using System;
using System.ComponentModel;
using System.Runtime.CompilerServices;

namespace DCFApixels.DragonECS
{
    public readonly ref struct EcsSpan
    {
        private readonly int _worldID;
        private readonly ReadOnlySpan<int> _values;

        #region Properties
        public int WorldID
        {
            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            get => _worldID;
        }
        public EcsWorld World
        {
            get => EcsWorld.GetWorld(_worldID);
        }
        public int Length
        {
            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            get => _values.Length;
        }
        public readonly int this[int index]
        {
            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            get => _values[index];
        }
        public bool IsNull
        {
            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            get => _values.IsEmpty;
    }
        #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 = 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 Object
#pragma warning disable CS0809 // Устаревший член переопределяет неустаревший член
        [Obsolete($"Equals() on {nameof(EcsSpan)} will always throw an exception. Use the equality operator instead.")]
        [EditorBrowsable(EditorBrowsableState.Never)]
        public override bool Equals(object obj) => throw new NotSupportedException();
        [Obsolete($"GetHashCode() on {nameof(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
        public override string ToString() => _values.ToString();
        #endregion

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

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

        #region Other
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public EcsSpan Slice(int start) => new EcsSpan(_worldID, _values.Slice(start));
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public EcsSpan Slice(int start, int length) => new EcsSpan(_worldID, _values.Slice(start, length));
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public int[] ToArray() => _values.ToArray();
        #endregion
    }
}