feat: complete TASK-WP0-08 logging

supervisor/Dada.Supervisor/ManagedChildProcess.cs

@@ -8,18 +8,32 @@ internal sealed class ManagedChildProcess : IAsyncDisposable
 {
     private readonly NamedPipeServerStream controlPipe;
     private readonly StreamWriter controlWriter;
+    private readonly StreamReader controlReader;
+    private Action<string>? statusReceived;
     private bool stopping;
 
-    private ManagedChildProcess(Process process, NamedPipeServerStream controlPipe, StreamWriter controlWriter)
+    private ManagedChildProcess(Process process, NamedPipeServerStream controlPipe, StreamReader controlReader, StreamWriter controlWriter)
     {
         Process = process;
         this.controlPipe = controlPipe;
+        this.controlReader = controlReader;
         this.controlWriter = controlWriter;
+        _ = ListenForStatusAsync();
     }
 
     internal Process Process { get; }
     internal bool IsStopping => stopping;
     internal static TimeSpan ShutdownDeadline { get; } = TimeSpan.FromSeconds(15);
+    internal string? LastStatus { get; private set; }
+    internal event Action<string> StatusReceived
+    {
+        add
+        {
+            statusReceived += value;
+            if (LastStatus is not null) value(LastStatus);
+        }
+        remove => statusReceived -= value;
+    }
 
     internal static async Task<ManagedChildProcess> StartAsync(
         ProcessStartInfo startInfo,
@@ -48,7 +62,7 @@ internal sealed class ManagedChildProcess : IAsyncDisposable
             var ready = await reader.ReadLineAsync(timeout.Token);
             if (!string.Equals(ready, "ready", StringComparison.Ordinal)) throw new InvalidOperationException("Managed child did not report ready.");
             var writer = new StreamWriter(pipe, new UTF8Encoding(false), leaveOpen: true) { AutoFlush = true };
-            return new ManagedChildProcess(process, pipe, writer);
+            return new ManagedChildProcess(process, pipe, reader, writer);
         }
         catch
         {
@@ -59,6 +73,23 @@ internal sealed class ManagedChildProcess : IAsyncDisposable
         }
     }
 
+    private async Task ListenForStatusAsync()
+    {
+        try
+        {
+            while (controlPipe.IsConnected && !Process.HasExited)
+            {
+                var status = await controlReader.ReadLineAsync();
+                if (status is null) return;
+                LastStatus = status;
+                statusReceived?.Invoke(status);
+            }
+        }
+        catch (IOException) when (stopping || Process.HasExited)
+        {
+        }
+    }
+
     internal async Task StopAsync(TimeSpan? timeout = null, CancellationToken cancellationToken = default)
     {
         if (stopping || Process.HasExited) return;
@@ -77,6 +108,7 @@ internal sealed class ManagedChildProcess : IAsyncDisposable
     {
         if (!Process.HasExited) await StopAsync();
         controlWriter.Dispose();
+        controlReader.Dispose();
         controlPipe.Dispose();
         Process.Dispose();
     }