SpeechApiReflectionHelper.cs


using System.Collections;
using System.Reflection;
using System.Speech.Synthesis;

namespace MarvinsAIRA
{
	internal static class SpeechApiReflectionHelper
	{
		private const string PROP_VOICE_SYNTHESIZER = "VoiceSynthesizer";
		private const string FIELD_INSTALLED_VOICES = "_installedVoices";

		private const string ONE_CORE_VOICES_REGISTRY = @"HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Speech_OneCore\Voices";

		private static readonly Type ObjectTokenCategoryType = typeof( SpeechSynthesizer ).Assembly
			.GetType( "System.Speech.Internal.ObjectTokens.ObjectTokenCategory" )!;

		private static readonly Type VoiceInfoType = typeof( SpeechSynthesizer ).Assembly
			.GetType( "System.Speech.Synthesis.VoiceInfo" )!;

		private static readonly Type InstalledVoiceType = typeof( SpeechSynthesizer ).Assembly
			.GetType( "System.Speech.Synthesis.InstalledVoice" )!;


		public static void InjectOneCoreVoices( this SpeechSynthesizer synthesizer )
		{
			var voiceSynthesizer = GetProperty( synthesizer, PROP_VOICE_SYNTHESIZER );
			if ( voiceSynthesizer == null ) throw new NotSupportedException( $"Property not found: {PROP_VOICE_SYNTHESIZER}" );

			var installedVoices = GetField( voiceSynthesizer, FIELD_INSTALLED_VOICES ) as IList;
			if ( installedVoices == null )
				throw new NotSupportedException( $"Field not found or null: {FIELD_INSTALLED_VOICES}" );

			if ( ObjectTokenCategoryType
					.GetMethod( "Create", BindingFlags.Static | BindingFlags.NonPublic )?
					.Invoke( null, new object?[] { ONE_CORE_VOICES_REGISTRY } ) is not IDisposable otc )
				throw new NotSupportedException( $"Failed to call Create on {ObjectTokenCategoryType} instance" );

			using ( otc )
			{
				if ( ObjectTokenCategoryType
						.GetMethod( "FindMatchingTokens", BindingFlags.Instance | BindingFlags.NonPublic )?
						.Invoke( otc, new object?[] { null, null } ) is not IList tokens )
					throw new NotSupportedException( $"Failed to list matching tokens" );

				foreach ( var token in tokens )
				{
					if ( token == null || GetProperty( token, "Attributes" ) == null ) continue;

					var voiceInfo =
						typeof( SpeechSynthesizer ).Assembly
							.CreateInstance( VoiceInfoType.FullName!, true,
								BindingFlags.Instance | BindingFlags.NonPublic, null,
								new object[] { token }, null, null );

					if ( voiceInfo == null )
						throw new NotSupportedException( $"Failed to instantiate {VoiceInfoType}" );

					var installedVoice =
						typeof( SpeechSynthesizer ).Assembly
							.CreateInstance( InstalledVoiceType.FullName!, true,
								BindingFlags.Instance | BindingFlags.NonPublic, null,
								new object[] { voiceSynthesizer, voiceInfo }, null, null );

					if ( installedVoice == null )
						throw new NotSupportedException( $"Failed to instantiate {InstalledVoiceType}" );

					installedVoices.Add( installedVoice );
				}
			}
		}

		private static object? GetProperty( object target, string propName )
		{
			return target.GetType().GetProperty( propName, BindingFlags.Instance | BindingFlags.NonPublic )?.GetValue( target );
		}

		private static object? GetField( object target, string propName )
		{
			return target.GetType().GetField( propName, BindingFlags.Instance | BindingFlags.NonPublic )?.GetValue( target );
		}
	}
}