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

namespace PKHeX.Core;

/// <summary>
/// Pokédex structure used for Generation 6 games.
/// </summary>
public abstract class Zukan6 : Zukan<SAV6>
{
    protected override int OFS_SEEN => OFS_CAUGHT + BitSeenSize;
    protected override int OFS_CAUGHT => 0x8;
    protected override int BitSeenSize => 0x60;
    protected override int DexLangFlagByteCount => 631; // 721 * 7, rounded up
    protected override int DexLangIDCount => 7;
    protected int SpindaOffset { get; init; }

    protected Zukan6(SAV6XY sav, Memory<byte> dex, int langflag) : base(sav, dex, langflag)
    {
        DexFormIndexFetcher = DexFormUtil.GetDexFormIndexXY;
    }

    private Func<ushort, byte, int> DexFormIndexFetcher { get; }

    protected Zukan6(SAV6AO sav, Memory<byte> dex, int langflag) : base(sav, dex, langflag)
    {
        DexFormIndexFetcher = DexFormUtil.GetDexFormIndexORAS;
    }

    protected override int GetDexLangFlag(int lang)
    {
        lang--;
        if (lang > 5)
            lang--; // 0-6 language values
        if ((uint)lang > 5)
            return -1;
        return lang;
    }

    protected override bool GetSaneFormsToIterate(ushort species, out int formStart, out int formEnd, int formIn)
    {
        formStart = 0;
        formEnd = 0;
        return false;
    }

    protected override void SetSpindaDexData(PKM pk, bool alreadySeen)
    {
    }

    protected override void SetAllDexFlagsLanguage(int bit, int lang, bool value = true)
    {
        lang = GetDexLangFlag(lang);
        if (lang < 0)
            return;

        int lbit = (bit * DexLangIDCount) + lang;
        if (lbit < DexLangFlagByteCount << 3) // Sanity check for max length of region
            SetFlag(PokeDexLanguageFlags, lbit, value);
    }

    protected override void SetAllDexSeenFlags(int baseBit, byte form, byte gender, bool isShiny, bool value = true)
    {
        var shiny = isShiny ? 1 : 0;
        SetDexFlags(baseBit, baseBit, gender, shiny);
        SetFormFlags((ushort)(baseBit + 1), form, shiny, value);
    }

    public override void SetDex(PKM pk)
    {
        if (pk.Species is 0 or > Legal.MaxSpeciesID_6)
            return;
        if (pk.IsEgg) // do not add
            return;

        int bit = pk.Species - 1;
        SetCaughtFlag(bit, pk.Version);

        // Set the [Species/Gender/Shiny] Seen Flag
        SetAllDexSeenFlags(pk.Species - 1, pk.Form, pk.Gender, pk.IsShiny);
        SetAllDexFlagsLanguage(bit, pk.Language);
        SetFormFlags(pk);
    }

    protected abstract void SetCaughtFlag(int bit, GameVersion origin);

    private int FormLen => SAV is SAV6XY ? 0x18 : 0x26;
    private int FormDex => 0x8 + (BitSeenSize * 9);
    public bool GetFormFlag(int formIndex, int flagRegion) => GetFlag(FormDex + (FormLen * flagRegion), formIndex);
    public void SetFormFlag(int formIndex, int flagRegion, bool value = true) => SetFlag(FormDex + (FormLen * flagRegion), formIndex, value);

    private void SetFormFlags(PKM pk)
    {
        var species = pk.Species;
        var form = pk.Form;
        var shiny = pk.IsShiny ? 1 : 0;
        SetFormFlags(species, form, shiny);
    }

    private void SetFormFlags(ushort species, byte form, int shiny, bool value = true)
    {
        var fc = SAV.Personal[species].FormCount;
        int f = DexFormIndexFetcher(species, fc);
        if (f < 0)
            return;

        var bit = f + form;

        // Set Form Seen Flag
        SetFormFlag(bit, shiny, value);

        // Set Displayed Flag if necessary, check all flags
        if (!value || !GetIsFormDisplayed(f, fc))
            SetFormFlag(bit, 2 + shiny, value);
    }

    private bool GetIsFormDisplayed(int form, byte formCount)
    {
        for (byte i = 0; i < formCount; i++)
        {
            var index = form + i;
            if (GetFormFlag(index, 2)) // Nonshiny
                return true; // already set
            if (GetFormFlag(index, 3)) // Shiny
                return true; // already set
        }
        return false;
    }

    public uint SpindaPID
    {
        get => ReadUInt32LittleEndian(Data[SpindaOffset..]);
        set => WriteUInt32LittleEndian(Data[SpindaOffset..], value);
    }

    public bool[] GetLanguageBitflags(ushort species)
    {
        var result = new bool[DexLangIDCount];
        int bit = species - 1;
        for (int i = 0; i < DexLangIDCount; i++)
        {
            int lbit = (bit * DexLangIDCount) + i;
            result[i] = GetFlag(PokeDexLanguageFlags, lbit);
        }
        return result;
    }

    public void SetLanguageBitflags(ushort species, ReadOnlySpan<bool> value)
    {
        int bit = species - 1;
        for (int i = 0; i < DexLangIDCount; i++)
        {
            int lbit = (bit * DexLangIDCount) + i;
            SetFlag(PokeDexLanguageFlags, lbit, value[i]);
        }
    }

    public void ToggleLanguageFlagsAll(bool value)
    {
        var arr = GetBlankLanguageBits(value);
        for (ushort i = 1; i <= SAV.MaxSpeciesID; i++)
            SetLanguageBitflags(i, arr);
    }

    public void ToggleLanguageFlagsSingle(ushort species, bool value)
    {
        var arr = GetBlankLanguageBits(value);
        SetLanguageBitflags(species, arr);
    }

    private bool[] GetBlankLanguageBits(bool value)
    {
        var result = new bool[DexLangIDCount];
        for (int i = 0; i < DexLangIDCount; i++)
            result[i] = value;
        return result;
    }
}

/// <summary>
/// Pokédex structure used for <see cref="GameVersion.ORAS"/>.
/// </summary>
public sealed class Zukan6AO : Zukan6
{
    public Zukan6AO(SAV6AO sav, Memory<byte> dex, int langflag) : base(sav, dex, langflag)
    {
        SpindaOffset = 0x680;
    }

    protected override void SetCaughtFlag(int bit, GameVersion origin)
    {
        SetFlag(OFS_CAUGHT, bit);
        if (GetEncounterCount(bit) == 0)
            SetEncounterCount(bit, 1);
    }

    public ushort GetEncounterCount(int index)
    {
        var ofs = 0x686 + (index * 2);
        return ReadUInt16LittleEndian(SAV.Data.AsSpan(ofs));
    }

    public void SetEncounterCount(int index, ushort value)
    {
        var ofs = 0x686 + (index * 2);
        WriteUInt16LittleEndian(SAV.Data.AsSpan(ofs), value);
    }
}

/// <summary>
/// Pokédex structure used for <see cref="GameVersion.XY"/>.
/// </summary>
public sealed class Zukan6XY : Zukan6
{
    public Zukan6XY(SAV6XY sav, Memory<byte> dex, int langflag) : base(sav, dex, langflag)
    {
        SpindaOffset = 0x648;
    }

    protected override void SetCaughtFlag(int bit, GameVersion origin)
    {
        // Species: 1-649 for X/Y, and not for OR/AS; Set the Foreign Owned Flag
        if (origin < GameVersion.X && bit < (int)Species.Genesect)
            SetForeignFlag(bit);
        else
            SetFlag(OFS_CAUGHT, bit);
    }

    public bool GetForeignFlag(int bit)
    {
        Debug.Assert(bit < (int)Species.Genesect);
        return GetFlag(0x64C, bit);
    }

    public void SetForeignFlag(int bit, bool value = true)
    {
        Debug.Assert(bit < (int)Species.Genesect);
        SetFlag(0x64C, bit, value);
    }
}