributes.Value, SamplingInterval = 50, QueueSize = 10,
        };
        item.Notification += (i, _) => { foreach (var v in i.DequeueValues()) lock (gate) values.Add(v); };
        subscription.AddItem(item);
        await subscription.ApplyChangesAsync(ct);
        return (subscription, item, values, gate);
    }

    private static async Task<(OtOpcUaSdkServer Server, OpcUaApplicationHost Host, int Port)> BootServerAsync(
        string pkiRoot, string appUri, CancellationToken ct)
    {
        var boundPort = 0;
        var started = await OpcUaHostStart.StartAsync(
            port =>
            {
                boundPort = port;
                return new OpcUaApplicationHost(
                    new OpcUaApplicationHostOptions
                    {
                        ApplicationName = appUri,
                        ApplicationUri = appUri,
                        OpcUaPort = port,
                        PublicHostname = "127.0.0.1",
                        PkiStoreRoot = pkiRoot,
                        EnabledSecurityProfiles = new List<OpcUaSecurityProfile> { OpcUaSecurityProfile.None },
                        AutoAcceptUntrustedClientCertificates = true,
                    },
                    NullLogger<OpcUaApplicationHost>.Instance);
            },
            () => new OtOpcUaSdkServer(), ct);
        return (started.Server, started.Host, boundPort);
    }

    private static async Task<ISession> OpenSessionAsync(string endpointUrl, CancellationToken ct)
    {
        var appConfig = new ApplicationConfiguration
        {
            ApplicationName = "OtOpcUa.StaleMonitoredNodeClient",
            ApplicationUri = $"urn:OtOpcUa.StaleMonitoredNodeClient.{Guid.NewGuid():N}",
            ApplicationType = ApplicationType.Client,
            SecurityConfiguration = TestClientSecurity.Build(TestClientSecurity.AllocatePkiRoot()),
            ClientConfiguration = new ClientConfiguration { DefaultSessionTimeout = 60_000 },
        };
        await appConfig.ValidateAsync(ApplicationType.Client, ct);
        appConfig.CertificateValidator.CertificateValidation += (_, e) => e.Accept = true;

        var endpoint = await CoreClientUtils.SelectEndpointAsync(
            appConfig, endpointUrl, false, DefaultTelemetry.Create(_ => { }), ct);
        var configuredEndpoint = new ConfiguredEndpoint(null, endpoint, EndpointConfiguration.Create(appConfig));

        return await new DefaultSessionFactory(DefaultTelemetry.Create(_ => { })).CreateAsync(
            appConfig, configuredEndpoint, updateBeforeConnect: false, checkDomain: false,
            sessionName: "StaleMonitoredNodeWireTests", sessionTimeout: 60_000,
            identity: new UserIdentity(new AnonymousIdentityToken()), preferredLocales: null, ct: ct);
    }

    private static async Task WaitUntilAsync(Func<bool> condition, TimeSpan timeout, string? because = null)
    {
        var deadline = DateTime.UtcNow + timeout;
        while (DateTime.UtcNow < deadline)
        {
            if (condition()) return;
            await Task.Delay(50);
        }
        condition().ShouldBeTrue(because ?? "condition not met within timeout");
    }

    private static void SafeDelete(string dir)
    {
        if (!Directory.Exists(dir)) return;
        try { Directory.Delete(dir, recursive: true); }
        catch { /* best-effort */ }
    }
}