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

namespace PKHeX.Core;

/// <summary> Generation 1 <see cref="PKM"/> format. </summary>
public sealed class PK1 : GBPKML, IPersonalType
{
    public override PersonalInfo1 PersonalInfo => PersonalTable.Y[Species];

    public override bool Valid => Species <= 151 && (Data[0] == 0 || Species != 0);

    public override int SIZE_PARTY => PokeCrypto.SIZE_1PARTY;
    public override int SIZE_STORED => PokeCrypto.SIZE_1STORED;
    public override bool Korean => false;

    public override EntityContext Context => EntityContext.Gen1;

    public PK1(bool jp = false) : base(PokeCrypto.SIZE_1PARTY, jp) { }
    public PK1(byte[] decryptedData, bool jp = false) : base(EnsurePartySize(decryptedData), jp) { }

    private static byte[] EnsurePartySize(byte[] data)
    {
        if (data.Length != PokeCrypto.SIZE_1PARTY)
            Array.Resize(ref data, PokeCrypto.SIZE_1PARTY);
        return data;
    }

    public override PK1 Clone()
    {
        PK1 clone = new((byte[])Data.Clone(), Japanese);
        OT_Trash.CopyTo(clone.OT_Trash);
        Nickname_Trash.CopyTo(clone.Nickname_Trash);
        return clone;
    }

    protected override byte[] Encrypt() => new PokeList1(this).Write();

    #region Stored Attributes
    public byte SpeciesInternal { get => Data[0]; set => Data[0] = value; } // raw access
    public override ushort Species { get => SpeciesConverter.GetNational1(SpeciesInternal); set => SetSpeciesValues(value); }
    public override int Stat_HPCurrent { get => ReadUInt16BigEndian(Data.AsSpan(0x1)); set => WriteUInt16BigEndian(Data.AsSpan(0x1), (ushort)value); }
    public int Stat_LevelBox { get => Data[3]; set => Data[3] = (byte)value; }
    public override int Status_Condition { get => Data[4]; set => Data[4] = (byte)value; }
    public byte Type1 { get => Data[5]; set => Data[5] = value; }
    public byte Type2 { get => Data[6]; set => Data[6] = value; }
    public byte Catch_Rate { get => Data[7]; set => Data[7] = value; }
    public override ushort Move1 { get => Data[8]; set => Data[8] = (byte)value; }
    public override ushort Move2 { get => Data[9]; set => Data[9] = (byte)value; }
    public override ushort Move3 { get => Data[10]; set => Data[10] = (byte)value; }
    public override ushort Move4 { get => Data[11]; set => Data[11] = (byte)value; }
    public override ushort TID16 { get => ReadUInt16BigEndian(Data.AsSpan(0xC)); set => WriteUInt16BigEndian(Data.AsSpan(0xC), value); }
    public override uint EXP { get => ReadUInt32BigEndian(Data.AsSpan(0xE)) >> 8; set => WriteUInt32BigEndian(Data.AsSpan(0xE), (value << 8) | Data[0x11]); }
    public override int EV_HP { get => ReadUInt16BigEndian(Data.AsSpan(0x11)); set => WriteUInt16BigEndian(Data.AsSpan(0x11), (ushort)value); }
    public override int EV_ATK { get => ReadUInt16BigEndian(Data.AsSpan(0x13)); set => WriteUInt16BigEndian(Data.AsSpan(0x13), (ushort)value); }
    public override int EV_DEF { get => ReadUInt16BigEndian(Data.AsSpan(0x15)); set => WriteUInt16BigEndian(Data.AsSpan(0x15), (ushort)value); }
    public override int EV_SPE { get => ReadUInt16BigEndian(Data.AsSpan(0x17)); set => WriteUInt16BigEndian(Data.AsSpan(0x17), (ushort)value); }
    public override int EV_SPC { get => ReadUInt16BigEndian(Data.AsSpan(0x19)); set => WriteUInt16BigEndian(Data.AsSpan(0x19), (ushort)value); }
    public override ushort DV16 { get => ReadUInt16BigEndian(Data.AsSpan(0x1B)); set => WriteUInt16BigEndian(Data.AsSpan(0x1B), value); }
    public override int Move1_PP { get => Data[0x1D] & 0x3F; set => Data[0x1D] = (byte)((Data[0x1D] & 0xC0) | Math.Min(63, value)); }
    public override int Move2_PP { get => Data[0x1E] & 0x3F; set => Data[0x1E] = (byte)((Data[0x1E] & 0xC0) | Math.Min(63, value)); }
    public override int Move3_PP { get => Data[0x1F] & 0x3F; set => Data[0x1F] = (byte)((Data[0x1F] & 0xC0) | Math.Min(63, value)); }
    public override int Move4_PP { get => Data[0x20] & 0x3F; set => Data[0x20] = (byte)((Data[0x20] & 0xC0) | Math.Min(63, value)); }
    public override int Move1_PPUps { get => (Data[0x1D] & 0xC0) >> 6; set => Data[0x1D] = (byte)((Data[0x1D] & 0x3F) | ((value & 0x3) << 6)); }
    public override int Move2_PPUps { get => (Data[0x1E] & 0xC0) >> 6; set => Data[0x1E] = (byte)((Data[0x1E] & 0x3F) | ((value & 0x3) << 6)); }
    public override int Move3_PPUps { get => (Data[0x1F] & 0xC0) >> 6; set => Data[0x1F] = (byte)((Data[0x1F] & 0x3F) | ((value & 0x3) << 6)); }
    public override int Move4_PPUps { get => (Data[0x20] & 0xC0) >> 6; set => Data[0x20] = (byte)((Data[0x20] & 0x3F) | ((value & 0x3) << 6)); }
    #endregion

    #region Party Attributes
    public override int Stat_Level { get => Data[0x21]; set => Stat_LevelBox = Data[0x21] = (byte)value; }
    public override int Stat_HPMax { get => ReadUInt16BigEndian(Data.AsSpan(0x22)); set => WriteUInt16BigEndian(Data.AsSpan(0x22), (ushort)value); }
    public override int Stat_ATK { get => ReadUInt16BigEndian(Data.AsSpan(0x24)); set => WriteUInt16BigEndian(Data.AsSpan(0x24), (ushort)value); }
    public override int Stat_DEF { get => ReadUInt16BigEndian(Data.AsSpan(0x26)); set => WriteUInt16BigEndian(Data.AsSpan(0x26), (ushort)value); }
    public override int Stat_SPE { get => ReadUInt16BigEndian(Data.AsSpan(0x28)); set => WriteUInt16BigEndian(Data.AsSpan(0x28), (ushort)value); }
    public int Stat_SPC { get => ReadUInt16BigEndian(Data.AsSpan(0x2A)); set => WriteUInt16BigEndian(Data.AsSpan(0x2A), (ushort)value); }
    // Leave SPA and SPD as alias for SPC
    public override int Stat_SPA { get => Stat_SPC; set => Stat_SPC = value; }
    public override int Stat_SPD { get => Stat_SPC; set { } }
    #endregion

    public static bool IsCatchRateHeldItem(byte rate) => rate == 0 || Array.IndexOf(Legal.HeldItems_GSC, rate) >= 0;

    private static bool IsCatchRatePreEvolutionRate(int baseSpecies, int finalSpecies, byte rate)
    {
        for (int species = baseSpecies; species <= finalSpecies; species++)
        {
            if (rate == PersonalTable.RB[species].CatchRate || rate == PersonalTable.Y[species].CatchRate)
                return true;
        }
        return false;
    }

    private void SetSpeciesValues(ushort value)
    {
        var updated = SpeciesConverter.GetInternal1(value);
        if (SpeciesInternal == updated)
            return;

        SpeciesInternal = updated;

        var pi = PersonalTable.RB[value];
        Type1 = pi.Type1;
        Type2 = pi.Type2;

        // Before updating catch rate, check if non-standard
        if (IsValidCatchRateAnyPreEvo((byte)value, Catch_Rate))
            return;

        // Matches nothing possible; just reset to current Species' rate.
        Catch_Rate = (byte)pi.CatchRate;
    }

    private static bool IsValidCatchRateAnyPreEvo(byte species, byte rate)
    {
        if (IsCatchRateHeldItem(rate))
            return true;
        if (species == (int)Core.Species.Pikachu && rate == 0xA3) // Light Ball (starter)
            return true;

        // Get de-evolution steps we should check for.
        var stage = PersonalInfo1.GetEvolutionStage(species);
        // For Eevee-lutions, Eevee evolves to (134,135,136), which are (1,1,1). All 3 have the same catch rate as Eevee.
        // In the event the current species is 135 or 136, we'd never check Eevee with this logic, but they're all 45.
        var baby = species - stage;
        return IsCatchRatePreEvolutionRate(baby, species, rate);
    }

    public override int Version { get => (int)GameVersion.RBY; set { } }
    public override int PKRS_Strain { get => 0; set { } }
    public override int PKRS_Days { get => 0; set { } }
    public override bool CanHoldItem(ReadOnlySpan<ushort> valid) => false;
    public override int Met_Location { get => 0; set { } }
    public override int OT_Gender { get => 0; set { } }
    public override int Met_Level { get => 0; set { } }
    public override int CurrentFriendship { get => 0; set { } }
    public override bool IsEgg { get => false; set { } }
    public override int HeldItem { get => 0; set { } }
    public override int OT_Friendship { get => 0; set { } }

    // Maximums
    public override ushort MaxMoveID => Legal.MaxMoveID_1;
    public override ushort MaxSpeciesID => Legal.MaxSpeciesID_1;
    public override int MaxAbilityID => Legal.MaxAbilityID_1;
    public override int MaxItemID => Legal.MaxItemID_1;

    // Extra
    public int Gen2Item => ItemConverter.GetItemFuture1(Catch_Rate);

    public PK2 ConvertToPK2()
    {
        PK2 pk2 = new(Japanese) {Species = Species};
        Data.AsSpan(7, 0x1A).CopyTo(pk2.Data.AsSpan(1));
        OT_Trash.CopyTo(pk2.OT_Trash);
        Nickname_Trash.CopyTo(pk2.Nickname_Trash);

        pk2.HeldItem = Gen2Item;
        pk2.CurrentFriendship = pk2.PersonalInfo.BaseFriendship;
        pk2.Stat_Level = CurrentLevel;

        return pk2;
    }

    public PK7 ConvertToPK7()
    {
        var rnd = Util.Rand;
        var pk7 = new PK7
        {
            EncryptionConstant = rnd.Rand32(),
            Species = Species,
            TID16 = TID16,
            CurrentLevel = CurrentLevel,
            EXP = EXP,
            Met_Level = CurrentLevel,
            Nature = Experience.GetNatureVC(EXP),
            PID = rnd.Rand32(),
            Ball = 4,
            MetDate = DateOnly.FromDateTime(DateTime.Now),
            Version = (int)GameVersion.RD, // Default to red
            Move1 = Move1,
            Move2 = Move2,
            Move3 = Move3,
            Move4 = Move4,
            Move1_PPUps = Move1_PPUps,
            Move2_PPUps = Move2_PPUps,
            Move3_PPUps = Move3_PPUps,
            Move4_PPUps = Move4_PPUps,
            Met_Location = Locations.Transfer1, // "Kanto region", hardcoded.
            Gender = Gender,
            IsNicknamed = false,

            CurrentHandler = 1,
            HT_Name = RecentTrainerCache.OT_Name,
            HT_Gender = RecentTrainerCache.OT_Gender,
        };
        RecentTrainerCache.SetConsoleRegionData3DS(pk7);
        RecentTrainerCache.SetFirstCountryRegion(pk7);
        pk7.HealPP();
        var lang = TransferLanguage(RecentTrainerCache.Language);
        pk7.Language = lang;
        pk7.Nickname = SpeciesName.GetSpeciesNameGeneration(pk7.Species, lang, pk7.Format);
        pk7.OT_Name = OT_Trash[0] != StringConverter12.G1TradeOTCode ? StringConverter12Transporter.GetString(OT_Trash, Japanese) : StringConverter12.G1TradeOTName[lang]; // In-game Trade
        pk7.OT_Friendship = pk7.HT_Friendship = PersonalTable.SM[Species].BaseFriendship;

        // IVs
        Span<int> finalIVs = stackalloc int[6];
        int flawless = Species == (int)Core.Species.Mew ? 5 : 3;
        for (var i = 0; i < finalIVs.Length; i++)
            finalIVs[i] = rnd.Next(32);
        for (var i = 0; i < flawless; i++)
            finalIVs[i] = 31;
        rnd.Shuffle(finalIVs);
        pk7.SetIVs(finalIVs);

        switch (IsShiny ? Shiny.Always : Shiny.Never)
        {
            case Shiny.Always when !pk7.IsShiny: // Force Square
                var low = pk7.PID & 0xFFFF;
                pk7.PID = (low ^ pk7.TID16 ^ 0u) << 16 | low;
                break;
            case Shiny.Never when pk7.IsShiny: // Force Not Shiny
                pk7.PID ^= 0x1000_0000;
                break;
        }

        int abil = TransporterLogic.IsHiddenDisallowedVC1(Species) ? 0 : 2; // Hidden
        pk7.RefreshAbility(abil); // 0/1/2 (not 1/2/4)

        if (Species == (int)Core.Species.Mew) // Mew gets special treatment.
        {
            pk7.FatefulEncounter = true;
        }
        else if (IsNicknamedBank)
        {
            pk7.IsNicknamed = true;
            pk7.Nickname = StringConverter12Transporter.GetString(Nickname_Trash, Japanese);
        }

        pk7.SetTradeMemoryHT6(bank:true); // oh no, memories on gen7 pk

        pk7.RefreshChecksum();
        return pk7;
    }
}