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

namespace AlicizaX.Timer.Runtime
{
    public delegate void TimerHandlerNoArgs();
    internal delegate void TimerGenericInvoker(object handler, object arg);

    internal static class TimerGenericInvokerCache<T> where T : class
    {
        public static readonly TimerGenericInvoker Invoke = InvokeGeneric;

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        private static void InvokeGeneric(object handler, object arg)
        {
            ((Action<T>)handler).Invoke((T)arg);
        }
    }

    [Il2CppSetOption(Option.NullChecks, false)]
    [Il2CppSetOption(Option.ArrayBoundsChecks, false)]
    [StructLayout(LayoutKind.Sequential, Pack = 4)]
    internal struct TimerInfo
    {
        public int TimerId;
        public int Version;
        public int QueueIndex;
        public int ActiveIndex;
        public float TriggerTime;
        public float Duration;
        public float RemainingTime;
        public TimerHandlerNoArgs NoArgsHandler;
        public TimerGenericInvoker GenericInvoker;
        public object GenericHandler;
        public object GenericArg;
        public bool IsLoop;
        public bool IsRunning;
        public bool IsUnscaled;
        public bool IsActive;
        public byte HandlerType;

#if UNITY_EDITOR
        public float CreationTime;
#endif

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public void Clear()
        {
            TimerId = 0;
            QueueIndex = -1;
            ActiveIndex = -1;
            TriggerTime = 0f;
            Duration = 0f;
            RemainingTime = 0f;
            NoArgsHandler = null;
            GenericInvoker = null;
            GenericHandler = null;
            GenericArg = null;
            IsLoop = false;
            IsRunning = false;
            IsUnscaled = false;
            IsActive = false;
            HandlerType = 0;
#if UNITY_EDITOR
            CreationTime = 0f;
#endif
        }
    }

    [UnityEngine.Scripting.Preserve]
    [Il2CppSetOption(Option.NullChecks, false)]
    [Il2CppSetOption(Option.ArrayBoundsChecks, false)]
    internal sealed class TimerService : ServiceBase, ITimerService, IServiceTickable, ITimerServiceDebugView
    {
        private const int MAX_CAPACITY = 256;
        private const int HANDLE_INDEX_BITS = 9;
        private const int HANDLE_INDEX_MASK = MAX_CAPACITY - 1;
        private const int HANDLE_VERSION_MASK = 0x3FFFFF;
        private const float MINIMUM_DELAY = 0.0001f;
        private const byte HANDLER_NO_ARGS = 0;
        private const byte HANDLER_GENERIC = 1;

#if UNITY_EDITOR
        private const float LEAK_DETECTION_THRESHOLD = 300f;
#endif

        private readonly TimerInfo[] _timerPool;
        private readonly int[] _freeIndices;
        private readonly int[] _activeIndices;
        private readonly TimerQueue _scaledQueue;
        private readonly TimerQueue _unscaledQueue;

        private int _freeCount;
        private int _activeCount;
        private int _peakActiveCount;

        private sealed class TimerQueue
        {
            private readonly TimerService _owner;
            private readonly int[] _heap;
            private int _count;

            public TimerQueue(TimerService owner)
            {
                _owner = owner;
                _heap = new int[MAX_CAPACITY];
            }

            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            public void Add(int poolIndex)
            {
                ref TimerInfo timer = ref _owner._timerPool[poolIndex];
                int index = _count++;
                _heap[index] = poolIndex;
                timer.QueueIndex = index;
                BubbleUp(index);
            }

            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            public void Remove(int poolIndex)
            {
                ref TimerInfo timer = ref _owner._timerPool[poolIndex];
                int index = timer.QueueIndex;
                if ((uint)index >= (uint)_count)
                {
                    timer.QueueIndex = -1;
                    return;
                }

                int lastIndex = --_count;
                int lastPoolIndex = _heap[lastIndex];
                timer.QueueIndex = -1;

                if (index == lastIndex)
                {
                    return;
                }

                _heap[index] = lastPoolIndex;
                _owner._timerPool[lastPoolIndex].QueueIndex = index;

                if (!BubbleUp(index))
                {
                    BubbleDown(index);
                }
            }

            public void Advance(float currentTime)
            {
                while (_count > 0)
                {
                    int poolIndex = _heap[0];
                    ref TimerInfo timer = ref _owner._timerPool[poolIndex];

                    if (!timer.IsActive || !timer.IsRunning)
                    {
                        RemoveRoot();
                        continue;
                    }

                    if (timer.TriggerTime > currentTime)
                    {
                        break;
                    }

                    RemoveRoot();
                    _owner.ProcessDueTimer(poolIndex, currentTime);
                }
            }

            public void Clear()
            {
                while (_count > 0)
                {
                    int poolIndex = _heap[--_count];
                    _owner._timerPool[poolIndex].QueueIndex = -1;
                }
            }

            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            private void RemoveRoot()
            {
                int rootPoolIndex = _heap[0];
                int lastIndex = --_count;
                _owner._timerPool[rootPoolIndex].QueueIndex = -1;

                if (lastIndex <= 0)
                {
                    return;
                }

                int lastPoolIndex = _heap[lastIndex];
                _heap[0] = lastPoolIndex;
                _owner._timerPool[lastPoolIndex].QueueIndex = 0;
                BubbleDown(0);
            }

            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            private bool BubbleUp(int index)
            {
                bool moved = false;
                while (index > 0)
                {
                    int parent = (index - 1) >> 1;
                    if (!Less(_heap[index], _heap[parent]))
                    {
                        break;
                    }

                    Swap(index, parent);
                    index = parent;
                    moved = true;
                }

                return moved;
            }

            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            private void BubbleDown(int index)
            {
                while (true)
                {
                    int left = (index << 1) + 1;
                    if (left >= _count)
                    {
                        return;
                    }

                    int right = left + 1;
                    int smallest = left;
                    if (right < _count && Less(_heap[right], _heap[left]))
                    {
                        smallest = right;
                    }

                    if (!Less(_heap[smallest], _heap[index]))
                    {
                        return;
                    }

                    Swap(index, smallest);
                    index = smallest;
                }
            }

            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            private bool Less(int leftPoolIndex, int rightPoolIndex)
            {
                ref TimerInfo left = ref _owner._timerPool[leftPoolIndex];
                ref TimerInfo right = ref _owner._timerPool[rightPoolIndex];

                if (left.TriggerTime < right.TriggerTime)
                {
                    return true;
                }

                if (left.TriggerTime > right.TriggerTime)
                {
                    return false;
                }

                return left.TimerId < right.TimerId;
            }

            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            private void Swap(int leftIndex, int rightIndex)
            {
                int leftPoolIndex = _heap[leftIndex];
                int rightPoolIndex = _heap[rightIndex];

                _heap[leftIndex] = rightPoolIndex;
                _heap[rightIndex] = leftPoolIndex;

                _owner._timerPool[leftPoolIndex].QueueIndex = rightIndex;
                _owner._timerPool[rightPoolIndex].QueueIndex = leftIndex;
            }
        }

        public TimerService()
        {
            _timerPool = new TimerInfo[MAX_CAPACITY];
            _freeIndices = new int[MAX_CAPACITY];
            _activeIndices = new int[MAX_CAPACITY];
            _scaledQueue = new TimerQueue(this);
            _unscaledQueue = new TimerQueue(this);

            _freeCount = MAX_CAPACITY;
            for (int i = 0; i < MAX_CAPACITY; i++)
            {
                _freeIndices[i] = i;
                _timerPool[i].QueueIndex = -1;
                _timerPool[i].ActiveIndex = -1;
            }
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public int AddTimer(TimerHandlerNoArgs callback, float time, bool isLoop = false, bool isUnscaled = false)
        {
            if (callback == null)
            {
                return 0;
            }

            int poolIndex = AcquireTimerIndex();
            if (poolIndex < 0)
            {
                return 0;
            }

            InitializeTimer(poolIndex, time, isLoop, isUnscaled);

            ref TimerInfo timer = ref _timerPool[poolIndex];
            timer.HandlerType = HANDLER_NO_ARGS;
            timer.NoArgsHandler = callback;

            AddToActiveSet(poolIndex);
            ScheduleTimer(poolIndex);
            return timer.TimerId;
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public int AddTimer<T>(Action<T> callback, T arg, float time, bool isLoop = false, bool isUnscaled = false) where T : class
        {
            if (callback == null)
            {
                return 0;
            }

            int poolIndex = AcquireTimerIndex();
            if (poolIndex < 0)
            {
                return 0;
            }

            InitializeTimer(poolIndex, time, isLoop, isUnscaled);

            ref TimerInfo timer = ref _timerPool[poolIndex];
            timer.HandlerType = HANDLER_GENERIC;
            timer.GenericInvoker = TimerGenericInvokerCache<T>.Invoke;
            timer.GenericHandler = callback;
            timer.GenericArg = arg;

            AddToActiveSet(poolIndex);
            ScheduleTimer(poolIndex);
            return timer.TimerId;
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public void Stop(int timerId)
        {
            int poolIndex = GetPoolIndex(timerId);
            if (poolIndex < 0)
            {
                return;
            }

            ref TimerInfo timer = ref _timerPool[poolIndex];
            if (!timer.IsRunning)
            {
                return;
            }

            if (timer.QueueIndex >= 0)
            {
                GetQueue(timer.IsUnscaled).Remove(poolIndex);
                float currentTime = GetCurrentTime(timer.IsUnscaled);
                float remainingTime = timer.TriggerTime - currentTime;
                timer.RemainingTime = remainingTime > MINIMUM_DELAY ? remainingTime : MINIMUM_DELAY;
            }
            else
            {
                timer.RemainingTime = timer.IsLoop ? timer.Duration : MINIMUM_DELAY;
            }

            timer.IsRunning = false;
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public void Resume(int timerId)
        {
            int poolIndex = GetPoolIndex(timerId);
            if (poolIndex < 0)
            {
                return;
            }

            ref TimerInfo timer = ref _timerPool[poolIndex];
            if (timer.IsRunning)
            {
                return;
            }

            float delay = timer.RemainingTime > MINIMUM_DELAY ? timer.RemainingTime : MINIMUM_DELAY;
            timer.TriggerTime = GetCurrentTime(timer.IsUnscaled) + delay;
            timer.RemainingTime = 0f;
            timer.IsRunning = true;
            ScheduleTimer(poolIndex);
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public bool IsRunning(int timerId)
        {
            int poolIndex = GetPoolIndex(timerId);
            return poolIndex >= 0 && _timerPool[poolIndex].IsRunning;
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public float GetLeftTime(int timerId)
        {
            int poolIndex = GetPoolIndex(timerId);
            if (poolIndex < 0)
            {
                return 0f;
            }

            ref TimerInfo timer = ref _timerPool[poolIndex];
            if (!timer.IsRunning)
            {
                return timer.RemainingTime;
            }

            float leftTime = timer.TriggerTime - GetCurrentTime(timer.IsUnscaled);
            return leftTime > 0f ? leftTime : 0f;
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public void Restart(int timerId)
        {
            int poolIndex = GetPoolIndex(timerId);
            if (poolIndex < 0)
            {
                return;
            }

            ref TimerInfo timer = ref _timerPool[poolIndex];
            if (timer.QueueIndex >= 0)
            {
                GetQueue(timer.IsUnscaled).Remove(poolIndex);
            }

            timer.TriggerTime = GetCurrentTime(timer.IsUnscaled) + timer.Duration;
            timer.RemainingTime = 0f;
            timer.IsRunning = true;
            ScheduleTimer(poolIndex);
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public void RemoveTimer(int timerId)
        {
            int poolIndex = GetPoolIndex(timerId);
            if (poolIndex >= 0)
            {
                ReleaseTimer(poolIndex);
            }
        }

        void IServiceTickable.Tick(float deltaTime)
        {
            _scaledQueue.Advance(Time.time);
            _unscaledQueue.Advance(Time.unscaledTime);
        }

        protected override void OnInitialize()
        {
        }

        protected override void OnDestroyService()
        {
            RemoveAllTimers();
        }

        public int Order => 0;

        void ITimerServiceDebugView.GetStatistics(out int activeCount, out int poolCapacity, out int peakActiveCount, out int freeCount)
        {
            activeCount = _activeCount;
            poolCapacity = MAX_CAPACITY;
            peakActiveCount = _peakActiveCount;
            freeCount = _freeCount;
        }

        int ITimerServiceDebugView.GetAllTimers(TimerDebugInfo[] results)
        {
            if (results == null || results.Length == 0)
            {
                return 0;
            }

            int count = _activeCount < results.Length ? _activeCount : results.Length;
            float currentTime = Time.time;
            float currentUnscaledTime = Time.unscaledTime;

            for (int i = 0; i < count; i++)
            {
                FillDebugInfo(_activeIndices[i], ref results[i], currentTime, currentUnscaledTime);
            }

            return count;
        }

#if UNITY_EDITOR
        int ITimerServiceDebugView.GetStaleOneShotTimers(TimerDebugInfo[] results)
        {
            if (results == null || results.Length == 0)
            {
                return 0;
            }

            int count = 0;
            float realtimeSinceStartup = Time.realtimeSinceStartup;
            float currentTime = Time.time;
            float currentUnscaledTime = Time.unscaledTime;

            for (int i = 0; i < _activeCount && count < results.Length; i++)
            {
                int poolIndex = _activeIndices[i];
                ref TimerInfo timer = ref _timerPool[poolIndex];
                if (timer.IsLoop)
                {
                    continue;
                }

                if (realtimeSinceStartup - timer.CreationTime <= LEAK_DETECTION_THRESHOLD)
                {
                    continue;
                }

                FillDebugInfo(poolIndex, ref results[count], currentTime, currentUnscaledTime);
                count++;
            }

            return count;
        }
#endif

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        private int AcquireTimerIndex()
        {
            if (_freeCount <= 0)
            {
                return -1;
            }

            return _freeIndices[--_freeCount];
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        private void InitializeTimer(int poolIndex, float time, bool isLoop, bool isUnscaled)
        {
            ref TimerInfo timer = ref _timerPool[poolIndex];
            float duration = NormalizeDelay(time);
            float currentTime = GetCurrentTime(isUnscaled);

            int version = NextVersion(timer.Version);
            timer.Version = version;
            timer.TimerId = ComposeTimerId(poolIndex, version);
            timer.TriggerTime = currentTime + duration;
            timer.Duration = duration;
            timer.RemainingTime = 0f;
            timer.NoArgsHandler = null;
            timer.GenericInvoker = null;
            timer.GenericHandler = null;
            timer.GenericArg = null;
            timer.IsLoop = isLoop;
            timer.IsRunning = true;
            timer.IsUnscaled = isUnscaled;
            timer.IsActive = true;
            timer.HandlerType = HANDLER_NO_ARGS;

#if UNITY_EDITOR
            timer.CreationTime = Time.realtimeSinceStartup;
#endif
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        private void RemoveAllTimers()
        {
            while (_activeCount > 0)
            {
                ReleaseTimer(_activeIndices[_activeCount - 1]);
            }

            _scaledQueue.Clear();
            _unscaledQueue.Clear();
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        private void ProcessDueTimer(int poolIndex, float currentTime)
        {
            ref TimerInfo timer = ref _timerPool[poolIndex];
            if (!timer.IsActive)
            {
                return;
            }

            bool shouldRemoveAfterCallback = !timer.IsLoop;

            switch (timer.HandlerType)
            {
                case HANDLER_NO_ARGS:
                    timer.NoArgsHandler();
                    break;

                case HANDLER_GENERIC:
                    timer.GenericInvoker(timer.GenericHandler, timer.GenericArg);
                    break;
            }

            if (!timer.IsActive)
            {
                return;
            }

            if (timer.QueueIndex >= 0)
            {
                return;
            }

            if (shouldRemoveAfterCallback)
            {
                ReleaseTimer(poolIndex);
            }
            else if (timer.IsRunning)
            {
                timer.TriggerTime = currentTime + timer.Duration;
                ScheduleTimer(poolIndex);
            }
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        private void ScheduleTimer(int poolIndex)
        {
            ref TimerInfo timer = ref _timerPool[poolIndex];
            if (!timer.IsActive || !timer.IsRunning)
            {
                return;
            }

            if (timer.QueueIndex >= 0)
            {
                return;
            }

            float currentTime = GetCurrentTime(timer.IsUnscaled);
            if (timer.TriggerTime <= currentTime)
            {
                timer.TriggerTime = currentTime + MINIMUM_DELAY;
            }

            GetQueue(timer.IsUnscaled).Add(poolIndex);
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        private void ReleaseTimer(int poolIndex)
        {
            ref TimerInfo timer = ref _timerPool[poolIndex];
            if (!timer.IsActive)
            {
                return;
            }

            if (timer.QueueIndex >= 0)
            {
                GetQueue(timer.IsUnscaled).Remove(poolIndex);
            }

            RemoveFromActiveSet(poolIndex);
            timer.Clear();
            _freeIndices[_freeCount++] = poolIndex;
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        private void AddToActiveSet(int poolIndex)
        {
            int position = _activeCount;
            _activeIndices[position] = poolIndex;
            _timerPool[poolIndex].ActiveIndex = position;
            _activeCount = position + 1;

            if (_activeCount > _peakActiveCount)
            {
                _peakActiveCount = _activeCount;
            }
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        private void RemoveFromActiveSet(int poolIndex)
        {
            ref TimerInfo timer = ref _timerPool[poolIndex];
            int position = timer.ActiveIndex;
            if ((uint)position >= (uint)_activeCount)
            {
                return;
            }

            int lastPosition = --_activeCount;
            int lastPoolIndex = _activeIndices[lastPosition];

            if (position != lastPosition)
            {
                _activeIndices[position] = lastPoolIndex;
                _timerPool[lastPoolIndex].ActiveIndex = position;
            }

            timer.ActiveIndex = -1;
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        private int GetPoolIndex(int timerId)
        {
            if (timerId <= 0)
            {
                return -1;
            }

            int poolIndex = (timerId & HANDLE_INDEX_MASK) - 1;
            if ((uint)poolIndex >= MAX_CAPACITY)
            {
                return -1;
            }

            ref TimerInfo timer = ref _timerPool[poolIndex];
            return timer.IsActive && timer.TimerId == timerId ? poolIndex : -1;
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        private static int ComposeTimerId(int poolIndex, int version)
        {
            return (version << HANDLE_INDEX_BITS) | (poolIndex + 1);
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        private static int NextVersion(int version)
        {
            version++;
            if (version > HANDLE_VERSION_MASK)
            {
                version = 1;
            }

            return version;
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        private static float NormalizeDelay(float time)
        {
            return time > MINIMUM_DELAY ? time : MINIMUM_DELAY;
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        private static float GetCurrentTime(bool isUnscaled)
        {
            return isUnscaled ? Time.unscaledTime : Time.time;
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        private TimerQueue GetQueue(bool isUnscaled)
        {
            return isUnscaled ? _unscaledQueue : _scaledQueue;
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        private void FillDebugInfo(int poolIndex, ref TimerDebugInfo info, float currentTime, float currentUnscaledTime)
        {
            ref TimerInfo timer = ref _timerPool[poolIndex];
            float leftTime;
            if (timer.IsRunning)
            {
                leftTime = timer.TriggerTime - (timer.IsUnscaled ? currentUnscaledTime : currentTime);
                if (leftTime < 0f)
                {
                    leftTime = 0f;
                }
            }
            else
            {
                leftTime = timer.RemainingTime;
            }

            info.TimerId = timer.TimerId;
            info.LeftTime = leftTime;
            info.Duration = timer.Duration;
            info.IsLoop = timer.IsLoop;
            info.IsRunning = timer.IsRunning;
            info.IsUnscaled = timer.IsUnscaled;
#if UNITY_EDITOR
            info.CreationTime = timer.CreationTime;
#endif
        }
    }
}