namespace Yuanshen.Common.Data.Excel;

public static class PackedBin
{
    public const string ClientScriptVersion = "0.9.10";

    public static byte GetKey(string scriptVersion)
    {
        int boundary = scriptVersion.LastIndexOf('.');
        int key = 0;

        for (int index = 0; index < boundary; index++)
            key = (key + (scriptVersion[index] & 0xFF)) & 0xFF;

        return key == 0 ? (byte)1 : (byte)key;
    }

    public static void Decode(Span<byte> bytes, byte key)
    {
        for (int index = 0; index < bytes.Length; index++)
        {
            bytes[index] ^= key;
        }
    }

    public static byte[] Decode(ReadOnlySpan<byte> bytes, string scriptVersion = ClientScriptVersion)
    {
        byte[] decoded = bytes.ToArray();
        Decode(decoded, GetKey(scriptVersion));
        return decoded;
    }

    public static byte[] DecodeFile(string path, string scriptVersion = ClientScriptVersion)
        => Decode(File.ReadAllBytes(path), scriptVersion);
}