using DCFApixels.DragonECS.Internal;
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Diagnostics;
using System.Runtime.CompilerServices;

namespace DCFApixels.DragonECS
{
    [DebuggerTypeProxy(typeof(DebuggerProxy))]
    public readonly ref struct EcsSpan
    {
        private readonly int _worldID;
        private readonly ReadOnlySpan<int> _values;

        #region Properties
        public bool IsNull
        {
            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            get { return _worldID == 0; }
        }
        public int WorldID
        {
            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            get { return _worldID; }
        }
        public EcsWorld World
        {
            get { return EcsWorld.GetWorld(_worldID); }
        }
        public int Length //TODO rename to Count
        {
            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            get { return _values.Length; }
        }
        public int this[int index]
        {
            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            get { return _values[index]; }
        }
        #endregion

        #region Constructors
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        internal EcsSpan(int worldID, ReadOnlySpan<int> span)
        {
            _worldID = worldID;
            _values = span;
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        internal EcsSpan(int worldID, int[] array)
        {
            _worldID = worldID;
            _values = new ReadOnlySpan<int>(array);
        }
        internal EcsSpan(int worldID, int[] array, int length)
        {
            _worldID = worldID;
            _values = new ReadOnlySpan<int>(array, 0, length);
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        internal EcsSpan(int worldID, int[] array, int start, int length)
        {
            _worldID = worldID;
            _values = new ReadOnlySpan<int>(array, start, length);
        }
        #endregion

        #region Methdos
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public int[] Bake()
        {
            return _values.ToArray();
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public int Bake(ref int[] entities)
        {
            if (entities.Length < _values.Length)
            {
                Array.Resize(ref entities, _values.Length);
            }
            int[] result = new int[_values.Length];
            _values.CopyTo(result);
            return _values.Length;
        }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public void Bake(List<int> entities)
        {
            entities.Clear();
            foreach (var e in _values)
            {
                entities.Add(e);
            }
        }
        #endregion

        #region operators
        public static bool operator ==(EcsSpan left, EcsSpan right) { return left._values == right._values; }
        public static bool operator !=(EcsSpan left, EcsSpan right) { return left._values != right._values; }
        #endregion

        #region Enumerator
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public ReadOnlySpan<int>.Enumerator GetEnumerator() { return _values.GetEnumerator(); }
        #endregion

        #region Other
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public EcsSpan Slice(int start) { return new EcsSpan(_worldID, _values.Slice(start)); }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public EcsSpan Slice(int start, int length) { return new EcsSpan(_worldID, _values.Slice(start, length)); }
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public int[] ToArray() { return _values.ToArray(); }
        public override string ToString()
        {
            return CollectionUtility.EntitiesToString(_values.ToArray(), "span");
        }
#pragma warning disable CS0809 // Устаревший член переопределяет неустаревший член
        [Obsolete("Equals() on EcsSpan will always throw an exception. Use the equality operator instead.")]
        [EditorBrowsable(EditorBrowsableState.Never)]
        public override bool Equals(object obj) { throw new NotSupportedException(); }
        [Obsolete("GetHashCode() on EcsSpan will always throw an exception.")]
        [EditorBrowsable(EditorBrowsableState.Never)]
        public override int GetHashCode() { throw new NotSupportedException(); }
#pragma warning restore CS0809 // Устаревший член переопределяет неустаревший член

        internal class DebuggerProxy
        {
            private int[] _values;
            private int _worldID;
            public EcsWorld World { get { return EcsWorld.GetWorld(_worldID); } }
            public EntitySlotInfo[] Entities
            {
                get
                {
                    EntitySlotInfo[] result = new EntitySlotInfo[_values.Length];
                    int i = 0;
                    foreach (var e in _values)
                    {
                        result[i++] = World.GetEntitySlotInfoDebug(e);
                    }
                    return result;
                }
            }
            public int Count { get { return _values.Length; } }
            public DebuggerProxy(EcsSpan span)
            {
                _values = new int[span.Length];
                span._values.CopyTo(_values);
                _worldID = span._worldID;
            }
        }
        #endregion
    }
}