[Run] Fix dark mode detection code, plus refactor (#37324)

* Fix risky int cast in dark mode detection.

* Refactored Helper and Manager classes. New unit tests and changes to support Registry access mocking.

* Spelling update.

* Improve documentation for the registry-related classes.

* Fix issue with UpdateTheme raised in review. Enhance documentation. Rewrite tests to use parameterised unit tests, and expand to cover more cases.

src/modules/launcher/PowerLauncher/Services/IRegistryService.cs

@@ -0,0 +1,82 @@
+// 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.Win32;
+
+namespace PowerLauncher.Services;
+
+#nullable enable
+
+/// <summary>
+/// Provides methods for interacting with the Windows Registry or an equivalent key-value data
+/// store.
+/// </summary>
+public interface IRegistryService
+{
+    /// <summary>
+    /// Retrieves the value associated with the specified name, in the specified registry key.
+    /// If the name is not found in the specified key, returns the specified default value, or
+    /// <c>null</c> if the specified key does not exist.
+    /// </summary>
+    /// <param name="keyName">The full registry path of the key, beginning with a valid registry
+    /// root, such as "HKEY_CURRENT_USER".</param>
+    /// <param name="valueName">The name of the name/value pair.</param>
+    /// <param name="defaultValue">The value to return if <see cref="valueName"/> does not exist.
+    /// </param>
+    /// <returns><c>null</c> if the subkey specified by <paramref name="keyName"/> does not exist;
+    /// otherwise, the value associated with <paramref name="valueName"/>, or
+    /// <paramref name="defaultValue"/> if <paramref name="valueName"/> is not found.</returns>
+    /// <exception cref="ArgumentException"><paramref name="keyName"/> does not begin with a valid
+    /// registry root.</exception>
+    /// <exception cref="UnauthorizedAccessException">Thrown if access to the registry or
+    /// equivalent store is denied.</exception>
+    /// <remarks>Implementations may throw additional exceptions depending on their internal
+    /// storage mechanism.</remarks>
+    object? GetValue(string keyName, string? valueName, object? defaultValue);
+
+    /// <summary>
+    /// Sets the specified name/value pair on the specified registry key. If the specified key does
+    /// not exist, it is created.
+    /// </summary>
+    /// <param name="keyName">The full registry path of the key, beginning with a valid registry
+    /// root, such as "HKEY_CURRENT_USER".</param>
+    /// <param name="valueName">The name of the name/value pair.</param>
+    /// <param name="value">The value to be stored.</param>
+    /// <exception cref="ArgumentException">
+    /// <paramref name="keyName"/> does not begin with a valid registry root.
+    ///
+    /// -or-
+    ///
+    /// <paramref name="keyName"> is longer than the maximum length allowed (255 characters).
+    /// </exception>
+    /// <exception cref="UnauthorizedAccessException">Access to the key is denied; for example,
+    /// it is a root-level node, or the key has not been opened with write access.</exception>
+    void SetValue(string keyName, string? valueName, object value);
+
+    /// <summary>
+    /// Sets the specified name/value pair on the specified registry key. If the specified key does
+    /// not exist, it is created.
+    /// </summary>
+    /// <param name="keyName">The full registry path of the key, beginning with a valid registry
+    /// root, such as "HKEY_CURRENT_USER".</param>
+    /// <param name="valueName">The name of the name/value pair.</param>
+    /// <param name="value">The value to be stored.</param>
+    /// <param name="valueKind">The registry data type to use when storing the data.</param>
+    /// <exception cref="ArgumentException">
+    /// <paramref name="keyName"/> does not begin with a valid registry root.
+    ///
+    /// -or-
+    ///
+    /// <paramref name="keyName"> is longer than the maximum length allowed (255 characters).
+    ///
+    /// -or-
+    ///
+    /// The type of <paramref name="value"/> did not match the registry data type specified by
+    /// <paramref name="valueKind"/>, therefore the data could not be converted properly.
+    /// </exception>
+    /// <exception cref="UnauthorizedAccessException">Access to the key is denied; for example,
+    /// it is a root-level node, or the key has not been opened with write access.</exception>
+    void SetValue(string keyName, string? valueName, object value, RegistryValueKind valueKind);
+}

src/modules/launcher/PowerLauncher/Services/RegistryService.cs

@@ -0,0 +1,34 @@
+// 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.IO;
+using System.Security;
+using Microsoft.Win32;
+
+namespace PowerLauncher.Services;
+
+#nullable enable
+
+public class RegistryService : IRegistryService
+{
+    /// <inheritdoc/>
+    /// <exception cref="SecurityException">The user does not have the permissions required to read
+    /// from the registry key.</exception>
+    /// <exception cref="IOException">The <see cref="RegistryKey"/> that contains the specified
+    /// value has been marked for deletion.</exception>
+    public object? GetValue(string keyName, string? valueName, object? defaultValue) =>
+        Registry.GetValue(keyName, valueName, defaultValue);
+
+    /// <inheritdoc/>
+    /// <exception cref="SecurityException">The user does not have the permissions required to
+    /// create or modify registry keys.</exception>"
+    public void SetValue(string keyName, string? valueName, object value) =>
+        Registry.SetValue(keyName, valueName, value);
+
+    /// <inheritdoc/>
+    /// <exception cref="SecurityException">The user does not have the permissions required to
+    /// create or modify registry keys.</exception>
+    public void SetValue(string keyName, string? valueName, object value, RegistryValueKind valueKind) =>
+        Registry.SetValue(keyName, valueName, value, valueKind);
+}

src/modules/launcher/PowerLauncher/Services/RegistryServiceFactory.cs

@@ -0,0 +1,17 @@
+// 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.
+
+namespace PowerLauncher.Services;
+
+/// <summary>
+/// Factory for creating instances of <see cref="IRegistryService"/>.
+/// </summary>
+public static class RegistryServiceFactory
+{
+    /// <summary>
+    /// Creates the default implementation of <see cref="IRegistryService"/>.
+    /// </summary>
+    /// <returns>An instance of the default <see cref="IRegistryService"/> implementation.</returns>
+    public static IRegistryService Create() => new RegistryService();
+}