using System;
using System.ComponentModel;
using System.IO;
using System.Runtime.InteropServices;
using Penumbra.GameData.Enums;

namespace Penumbra.GameData.Structs
{
    [StructLayout( LayoutKind.Sequential, Pack = 1 )]
    public readonly struct RspEntry
    {
        public const int ByteSize = ( int )RspAttribute.NumAttributes * 4;

        private readonly float[] Attributes;

        public RspEntry( RspEntry copy )
            => Attributes = ( float[] )copy.Attributes.Clone();

        public RspEntry( byte[] bytes, int offset )
        {
            if( offset < 0 || offset + ByteSize > bytes.Length )
            {
                throw new ArgumentOutOfRangeException();
            }

            Attributes = new float[( int )RspAttribute.NumAttributes];
            using MemoryStream s  = new( bytes ) { Position = offset };
            using BinaryReader br = new( s );
            for( var i = 0; i < ( int )RspAttribute.NumAttributes; ++i )
            {
                Attributes[ i ] = br.ReadSingle();
            }
        }

        private static int ToIndex( RspAttribute attribute )
            => attribute < RspAttribute.NumAttributes && attribute >= 0
                ? ( int )attribute
                : throw new InvalidEnumArgumentException();

        public float this[ RspAttribute attribute ]
        {
            get => Attributes[ ToIndex( attribute ) ];
            set => Attributes[ ToIndex( attribute ) ] = value;
        }

        public byte[] ToBytes()
        {
            using var s  = new MemoryStream( ByteSize );
            using var bw = new BinaryWriter( s );
            foreach( var attribute in Attributes )
            {
                bw.Write( attribute );
            }

            return s.ToArray();
        }
    }
}