Locked busy scope to handle disconnections properly.

Wino.Core/Integration/WinoImapClient.cs

@@ -1,4 +1,6 @@
-using MailKit;
+using System;
+using System.Threading;
+using MailKit;
 using MailKit.Net.Imap;
 using Serilog;
 
@@ -9,6 +11,8 @@ namespace Wino.Core.Integration;
 /// </summary>
 internal class WinoImapClient : ImapClient
 {
+    private int _busyCount;
+
     /// <summary>
     /// Gets or internally sets whether the QRESYNC extension is enabled.
     /// It is set by ImapClientPool immidiately after the authentication.
@@ -47,6 +51,34 @@ internal class WinoImapClient : ImapClient
         }
     }
 
+    public bool IsBusy() => _busyCount > 0;
+
+    public IDisposable GetBusyScope()
+    {
+        Interlocked.Increment(ref _busyCount);
+        return new BusyScope(this);
+    }
+
+    private class BusyScope : IDisposable
+    {
+        private readonly WinoImapClient _client;
+        private bool _disposed;
+
+        public BusyScope(WinoImapClient client)
+        {
+            _client = client;
+        }
+
+        public void Dispose()
+        {
+            if (!_disposed)
+            {
+                Interlocked.Decrement(ref _client._busyCount);
+                _disposed = true;
+            }
+        }
+    }
+
     protected override void Dispose(bool disposing)
     {
         base.Dispose(disposing);