added sending closing event message to settings windows (#7)

Reviewed-on: #7
Co-authored-by: Aleksandr Neychev <alexnejchev73@gmail.com>

CursorLang.Core.Tests/Services/SettingsCloseSignalTests.cs

@@ -0,0 +1,115 @@
+using System.Collections.Concurrent;
+using CursorLang.Core.Services;
+using CursorLang.Tests.Shared;
+
+namespace CursorLang.Core.Tests.Services;
+
+/// <summary>
+/// The one thing the agent says to the settings window: quit with me.
+/// </summary>
+/// <remarks>
+/// The event names here are the tests' own. The application's name is fixed, and a test
+/// listening on it would answer for a settings window someone is using — or, signalling,
+/// close it.
+/// </remarks>
+public sealed class SettingsCloseSignalTests
+{
+    [Fact]
+    public void The_request_reaches_the_settings_window()
+    {
+        string suffix = UniqueSuffix();
+        var signal = new SettingsCloseSignal(suffix);
+
+        ConcurrentQueue<EventArgs> requests = new();
+        signal.CloseRequested += (_, e) => requests.Enqueue(e);
+
+        try
+        {
+            signal.Listen();
+
+            Assert.True(RequestApart(suffix), "the request found nobody listening");
+            Pump.WaitFor(() => !requests.IsEmpty, "the settings window got the request to close");
+        }
+        finally
+        {
+            signal.Dispose();
+        }
+    }
+
+    // The usual case: the user quits from the tray with no settings window on the screen
+    [Fact]
+    public void A_request_with_no_settings_window_open_passes_without_consequence()
+    {
+        Assert.False(RequestApart(UniqueSuffix()));
+    }
+
+    // The window has closed on its own, and the process is on its way out anyway
+    [Fact]
+    public void No_request_arrives_after_the_window_is_gone()
+    {
+        string suffix = UniqueSuffix();
+        var signal = new SettingsCloseSignal(suffix);
+
+        ConcurrentQueue<EventArgs> requests = new();
+        signal.CloseRequested += (_, e) => requests.Enqueue(e);
+
+        signal.Listen();
+        signal.Dispose();
+
+        RequestApart(suffix);
+        Pump.Pause(TimeSpan.FromMilliseconds(80));
+
+        Assert.Empty(requests);
+    }
+
+    [Fact]
+    public void Listening_twice_leaves_one_listener()
+    {
+        string suffix = UniqueSuffix();
+        var signal = new SettingsCloseSignal(suffix);
+
+        var requests = 0;
+        signal.CloseRequested += (_, _) => Interlocked.Increment(ref requests);
+
+        try
+        {
+            signal.Listen();
+            signal.Listen();
+
+            Assert.True(RequestApart(suffix));
+            Pump.WaitFor(() => Volatile.Read(ref requests) > 0, "the request arrived");
+            Pump.Pause(TimeSpan.FromMilliseconds(80));
+
+            Assert.Equal(1, Volatile.Read(ref requests));
+        }
+        finally
+        {
+            signal.Dispose();
+        }
+    }
+
+    [Fact]
+    public void Closing_without_listening_passes_without_consequence()
+    {
+        var signal = new SettingsCloseSignal(UniqueSuffix());
+
+        signal.Dispose();
+        signal.Dispose();
+    }
+
+    // Every test gets a namespace of kernel objects of its own
+    private static string UniqueSuffix() => "." + Guid.NewGuid().ToString("N");
+
+    /// <summary>
+    /// Asks for the close the way the agent does it — from another process, and here
+    /// from another thread, which is as foreign as a test can get.
+    /// </summary>
+    private static bool RequestApart(string suffix)
+    {
+        var heard = false;
+
+        Pump.RunApart(() => heard = SettingsCloseSignal.RequestClose(suffix));
+
+        return heard;
+    }
+}