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

namespace PKHeX.Core;

public sealed class Roamer3 : IContestStats
{
    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 ushort Species
    {
        get => SpeciesConverter.GetNational3(ReadUInt16LittleEndian(Data.AsSpan(Offset + 8)));
        set => WriteUInt16LittleEndian(Data.AsSpan(Offset + 8), SpeciesConverter.GetInternal3(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 tmp = SAV.ID32 ^ pid;
        var xor = (tmp >> 16) ^ (tmp & 0xFFFF);
        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;
        }
    }
}