using System;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using static UnityEngine.Networking.UnityWebRequest;
using delayedOp = System.Int32;

namespace DCFApixels.DragonECS
{
    [StructLayout(LayoutKind.Sequential, Pack = 0, Size = 8)]
    public readonly ref struct EcsReadonlyGroup
    {
        private readonly EcsGroup _source;


        #region Constructors
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public EcsReadonlyGroup(EcsGroup source) => _source = source;
        #endregion

        #region Properties
        public int Count
        {
            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            get => _source.Count;
        }
        public int CapacityDense
        {
            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            get => _source.CapacityDense;
        }
        public int CapacitySparce
        {
            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            get => _source.CapacitySparce;
        }
        #endregion

        #region Methods
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public bool Contains(int entityID) => _source.Contains(entityID);
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public EcsGroup.Enumerator GetEnumerator() => _source.GetEnumerator();

        public EcsGroup Extract()
        {
            return new EcsGroup(_source);
        }
        #endregion

        #region Object
        public override string ToString()
        {
            if (_source != null)
                return _source.ToString();
            return "NULL";
        }
        #endregion

        #region Internal
        internal void Release()
        {
            _source.World.ReleaseGroup(_source);
        }
        internal EcsGroup GetGroupInternal() => _source;

        #endregion
    }

    // не может содержать значение 0
    // _delayedOps это int[] для отложенных операций, хранятся отложенные операции в виде int значения, если старший бит = 0 то это опреация добавленияб если = 1 то это операция вычитания

    // this collection can only store numbers greater than 0
    public class EcsGroup
    {
        public const int DEALAYED_ADD = 0;
        public const int DEALAYED_REMOVE = int.MinValue;

        private IEcsWorld _source;

        private int[] _dense;
        private int[] _sparse;

        private int _count;

        private delayedOp[] _delayedOps;
        private int _delayedOpsCount;

        private int _lockCount;

        #region Properties
        public IEcsWorld World => _source;
        public int Count
        {
            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            get => _count;
        }
        public int CapacityDense
        {
            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            get => _dense.Length;
        }
        public int CapacitySparce
        {
            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            get => _sparse.Length;
        }
        public EcsReadonlyGroup Readonly
        {
            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            get => new EcsReadonlyGroup(this);
        }
        #endregion

        #region Constrcutors
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public EcsGroup(IEcsWorld source, int denseCapacity = 64, int delayedOpsCapacity = 128)
        {
            _source = source;
            _source.RegisterGroup(this);
            _dense = new int[denseCapacity];
            _sparse = new int[source.EntitesCapacity];

            _delayedOps = new delayedOp[delayedOpsCapacity];

            _lockCount = 0;
            _delayedOpsCount = 0;
            _count = 0;
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public EcsGroup(EcsGroup copyFrom, int delayedOpsCapacity = 128)
        {
            _source = copyFrom._source;
            _source.RegisterGroup(this);
            _dense = new int[copyFrom._dense.Length];
            _sparse = new int[copyFrom._sparse.Length];

            _delayedOps = new delayedOp[delayedOpsCapacity];

            _lockCount = 0;
            _delayedOpsCount = 0;
            _count = 0;

            foreach (var item in copyFrom)
                AggressiveAdd(item.id);
        }
        #endregion

        #region Contains
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public bool Contains(int entityID)
        {
            //TODO добавить проверку на больше 0 в #if (DEBUG && !DISABLE_DRAGONECS_DEBUG) || !DRAGONECS_NO_SANITIZE_CHECKS
#if (DEBUG && !DISABLE_DRAGONECS_DEBUG) || !DRAGONECS_NO_SANITIZE_CHECKS
#endif
            return /*entityID > 0 && entityID < _sparse.Length && */ _sparse[entityID] > 0;
        }
        #endregion

        #region IndexOf
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public int IndexOf(int entityID)
        {
            return _sparse[entityID];
        }
        #endregion

        #region Add/Remove
        public void UncheckedAdd(int entityID) => AddInternal(entityID);
        public void Add(int entityID)
        {
            if (Contains(entityID)) return;
            AddInternal(entityID);
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        internal void AddInternal(int entityID)
        {
            if (_lockCount > 0)
            {
                AddDelayedOp(entityID, DEALAYED_ADD);
                return;
            }
            AggressiveAdd(entityID);
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        internal void AggressiveAdd(int entityID)
        {
            if (++_count >= _dense.Length)
                Array.Resize(ref _dense, _dense.Length << 1);
            _dense[_count] = entityID;
            _sparse[entityID] = _count;
        }

        public void UncheckedRemove(int entityID) => RemoveInternal(entityID);
        public void Remove(int entityID)
        {
            if (!Contains(entityID)) return;
            RemoveInternal(entityID);
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        internal void RemoveInternal(int entityID)
        {
            if (_lockCount > 0)
            {
                AddDelayedOp(entityID, DEALAYED_REMOVE);
                return;
            }
            AggressiveRemove(entityID);
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        internal void AggressiveRemove(int entityID)
        {
            _dense[_sparse[entityID]] = _dense[_count];
            _sparse[_dense[_count--]] = _sparse[entityID];
            _sparse[entityID] = 0;
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        private void AddDelayedOp(int entityID, int isAddBitFlag)
        {
            if (_delayedOpsCount >= _delayedOps.Length)
            {
                Array.Resize(ref _delayedOps, _delayedOps.Length << 1);
            }
            _delayedOps[_delayedOpsCount++] = entityID | isAddBitFlag; // delayedOp = entityID add isAddBitFlag
        }
        #endregion

        internal void OnWorldResize(int newSize)
        {
            Array.Resize(ref _sparse, newSize);
        }

        public void Sort()
        {
            int increment = 1;
            for (int i = 0; i < _dense.Length; i++)
            {
                if (_sparse[i] > 0)
                {
                    _sparse[i] = increment;
                    _dense[increment++] = i;
                }
            }
        }
        public void Clear() => _count = 0;

        public void CopyFrom(EcsGroup group)
        {
#if (DEBUG && !DISABLE_DEBUG) || !DRAGONECS_NO_SANITIZE_CHECKS
            if (group.World != _source) throw new ArgumentException("group.World != World");
#endif
            Clear();
            foreach (var item in group)
                AggressiveAdd(item.id);
        }

        #region Set operations
        /// <summary>as Union sets</summary>
        public void AddGroup(EcsGroup group)
        {
#if (DEBUG && !DISABLE_DEBUG) || !DRAGONECS_NO_SANITIZE_CHECKS
            if (_source != group.World) throw new ArgumentException("World != group.World");
#endif
            foreach (var item in group)
                if (!Contains(item.id))
                    AggressiveAdd(item.id);
        }
        /// <summary>as Except sets</summary>
        public void RemoveGroup(EcsGroup group)
        {
#if (DEBUG && !DISABLE_DEBUG) || !DRAGONECS_NO_SANITIZE_CHECKS
            if (_source != group.World) throw new ArgumentException("World != group.World");
#endif
            foreach (var item in group)
                if (Contains(item.id))
                    AggressiveRemove(item.id);
        }
        /// <summary>as Intersect sets</summary>
        public void AndWith(EcsGroup group)
        {
#if (DEBUG && !DISABLE_DEBUG) || !DRAGONECS_NO_SANITIZE_CHECKS
            if (World != group.World) throw new ArgumentException("World != group.World");
#endif
            foreach (var item in this)
                if (group.Contains(item.id))
                    AggressiveRemove(item.id);
        }
        /// <summary>as Symmetric Except sets</summary>
        public void XorWith(EcsGroup group)
        {
#if (DEBUG && !DISABLE_DEBUG) || !DRAGONECS_NO_SANITIZE_CHECKS
            if (_source != group.World) throw new ArgumentException("World != group.World");
#endif
            foreach (var item in group)
                if (Contains(item.id))
                    AggressiveRemove(item.id);
                else
                    AggressiveAdd(item.id);
        }
        #endregion

        #region GetEnumerator
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        private void Unlock()
        {
#if (DEBUG && !DISABLE_DRAGONECS_DEBUG) || !DRAGONECS_NO_SANITIZE_CHECKS
            if (_lockCount <= 0)
            {
                throw new Exception($"Invalid lock-unlock balance for {nameof(EcsGroup)}.");
            }
#endif
            if (--_lockCount <= 0)
            {
                for (int i = 0; i < _delayedOpsCount; i++)
                {
                    delayedOp op = _delayedOps[i];
                    if (op >= 0) //delayedOp.IsAdded
                        UncheckedAdd(op & int.MaxValue); //delayedOp.EcsEntity
                    else
                        UncheckedRemove(op & int.MaxValue); //delayedOp.EcsEntity
                }
            }
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public Enumerator GetEnumerator()
        {
            Sort();
            _lockCount++;
            return new Enumerator(this);
        }
        #endregion

        #region Enumerator
        public ref struct Enumerator
        {
            private readonly EcsGroup _source;
            private readonly int[] _dense;
            private readonly int _count;
            private int _index;

            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            public Enumerator(EcsGroup group)
            {
                _source = group;
                _dense = group._dense;
                _count = group.Count;
                _index = 0;
            }
            public ent Current
            {
                [MethodImpl(MethodImplOptions.AggressiveInlining)]
                get => new ent(_dense[_index]);
            }
            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            public bool MoveNext() => ++_index <= _count && _count<_dense.Length; // <= потму что отсчет начинается с индекса 1 //_count < _dense.Length дает среде понять что проверки на выход за границы не нужны
            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            public void Dispose() => _source.Unlock();
        }
        #endregion

        #region OObject
        public override string ToString()
        {
            return string.Join(", ", _dense.AsSpan(1, _count).ToArray());
        }
        #endregion
    }

    public static class EcsGroupExtensions
    {
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static void Normalize<T>(this EcsGroup self, ref T[] array)
        {
            if (array.Length < self.CapacityDense) Array.Resize(ref array, self.CapacityDense);
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static void Normalize<T>(this EcsReadonlyGroup self, ref T[] array)
        {
            if (array.Length < self.CapacityDense) Array.Resize(ref array, self.CapacityDense);
        }
    }
}