using System;

namespace PKHeX.Core;

/// <summary>
/// Mainline format for Generation 1 &amp; 2 <see cref="PKM"/> objects.
/// </summary>
/// <remarks>This format stores <see cref="PKM.Nickname"/> and <see cref="PKM.OT_Name"/> in buffers separate from the rest of the details.</remarks>
public abstract class GBPKML : GBPKM
{
    internal const int StringLengthJapanese = 6;
    internal const int StringLengthNotJapan = 11;
    public sealed override int OTLength => Japanese ? 5 : 7;
    public sealed override int NickLength => Japanese ? 5 : 10;
    public sealed override bool Japanese => RawOT.Length == StringLengthJapanese;

    internal readonly byte[] RawOT;
    internal readonly byte[] RawNickname;

    // Trash Bytes
    public sealed override Span<byte> Nickname_Trash => RawNickname;
    public sealed override Span<byte> OT_Trash => RawOT;

    protected GBPKML(int size, bool jp = false) : base(size)
    {
        int strLen = jp ? StringLengthJapanese : StringLengthNotJapan;

        // initialize string buffers
        RawOT = new byte[strLen];
        RawNickname = new byte[strLen];
        RawOT.AsSpan().Fill(StringConverter12.G1TerminatorCode);
        RawNickname.AsSpan().Fill(StringConverter12.G1TerminatorCode);
    }

    protected GBPKML(byte[] data, bool jp = false) : base(data)
    {
        int strLen = jp ? StringLengthJapanese : StringLengthNotJapan;

        // initialize string buffers
        RawOT = new byte[strLen];
        RawNickname = new byte[strLen];
        RawOT.AsSpan().Fill(StringConverter12.G1TerminatorCode);
        RawNickname.AsSpan().Fill(StringConverter12.G1TerminatorCode);
    }

    public override void SetNotNicknamed(int language) => GetNonNickname(language).CopyTo(RawNickname);

    protected override byte[] GetNonNickname(int language)
    {
        var name = SpeciesName.GetSpeciesNameGeneration(Species, language, Format);
        var len = Nickname_Trash.Length;
        byte[] data = new byte[len];
        SetString(name.AsSpan(), data, len, StringConverterOption.Clear50);
        if (!Korean)
        {
            // Decimal point<->period fix
            for (int i = 0; i < data.Length; i++)
            {
                if (data[i] == 0xF2)
                    data[i] = 0xE8;
            }
        }
        return data;
    }

    private int SetString(ReadOnlySpan<char> value, Span<byte> destBuffer, int maxLength, StringConverterOption option = StringConverterOption.None)
    {
        if (Korean)
            return StringConverter2KOR.SetString(destBuffer, value, maxLength, option);
        return StringConverter12.SetString(destBuffer, value, maxLength, Japanese, option);
    }

    public sealed override string Nickname
    {
        get
        {
            if (Korean)
                return StringConverter2KOR.GetString(RawNickname);
            return StringConverter12.GetString(RawNickname, Japanese);
        }
        set
        {
            if (!IsNicknamed && Nickname == value)
                return;

            SetStringKeepTerminatorStyle(value.AsSpan(), RawNickname);
        }
    }

    public sealed override string OT_Name
    {
        get
        {
            if (Korean)
                return StringConverter2KOR.GetString(RawOT.AsSpan());
            return StringConverter12.GetString(RawOT.AsSpan(), Japanese);
        }
        set
        {
            if (value == OT_Name)
                return;
            SetStringKeepTerminatorStyle(value.AsSpan(), RawOT);
        }
    }

    private void SetStringKeepTerminatorStyle(ReadOnlySpan<char> value, Span<byte> exist)
    {
        // Reset the destination buffer based on the termination style of the existing string.
        bool zeroed = exist.IndexOf((byte)0) != -1;
        byte fill = zeroed ? (byte)0 : StringConverter12.G1TerminatorCode;
        exist.Fill(fill);

        int finalLength = Math.Min(value.Length + 1, exist.Length);
        SetString(value, exist, finalLength);
    }
}