using System;
using static System.Buffers.Binary.BinaryPrimitives;

namespace PKHeX.Core
{
    public sealed class Roamer3 : IContestStats, IContestStatsMutable
    {
        private readonly int Offset;
        public bool IsGlitched { get; }
        private readonly byte[] Data;
        private readonly SAV3 SAV;

        public Roamer3(SAV3 sav)
        {
            Data = (SAV = sav).Large;
            Offset = sav.Version switch
            {
                GameVersion.RS => 0x3144,
                GameVersion.E => 0x31DC,
                _ => 0x30D0, // FRLG
            };
            IsGlitched = sav.Version != GameVersion.E;
        }

        private uint IV32
        {
            get => ReadUInt32LittleEndian(Data.AsSpan(Offset));
            set => WriteUInt32LittleEndian(Data.AsSpan(Offset), value);
        }

        public uint PID
        {
            get => ReadUInt32LittleEndian(Data.AsSpan(Offset + 4));
            set => WriteUInt32LittleEndian(Data.AsSpan(Offset + 4), value);
        }

        public int Species
        {
            get => SpeciesConverter.GetG4Species(ReadInt16LittleEndian(Data.AsSpan(Offset + 8)));
            set => WriteInt16LittleEndian(Data.AsSpan(Offset + 8), (short)SpeciesConverter.GetG3Species(value));
        }

        public int HP_Current
        {
            get => ReadInt16LittleEndian(Data.AsSpan(Offset + 10));
            set => WriteInt16LittleEndian(Data.AsSpan(Offset + 10), (short)value);
        }

        public int CurrentLevel
        {
            get => Data[Offset + 12];
            set => Data[Offset + 12] = (byte)value;
        }

        public int Status { get => Data[Offset + 0x0D]; set => Data[Offset + 0x0D] = (byte)value; }

        public byte CNT_Cool   { get => Data[Offset + 0x0E]; set => Data[Offset + 0x0E] = value; }
        public byte CNT_Beauty { get => Data[Offset + 0x0F]; set => Data[Offset + 0x0F] = value; }
        public byte CNT_Cute   { get => Data[Offset + 0x10]; set => Data[Offset + 0x10] = value; }
        public byte CNT_Smart  { get => Data[Offset + 0x11]; set => Data[Offset + 0x11] = value; }
        public byte CNT_Tough  { get => Data[Offset + 0x12]; set => Data[Offset + 0x12] = value; }
        public byte CNT_Sheen  { get => 0; set { } }
        public bool Active    { get => Data[Offset + 0x13] == 1; set => Data[Offset + 0x13] = value ? (byte)1 : (byte)0; }

        // Derived Properties
        private int IV_HP { get => (int)(IV32 >> 00) & 0x1F; set => IV32 = (uint)((IV32 & ~(0x1F << 00)) | (uint)((value > 31 ? 31 : value) << 00)); }
        private int IV_ATK { get => (int)(IV32 >> 05) & 0x1F; set => IV32 = (uint)((IV32 & ~(0x1F << 05)) | (uint)((value > 31 ? 31 : value) << 05)); }
        private int IV_DEF { get => (int)(IV32 >> 10) & 0x1F; set => IV32 = (uint)((IV32 & ~(0x1F << 10)) | (uint)((value > 31 ? 31 : value) << 10)); }
        private int IV_SPE { get => (int)(IV32 >> 15) & 0x1F; set => IV32 = (uint)((IV32 & ~(0x1F << 15)) | (uint)((value > 31 ? 31 : value) << 15)); }
        private int IV_SPA { get => (int)(IV32 >> 20) & 0x1F; set => IV32 = (uint)((IV32 & ~(0x1F << 20)) | (uint)((value > 31 ? 31 : value) << 20)); }
        private int IV_SPD { get => (int)(IV32 >> 25) & 0x1F; set => IV32 = (uint)((IV32 & ~(0x1F << 25)) | (uint)((value > 31 ? 31 : value) << 25)); }

        /// <summary>
        /// Roamer's IVs.
        /// </summary>
        public int[] IVs
        {
            get => new[] { IV_HP, IV_ATK, IV_DEF, IV_SPE, IV_SPA, IV_SPD };
            set => SetIVs(value);
        }

        public void SetIVs(ReadOnlySpan<int> value)
        {
            if (value.Length != 6)
                return;
            IV_HP = value[0];
            IV_ATK = value[1];
            IV_DEF = value[2];
            IV_SPE = value[3];
            IV_SPA = value[4];
            IV_SPD = value[5];
        }

        /// <summary>
        /// Indicates if the Roamer is shiny with the <see cref="SAV"/>'s Trainer Details.
        /// </summary>
        /// <param name="pid">PID to check for</param>
        /// <returns>Indication if the PID is shiny for the trainer.</returns>
        public bool IsShiny(uint pid)
        {
            var xor = (ushort)(SAV.SID ^ SAV.TID ^ (pid >> 16) ^ pid);
            return xor < 8;
        }

        /// <summary>
        /// Gets the glitched Roamer IVs, where only 1 byte of IV data is loaded when encountered.
        /// </summary>
        public int[] IVsGlitch
        {
            get
            {
                var ivs = IV32; // store for restoration later
                IV32 &= 0xFF; // only 1 byte is loaded to the encounter
                var glitch = IVs; // get glitched IVs
                IV32 = ivs; // restore unglitched IVs
                return glitch;
            }
        }
    }
}
