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using System;
using System.Collections.Generic;
using System.Security.Cryptography;
using System.Threading.Tasks;
using NUnit.Framework;
using Opc.Ua.PubSub.Tests;
using Opc.Ua.Redundancy;
using Opc.Ua.Redundancy.Server;
using Opc.Ua.Tests;

namespace Opc.Ua.Server.Tests.Redundancy
{
    /// <summary>
    /// Unit tests for <see cref="SharedKeyValueMonitoredItemQueueFactory"/> and its integration with
    /// <see cref="SharedKeyValueSubscriptionStore"/> queue restore.
    /// </summary>
    [TestFixture]
    [Category("Distributed")]
    [Category("Subscription")]
    [Parallelizable(ParallelScope.All)]
    public class SharedKeyValueMonitoredItemQueueFactoryTests
    {
        [TestCase(false)]
        [TestCase(true)]
        public async Task ProtectedQueuesRejectAnotherMonitoredItemKeyAsync(bool eventQueue)
        {
            using var kv = new InMemorySharedKeyValueStore();
            IServiceMessageContext context = CreateContext();
            ITelemetryContext telemetry = NUnitTelemetryContext.Create();
            using var random = RandomNumberGenerator.Create();
            byte[] key = new byte[32];
            random.GetBytes(key);
            using var protector = new AesCbcHmacRecordProtector(key);
            await using var factory = new SharedKeyValueMonitoredItemQueueFactory(
                kv, context, protector, telemetry);
            if (eventQueue)
            {
                IEventMonitoredItemQueue queue = factory.CreateEventQueue(false, 11);
                queue.SetQueueSize(2, false);
                queue.Enqueue(new EventFieldList { ClientHandle = 5, EventFields = [Variant.From(12)] });
            }
            else
            {
                IDataChangeMonitoredItemQueue queue = factory.CreateDataChangeQueue(false, 11);
                queue.ResetQueue(2, false);
                queue.Enqueue(new DataValue(Variant.From(12)), ServiceResult.Good);
            }
            await factory.FlushAsync().ConfigureAwait(false);
            string prefix = eventQueue ? "monitored-item-queue/event/" : "monitored-item-queue/data/";
            (bool found, ByteString record) = await kv.TryGetAsync(prefix + "11").ConfigureAwait(false);
            Assert.That(found, Is.True);
            await kv.SetAsync(prefix + "12", record).ConfigureAwait(false);

            if (eventQueue)
            {
                Assert.That(await factory.RestoreEventQueueAsync(12).ConfigureAwait(false), Is.Null);
                IEventMonitoredItemQueue restored = (await factory.RestoreEventQueueAsync(11).ConfigureAwait(false))!;
                Assert.That(restored, Is.Not.Null);
                Assert.That(restored.Dequeue(out EventFieldList value), Is.True);
                Assert.That(value.ClientHandle, Is.EqualTo(5));
                Assert.That(value.EventFields[0], Is.EqualTo(Variant.From(12)));
            }
            else
            {
                Assert.That(await factory.RestoreDataChangeQueueAsync(12).ConfigureAwait(false), Is.Null);
                IDataChangeMonitoredItemQueue restored = (await factory.RestoreDataChangeQueueAsync(11)
                    .ConfigureAwait(false))!;
                Assert.That(restored, Is.Not.Null);
                Assert.That(restored.Dequeue(out DataValue value, out _), Is.True);
                Assert.That(value.WrappedValue, Is.EqualTo(Variant.From(12)));
            }
        }

        [Test]
        public async Task DataChangeQueueMirrorsAndRestoresAsync()
        {
            using var kv = new InMemorySharedKeyValueStore();
            IServiceMessageContext context = CreateContext();
            ITelemetryContext telemetry = NUnitTelemetryContext.Create();

            var values = new DataValue[3];
            await using (var factory = new SharedKeyValueMonitoredItemQueueFactory(kv, context, telemetry: telemetry))
            {
                IDataChangeMonitoredItemQueue queue = factory.CreateDataChangeQueue(false, 42);
                queue.ResetQueue(5, false);
                for (int i = 0; i < 3; i++)
                {
                    values[i] = new DataValue(new Variant(i));
                    queue.Enqueue(values[i], ServiceResult.Good);
                }
                await factory.FlushAsync().ConfigureAwait(false);
            }

            await using var restoreFactory = new SharedKeyValueMonitoredItemQueueFactory(
                kv, context, telemetry: telemetry);
            IDataChangeMonitoredItemQueue restored = (await restoreFactory
                .RestoreDataChangeQueueAsync(42)
                .ConfigureAwait(false))!;

            Assert.That(restored, Is.Not.Null);
            Assert.That(restored.QueueSize, Is.EqualTo(5));
            Assert.That(restored.ItemsInQueue, Is.EqualTo(3));
            for (int i = 0; i < 3; i++)
            {
                Assert.That(restored.Dequeue(out DataValue result, out _), Is.True);
                Assert.That(result, Is.EqualTo(values[i]));
            }
        }

        [Test]
        public async Task DataChangeQueuePreservesErrorsWhenQueuedAsync()
        {
            using var kv = new InMemorySharedKeyValueStore();
            IServiceMessageContext context = CreateContext();
            ITelemetryContext telemetry = NUnitTelemetryContext.Create();

            var error = new ServiceResult(StatusCodes.BadNoData);
            await using (var factory = new SharedKeyValueMonitoredItemQueueFactory(kv, context, telemetry: telemetry))
            {
                IDataChangeMonitoredItemQueue queue = factory.CreateDataChangeQueue(false, 7);
                queue.ResetQueue(3, true);
                queue.Enqueue(new DataValue(new Variant(1)), error);
                await factory.FlushAsync().ConfigureAwait(false);
            }

            await using var restoreFactory = new SharedKeyValueMonitoredItemQueueFactory(
                kv, context, telemetry: telemetry);
            IDataChangeMonitoredItemQueue restored = (await restoreFactory
                .RestoreDataChangeQueueAsync(7)
                .ConfigureAwait(false))!;

            Assert.That(restored, Is.Not.Null);
            Assert.That(restored.Dequeue(out _, out ServiceResult restoredError), Is.True);
            Assert.That(restoredError.StatusCode, Is.EqualTo(StatusCodes.BadNoData));
        }

        [Test]
        public async Task EventQueueMirrorsAndRestoresAsync()
        {
            using var kv = new InMemorySharedKeyValueStore();
            IServiceMessageContext context = CreateContext();
            ITelemetryContext telemetry = NUnitTelemetryContext.Create();

            await using (var factory = new SharedKeyValueMonitoredItemQueueFactory(kv, context, telemetry: telemetry))
            {
                IEventMonitoredItemQueue queue = factory.CreateEventQueue(false, 11);
                queue.SetQueueSize(5, true);
                for (uint i = 0; i < 3; i++)
                {
                    queue.Enqueue(new EventFieldList { ClientHandle = i, EventFields = [new Variant(i)] });
                }
                await factory.FlushAsync().ConfigureAwait(false);
            }

            await using var restoreFactory = new SharedKeyValueMonitoredItemQueueFactory(
                kv, context, telemetry: telemetry);
            IEventMonitoredItemQueue restored = (await restoreFactory
                .RestoreEventQueueAsync(11)
                .ConfigureAwait(false))!;

            Assert.That(restored, Is.Not.Null);
            Assert.That(restored.QueueSize, Is.EqualTo(5));
            Assert.That(restored.ItemsInQueue, Is.EqualTo(3));
            for (uint i = 0; i < 3; i++)
            {
                Assert.That(restored.Dequeue(out EventFieldList result), Is.True);
                Assert.That(result.ClientHandle, Is.EqualTo(i));
            }
        }

        [Test]
        public async Task DequeueShrinksMirroredQueueAsync()
        {
            using var kv = new InMemorySharedKeyValueStore();
            IServiceMessageContext context = CreateContext();
            ITelemetryContext telemetry = NUnitTelemetryContext.Create();

            await using var factory = new SharedKeyValueMonitoredItemQueueFactory(kv, context, telemetry: telemetry);
            IDataChangeMonitoredItemQueue queue = factory.CreateDataChangeQueue(false, 3);
            queue.ResetQueue(5, false);
            for (int i = 0; i < 4; i++)
            {
                queue.Enqueue(new DataValue(new Variant(i)), ServiceResult.Good);
            }
            queue.Dequeue(out _, out _);
            queue.Dequeue(out _, out _);
            await factory.FlushAsync().ConfigureAwait(false);

            await using var restoreFactory = new SharedKeyValueMonitoredItemQueueFactory(
                kv, context, telemetry: telemetry);
            IDataChangeMonitoredItemQueue restored = (await restoreFactory
                .RestoreDataChangeQueueAsync(3)
                .ConfigureAwait(false))!;

            Assert.That(restored, Is.Not.Null);
            Assert.That(restored.ItemsInQueue, Is.EqualTo(2));
        }

        [Test]
        public async Task OverwriteLastValueUpdatesMirroredSnapshotAsync()
        {
            using var kv = new InMemorySharedKeyValueStore();
            IServiceMessageContext context = CreateContext();
            ITelemetryContext telemetry = NUnitTelemetryContext.Create();

            await using var factory = new SharedKeyValueMonitoredItemQueueFactory(kv, context, telemetry: telemetry);
            IDataChangeMonitoredItemQueue queue = factory.CreateDataChangeQueue(false, 33);
            queue.ResetQueue(1, false);
            queue.Enqueue(new DataValue(new Variant(1)), ServiceResult.Good);
            queue.OverwriteLastValue(new DataValue(new Variant(99)), ServiceResult.Good);
            await factory.FlushAsync().ConfigureAwait(false);

            await using var restoreFactory = new SharedKeyValueMonitoredItemQueueFactory(
                kv,
                context,
                telemetry: telemetry);
            IDataChangeMonitoredItemQueue restored = (await restoreFactory
                .RestoreDataChangeQueueAsync(33)
                .ConfigureAwait(false))!;

            Assert.That(restored, Is.Not.Null);
            Assert.That(restored.Dequeue(out DataValue restoredValue, out _), Is.True);
            Assert.That(restoredValue.WrappedValue.TryGetValue(out int restoredInt), Is.True);
            Assert.That(restoredInt, Is.EqualTo(99));
        }

        [Test]
        public async Task RestoreReturnsNullWhenNothingStoredAsync()
        {
            using var kv = new InMemorySharedKeyValueStore();
            IServiceMessageContext context = CreateContext();
            ITelemetryContext telemetry = NUnitTelemetryContext.Create();

            await using var factory = new SharedKeyValueMonitoredItemQueueFactory(kv, context, telemetry: telemetry);

            Assert.That(await factory.RestoreDataChangeQueueAsync(99).ConfigureAwait(false), Is.Null);
            Assert.That(await factory.RestoreEventQueueAsync(99).ConfigureAwait(false), Is.Null);
        }

        [Test]
        public async Task DisposingQueueRemovesMirroredStateAsync()
        {
            using var kv = new InMemorySharedKeyValueStore();
            IServiceMessageContext context = CreateContext();
            ITelemetryContext telemetry = NUnitTelemetryContext.Create();

            await using var factory = new SharedKeyValueMonitoredItemQueueFactory(kv, context, telemetry: telemetry);
            IDataChangeMonitoredItemQueue queue = factory.CreateDataChangeQueue(false, 5);
            queue.ResetQueue(2, false);
            queue.Enqueue(new DataValue(new Variant(1)), ServiceResult.Good);
            await factory.FlushAsync().ConfigureAwait(false);

            Assert.That(await factory.RestoreDataChangeQueueAsync(5).ConfigureAwait(false), Is.Not.Null);

            queue.Dispose();
            await factory.FlushAsync().ConfigureAwait(false);

            Assert.That(await factory.RestoreDataChangeQueueAsync(5).ConfigureAwait(false), Is.Null);
        }

        [Test]
        public async Task CleanupRemovesStaleQueuesAsync()
        {
            using var kv = new InMemorySharedKeyValueStore();
            IServiceMessageContext context = CreateContext();
            ITelemetryContext telemetry = NUnitTelemetryContext.Create();

            await using var factory = new SharedKeyValueMonitoredItemQueueFactory(kv, context, telemetry: telemetry);
            foreach (uint id in new uint[] { 1, 2 })
            {
                IDataChangeMonitoredItemQueue queue = factory.CreateDataChangeQueue(false, id);
                queue.ResetQueue(2, false);
                queue.Enqueue(new DataValue(new Variant((int)id)), ServiceResult.Good);
            }
            await factory.FlushAsync().ConfigureAwait(false);

            await factory.CleanupAsync([1]).ConfigureAwait(false);

            Assert.That(await factory.RestoreDataChangeQueueAsync(1).ConfigureAwait(false), Is.Not.Null);
            Assert.That(await factory.RestoreDataChangeQueueAsync(2).ConfigureAwait(false), Is.Null);
        }

        [Test]
        public async Task SubscriptionStoreDelegatesQueueRestoreToFactoryAsync()
        {
            using var kv = new InMemorySharedKeyValueStore();
            IServiceMessageContext context = CreateContext();
            ITelemetryContext telemetry = NUnitTelemetryContext.Create();

            await using (var factory = new SharedKeyValueMonitoredItemQueueFactory(kv, context, telemetry: telemetry))
            {
                IDataChangeMonitoredItemQueue queue = factory.CreateDataChangeQueue(false, 21);
                queue.ResetQueue(3, false);
                queue.Enqueue(new DataValue(new Variant(123)), ServiceResult.Good);
                await factory.FlushAsync().ConfigureAwait(false);
            }

            await using var restoreFactory = new SharedKeyValueMonitoredItemQueueFactory(
                kv, context, telemetry: telemetry);
            await using var store = new SharedKeyValueSubscriptionStore(
                kv, context, queueFactory: restoreFactory);

            IDataChangeMonitoredItemQueue restored = (await store
                .RestoreDataChangeMonitoredItemQueueAsync(21)
                .ConfigureAwait(false))!;

            Assert.That(restored, Is.Not.Null);
            Assert.That(restored.ItemsInQueue, Is.EqualTo(1));
        }

        [Test]
        public async Task SubscriptionStoreWithoutFactoryReturnsNullQueuesAsync()
        {
            using var kv = new InMemorySharedKeyValueStore();
            await using var store = new SharedKeyValueSubscriptionStore(kv, CreateContext());

            Assert.That(await store.RestoreDataChangeMonitoredItemQueueAsync(1).ConfigureAwait(false), Is.Null);
            Assert.That(await store.RestoreEventMonitoredItemQueueAsync(1).ConfigureAwait(false), Is.Null);
        }

        [Test]
        public async Task DisposeAsyncCancelsBlockedQueueMirrorWritesAsync()
        {
            await using var kv = new HangingWriteSharedKeyValueStore();
            IServiceMessageContext context = CreateContext();
            ITelemetryContext telemetry = NUnitTelemetryContext.Create();
            var factory = new SharedKeyValueMonitoredItemQueueFactory(kv, context, telemetry: telemetry);
            IDataChangeMonitoredItemQueue queue = factory.CreateDataChangeQueue(false, 55);
            queue.ResetQueue(2, false);
            queue.Enqueue(new DataValue(new Variant(1)), ServiceResult.Good);

            await kv.WaitForWriteAsync().ConfigureAwait(false);
            Task disposeTask = factory.DisposeAsync().AsTask();
            Task completed = await Task.WhenAny(disposeTask, Task.Delay(2000)).ConfigureAwait(false);

            Assert.That(completed, Is.SameAs(disposeTask));
            await disposeTask.ConfigureAwait(false);
        }

        private static ServiceMessageContext CreateContext()
        {
            ITelemetryContext telemetry = NUnitTelemetryContext.Create();
            var context = ServiceMessageContext.CreateEmpty(telemetry);
            context.NamespaceUris.GetIndexOrAppend("urn:test:queues");
            return context;
        }

        private sealed class HangingWriteSharedKeyValueStore : ISharedKeyValueStore, IAsyncDisposable
        {
            public Task<bool> WaitForWriteAsync()
            {
                return m_writeStarted.Task;
            }

            public ValueTask<(bool Found, ByteString Value)> TryGetAsync(string key, System.Threading.CancellationToken ct = default)
            {
                return new ValueTask<(bool Found, ByteString Value)>((false, default));
            }

            public ValueTask SetAsync(string key, ByteString value, System.Threading.CancellationToken ct = default)
            {
                m_writeStarted.TrySetResult(true);
                return new ValueTask(Task.Delay(System.Threading.Timeout.Infinite, ct));
            }

            public ValueTask<bool> CompareAndSwapAsync(
                string key,
                ByteString expected,
                ByteString value,
                System.Threading.CancellationToken ct = default)
            {
                return new ValueTask<bool>(true);
            }

            public ValueTask<bool> DeleteAsync(string key, System.Threading.CancellationToken ct = default)
            {
                m_writeStarted.TrySetResult(true);
                return WaitForDeleteCancellationAsync(ct);
            }

            public IAsyncEnumerable<KeyValuePair<string, ByteString>> ScanAsync(
                string keyPrefix,
                System.Threading.CancellationToken ct = default)
            {
                return TestAsyncEnumerable.Empty<KeyValuePair<string, ByteString>>();
            }

            public IAsyncEnumerable<KeyValueChange> WatchAsync(
                string keyPrefix,
                System.Threading.CancellationToken ct = default)
            {
                return TestAsyncEnumerable.Empty<KeyValueChange>();
            }

            public ValueTask DisposeAsync()
            {
                return default;
            }

            private static async ValueTask<bool> WaitForDeleteCancellationAsync(System.Threading.CancellationToken ct)
            {
                await Task.Delay(System.Threading.Timeout.Infinite, ct).ConfigureAwait(false);
                return false;
            }

            private readonly TaskCompletionSource<bool> m_writeStarted =
                new(TaskCreationOptions.RunContinuationsAsynchronously);
        }
    }
}