AppSettings.cs

using System.IO;
using System.Text.Json;
using System.Text.Json.Serialization;
using System.Security.Cryptography;

namespace PCRemoteControlServer;

public class AppSettings
{
    private static readonly string SettingsDir = Path.Combine(
        Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData),
        "PCRemoteControlServer");

    private static readonly string SettingsPath = Path.Combine(SettingsDir, "settings.json");

    public int Port { get; set; } = 8080;
    public bool RequireAuth { get; set; } = false;
    public string Secret { get; set; } = GenerateSecret();

    public void Save()
    {
        Directory.CreateDirectory(SettingsDir);
        var json = JsonSerializer.Serialize(this, AppSettingsContext.Default.AppSettings);
        File.WriteAllText(SettingsPath, json);
    }

    public static AppSettings Load()
    {
        if (!File.Exists(SettingsPath))
            return new AppSettings();

        try
        {
            var json = File.ReadAllText(SettingsPath);
            return JsonSerializer.Deserialize(json, AppSettingsContext.Default.AppSettings) ?? new AppSettings();
        }
        catch
        {
            return new AppSettings();
        }
    }

    public static string GenerateSecret()
    {
        return string.Create(6, 0, static (span, _) =>
        {
            Span<byte> bytes = stackalloc byte[6];
            RandomNumberGenerator.Fill(bytes);
            for (int i = 0; i < span.Length; i++)
                span[i] = (char)('0' + bytes[i] % 10);
        });
    }
}

[JsonSerializable(typeof(AppSettings))]
internal partial class AppSettingsContext : JsonSerializerContext;