#nullable enable
using System;
using System.Linq;
using System.Runtime.CompilerServices;
using Cysharp.Threading.Tasks;
using NUnit.Framework;

namespace ShrinkContext.Tests
{
    public class RetirementRetentionTests
    {
        [Test]
        public void DeepDependencyChainRetiresWithoutGrowingTheCallStack()
        {
            var runtime = new ShrinkContextRuntime();
            ShrinkFiber first = null;
            for (var i = 0; i < 1000; i++)
            {
                var fiber = runtime.Use(new ChainComponent(i));
                if (i == 0) first = fiber;
            }
            TestAwait.Run(runtime.RetireAsync(first));
            Assert.That(runtime.Fibers.All(f => f.State == ShrinkFiberState.Inactive));
            Assert.That(runtime.CaptureDiagnostic().BindingCount, Is.Zero);
            TestAwait.Run(runtime.ShutdownAsync());
            Assert.That(runtime.Fibers, Is.Empty);
        }

        private sealed class ChainComponent : IShrinkComponent
        {
            public ChainComponent(int index)
            {
                Name = "chain-" + index;
                Inject = index == 0 ? Array.Empty<string>() : new[] { "chain-" + (index - 1) };
                Provide = new[] { Name };
            }
            public string Name { get; }
            public System.Collections.Generic.IReadOnlyList<string> Inject { get; }
            public System.Collections.Generic.IReadOnlyList<string> Provide { get; }
            public UniTask ApplyAsync(ShrinkCtx ctx, object config) { ctx.Set(Name, this); return UniTask.CompletedTask; }
        }

        [Test]
        public void RepeatedRetirementKeepsOnlyBoundedValueHistory()
        {
            var runtime = new ShrinkContextRuntime(8);
            for (var i = 0; i < 10000; i++)
                TestAwait.Run(runtime.RetireAsync(runtime.Use(new ProviderComponent("provider", "value", i))));
            Assert.That(runtime.Fibers, Is.Empty);
            var diagnostic = runtime.CaptureDiagnostic();
            Assert.That(diagnostic.Fibers.Count, Is.EqualTo(8));
            Assert.That(diagnostic.Fibers.All(f => f.Retired));
            Assert.That(diagnostic.BindingCount, Is.Zero);
            TestAwait.Run(runtime.ShutdownAsync());
        }

        [Test]
        public void RuntimeAndParentEffectsDoNotRetainRetiredComponent()
        {
            var runtime = new ShrinkContextRuntime();
            var weak = CreateAndRetire(runtime);
            GC.Collect(); GC.WaitForPendingFinalizers(); GC.Collect();
            Assert.That(weak.IsAlive, Is.False);
            GC.KeepAlive(runtime);
        }

        [MethodImpl(MethodImplOptions.NoInlining)]
        private static WeakReference CreateAndRetire(ShrinkContextRuntime runtime)
        {
            var component = new ProviderComponent("collectible", "key", new byte[1024]);
            var weak = new WeakReference(component);
            TestAwait.Run(runtime.RetireAsync(runtime.Use(component)));
            return weak;
        }

        [Test]
        public void DiagnosticProvidersRespectRealmsAndExcludeRetired()
        {
            var runtime = new ShrinkContextRuntime();
            var p = runtime.Use(new ProviderComponent("p", "key", "value"));
            var c = runtime.Use(new ConsumerComponent("c", "key"));
            Assert.That(runtime.CaptureDiagnostic().Fibers.Single(f => f.Uid == c.Uid).Dependencies.Single().PotentialProviderUids, Is.EqualTo(new[] { p.Uid }));
            TestAwait.Run(runtime.RetireAsync(p));
            Assert.That(runtime.CaptureDiagnostic().Fibers.Single(f => f.Uid == c.Uid).Dependencies.Single().PotentialProviderUids, Is.Empty);
            TestAwait.Run(runtime.ShutdownAsync());
        }
    }
}