using System;
using System.Collections.Generic;

namespace PKHeX.Core;

/// <summary>
/// Base format for Generation 1 &amp; 2 <see cref="PKM"/> objects.
/// </summary>
/// <remarks>
/// <see cref="SK2"/> store text buffers with the rest of the data.
/// <see cref="PK1"/> and <see cref="PK2"/> store them separately; see <see cref="GBPKML"/>.
/// </remarks>
public abstract class GBPKM : PKM
{
    public sealed override int MaxBallID => -1;
    public sealed override int MinGameID => (int)GameVersion.RD;
    public sealed override int MaxGameID => (int)GameVersion.C;
    public sealed override int MaxIV => 15;
    public sealed override int MaxEV => ushort.MaxValue;

    public sealed override IReadOnlyList<ushort> ExtraBytes => Array.Empty<ushort>();

    protected GBPKM(int size) : base(size) { }
    protected GBPKM(byte[] data) : base(data) { }

    public sealed override byte[] EncryptedPartyData => Encrypt();
    public sealed override byte[] EncryptedBoxData => Encrypt();
    public sealed override byte[] DecryptedBoxData => Encrypt();
    public sealed override byte[] DecryptedPartyData => Encrypt();

    public override bool Valid { get => true; set { } }
    public sealed override void RefreshChecksum() { }

    protected abstract byte[] GetNonNickname(int language);

    private bool? _isnicknamed;

    public sealed override bool IsNicknamed
    {
        get => _isnicknamed ??= !Nickname_Trash.SequenceEqual(GetNonNickname(GuessedLanguage()));
        set
        {
            _isnicknamed = value;
            if (_isnicknamed == false)
                SetNotNicknamed(GuessedLanguage());
        }
    }

    protected bool IsNicknamedBank
    {
        get
        {
            var spName = SpeciesName.GetSpeciesNameGeneration(Species, GuessedLanguage(), Format);
            return Nickname != spName;
        }
    }

    public sealed override int Language
    {
        get
        {
            if (Japanese)
                return (int)LanguageID.Japanese;
            if (Korean)
                return (int)LanguageID.Korean;
            if (StringConverter12.IsG12German(OT_Trash))
                return (int)LanguageID.German; // german
            int lang = SpeciesName.GetSpeciesNameLanguage(Species, Nickname, Format);
            if (lang > 0)
                return lang;
            return 0;
        }
        set
        {
            if (Japanese)
                return;
            if (Korean)
                return;

            if (IsNicknamed)
                return;
            SetNotNicknamed(value);
        }
    }

    public sealed override int Gender
    {
        get
        {
            int gv = PersonalInfo.Gender;
            return gv switch
            {
                PersonalInfo.RatioMagicGenderless => 2,
                PersonalInfo.RatioMagicFemale => 1,
                PersonalInfo.RatioMagicMale => 0,
                _ => IV_ATK > gv >> 4 ? 0 : 1,
            };
        }
        set { }
    }

    #region Future, Unused Attributes
    public sealed override bool IsGenderValid() => true; // not a separate property, derived via IVs
    public sealed override uint EncryptionConstant { get => 0; set { } }
    public sealed override uint PID { get => 0; set { } }
    public sealed override int Nature { get => 0; set { } }
    public sealed override bool ChecksumValid => true;
    public sealed override bool FatefulEncounter { get => false; set { } }
    public sealed override uint TSV => 0x0000;
    public sealed override uint PSV => 0xFFFF;
    public sealed override int Characteristic => -1;
    public sealed override int MarkValue { get => 0; set { } }
    public sealed override int Ability { get => -1; set { } }
    public sealed override int CurrentHandler { get => 0; set { } }
    public sealed override int Egg_Location { get => 0; set { } }
    public sealed override int Ball { get => 0; set { } }
    public sealed override uint ID32 { get => TID16; set => TID16 = (ushort)value; }
    public sealed override ushort SID16 { get => 0; set { } }
    #endregion

    public sealed override bool IsShiny => IV_DEF == 10 && IV_SPE == 10 && IV_SPC == 10 && (IV_ATK & 2) == 2;
    private int HPBitValPower => ((IV_ATK & 8) >> 0) | ((IV_DEF & 8) >> 1) | ((IV_SPE & 8) >> 2) | ((IV_SPC & 8) >> 3);
    public sealed override int HPPower => (((5 * HPBitValPower) + (IV_SPC & 3)) >> 1) + 31;

    public sealed override int HPType
    {
        get => ((IV_ATK & 3) << 2) | (IV_DEF & 3);
        set
        {
            IV_DEF = ((IV_DEF >> 2) << 2) | (value & 3);
            IV_DEF = ((IV_ATK >> 2) << 2) | ((value >> 2) & 3);
        }
    }

    public sealed override byte Form
    {
        get
        {
            if (Species != 201) // Unown
                return 0;
            return GetUnownFormValue(IV_ATK, IV_DEF, IV_SPE, IV_SPC);
        }
        set
        {
            if (Species != 201) // Unown
                return;
            while (Form != value)
                SetRandomIVs(0);
        }
    }

    private static byte GetUnownFormValue(int atk, int def, int spe, int spc)
    {
        ushort formeVal = 0;
        formeVal |= (ushort)((atk & 0x6) << 5);
        formeVal |= (ushort)((def & 0x6) << 3);
        formeVal |= (ushort)((spe & 0x6) << 1);
        formeVal |= (ushort)((spc & 0x6) >> 1);
        return (byte)(formeVal / 10);
    }

    public abstract int EV_SPC { get; set; }
    public sealed override int EV_SPA { get => EV_SPC; set => EV_SPC = value; }
    public sealed override int EV_SPD { get => EV_SPC; set { } }
    public abstract ushort DV16 { get; set; }
    public sealed override int IV_HP { get => ((IV_ATK & 1) << 3) | ((IV_DEF & 1) << 2) | ((IV_SPE & 1) << 1) | ((IV_SPC & 1) << 0); set { } }
    public sealed override int IV_ATK { get => (DV16 >> 12) & 0xF; set => DV16 = (ushort)((DV16 & ~(0xF << 12)) | (ushort)((value > 0xF ? 0xF : value) << 12)); }
    public sealed override int IV_DEF { get => (DV16 >> 8) & 0xF; set => DV16 = (ushort)((DV16 & ~(0xF << 8)) | (ushort)((value > 0xF ? 0xF : value) << 8)); }
    public sealed override int IV_SPE { get => (DV16 >> 4) & 0xF; set => DV16 = (ushort)((DV16 & ~(0xF << 4)) | (ushort)((value > 0xF ? 0xF : value) << 4)); }
    public int IV_SPC { get => (DV16 >> 0) & 0xF; set => DV16 = (ushort)((DV16 & ~(0xF << 0)) | (ushort)((value > 0xF ? 0xF : value) << 0)); }
    public sealed override int IV_SPA { get => IV_SPC; set => IV_SPC = value; }
    public sealed override int IV_SPD { get => IV_SPC; set { } }
    public override int MarkingCount => 0;
    public override int GetMarking(int index) => 0;
    public override void SetMarking(int index, int value) { }

    public void SetNotNicknamed() => SetNotNicknamed(GuessedLanguage());
    public abstract void SetNotNicknamed(int language);

    public int GuessedLanguage(int fallback = (int)LanguageID.English)
    {
        int lang = Language;
        if (lang > 0)
            return lang;
        if (fallback is (int)LanguageID.French or (int)LanguageID.German) // only other permitted besides English
            return fallback;
        return (int)LanguageID.English;
    }

    /// <summary>
    /// Tries to guess the source language ID when transferred to future generations (7+)
    /// </summary>
    /// <param name="destLanguage">Destination language ID</param>
    /// <returns>Source language ID</returns>
    protected int TransferLanguage(int destLanguage)
    {
        // if the Species name of the destination language matches the current nickname, transfer with that language.
        var expect = SpeciesName.GetSpeciesNameGeneration(Species, destLanguage, 2);
        if (Nickname == expect)
            return destLanguage;
        return GuessedLanguage(destLanguage);
    }

    public override void LoadStats(IBaseStat p, Span<ushort> stats)
    {
        var lv = CurrentLevel; // recalculate instead of checking Stat_Level
        stats[0] = (ushort)(GetStat(p.HP, IV_HP, EV_HP, lv) + (5 + lv)); // HP
        stats[1] = GetStat(p.ATK, IV_ATK, EV_ATK, lv);
        stats[2] = GetStat(p.DEF, IV_DEF, EV_DEF, lv);
        stats[3] = GetStat(p.SPE, IV_SPE, EV_SPE, lv);
        stats[4] = GetStat(p.SPA, IV_SPA, EV_SPA, lv);
        stats[5] = GetStat(p.SPD, IV_SPD, EV_SPD, lv);
    }

    protected static ushort GetStat(int baseStat, int iv, int effort, int level)
    {
        effort = (ushort)Math.Min(255, Math.Sqrt(effort) + 1) >> 2;
        return (ushort)((((2 * (baseStat + iv)) + effort) * level / 100) + 5);
    }

    public sealed override int GetMovePP(ushort move, int ppUpCount)
    {
        var pp = base.GetMovePP(move, 0);
        return pp + (ppUpCount * Math.Min(7, pp / 5));
    }

    public void MaxEVs() => EV_HP = EV_ATK = EV_DEF = EV_SPC = EV_SPE = MaxEV;

    /// <summary>
    /// Applies <see cref="PKM.IVs"/> to the <see cref="PKM"/> to make it shiny.
    /// </summary>
    public sealed override void SetShiny()
    {
        IV_ATK |= 2;
        IV_DEF = 10;
        IV_SPE = 10;
        IV_SPA = 10;
    }

    internal void ImportFromFuture(PKM pk)
    {
        Nickname = pk.Nickname;
        OT_Name = pk.OT_Name;
        IV_ATK = pk.IV_ATK / 2;
        IV_DEF = pk.IV_DEF / 2;
        IV_SPC = pk.IV_SPA / 2;
        //IV_SPD = pk.IV_ATK / 2;
        IV_SPE = pk.IV_SPE / 2;

        if (pk.HasMove((int)Move.HiddenPower))
            HPType = pk.HPType;
    }
}