using System;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using Unity.IL2CPP.CompilerServices;
using UnityEngine;

namespace AlicizaX
{
    [Il2CppSetOption(Option.NullChecks, false)]
    [Il2CppSetOption(Option.DivideByZeroChecks, false)]
    [Il2CppSetOption(Option.ArrayBoundsChecks, false)]
    public static class EventContainer<TPayload> where TPayload : struct, IEventArgs
    {
        private static readonly int InitialSize = EventInitialSize<TPayload>.Size;
        private static readonly int TypeId;

        // 优化3: SoA布局，提升缓存命中率
        private static Action<TPayload>[] _callbacks;
        private static int[] _versions;
        private static int[] _activeSlots;

        private static int[] _freeSlots;
        private static int _freeCount;
        private static int[] _activeIndices;
        private static int _activeCount;
        private static int _version;

#if Event_StrictCheck
        private static System.Collections.Generic.HashSet<Action<TPayload>> _activeHandlers;
#endif

        static EventContainer()
        {
            TypeId = UnsubscribeRegistry.Register(Unsubscribe);

            _callbacks = new Action<TPayload>[InitialSize];
            _versions = new int[InitialSize];
            _activeSlots = new int[InitialSize];
            _freeSlots = new int[InitialSize];
            _activeIndices = new int[InitialSize];
            _freeCount = InitialSize;

            for (int i = 0; i < InitialSize; i++)
            {
                _freeSlots[i] = i;
            }

#if Event_StrictCheck
            _activeHandlers = new System.Collections.Generic.HashSet<Action<TPayload>>();
#endif
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static EventRuntimeHandle Subscribe(Action<TPayload> callback)
        {
#if Event_StrictCheck
            if (_activeHandlers.Contains(callback))
            {
                UnityEngine.Debug.LogWarning($"重复订阅事件处理程序: {callback.Method.Name}");
                return default;
            }

            _activeHandlers.Add(callback);
#endif

            int handlerIndex = GetFreeSlot();

            // 优化4: 提前扩容检查
            if (_activeCount >= _activeIndices.Length)
            {
                Array.Resize(ref _activeIndices, _activeIndices.Length << 1);
            }

            int activeIndex = _activeCount++;
            _activeIndices[activeIndex] = handlerIndex;

            int version = ++_version;
            _callbacks[handlerIndex] = callback;
            _versions[handlerIndex] = version;
            _activeSlots[handlerIndex] = activeIndex;

            return new EventRuntimeHandle(TypeId, handlerIndex, version);
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        private static int GetFreeSlot()
        {
            if (_freeCount > 0)
            {
                return _freeSlots[--_freeCount];
            }

            int oldLen = _callbacks.Length;
            int newSize = oldLen == 0 ? 64 : oldLen << 1;

            // 批量扩容
            Array.Resize(ref _callbacks, newSize);
            Array.Resize(ref _versions, newSize);
            Array.Resize(ref _activeSlots, newSize);
            Array.Resize(ref _freeSlots, newSize);

            // 逆序添加，保持小索引优先（缓存友好）
            for (int i = newSize - 1; i >= oldLen; i--)
            {
                _freeSlots[_freeCount++] = i;
            }

            return _freeSlots[--_freeCount];
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        private static void Unsubscribe(int handlerIndex, int version)
        {
            // 优化5: 提前版本检查
            if (_versions[handlerIndex] != version) return;

            int lastActiveIndex = --_activeCount;
            int lastHandlerIndex = _activeIndices[lastActiveIndex];
            int currentActiveIndex = _activeSlots[handlerIndex];

            // Swap-remove
            _activeIndices[currentActiveIndex] = lastHandlerIndex;
            _activeSlots[lastHandlerIndex] = currentActiveIndex;

#if Event_StrictCheck
            _activeHandlers.Remove(_callbacks[handlerIndex]);
#endif

            _callbacks[handlerIndex] = null;
            _versions[handlerIndex] = 0;

            if (_freeCount >= _freeSlots.Length)
            {
                Array.Resize(ref _freeSlots, _freeSlots.Length << 1);
            }

            _freeSlots[_freeCount++] = handlerIndex;
        }

        // 优化6: 改进Publish，减少数组访问和分支
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static void Publish(in TPayload payload)
        {
            int count = _activeCount;
            if (count == 0) return; // 快速路径

            int[] indices = _activeIndices;
            Action<TPayload>[] callbacks = _callbacks;

            // 优化7: 更高效的循环展开
            int i = 0;
            int unrolled = count & ~3; // count - (count % 4)

            // 4路展开主循环
            for (; i < unrolled; i += 4)
            {
                int idx0 = indices[i];
                int idx1 = indices[i + 1];
                int idx2 = indices[i + 2];
                int idx3 = indices[i + 3];

                callbacks[idx0](payload);
                callbacks[idx1](payload);
                callbacks[idx2](payload);
                callbacks[idx3](payload);
            }

            // 优化8: 使用Duff's Device处理剩余
            switch (count - i)
            {
                case 3:
                    callbacks[indices[i + 2]](payload);
                    goto case 2;
                case 2:
                    callbacks[indices[i + 1]](payload);
                    goto case 1;
                case 1: callbacks[indices[i]](payload); break;
            }
        }

        // 额外优化方法
        public static int SubscriberCount
        {
            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            get => _activeCount;
        }

        // 预热容量，避免运行时扩容
        public static void EnsureCapacity(int capacity)
        {
            if (_callbacks.Length >= capacity) return;

            int oldLen = _callbacks.Length;
            Array.Resize(ref _callbacks, capacity);
            Array.Resize(ref _versions, capacity);
            Array.Resize(ref _activeSlots, capacity);
            Array.Resize(ref _freeSlots, capacity);
            Array.Resize(ref _activeIndices, capacity);

            for (int i = capacity - 1; i >= oldLen; i--)
            {
                _freeSlots[_freeCount++] = i;
            }
        }

        // 清空所有订阅
        public static void Clear()
        {
            for (int i = 0; i < _activeCount; i++)
            {
                int idx = _activeIndices[i];
                _callbacks[idx] = null;
                _versions[idx] = 0;
                _freeSlots[_freeCount++] = idx;
            }

            _activeCount = 0;

#if Event_StrictCheck
            _activeHandlers.Clear();
#endif
        }
    }
}