fix(cli): resolve CLI-008..013 — format validation, exit-code semantics, debug-stream cancellation/disposal, test coverage

src/ScadaLink.CLI/Commands/DebugStreamHelpers.cs

@@ -0,0 +1,54 @@
+namespace ScadaLink.CLI.Commands;
+
+/// <summary>
+/// Pure, testable helpers for the <c>debug stream</c> command. The SignalR-driven
+/// <see cref="DebugCommands"/> body itself cannot be unit-tested without a live hub, so
+/// the decision logic — connect-failure classification (CLI-010) and exit-code
+/// resolution after stream termination (CLI-012) — is extracted here.
+/// </summary>
+internal static class DebugStreamHelpers
+{
+    /// <summary>
+    /// The maximum time <see cref="ResolveStreamExitCodeAsync"/> waits for an in-flight
+    /// <c>TrySetResult</c> (from <c>OnStreamTerminated</c>/<c>Closed</c>) to land after
+    /// the wait was cancelled by Ctrl+C, so a termination racing with cancellation is
+    /// observed deterministically rather than depending on scheduling.
+    /// </summary>
+    internal static readonly TimeSpan ExitGracePeriod = TimeSpan.FromMilliseconds(250);
+
+    /// <summary>Outcome of classifying an exception thrown while connecting.</summary>
+    internal readonly record struct ConnectFailure(bool IsCancellation, int ExitCode);
+
+    /// <summary>
+    /// Classifies an exception thrown by <c>HubConnection.StartAsync</c>. A
+    /// cancellation exception that coincides with a user-requested cancellation
+    /// (Ctrl+C during connect) is a graceful shutdown — exit 0, no error printed.
+    /// Anything else is a genuine connection failure — exit 1.
+    /// </summary>
+    internal static ConnectFailure ClassifyConnectFailure(Exception ex, bool cancellationRequested)
+    {
+        if (cancellationRequested && ex is OperationCanceledException)
+            return new ConnectFailure(IsCancellation: true, ExitCode: 0);
+
+        return new ConnectFailure(IsCancellation: false, ExitCode: 1);
+    }
+
+    /// <summary>
+    /// Resolves the <c>debug stream</c> exit code from a single authoritative source —
+    /// the <c>exitTcs</c> task. If a result was set by <c>OnStreamTerminated</c> or the
+    /// <c>Closed</c> handler it is always preferred (even when Ctrl+C also fired);
+    /// a brief grace period covers a termination that races with cancellation. If no
+    /// result is ever produced (pure Ctrl+C), the stream ended gracefully — exit 0.
+    /// </summary>
+    internal static async Task<int> ResolveStreamExitCodeAsync(Task<int> exitTask)
+    {
+        if (exitTask.IsCompletedSuccessfully)
+            return exitTask.Result;
+
+        var completed = await Task.WhenAny(exitTask, Task.Delay(ExitGracePeriod));
+        if (ReferenceEquals(completed, exitTask) && exitTask.IsCompletedSuccessfully)
+            return exitTask.Result;
+
+        return 0;
+    }
+}