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 * OPC Foundation MIT License 1.00
 *
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 * obtaining a copy of this software and associated documentation
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// CA2000: test code; the created queues/monitored items are short-lived and disposed by the runtime.
#pragma warning disable CA2000
using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Diagnostics;
using System.Diagnostics.Metrics;
using System.Linq;
using System.Reflection;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.Extensions.Logging;
using Moq;
using NUnit.Framework;
using Opc.Ua.Server.TestFramework;
using Opc.Ua.Tests;

namespace Opc.Ua.Server.Tests
{
    /// <summary>
    /// Tests that the monitored-item restore path consumes a pre-hydrated queue supplied by an asynchronous
    /// <see cref="ISubscriptionStore"/> and otherwise falls back to the synchronous restore.
    /// </summary>
    [TestFixture]
    [Category("MonitoredItem")]
    [Parallelizable]
    public class MonitoredItemQueueRestoreTests
    {
        /// <summary>
        /// Verifies that restoration uses a prehydrated data-change queue without invoking synchronous fallback.
        /// </summary>
        [Test]
        public void RestoreUsesPreHydratedDataChangeQueueAndSkipsSyncFallback()
        {
            ITelemetryContext telemetry = NUnitTelemetryContext.Create();
            var storeMock = new Mock<ISubscriptionStore>();
            using var queueFactory = new MonitoredItemQueueFactory(telemetry);
            Mock<IServerInternal> serverMock = CreateServerMock(telemetry, queueFactory, storeMock.Object);

            IDataChangeMonitoredItemQueue preHydrated = queueFactory.CreateDataChangeQueue(false, 2);
            preHydrated.ResetQueue(10, false);
            preHydrated.Enqueue(new DataValue(new Variant(7)), ServiceResult.Good);

            StoredMonitoredItem stored = CreateStoredItem();
            stored.RestoredDataChangeQueue = preHydrated;

            using var item = new MonitoredItem(
                serverMock.Object,
                new Mock<IAsyncNodeManager>().Object,
                new object(),
                stored);

            Assert.That(item.Id, Is.EqualTo(stored.Id));
            storeMock.Verify(
                s => s.RestoreDataChangeMonitoredItemQueue(It.IsAny<uint>()),
                Times.Never);
        }

        /// <summary>
        /// Verifies that restoration uses synchronous queue fallback when no prehydrated queue is available.
        /// </summary>
        [Test]
        public void RestoreFallsBackToSyncRestoreWhenNotPreHydrated()
        {
            ITelemetryContext telemetry = NUnitTelemetryContext.Create();
            var storeMock = new Mock<ISubscriptionStore>();
            storeMock
                .Setup(s => s.RestoreDataChangeMonitoredItemQueue(It.IsAny<uint>()))
                .Returns((IDataChangeMonitoredItemQueue)null!);
            using var queueFactory = new MonitoredItemQueueFactory(telemetry);
            Mock<IServerInternal> serverMock = CreateServerMock(telemetry, queueFactory, storeMock.Object);

            StoredMonitoredItem stored = CreateStoredItem();

            using var item = new MonitoredItem(
                serverMock.Object,
                new Mock<IAsyncNodeManager>().Object,
                new object(),
                stored);

            storeMock.Verify(
                s => s.RestoreDataChangeMonitoredItemQueue(stored.Id),
                Times.Once);
        }

        /// <summary>
        /// Verifies that restoring a queue does not reinstate transient required-notification protection.
        /// </summary>
        [TestCase(1u, false, false)]
        [TestCase(2u, false, false)]
        [TestCase(2u, true, false)]
        [TestCase(2u, true, true)]
        public void RestoreDoesNotReinstateRequiredNotificationProtection(
            uint queueSize,
            bool restoreQueue,
            bool queueContainsRequired)
        {
            ITelemetryContext telemetry = NUnitTelemetryContext.Create();
            ILogger logger =
                telemetry.CreateLogger<MonitoredItemQueueRestoreTests>();
            var storeMock = new Mock<ISubscriptionStore>();
            using var queueFactory = new MonitoredItemQueueFactory(telemetry);
            Mock<IServerInternal> serverMock =
                CreateServerMock(telemetry, queueFactory, storeMock.Object);
            DateTime timestamp = DateTime.UtcNow;
            var requiredValue = new DataValue(
                Variant.Null,
                StatusCodes.BadCommunicationError,
                timestamp,
                timestamp);
            StoredMonitoredItem stored = StoreItemWithPendingHistoryFailure(
                serverMock.Object,
                queueSize,
                requiredValue);
            if (restoreQueue)
            {
                IDataChangeMonitoredItemQueue preHydrated =
                    queueFactory.CreateDataChangeQueue(false, stored.Id);
                preHydrated.ResetQueue(queueSize, false);
                preHydrated.Enqueue(
                    queueContainsRequired
                        ? requiredValue
                        : new DataValue(Variant.From(7), StatusCodes.Good),
                    queueContainsRequired
                        ? stored.LastError
                        : ServiceResult.Good);
                stored.RestoredDataChangeQueue = preHydrated;
            }

            using var item = new MonitoredItem(
                serverMock.Object,
                new Mock<IAsyncNodeManager>().Object,
                new object(),
                stored);
            item.QueueValue(
                new DataValue(Variant.From(42), StatusCodes.Good),
                ServiceResult.Good);
            item.QueueValue(
                new DataValue(Variant.From(43), StatusCodes.Good),
                ServiceResult.Good);
            var notifications = new Queue<MonitoredItemNotification>();
            var diagnostics = new Queue<DiagnosticInfo>();

            _ = item.Publish(
                new OperationContext(item),
                notifications,
                diagnostics,
                10,
                logger);

            Assert.That(
                notifications.Any(value =>
                    value.Value.StatusCode.Code ==
                        StatusCodes.BadCommunicationError),
                Is.False,
                "A restored error value follows ordinary queue replacement, not live priming protection.");
            Assert.That(notifications, Has.Count.EqualTo(queueSize));
            Assert.That(
                notifications.Last().Value.WrappedValue.TryGetValue(out int lastValue),
                Is.True);
            Assert.That(lastValue, Is.EqualTo(43));
        }

        /// <summary>
        /// Verifies that restoration preserves raw error values without synthesizing missing notifications.
        /// </summary>
        [TestCase(false)]
        [TestCase(true)]
        public void RestoreKeepsRawErrorValuesWithoutSynthesizingMissingNotifications(bool queueContainsError)
        {
            ITelemetryContext telemetry = NUnitTelemetryContext.Create();
            using var queueFactory = new MonitoredItemQueueFactory(telemetry);
            Mock<IServerInternal> server = CreateServerMock(
                telemetry,
                queueFactory,
                Mock.Of<ISubscriptionStore>());
            var errorValue = new DataValue(Variant.Null, StatusCodes.BadCommunicationError);
            StoredMonitoredItem stored = StoreItemWithPendingHistoryFailure(server.Object, 2, errorValue);
            IDataChangeMonitoredItemQueue queue = queueFactory.CreateDataChangeQueue(false, stored.Id);
            queue.ResetQueue(2, false);
            queue.Enqueue(
                queueContainsError ? errorValue : new DataValue(Variant.From(7)),
                queueContainsError ? stored.LastError : ServiceResult.Good);
            stored.RestoredDataChangeQueue = queue;
            using var item = new MonitoredItem(
                server.Object,
                Mock.Of<IAsyncNodeManager>(),
                new object(),
                stored);

            item.QueueValue(new DataValue(Variant.From(42)), ServiceResult.Good);
            var notifications = new Queue<MonitoredItemNotification>();
            var diagnostics = new Queue<DiagnosticInfo>();
            _ = item.Publish(
                new OperationContext(item),
                notifications,
                diagnostics,
                10,
                telemetry.CreateLogger<MonitoredItemQueueRestoreTests>());

            Assert.That(notifications, Has.Count.EqualTo(2));
            Assert.That(
                notifications.Any(value => value.Value.StatusCode.Code == StatusCodes.BadCommunicationError),
                Is.EqualTo(queueContainsError),
                "Only values actually present in the restored raw queue should be delivered.");
            Assert.That(
                notifications.Last().Value.WrappedValue.TryGetValue(out int lastValue),
                Is.True);
            Assert.That(lastValue, Is.EqualTo(42));
        }

        /// <summary>
        /// Verifies that queue prehydration continues after a store failure and respects the queue-size gate.
        /// </summary>
        [Test]
        public async Task PreHydrateContinuesAfterStoreFailureAndHonorsQueueSizeGateAsync()
        {
            using var loggerProvider = new CapturingLoggerProvider();
            using ILoggerFactory loggerFactory = LoggerFactory.Create(builder => builder.AddProvider(loggerProvider));
            await using MasterNodeManagerFixture fixture = await CreateMasterNodeManagerFixtureAsync(loggerFactory).ConfigureAwait(false);
            using var queueFactory = new MonitoredItemQueueFactory(fixture.Telemetry);
            var storeMock = new Mock<ISubscriptionStore>();
            IDataChangeMonitoredItemQueue restoredQueue = queueFactory.CreateDataChangeQueue(false, 2);
            restoredQueue.ResetQueue(10, false);
            restoredQueue.Enqueue(new DataValue(new Variant(7)), ServiceResult.Good);
            storeMock.Setup(s => s.RestoreDataChangeMonitoredItemQueueAsync(2, It.IsAny<CancellationToken>()))
                .Returns(new ValueTask<IDataChangeMonitoredItemQueue?>(restoredQueue));
            storeMock.Setup(s => s.RestoreDataChangeMonitoredItemQueueAsync(3, It.IsAny<CancellationToken>()))
                .Returns(new ValueTask<IDataChangeMonitoredItemQueue?>(
                    Task.FromException<IDataChangeMonitoredItemQueue?>(
                        new InvalidOperationException("store failed"))));

            fixture.Server.Setup(s => s.SubscriptionStore).Returns(storeMock.Object);

            List<IStoredMonitoredItem> items =
            [
                CreateStoredItem(id: 2, queueSize: 10),
                CreateStoredItem(id: 3, queueSize: 10),
                CreateStoredItem(id: 4, queueSize: 1)
            ];

            await InvokePreHydrateAsync(fixture.Manager, items).ConfigureAwait(false);

            Assert.That(items[0].RestoredDataChangeQueue, Is.SameAs(restoredQueue));
            Assert.That(items[1].RestoredDataChangeQueue, Is.Null);
            Assert.That(items[2].RestoredDataChangeQueue, Is.Null);
            storeMock.Verify(s => s.RestoreDataChangeMonitoredItemQueueAsync(2, It.IsAny<CancellationToken>()), Times.Once);
            storeMock.Verify(s => s.RestoreDataChangeMonitoredItemQueueAsync(3, It.IsAny<CancellationToken>()), Times.Once);
            storeMock.Verify(s => s.RestoreDataChangeMonitoredItemQueueAsync(4, It.IsAny<CancellationToken>()), Times.Never);
            Assert.That(
                loggerProvider.Messages,
                Has.Some.Contains("Failed to pre-hydrate queue for monitored item with id 3"));
        }

        private static StoredMonitoredItem StoreItemWithPendingHistoryFailure(
            IServerInternal server,
            uint queueSize,
            in DataValue failure)
        {
            StoredMonitoredItem initialState = CreateStoredItem(queueSize: queueSize);
            initialState.SamplingInterval = 0;
            using var original = new MonitoredItem(
                server,
                Mock.Of<IAsyncNodeManager>(),
                new object(),
                initialState);
            ((IInitialValueMonitoredItem)original).QueueInitialValue(
                failure,
                new ServiceResult(failure.StatusCode),
                ignoreFilters: true);

            return (StoredMonitoredItem)original.ToStorableMonitoredItem();
        }

        private static StoredMonitoredItem CreateStoredItem(uint id = 2, uint queueSize = 10)
        {
            return new StoredMonitoredItem
            {
                Id = id,
                SubscriptionId = 1,
                TypeMask = MonitoredItemTypeMask.DataChange,
                MonitoringMode = MonitoringMode.Reporting,
                NodeId = new NodeId(1),
                AttributeId = Attributes.Value,
                QueueSize = queueSize,
                DiscardOldest = true,
                SamplingInterval = 1000,
                TimestampsToReturn = TimestampsToReturn.Both,
                DiagnosticsMasks = DiagnosticsMasks.All,
                FilterToUse = new MonitoringFilter(),
                IndexRange = string.Empty,
                ParsedIndexRange = NumericRange.Null,
                LastValue = new DataValue(new Variant(0))
            };
        }

        private static Mock<IServerInternal> CreateServerMock(
            ITelemetryContext telemetry,
            IMonitoredItemQueueFactory queueFactory,
            ISubscriptionStore subscriptionStore)
        {
            var serverMock = new Mock<IServerInternal>();
            serverMock.Setup(s => s.Telemetry).Returns(telemetry);
            serverMock.Setup(s => s.NamespaceUris).Returns(new NamespaceTable());
            serverMock.Setup(s => s.TypeTree).Returns(new TypeTable(new NamespaceTable()));
            serverMock.Setup(s => s.MonitoredItemQueueFactory).Returns(queueFactory);
            serverMock.Setup(s => s.SubscriptionStore).Returns(subscriptionStore);
            return serverMock;
        }

        private static async Task<MasterNodeManagerFixture> CreateMasterNodeManagerFixtureAsync(ILoggerFactory loggerFactory)
        {
            var fixture = new ServerFixture<StandardServer>(t => new StandardServer(t))
            {
                SecurityNone = true
            };
            await fixture.StartAsync().ConfigureAwait(false);

            var telemetry = new TestTelemetryContext(loggerFactory);
            var serverMock = new Mock<IServerInternal>();
            serverMock.Setup(s => s.Telemetry).Returns(telemetry);
            serverMock.Setup(s => s.NamespaceUris).Returns(fixture.Server.CurrentInstance.NamespaceUris);
            serverMock.Setup(s => s.MainNodeManagerFactory).Returns(fixture.Server.CurrentInstance.MainNodeManagerFactory);
            serverMock.Setup(s => s.SubscriptionStore).Returns((ISubscriptionStore)null!);

            var manager = new MasterNodeManager(serverMock.Object, fixture.Config, null, Array.Empty<INodeManager>());
            return new MasterNodeManagerFixture(fixture, serverMock, manager, telemetry);
        }

        private static ValueTask InvokePreHydrateAsync(
            MasterNodeManager manager,
            IList<IStoredMonitoredItem> items)
        {
            FieldInfo field = typeof(MasterNodeManager).GetField(
                "m_serviceDispatch", BindingFlags.Instance | BindingFlags.NonPublic)!;
            Assert.That(field, Is.Not.Null);
            var dispatcher = (NodeManagerServiceDispatcher)field!.GetValue(manager)!;
            return dispatcher.PreHydrateMonitoredItemQueuesAsync(items, CancellationToken.None);
        }

        private sealed class MasterNodeManagerFixture : IAsyncDisposable
        {
            public MasterNodeManagerFixture(
                ServerFixture<StandardServer> fixture,
                Mock<IServerInternal> server,
                MasterNodeManager manager,
                TestTelemetryContext telemetry)
            {
                Fixture = fixture;
                Server = server;
                Manager = manager;
                Telemetry = telemetry;
            }

            public ServerFixture<StandardServer> Fixture { get; }

            public Mock<IServerInternal> Server { get; }

            public MasterNodeManager Manager { get; }

            public TestTelemetryContext Telemetry { get; }

            public async ValueTask DisposeAsync()
            {
                Manager.Dispose();
                Telemetry.Dispose();
                await Fixture.StopAsync().ConfigureAwait(false);
            }
        }

        private sealed class TestTelemetryContext : ITelemetryContext, IDisposable
        {
            public TestTelemetryContext(ILoggerFactory loggerFactory)
            {
                LoggerFactory = loggerFactory;
                ActivitySource = new ActivitySource(nameof(MonitoredItemQueueRestoreTests));
                m_meter = new Meter(nameof(MonitoredItemQueueRestoreTests));
            }

            public Meter CreateMeter()
            {
                return m_meter;
            }

            public Meter CreateMeter(Assembly assembly)
            {
                return m_meter;
            }

            public ILoggerFactory LoggerFactory { get; }

            public ActivitySource ActivitySource { get; }

            public ActivitySource GetActivitySource(Assembly assembly)
            {
                return ActivitySource;
            }

            private readonly Meter m_meter;

            public void Dispose()
            {
                ActivitySource.Dispose();
                m_meter.Dispose();
            }
        }

        private sealed class CapturingLoggerProvider : ILoggerProvider
        {
            public ConcurrentBag<string> Messages { get; } = [];

            public ILogger CreateLogger(string categoryName)
            {
                return new CapturingLogger(Messages);
            }

            public void Dispose()
            {
            }
        }

        private sealed class CapturingLogger : ILogger
        {
            public CapturingLogger(ConcurrentBag<string> messages)
            {
                m_messages = messages;
            }

            public IDisposable BeginScope<TState>(TState state)
                where TState : notnull
            {
                return NoopDisposable.Instance;
            }

            public bool IsEnabled(LogLevel logLevel)
            {
                return true;
            }

            public void Log<TState>(
                LogLevel logLevel,
                EventId eventId,
                TState state,
                Exception? exception,
                Func<TState, Exception, string> formatter)
            {
                m_messages.Add(formatter(state, exception!));
            }

            private readonly ConcurrentBag<string> m_messages;
        }

        private sealed class NoopDisposable : IDisposable
        {
            public static NoopDisposable Instance { get; } = new();

            public void Dispose()
            {
            }
        }
    }
}