Add system mute control via setMute action

Introduce a setMute protocol action and an NAudio-backed
AudioControlService so the Android client can toggle the Windows
render endpoint mute state over WebSocket.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

WirelessTextSyncer.Windows.Tests/SyncMessageTests.cs

@@ -46,7 +46,7 @@ public sealed class SyncMessageTests
     public void ReplaceAllAppendsSubmittedText()
     {
         var keyboard = new RecordingKeyboardInjectionService();
-        var handler = new SyncMessageHandler(keyboard);
+        var handler = new SyncMessageHandler(keyboard, new RecordingAudioControlService());
 
         handler.Handle(new SyncMessage
         {
@@ -59,6 +59,33 @@ public sealed class SyncMessageTests
             keyboard.Calls);
     }
 
+    [TestMethod]
+    public void DeserializeAndroidSetMuteMessage()
+    {
+        var message = JsonSerializer.Deserialize<SyncMessage>(
+            """{"action":"setMute","muted":true}""",
+            new JsonSerializerOptions(JsonSerializerDefaults.Web));
+
+        Assert.IsNotNull(message);
+        Assert.AreEqual(SyncAction.SetMute, message.Action);
+        Assert.AreEqual(true, message.Muted);
+    }
+
+    [TestMethod]
+    public void SetMuteForwardsToAudioService()
+    {
+        var audio = new RecordingAudioControlService();
+        var handler = new SyncMessageHandler(new RecordingKeyboardInjectionService(), audio);
+
+        handler.Handle(new SyncMessage
+        {
+            Action = SyncAction.SetMute,
+            Muted = true
+        });
+
+        CollectionAssert.AreEqual(new[] { "mute:True" }, audio.Calls);
+    }
+
     [TestMethod]
     public void DiscoveryResponseContainsServiceEndpoint()
     {
@@ -77,7 +104,7 @@ public sealed class SyncMessageTests
     [TestMethod]
     public void WebSocketServiceInfoContainsDeviceName()
     {
-        using var server = new WebSocketServerService(new SyncMessageHandler(new RecordingKeyboardInjectionService()), "Desktop-WIN11");
+        using var server = new WebSocketServerService(new SyncMessageHandler(new RecordingKeyboardInjectionService(), new RecordingAudioControlService()), "Desktop-WIN11");
 
         using var document = JsonDocument.Parse(server.BuildServiceInfoJson());
         var root = document.RootElement;
@@ -112,4 +139,16 @@ public sealed class SyncMessageTests
             Calls.Add("enter");
         }
     }
+
+    private sealed class RecordingAudioControlService : IAudioControlService
+    {
+        public List<string> Calls { get; } = [];
+
+        public bool IsMuted => Calls.Count > 0 && Calls[^1] == "mute:True";
+
+        public void SetMute(bool muted)
+        {
+            Calls.Add($"mute:{muted}");
+        }
+    }
 }

WirelessTextSyncer.Windows/Models/SyncAction.cs

@@ -9,5 +9,6 @@ public enum SyncAction
     ReplaceAll,
     Backspace,
     Enter,
-    Ping
+    Ping,
+    SetMute
 }

WirelessTextSyncer.Windows/Models/SyncActionJsonConverter.cs

@@ -19,6 +19,7 @@ public sealed class SyncActionJsonConverter : JsonConverter<SyncAction>
             "backspace" => SyncAction.Backspace,
             "enter" => SyncAction.Enter,
             "ping" => SyncAction.Ping,
+            "setMute" => SyncAction.SetMute,
             _ => throw new JsonException($"Unsupported sync action: {value}")
         };
     }
@@ -35,6 +36,7 @@ public sealed class SyncActionJsonConverter : JsonConverter<SyncAction>
             SyncAction.Backspace => "backspace",
             SyncAction.Enter => "enter",
             SyncAction.Ping => "ping",
+            SyncAction.SetMute => "setMute",
             _ => throw new JsonException($"Unsupported sync action: {value}")
         };
 

WirelessTextSyncer.Windows/Models/SyncMessage.cs

@@ -9,4 +9,7 @@ public sealed record SyncMessage
 
     [JsonPropertyName("text")]
     public string? Text { get; init; }
+
+    [JsonPropertyName("muted")]
+    public bool? Muted { get; init; }
 }

WirelessTextSyncer.Windows/Services/AudioControlService.cs

@@ -0,0 +1,52 @@
+using System.Runtime.InteropServices;
+using NAudio.CoreAudioApi;
+
+namespace WirelessTextSyncer.Windows.Services;
+
+public sealed class AudioControlService : IAudioControlService, IDisposable
+{
+    private readonly MMDeviceEnumerator enumerator = new();
+    private bool disposed;
+
+    public bool IsMuted
+    {
+        get
+        {
+            try
+            {
+                using var device = enumerator.GetDefaultAudioEndpoint(DataFlow.Render, Role.Multimedia);
+                return device.AudioEndpointVolume.Mute;
+            }
+            catch (COMException exception)
+            {
+                AppLogger.Error("Failed to read audio mute state.", exception);
+                return false;
+            }
+        }
+    }
+
+    public void SetMute(bool muted)
+    {
+        try
+        {
+            using var device = enumerator.GetDefaultAudioEndpoint(DataFlow.Render, Role.Multimedia);
+            device.AudioEndpointVolume.Mute = muted;
+            AppLogger.Info($"Audio mute set to {muted}.");
+        }
+        catch (COMException exception)
+        {
+            AppLogger.Error($"Failed to set audio mute to {muted}.", exception);
+        }
+    }
+
+    public void Dispose()
+    {
+        if (disposed)
+        {
+            return;
+        }
+
+        disposed = true;
+        enumerator.Dispose();
+    }
+}

WirelessTextSyncer.Windows/Services/IAudioControlService.cs

@@ -0,0 +1,8 @@
+namespace WirelessTextSyncer.Windows.Services;
+
+public interface IAudioControlService
+{
+    bool IsMuted { get; }
+
+    void SetMute(bool muted);
+}

WirelessTextSyncer.Windows/Services/SyncMessageHandler.cs

@@ -5,11 +5,13 @@ namespace WirelessTextSyncer.Windows.Services;
 public sealed class SyncMessageHandler
 {
     private readonly IKeyboardInjectionService keyboard;
+    private readonly IAudioControlService audio;
     private string remoteText = string.Empty;
 
-    public SyncMessageHandler(IKeyboardInjectionService keyboard)
+    public SyncMessageHandler(IKeyboardInjectionService keyboard, IAudioControlService audio)
     {
         this.keyboard = keyboard;
+        this.audio = audio;
     }
 
     public void Handle(SyncMessage message)
@@ -38,11 +40,21 @@ public sealed class SyncMessageHandler
                 break;
             case SyncAction.Ping:
                 break;
+            case SyncAction.SetMute:
+                HandleSetMute(message);
+                break;
             default:
                 throw new InvalidOperationException($"Unsupported sync action: {message.Action}");
         }
     }
 
+    private void HandleSetMute(SyncMessage message)
+    {
+        var muted = message.Muted ?? false;
+        AppLogger.Info($"SetMute received muted={muted}.");
+        audio.SetMute(muted);
+    }
+
     private void AppendSubmittedText(string text)
     {
         if (string.IsNullOrEmpty(text))

WirelessTextSyncer.Windows/Tray/TrayApplicationContext.cs

@@ -5,6 +5,7 @@ namespace WirelessTextSyncer.Windows.Tray;
 public sealed class TrayApplicationContext : ApplicationContext
 {
     private readonly KeyboardInjectionService keyboard;
+    private readonly AudioControlService audio;
     private readonly WebSocketServerService server;
     private readonly DiscoveryResponderService discovery;
     private readonly NotifyIcon notifyIcon;
@@ -21,7 +22,8 @@ public sealed class TrayApplicationContext : ApplicationContext
         AppLogger.Info("Tray application starting.");
         uiContext = SynchronizationContext.Current ?? new WindowsFormsSynchronizationContext();
         keyboard = new KeyboardInjectionService();
-        var handler = new SyncMessageHandler(keyboard);
+        audio = new AudioControlService();
+        var handler = new SyncMessageHandler(keyboard, audio);
 
         server = new WebSocketServerService(handler);
         server.StatusChanged += (_, _) => uiContext.Post(_ => UpdateTrayStatus(), null);
@@ -62,6 +64,7 @@ public sealed class TrayApplicationContext : ApplicationContext
             connectedIcon.Dispose();
             waitIcon.Dispose();
             discovery.Dispose();
+            audio.Dispose();
             server.Dispose();
         }
 

WirelessTextSyncer.Windows/WirelessTextSyncer.Windows.csproj

@@ -12,6 +12,7 @@
   <ItemGroup>
     <PackageReference Include="Fleck" Version="1.2.0" />
     <PackageReference Include="Microsoft.Extensions.Configuration.Json" Version="10.0.8" />
+    <PackageReference Include="NAudio" Version="2.2.1" />
   </ItemGroup>
 
   <ItemGroup>