Discord.Net/src/Discord.Net.Interactions/LocalizationManagers/ResxLocalizationManager.cs

using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Globalization;
using System.Reflection;
using System.Resources;
using System.Threading.Tasks;

namespace Discord.Interactions
{
    internal sealed class ResxLocalizationManager : ILocalizationManager
    {
        private const string NameIdentifier = "name";
        private const string DescriptionIdentifier = "description";

        private readonly string _baseResource;
        private readonly Assembly _assembly;
        private readonly ConcurrentDictionary<string, ResourceManager> _localizerCache = new();
        private readonly IEnumerable<CultureInfo> _supportedLocales;

        public ResxLocalizationManager(string baseResource, Assembly assembly, params CultureInfo[] supportedLocales)
        {
            _baseResource = baseResource;
            _assembly = assembly;
            _supportedLocales = supportedLocales;
        }

        public Task<IDictionary<string, string>> GetAllDescriptionsAsync(IList<string> key, LocalizationTarget destinationType, IServiceProvider serviceProvider) =>
            Task.FromResult(GetValues(key, DescriptionIdentifier));

        public Task<IDictionary<string, string>> GetAllNamesAsync(IList<string> key, LocalizationTarget destinationType, IServiceProvider serviceProvider) =>
            Task.FromResult(GetValues(key, NameIdentifier));

        private IDictionary<string, string> GetValues(IList<string> key, string identifier)
        {
            var result = new Dictionary<string, string>();

            var resourceName = _baseResource + "." + string.Join(".", key);
            var resourceManager = _localizerCache.GetOrAdd(resourceName, new ResourceManager(resourceName, _assembly));

            foreach (var locale in _supportedLocales)
                result[locale.Name] = resourceManager.GetString(identifier, locale);

            return result;
        }
    }
}