#nullable enable

using System;
using System.Diagnostics;
using System.Text;
using System.Threading;
using Cysharp.Threading.Tasks;
using UnityEngine;

namespace ShrinkEventBus.Benchmark
{
    public static class ShrinkEventBusBenchmark
    {
        private readonly struct BenchmarkEvent : IShrinkEvent
        {
            public BenchmarkEvent(int value) => Value = value;
            public int Value { get; }
        }

        private sealed class BenchmarkClassEvent : IShrinkEvent
        {
            public int Value { get; set; }
        }

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

        [ShrinkEventSubscriber]
        private sealed class OneHandler
        {
            [ShrinkSubscribe(Bus = "benchmark:one")]
            private void H01(BenchmarkEvent value) => Consume(value);
        }

        [ShrinkEventSubscriber]
        private sealed class EightHandlers
        {
            [ShrinkSubscribe(Bus = "benchmark:eight")] private void H01(BenchmarkEvent value) => Consume(value);
            [ShrinkSubscribe(Bus = "benchmark:eight")] private void H02(BenchmarkEvent value) => Consume(value);
            [ShrinkSubscribe(Bus = "benchmark:eight")] private void H03(BenchmarkEvent value) => Consume(value);
            [ShrinkSubscribe(Bus = "benchmark:eight")] private void H04(BenchmarkEvent value) => Consume(value);
            [ShrinkSubscribe(Bus = "benchmark:eight")] private void H05(BenchmarkEvent value) => Consume(value);
            [ShrinkSubscribe(Bus = "benchmark:eight")] private void H06(BenchmarkEvent value) => Consume(value);
            [ShrinkSubscribe(Bus = "benchmark:eight")] private void H07(BenchmarkEvent value) => Consume(value);
            [ShrinkSubscribe(Bus = "benchmark:eight")] private void H08(BenchmarkEvent value) => Consume(value);
        }

        [ShrinkEventSubscriber]
        private sealed class EightClassHandlers
        {
            [ShrinkSubscribe(Bus = "benchmark:eight-class")] private void H01(BenchmarkClassEvent value) => Consume(value);
            [ShrinkSubscribe(Bus = "benchmark:eight-class")] private void H02(BenchmarkClassEvent value) => Consume(value);
            [ShrinkSubscribe(Bus = "benchmark:eight-class")] private void H03(BenchmarkClassEvent value) => Consume(value);
            [ShrinkSubscribe(Bus = "benchmark:eight-class")] private void H04(BenchmarkClassEvent value) => Consume(value);
            [ShrinkSubscribe(Bus = "benchmark:eight-class")] private void H05(BenchmarkClassEvent value) => Consume(value);
            [ShrinkSubscribe(Bus = "benchmark:eight-class")] private void H06(BenchmarkClassEvent value) => Consume(value);
            [ShrinkSubscribe(Bus = "benchmark:eight-class")] private void H07(BenchmarkClassEvent value) => Consume(value);
            [ShrinkSubscribe(Bus = "benchmark:eight-class")] private void H08(BenchmarkClassEvent value) => Consume(value);
        }

        [ShrinkEventSubscriber]
        private sealed class ThirtyHandlers
        {
            [ShrinkSubscribe(Bus = "benchmark:thirty")] private void H01(BenchmarkEvent value) => Consume(value);
            [ShrinkSubscribe(Bus = "benchmark:thirty")] private void H02(BenchmarkEvent value) => Consume(value);
            [ShrinkSubscribe(Bus = "benchmark:thirty")] private void H03(BenchmarkEvent value) => Consume(value);
            [ShrinkSubscribe(Bus = "benchmark:thirty")] private void H04(BenchmarkEvent value) => Consume(value);
            [ShrinkSubscribe(Bus = "benchmark:thirty")] private void H05(BenchmarkEvent value) => Consume(value);
            [ShrinkSubscribe(Bus = "benchmark:thirty")] private void H06(BenchmarkEvent value) => Consume(value);
            [ShrinkSubscribe(Bus = "benchmark:thirty")] private void H07(BenchmarkEvent value) => Consume(value);
            [ShrinkSubscribe(Bus = "benchmark:thirty")] private void H08(BenchmarkEvent value) => Consume(value);
            [ShrinkSubscribe(Bus = "benchmark:thirty")] private void H09(BenchmarkEvent value) => Consume(value);
            [ShrinkSubscribe(Bus = "benchmark:thirty")] private void H10(BenchmarkEvent value) => Consume(value);
            [ShrinkSubscribe(Bus = "benchmark:thirty")] private void H11(BenchmarkEvent value) => Consume(value);
            [ShrinkSubscribe(Bus = "benchmark:thirty")] private void H12(BenchmarkEvent value) => Consume(value);
            [ShrinkSubscribe(Bus = "benchmark:thirty")] private void H13(BenchmarkEvent value) => Consume(value);
            [ShrinkSubscribe(Bus = "benchmark:thirty")] private void H14(BenchmarkEvent value) => Consume(value);
            [ShrinkSubscribe(Bus = "benchmark:thirty")] private void H15(BenchmarkEvent value) => Consume(value);
            [ShrinkSubscribe(Bus = "benchmark:thirty")] private void H16(BenchmarkEvent value) => Consume(value);
            [ShrinkSubscribe(Bus = "benchmark:thirty")] private void H17(BenchmarkEvent value) => Consume(value);
            [ShrinkSubscribe(Bus = "benchmark:thirty")] private void H18(BenchmarkEvent value) => Consume(value);
            [ShrinkSubscribe(Bus = "benchmark:thirty")] private void H19(BenchmarkEvent value) => Consume(value);
            [ShrinkSubscribe(Bus = "benchmark:thirty")] private void H20(BenchmarkEvent value) => Consume(value);
            [ShrinkSubscribe(Bus = "benchmark:thirty")] private void H21(BenchmarkEvent value) => Consume(value);
            [ShrinkSubscribe(Bus = "benchmark:thirty")] private void H22(BenchmarkEvent value) => Consume(value);
            [ShrinkSubscribe(Bus = "benchmark:thirty")] private void H23(BenchmarkEvent value) => Consume(value);
            [ShrinkSubscribe(Bus = "benchmark:thirty")] private void H24(BenchmarkEvent value) => Consume(value);
            [ShrinkSubscribe(Bus = "benchmark:thirty")] private void H25(BenchmarkEvent value) => Consume(value);
            [ShrinkSubscribe(Bus = "benchmark:thirty")] private void H26(BenchmarkEvent value) => Consume(value);
            [ShrinkSubscribe(Bus = "benchmark:thirty")] private void H27(BenchmarkEvent value) => Consume(value);
            [ShrinkSubscribe(Bus = "benchmark:thirty")] private void H28(BenchmarkEvent value) => Consume(value);
            [ShrinkSubscribe(Bus = "benchmark:thirty")] private void H29(BenchmarkEvent value) => Consume(value);
            [ShrinkSubscribe(Bus = "benchmark:thirty")] private void H30(BenchmarkEvent value) => Consume(value);
        }

        [ShrinkEventSubscriber]
        private sealed class CanceledHandlers
        {
            [ShrinkSubscribe(Bus = "benchmark:canceled")] private void H01(CanceledBenchmarkEvent value) => _sink++;
            [ShrinkSubscribe(Bus = "benchmark:canceled")] private void H02(CanceledBenchmarkEvent value) => _sink++;
            [ShrinkSubscribe(Bus = "benchmark:canceled")] private void H03(CanceledBenchmarkEvent value) => _sink++;
            [ShrinkSubscribe(Bus = "benchmark:canceled")] private void H04(CanceledBenchmarkEvent value) => _sink++;
            [ShrinkSubscribe(Bus = "benchmark:canceled")] private void H05(CanceledBenchmarkEvent value) => _sink++;
            [ShrinkSubscribe(Bus = "benchmark:canceled")] private void H06(CanceledBenchmarkEvent value) => _sink++;
            [ShrinkSubscribe(Bus = "benchmark:canceled")] private void H07(CanceledBenchmarkEvent value) => _sink++;
            [ShrinkSubscribe(Bus = "benchmark:canceled")] private void H08(CanceledBenchmarkEvent value) => _sink++;
            [ShrinkSubscribe(Bus = "benchmark:canceled")] private void H09(CanceledBenchmarkEvent value) => _sink++;
            [ShrinkSubscribe(Bus = "benchmark:canceled")] private void H10(CanceledBenchmarkEvent value) => _sink++;
        }

        [ShrinkEventSubscriber]
        private sealed class AsyncHandler
        {
            [ShrinkSubscribe(Bus = "benchmark:async")]
            private UniTask Handle(BenchmarkEvent value, CancellationToken cancellationToken)
            {
                Consume(value);
                return UniTask.CompletedTask;
            }
        }

        [ShrinkEventSubscriber]
        private sealed class RegistrationHandler
        {
            [ShrinkSubscribe(Bus = "benchmark:registration")]
            private void Handle(BenchmarkEvent value) => Consume(value);
        }

        private static int _sink;

        public static string Run(int iterations = 1_000_000, int massIterations = 10_000,
            int registrationIterations = 5_000)
        {
            var keys = new[]
            {
                new ShrinkBusKey("benchmark", "empty"),
                new ShrinkBusKey("benchmark", "one"),
                new ShrinkBusKey("benchmark", "eight"),
                new ShrinkBusKey("benchmark", "eight-class"),
                new ShrinkBusKey("benchmark", "thirty"),
                new ShrinkBusKey("benchmark", "canceled"),
                new ShrinkBusKey("benchmark", "async"),
                new ShrinkBusKey("benchmark", "registration")
            };
            using var host = new ShrinkEventBusHost();
            var empty = host.CreateBus(keys[0], ShrinkBusOptions.Inline());
            var one = host.CreateBus(keys[1], ShrinkBusOptions.Inline());
            var eight = host.CreateBus(keys[2], ShrinkBusOptions.Inline());
            var eightClass = host.CreateBus(keys[3], ShrinkBusOptions.Inline());
            var thirty = host.CreateBus(keys[4], ShrinkBusOptions.Inline());
            var canceled = host.CreateBus(keys[5], ShrinkBusOptions.Inline());
            var asyncBus = host.CreateBus(keys[6], ShrinkBusOptions.Inline());
            host.CreateBus(keys[7], ShrinkBusOptions.Inline());

            using var oneBinding = host.Attach(new OneHandler());
            using var eightBinding = host.Attach(new EightHandlers());
            using var eightClassBinding = host.Attach(new EightClassHandlers());
            using var thirtyBinding = host.Attach(new ThirtyHandlers());
            using var canceledBinding = host.Attach(new CanceledHandlers());
            using var asyncBinding = host.Attach(new AsyncHandler());

            var report = new StringBuilder(2048);
            report.AppendLine("ShrinkEventBus 2.0 Benchmark Report");
            report.AppendLine($"iter={iterations} mass={massIterations} reg={registrationIterations}");
            report.AppendLine($"Unity {Application.unityVersion}, {Application.platform}, PlayMode={Application.isPlaying}");
            report.AppendLine();

            var value = new BenchmarkEvent(1);
            var classValue = new BenchmarkClassEvent { Value = 1 };
            var canceledValue = new CanceledBenchmarkEvent();
            Warmup(empty, one, eight, eightClass, thirty, canceled,
                value, classValue, canceledValue);

            MeasurePost(report, "Post / 0 handlers", iterations, empty, in value);
            MeasurePost(report, "Post / 1 handler", iterations, one, in value);
            MeasurePost(report, "Post / 8 handlers", massIterations, eight, in value);
            MeasurePost(report, "Post / 8 handlers class", massIterations, eightClass, in classValue);
            MeasurePost(report, "Post / 30 handlers", massIterations, thirty, in value);
            MeasurePost(report, "Post / canceled skips 10", massIterations,
                canceled, in canceledValue);
            MeasureAsync(report, "PostAsync / 1 async handler", massIterations,
                () => asyncBus.PostAsync(value));
            Measure(report, "Generated Attach + Dispose", registrationIterations, () =>
            {
                host.Attach(new RegistrationHandler()).Dispose();
            });

            var before = GC.GetAllocatedBytesForCurrentThread();
            for (var i = 0; i < iterations; i++)
                one.Post(in value);
            var allocated = GC.GetAllocatedBytesForCurrentThread() - before;
            report.AppendLine($"Post / struct hot path allocation : {allocated} B / {iterations} ops");
            report.AppendLine($"sink={_sink}");

            var result = report.ToString();
            UnityEngine.Debug.Log(result);
            return result;
        }

        private static void Warmup(IShrinkEventBus empty, IShrinkEventBus one,
            IShrinkEventBus eight, IShrinkEventBus eightClass, IShrinkEventBus thirty,
            IShrinkEventBus canceled, BenchmarkEvent value, BenchmarkClassEvent classValue,
            CanceledBenchmarkEvent canceledValue)
        {
            for (var i = 0; i < 10_000; i++)
            {
                empty.Post(in value);
                one.Post(in value);
                eight.Post(in value);
                eightClass.Post(classValue);
                thirty.Post(in value);
                canceled.Post(canceledValue);
            }
            GC.Collect();
            GC.WaitForPendingFinalizers();
            GC.Collect();
        }

        private static void Measure(StringBuilder report, string name, int iterations, Action action)
        {
            var gen0 = GC.CollectionCount(0);
            var beforeBytes = GC.GetAllocatedBytesForCurrentThread();
            var stopwatch = Stopwatch.StartNew();
            for (var i = 0; i < iterations; i++)
                action();
            stopwatch.Stop();
            AppendResult(report, name, iterations, stopwatch.Elapsed.TotalMilliseconds,
                GC.GetAllocatedBytesForCurrentThread() - beforeBytes,
                GC.CollectionCount(0) - gen0);
        }

        private static void MeasurePost<TEvent>(StringBuilder report, string name, int iterations,
            IShrinkEventBus bus, in TEvent eventData) where TEvent : IShrinkEvent
        {
            var gen0 = GC.CollectionCount(0);
            var beforeBytes = GC.GetAllocatedBytesForCurrentThread();
            var stopwatch = Stopwatch.StartNew();
            for (var i = 0; i < iterations; i++)
                bus.Post(in eventData);
            stopwatch.Stop();
            AppendResult(report, name, iterations, stopwatch.Elapsed.TotalMilliseconds,
                GC.GetAllocatedBytesForCurrentThread() - beforeBytes,
                GC.CollectionCount(0) - gen0);
        }

        private static void MeasureAsync(StringBuilder report, string name, int iterations,
            Func<UniTask<ShrinkPostResult>> action)
        {
            var gen0 = GC.CollectionCount(0);
            var beforeBytes = GC.GetAllocatedBytesForCurrentThread();
            var stopwatch = Stopwatch.StartNew();
            for (var i = 0; i < iterations; i++)
                action().GetAwaiter().GetResult();
            stopwatch.Stop();
            AppendResult(report, name, iterations, stopwatch.Elapsed.TotalMilliseconds,
                GC.GetAllocatedBytesForCurrentThread() - beforeBytes,
                GC.CollectionCount(0) - gen0);
        }

        private static void AppendResult(StringBuilder report, string name, int iterations,
            double milliseconds, long allocatedBytes, int gen0Collections)
        {
            var microseconds = milliseconds * 1000d / iterations;
            var throughput = iterations / (milliseconds / 1000d);
            report.AppendLine($"{name,-34} {milliseconds,10:F3} ms  {microseconds,9:F4} us/op  " +
                              $"{throughput,12:F0} ops/s  alloc={allocatedBytes} B  gen0={gen0Collections}");
        }

        private static void Consume(BenchmarkEvent value)
        {
            _sink = unchecked(_sink + value.Value);
        }

        private static void Consume(BenchmarkClassEvent value)
        {
            _sink = unchecked(_sink + value.Value);
        }
    }
}