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

namespace PKHeX.Core;

/// <summary> Generation 8 <see cref="PKM"/> format. </summary>
public sealed class PK8 : G8PKM
{
    private static readonly ushort[] Unused =
    {
        // Alignment bytes
        0x17, 0x1A, 0x1B, 0x23, 0x33, 0x3E, 0x3F,
        0x4C, 0x4D, 0x4E, 0x4F,
        0x52, 0x53, 0x54, 0x55, 0x56, 0x57,

        0x91, 0x92, 0x93,
        0x9C, 0x9D, 0x9E, 0x9F, 0xA0, 0xA1, 0xA2, 0xA3, 0xA4, 0xA5, 0xA6, 0xA7,

        0xC5,
        0xCE, 0xCF, 0xD0, 0xD1, 0xD2, 0xD3, 0xD4, 0xD5, 0xD6, 0xD7, 0xD8, 0xD9, 0xDA, 0xDB,
        0xE0, 0xE1, // Old Console Region / Region
        0xE9, 0xEA, 0xEB, 0xEC, 0xED, 0xEE, 0xEF, 0xF0, 0xF1, 0xF2, 0xF3, 0xF4, 0xF5, 0xF6, 0xF7,
        0x115, 0x11F, // Alignment

        0x13D, 0x13E, 0x13F,
        0x140, 0x141, 0x142, 0x143, 0x144, 0x145, 0x146, 0x147,
    };

    public override IReadOnlyList<ushort> ExtraBytes => Unused;
    public override PersonalInfo PersonalInfo => PersonalTable.SWSH.GetFormEntry(Species, Form);
    public override bool IsNative => SWSH;
    public override EntityContext Context => EntityContext.Gen8;

    public PK8() => AffixedRibbon = -1; // 00 would make it show Kalos Champion :)
    public PK8(byte[] data) : base(data) { }
    public override PKM Clone() => new PK8((byte[])Data.Clone());

    public void Trade(ITrainerInfo tr, int Day = 1, int Month = 1, int Year = 2015)
    {
        if (IsEgg)
        {
            // Eggs do not have any modifications done if they are traded
            // Apply link trade data, only if it left the OT (ignore if dumped & imported, or cloned, etc)
            if ((tr.TID != TID) || (tr.SID != SID) || (tr.Gender != OT_Gender) || (tr.OT != OT_Name))
                SetLinkTradeEgg(Day, Month, Year, Locations.LinkTrade6);
            return;
        }

        // Process to the HT if the OT of the Pokémon does not match the SAV's OT info.
        if (!TradeOT(tr))
            TradeHT(tr);
    }

    public int DynamaxType { get => ReadUInt16LittleEndian(Data.AsSpan(0x156)); set => WriteUInt16LittleEndian(Data.AsSpan(0x156), (ushort)value); }

    public void FixMemories()
    {
        if (IsEgg) // No memories if is egg.
        {
            HT_Friendship = HT_TextVar = HT_Memory = HT_Intensity = HT_Feeling = HT_Language = 0;
            /* OT_Friendship */ OT_TextVar = OT_Memory = OT_Intensity = OT_Feeling = 0;

            // Clear Handler
            HT_Trash.Clear();
            return;
        }

        if (IsUntraded)
            HT_Friendship = HT_TextVar = HT_Memory = HT_Intensity = HT_Feeling = HT_Language = 0;

        int gen = Generation;
        if (gen < 6)
            OT_TextVar = OT_Memory = OT_Intensity = OT_Feeling = 0;
        if (gen != 8) // must be transferred via HOME, and must have memories
            this.SetTradeMemoryHT8(); // not faking HOME tracker.
    }

    private bool TradeOT(ITrainerInfo tr)
    {
        // Check to see if the OT matches the SAV's OT info.
        if (!(tr.TID == TID && tr.SID == SID && tr.Gender == OT_Gender && tr.OT == OT_Name))
            return false;

        CurrentHandler = 0;
        return true;
    }

    private void TradeHT(ITrainerInfo tr)
    {
        if (HT_Name != tr.OT)
        {
            HT_Friendship = 50;
            HT_Name = tr.OT;
        }
        CurrentHandler = 1;
        HT_Gender = tr.Gender;
        HT_Language = (byte)tr.Language;
        this.SetTradeMemoryHT8();
    }

    // Maximums
    public override int MaxMoveID => Legal.MaxMoveID_8;
    public override int MaxSpeciesID => Legal.MaxSpeciesID_8;
    public override int MaxAbilityID => Legal.MaxAbilityID_8;
    public override int MaxItemID => Legal.MaxItemID_8;
    public override int MaxBallID => Legal.MaxBallID_8;
    public override int MaxGameID => Legal.MaxGameID_8;

    public PB8 ConvertToPB8()
    {
        var pk = ConvertTo<PB8>();
        if (pk.Egg_Location == 0)
            pk.Egg_Location = Locations.Default8bNone;
        UnmapLocation(pk);
        return pk;
    }

    public override PA8 ConvertToPA8()
    {
        var pk = base.ConvertToPA8();
        UnmapLocation(pk);
        return pk;
    }

    private static void UnmapLocation(PKM pk)
    {
        switch (pk.Met_Location)
        {
            case Locations.HOME_SWLA:
                pk.Version = (int)GameVersion.PLA;
                // Keep location due to bad transfer logic (official) -- server legal.
                break;
            case Locations.HOME_SWBD:
                pk.Version = (int)GameVersion.BD;
                pk.Met_Location = 0; // Load whatever value from the server. We don't know.
                break;
            case Locations.HOME_SHSP:
                pk.Version = (int)GameVersion.SP;
                pk.Met_Location = 0; // Load whatever value from the server. We don't know.
                break;
        }
    }

    public override void ResetMoves()
    {
        var learnsets = Legal.LevelUpSWSH;
        var table = PersonalTable.SWSH;

        var index = table.GetFormIndex(Species, Form);
        var learn = learnsets[index];
        Span<int> moves = stackalloc int[4];
        learn.SetEncounterMoves(CurrentLevel, moves);
        SetMoves(moves);
        this.SetMaximumPPCurrent(moves);
    }

    public override bool BDSP => Met_Location is Locations.HOME_SWBD or Locations.HOME_SHSP;
    public override bool LA => Met_Location is Locations.HOME_SWLA;
    public override bool HasOriginalMetLocation => base.HasOriginalMetLocation && !(BDSP || LA);

    public void SanitizeImport()
    {
        var ver = Version;
        if (ver is (int)GameVersion.SP)
        {
            Met_Location = Locations.HOME_SHSP;
            Version = (int)GameVersion.SH;
            if (Egg_Location != 0)
                Egg_Location = Locations.HOME_SHSP;
        }
        else if (ver is (int)GameVersion.BD)
        {
            Met_Location = Locations.HOME_SWBD;
            Version = (int)GameVersion.SW;
            if (Egg_Location != 0)
                Egg_Location = Locations.HOME_SWBD;
        }
        else if (ver is (int)GameVersion.PLA)
        {
            Met_Location = Locations.HOME_SWLA;
            Version = (int)GameVersion.SW;
            if (Egg_Location != 0)
                Egg_Location = Locations.HOME_SWLA;
        }
        else if (ver > (int)GameVersion.PLA)
        {
            Met_Location = Met_Location <= Locations.HOME_SWLA ? Locations.HOME_SWLA : Locations.HOME_SWSHBDSPEgg;
        }

        if (Ball > (int)Core.Ball.Beast)
            Ball = (int)Core.Ball.Poke;
    }
}