MeWeb/src/MeWeb.App/Services/Localizer.cs

using System.ComponentModel;
using System.Globalization;
using System.Resources;

using Avalonia.Data;
using Avalonia.Markup.Xaml;
using Avalonia.Markup.Xaml.MarkupExtensions;

namespace MeWeb.App.Services;

public sealed class Localizer : INotifyPropertyChanged
{
  readonly ResourceManager resources = new("MeWeb.App.Strings.Strings", typeof(Localizer).Assembly);

  public static Localizer Instance { get; } = new();

  public event PropertyChangedEventHandler PropertyChanged;

  public Language Language { get; private set; } = Languages.Fallback;

  public CultureInfo Culture { get; private set; } = CultureInfo.GetCultureInfo(Languages.Fallback.Code);

  public bool IsRightToLeft => Culture.TextInfo.IsRightToLeft;

  public string this[string key] => resources.GetString(key, Culture) ?? key;

  public string Format(string key, params object[] args) => string.Format(Culture, this[key], args);

  public void SetLanguage(Language language)
  {
    Language = language ?? Languages.Fallback;
    Culture = CultureInfo.GetCultureInfo(Language.Code);
    CultureInfo.DefaultThreadCurrentCulture = CultureInfo.DefaultThreadCurrentUICulture = Culture;
    CultureInfo.CurrentCulture = CultureInfo.CurrentUICulture = Culture;
    PropertyChanged?.Invoke(this, new PropertyChangedEventArgs("Item[]"));
    PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(string.Empty));
  }
}

public sealed class TrExtension : MarkupExtension
{
  public TrExtension()
  {
  }

  public TrExtension(string key) => Key = key;

  public string Key { get; set; }

  public override object ProvideValue(IServiceProvider serviceProvider) =>
      new ReflectionBindingExtension($"[{Key}]") { Mode = BindingMode.OneWay, Source = Localizer.Instance }.ProvideValue(serviceProvider);
}