PowerToys/src/settings-ui/Microsoft.PowerToys.Settings.UI.Library/SettingsRepository`1.cs

// Copyright (c) Microsoft Corporation
// The Microsoft Corporation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.

using System;
using Microsoft.PowerToys.Settings.UI.Library.Interfaces;

namespace Microsoft.PowerToys.Settings.UI.Library
{
    // This Singleton class is a wrapper around the settings configurations that are accessed by viewmodels.
    // This class can have only one instance and therefore the settings configurations are common to all.
    public class SettingsRepository<T> : ISettingsRepository<T>
        where T : class, ISettingsConfig, new()
    {
        private static readonly object _SettingsRepoLock = new object();

        private static ISettingsUtils _settingsUtils;

        private static SettingsRepository<T> settingsRepository;

        private T settingsConfig;

        // Suppressing the warning as this is a singleton class and this method is
        // necessarily static
#pragma warning disable CA1000 // Do not declare static members on generic types
        public static SettingsRepository<T> GetInstance(ISettingsUtils settingsUtils)
#pragma warning restore CA1000 // Do not declare static members on generic types
        {
            // To ensure that only one instance of Settings Repository is created in a multi-threaded environment.
            lock (_SettingsRepoLock)
            {
                if (settingsRepository == null)
                {
                    settingsRepository = new SettingsRepository<T>();
                    _settingsUtils = settingsUtils ?? throw new ArgumentNullException(nameof(settingsUtils));
                }

                return settingsRepository;
            }
        }

        // The Singleton class must have a private constructor so that it cannot be instantiated by any other object other than itself.
        private SettingsRepository()
        {
        }

        // Settings configurations shared across all viewmodels
        public T SettingsConfig
        {
            get
            {
                if (settingsConfig == null)
                {
                    T settingsItem = new T();
                    settingsConfig = _settingsUtils.GetSettingsOrDefault<T>(settingsItem.GetModuleName());
                }

                return settingsConfig;
            }

            set
            {
                if (value != null)
                {
                    settingsConfig = value;
                }
            }
        }
    }
}