#nullable enable

using System;
using System.Collections;
using System.Collections.Generic;
using System.Threading;
using Cysharp.Threading.Tasks;
using NUnit.Framework;
using UnityEngine;
using UnityEngine.TestTools;

namespace ShrinkEventBus.Tests
{
    internal readonly struct GeneratedPingEvent : IShrinkEvent
    {
        public GeneratedPingEvent(int value) => Value = value;
        public int Value { get; }
    }

    [ShrinkEventSubscriber(DefaultBus = "game")]
    internal sealed class CodeGeneratedTarget
    {
        public int Sum { get; private set; }

        [ShrinkSubscribe]
        private void OnPing(GeneratedPingEvent evt) => Sum += evt.Value;
    }

    [ShrinkEventSubscriber(DefaultBus = "game")]
    internal static class StaticCodeGeneratedTarget
    {
        public static int Sum { get; set; }

        [ShrinkSubscribe]
        private static void OnPing(GeneratedPingEvent evt) => Sum += evt.Value;
    }

    [ShrinkEventSubscriber(DefaultBus = "mod:late-static")]
    internal static class DelayedStaticCodeGeneratedTarget
    {
        public static int Sum { get; set; }

        [ShrinkSubscribe]
        private static void OnPing(GeneratedPingEvent evt) => Sum += evt.Value;
    }

    [ShrinkEventSubscriber(DefaultBus = "game")]
    internal sealed class MonoCodeGeneratedTarget : MonoBehaviour
    {
        public int Sum { get; private set; }

        [ShrinkSubscribe]
        private void OnPing(GeneratedPingEvent evt) => Sum += evt.Value;
    }

    public sealed class ShrinkEventBusV2Tests
    {
        private readonly struct PingEvent : IShrinkEvent
        {
            public PingEvent(int value) => Value = value;
            public int Value { get; }
        }

        private readonly struct DiagnosticEvent : IShrinkEvent
        {
        }

        private sealed class CancelEvent : IShrinkCancelableEvent
        {
            public bool IsCanceled { get; private set; }
            public void SetCanceled(bool value) => IsCanceled = value;
        }

        private sealed class ResultEvent : IShrinkResultEvent<int>
        {
            public int Result { get; private set; }
            public void SetResult(int result) => Result = result;
        }

        private sealed class GeneratedTarget : IShrinkGeneratedSubscriber
        {
            public int Sum;

            public IDisposable AttachGenerated(IShrinkBusResolver resolver, ShrinkBusKey? defaultBus = null)
            {
                var binding = new ShrinkEventBinding();
                binding.Add(ShrinkGeneratedBinding.Subscribe<PingEvent>(resolver, defaultBus, string.Empty,
                    this, OnPing, ShrinkEventPriority.Normal, 0, false));
                return binding;
            }

            private void OnPing(PingEvent evt) => Sum += evt.Value;
        }

        [Test]
        public void MultipleBusesAreIsolated()
        {
            using var host = new ShrinkEventBusHost();
            var game = host.CreateBus(ShrinkBusKey.Game, ShrinkBusOptions.Inline());
            var mod = host.CreateBus(ShrinkBusKey.Mod("sample"), ShrinkBusOptions.Inline());
            var gameHits = 0;
            var modHits = 0;
            using var gameBinding = ShrinkGeneratedBinding.Subscribe<PingEvent>(host, ShrinkBusKey.Game,
                string.Empty, this, evt => gameHits += evt.Value, ShrinkEventPriority.Normal, 0, false);
            using var modBinding = ShrinkGeneratedBinding.Subscribe<PingEvent>(host, ShrinkBusKey.Mod("sample"),
                string.Empty, this, evt => modHits += evt.Value, ShrinkEventPriority.Normal, 0, false);

            game.Post(new PingEvent(2));
            mod.Post(new PingEvent(3));

            Assert.AreEqual(2, gameHits);
            Assert.AreEqual(3, modHits);
        }

        [Test]
        public void GeneratedTargetAttachDisposesAllHandlers()
        {
            using var host = new ShrinkEventBusHost();
            var game = host.CreateBus(ShrinkBusKey.Game, ShrinkBusOptions.Inline());
            var target = new GeneratedTarget();
            var binding = host.Attach(target, ShrinkBusKey.Game);

            game.Post(new PingEvent(4));
            binding.Dispose();
            game.Post(new PingEvent(7));

            Assert.AreEqual(4, target.Sum);
        }

        [Test]
        public void AttributeOnlyTargetUsesIlGeneratedBinding()
        {
            using var host = new ShrinkEventBusHost();
            var game = host.CreateBus(ShrinkBusKey.Game, ShrinkBusOptions.Inline());
            var target = new CodeGeneratedTarget();

            using (host.Attach(target, ShrinkBusKey.Game))
                game.Post(new GeneratedPingEvent(9));
            game.Post(new GeneratedPingEvent(4));

            Assert.AreEqual(9, target.Sum);
        }

        [Test]
        public void StaticAttributeSubscriberUsesModuleInitializerBinding()
        {
            StaticCodeGeneratedTarget.Sum = 0;

            EventBus.Post(new GeneratedPingEvent(11));

            Assert.AreEqual(11, StaticCodeGeneratedTarget.Sum);
        }

        [Test]
        public void StaticSubscriberAttachesWhenNamedBusIsCreatedLater()
        {
            var key = ShrinkBusKey.Mod("late-static");
            EventBus.RemoveBus(key);
            DelayedStaticCodeGeneratedTarget.Sum = 0;
            var bus = EventBus.CreateBus(key, ShrinkBusOptions.Inline());

            bus.Post(new GeneratedPingEvent(13));

            Assert.AreEqual(13, DelayedStaticCodeGeneratedTarget.Sum);
            Assert.IsTrue(EventBus.RemoveBus(key));
        }

        [UnityTest]
        public IEnumerator MonoScopeRefreshAndReleaseControlGeneratedBindings()
        {
            var gameObject = new GameObject("ShrinkEventBusV2-MonoScope");
            gameObject.SetActive(false);
            var target = gameObject.AddComponent<MonoCodeGeneratedTarget>();
            var scope = gameObject.AddComponent<ShrinkMonoEventScope>();
            Assert.IsInstanceOf<IShrinkGeneratedSubscriber>(target);

            scope.RefreshBindings();
            yield return null;
            yield return EventBus.PostAsync(new GeneratedPingEvent(5)).ToCoroutine();
            Assert.AreEqual(5, target.Sum);

            scope.ReleaseBindings();
            yield return EventBus.PostAsync(new GeneratedPingEvent(7)).ToCoroutine();
            Assert.AreEqual(5, target.Sum);
            UnityEngine.Object.DestroyImmediate(gameObject);
        }

        [Test]
        public void CanceledEventsSkipNormalHandlersButReachMonitors()
        {
            using var host = new ShrinkEventBusHost();
            var game = host.CreateBus(ShrinkBusKey.Game, ShrinkBusOptions.Inline());
            var normal = 0;
            var monitor = 0;
            using var first = ShrinkGeneratedBinding.Subscribe<CancelEvent>(host, ShrinkBusKey.Game,
                string.Empty, this, evt => evt.SetCanceled(true), ShrinkEventPriority.Highest, 0, false);
            using var second = ShrinkGeneratedBinding.Subscribe<CancelEvent>(host, ShrinkBusKey.Game,
                string.Empty, this, _ => normal++, ShrinkEventPriority.Normal, 0, false);
            using var third = ShrinkGeneratedBinding.Subscribe<CancelEvent>(host, ShrinkBusKey.Game,
                string.Empty, this, _ => monitor++, ShrinkEventPriority.Monitor, 0, true);

            var result = game.Post(new CancelEvent());

            Assert.IsTrue(result.Canceled);
            Assert.AreEqual(0, normal);
            Assert.AreEqual(1, monitor);
        }

        [Test]
        public void PriorityAndNumericPriorityAreStable()
        {
            using var host = new ShrinkEventBusHost();
            var game = host.CreateBus(ShrinkBusKey.Game, ShrinkBusOptions.Inline());
            var order = new List<string>();
            using var normal = ShrinkGeneratedBinding.Subscribe<PingEvent>(host, ShrinkBusKey.Game,
                string.Empty, this, _ => order.Add("normal"), ShrinkEventPriority.Normal, 0, false);
            using var high = ShrinkGeneratedBinding.Subscribe<PingEvent>(host, ShrinkBusKey.Game,
                string.Empty, this, _ => order.Add("high"), ShrinkEventPriority.High, 0, false);
            using var numeric = ShrinkGeneratedBinding.Subscribe<PingEvent>(host, ShrinkBusKey.Game,
                string.Empty, this, _ => order.Add("numeric"), ShrinkEventPriority.Normal, 75, false);

            game.Post(new PingEvent(1));

            CollectionAssert.AreEqual(new[] { "numeric", "high", "normal" }, order);
        }

        [Test]
        public void ResultEventUsesTypedResultContract()
        {
            using var host = new ShrinkEventBusHost();
            var game = host.CreateBus(ShrinkBusKey.Game, ShrinkBusOptions.Inline());
            using var binding = ShrinkGeneratedBinding.Subscribe<ResultEvent>(host, ShrinkBusKey.Game,
                string.Empty, this, value => value.SetResult(42),
                ShrinkEventPriority.Normal, 0, false);
            var value = new ResultEvent();

            var result = game.Post(value);

            Assert.IsTrue(result.Handled);
            Assert.AreEqual(42, value.Result);
        }

        [Test]
        public void HandlerExceptionPropagatesFromPost()
        {
            using var host = new ShrinkEventBusHost();
            var game = host.CreateBus(ShrinkBusKey.Game, ShrinkBusOptions.Inline());
            using var binding = ShrinkGeneratedBinding.Subscribe<PingEvent>(host, ShrinkBusKey.Game,
                string.Empty, this, _ => throw new InvalidOperationException("expected"),
                ShrinkEventPriority.Normal, 0, false);

            var exception = Assert.Throws<InvalidOperationException>(() => game.Post(new PingEvent(1)));

            Assert.AreEqual("expected", exception!.Message);
        }

        [UnityTest]
        public IEnumerator PostAsyncCancellationReturnsCanceledFailure()
        {
            using var host = new ShrinkEventBusHost();
            var bus = host.CreateBus(new ShrinkBusKey("worker", "cancellation"),
                ShrinkBusOptions.DedicatedThread());
            using var source = new CancellationTokenSource();
            source.Cancel();
            ShrinkPostResult result = default;

            yield return bus.PostAsync(new PingEvent(1), source.Token)
                .ContinueWith(value => result = value)
                .ToCoroutine();

            Assert.AreEqual(ShrinkPostFailure.Canceled, result.Failure);
        }

        [UnityTest]
        public IEnumerator DedicatedThreadShutdownDrainsAcceptedWork()
        {
            var host = new ShrinkEventBusHost();
            var key = new ShrinkBusKey("worker", "drain");
            var bus = host.CreateBus(key, ShrinkBusOptions.DedicatedThread(queueCapacity: 4));
            var hits = 0;
            using var binding = ShrinkGeneratedBinding.Subscribe<PingEvent>(host, key,
                string.Empty, this, _ => Interlocked.Increment(ref hits),
                ShrinkEventPriority.Normal, 0, false);
            Assert.IsTrue(bus.Post(new PingEvent(1)).Accepted);
            Assert.IsTrue(bus.Post(new PingEvent(2)).Accepted);

            yield return host.ShutdownAsync().ToCoroutine();

            Assert.AreEqual(2, Volatile.Read(ref hits));
        }

        [Test]
        public void DedicatedThreadRejectsWhenBoundedQueueIsFull()
        {
            using var host = new ShrinkEventBusHost();
            var key = new ShrinkBusKey("worker", "bounded");
            var options = ShrinkBusOptions.DedicatedThread(queueCapacity: 1);
            options.OverflowPolicy = ShrinkQueueOverflowPolicy.Reject;
            var bus = host.CreateBus(key, options);
            using var entered = new ManualResetEventSlim(false);
            using var release = new ManualResetEventSlim(false);
            var hits = 0;
            using var binding = ShrinkGeneratedBinding.Subscribe<PingEvent>(host, key, string.Empty,
                this, _ =>
                {
                    Interlocked.Increment(ref hits);
                    entered.Set();
                    release.Wait(TimeSpan.FromSeconds(2));
                }, ShrinkEventPriority.Normal, 0, false);

            Assert.IsTrue(bus.Post(new PingEvent(1)).Accepted);
            Assert.IsTrue(entered.Wait(TimeSpan.FromSeconds(2)));
            Assert.IsTrue(bus.Post(new PingEvent(2)).Accepted);
            var rejected = bus.Post(new PingEvent(3));
            release.Set();

            Assert.IsFalse(rejected.Accepted);
            Assert.AreEqual(ShrinkPostFailure.QueueFull, rejected.Failure);
            Assert.IsTrue(SpinWait.SpinUntil(() => Volatile.Read(ref hits) == 2, TimeSpan.FromSeconds(2)));
        }

        [UnityTest]
        public IEnumerator TaskPoolHonorsMaximumConcurrency()
        {
            using var host = new ShrinkEventBusHost();
            var key = new ShrinkBusKey("worker", "parallel");
            var bus = host.CreateBus(key, ShrinkBusOptions.TaskPool(maxConcurrency: 2, queueCapacity: 8));
            var active = 0;
            var maxActive = 0;
            using var binding = ShrinkGeneratedBinding.SubscribeAsync<PingEvent>(host, key, string.Empty,
                this, async (_, _) =>
                {
                    var current = Interlocked.Increment(ref active);
                    UpdateMaximum(ref maxActive, current);
                    Thread.Sleep(30);
                    Interlocked.Decrement(ref active);
                    await UniTask.CompletedTask;
                }, ShrinkEventPriority.Normal, 0, false);
            var posts = new List<UniTask<ShrinkPostResult>>();
            for (var i = 0; i < 4; i++)
                posts.Add(bus.PostAsync(new PingEvent(i)));

            yield return UniTask.WhenAll(posts).ToCoroutine();

            Assert.AreEqual(2, maxActive);
        }

        [Test]
        public void WarmStructPostDoesNotAllocate()
        {
            using var host = new ShrinkEventBusHost();
            var game = host.CreateBus(ShrinkBusKey.Game, ShrinkBusOptions.Inline());
            var sum = 0;
            using var binding = ShrinkGeneratedBinding.Subscribe<PingEvent>(host, ShrinkBusKey.Game,
                string.Empty, this, evt => sum += evt.Value, ShrinkEventPriority.Normal, 0, false);
            for (var i = 0; i < 100; i++)
                game.Post(new PingEvent(i));

            var before = GC.GetAllocatedBytesForCurrentThread();
            for (var i = 0; i < 10_000; i++)
                game.Post(new PingEvent(i));
            var allocated = GC.GetAllocatedBytesForCurrentThread() - before;

            Assert.AreEqual(0, allocated);
            Assert.Greater(sum, 0);
        }

        [Test]
        public void GlobalDetailedObserverReportsDispatchMetadata()
        {
            var captured = false;
            var trace = default(ShrinkEventTrace);
            void Capture(ShrinkEventTrace value)
            {
                trace = value;
                captured = true;
            }

            EventBus.DetailedPosted += Capture;
            try
            {
                EventBus.Post(new DiagnosticEvent());
            }
            finally
            {
                EventBus.DetailedPosted -= Capture;
            }

            Assert.IsTrue(captured);
            Assert.AreEqual(typeof(DiagnosticEvent), trace.EventType);
            Assert.AreEqual(ShrinkBusKey.Game, trace.BusKey);
            Assert.AreEqual(ShrinkBusSchedulerKind.MainThread, trace.Scheduler);
            Assert.IsTrue(trace.Result.Accepted);
            Assert.GreaterOrEqual(trace.ElapsedTimestampTicks, 0L);
        }

        [Test]
        public void GlobalStructPostDoesNotAllocateWithoutObservers()
        {
            var value = new DiagnosticEvent();
            for (var i = 0; i < 100; i++)
                EventBus.Post(in value);

            var before = GC.GetAllocatedBytesForCurrentThread();
            for (var i = 0; i < 10_000; i++)
                EventBus.Post(in value);
            var allocated = GC.GetAllocatedBytesForCurrentThread() - before;

            Assert.AreEqual(0, allocated);
        }

        [UnityTest]
        public IEnumerator DedicatedThreadPostAsyncRunsOnDedicatedThread()
        {
            using var host = new ShrinkEventBusHost();
            var bus = host.CreateBus(new ShrinkBusKey("worker", "tests"),
                ShrinkBusOptions.DedicatedThread());
            var callerThread = Thread.CurrentThread.ManagedThreadId;
            var handlerThread = callerThread;
            using var binding = ShrinkGeneratedBinding.Subscribe<PingEvent>(host,
                new ShrinkBusKey("worker", "tests"), string.Empty, this,
                _ => handlerThread = Thread.CurrentThread.ManagedThreadId,
                ShrinkEventPriority.Normal, 0, false);

            yield return bus.PostAsync(new PingEvent(1)).ToCoroutine();

            Assert.AreNotEqual(callerThread, handlerThread);
        }

        private static void UpdateMaximum(ref int location, int candidate)
        {
            while (true)
            {
                var current = Volatile.Read(ref location);
                if (candidate <= current || Interlocked.CompareExchange(ref location, candidate, current) == current)
                    return;
            }
        }
    }
}