app/APP/Utility/StringAssemble.cs

using System.Security.Cryptography;
using System.Text;
using APP.DTO;

namespace APP.Utility;

internal static class StringAssemble
{
    private const string RegisterSecret = "綾波レイ";

    internal static string UserInfo(User? user)
    {
        if (user == null)
        {
            return string.Empty;
        }

        var sb = new StringBuilder();
        sb.Append("MAL ID:");
        sb.AppendLine();

        sb.Append("Last online:");
        sb.AppendLine();

        if (!string.IsNullOrEmpty(user.Location))
        {
            sb.Append("Location:");
            sb.AppendLine();
        }

        sb.Append("Joined:");
        sb.AppendLine();

        return sb.ToString();
    }

    internal static string UserData(User? user)
    {
        if (user == null)
        {
            return string.Empty;
        }

        var sb = new StringBuilder();
        sb.Append(user.Id);
        sb.AppendLine();

        sb.Append(user.LastOnline);
        sb.AppendLine();

        if (!string.IsNullOrEmpty(user.Location))
        {
            sb.Append(user.Location);
            sb.AppendLine();
        }

        sb.Append(user.Joined.ToShortDateString());
        sb.AppendLine();

        return sb.ToString();
    }

    internal static string CalcSha512(string input)
    {
        var bytes = Encoding.UTF8.GetBytes(input);
        using var hash = SHA512.Create();
        var hashedInputBytes = hash.ComputeHash(bytes);
        var hashedInputStringBuilder = new StringBuilder(128);
        foreach (var b in hashedInputBytes)
            hashedInputStringBuilder.Append(b.ToString("X2"));
        return hashedInputStringBuilder.ToString().ToLower();
    }

    internal static string CalcSauce(long malId, string username)
    {
        return CalcSha512(RegisterSecret + malId + username);
    }
}