Add INetMQMonitor interface and update NetMQMonitor to implement it

Co-authored-by: drewnoakes <350947+drewnoakes@users.noreply.github.com>

Author: Copilot

src/NetMQ/Monitoring/INetMQMonitor.cs

@@ -0,0 +1,121 @@
+using System;
+using System.Threading.Tasks;
+
+namespace NetMQ.Monitoring
+{
+    /// <summary>
+    /// NetMQMonitor interface, implement to fake the NetMQMonitor in tests.
+    /// </summary>
+    public interface INetMQMonitor : IDisposable
+    {
+        /// <summary>
+        /// The monitoring address.
+        /// </summary>
+        string Endpoint { get; }
+
+        /// <summary>
+        /// Get whether this monitor is currently running.
+        /// </summary>
+        /// <remarks>
+        /// Start the monitor running via either <see cref="Start"/> or <see cref="AttachToPoller{T}"/>.
+        /// Stop the monitor via either <see cref="Stop"/> or <see cref="DetachFromPoller()"/>.
+        /// </remarks>
+        bool IsRunning { get; }
+
+        /// <summary>
+        /// Gets and sets the timeout interval for poll iterations when using <see cref="Start"/> and <see cref="Stop"/>.
+        /// </summary>
+        /// <remarks>
+        /// The higher the number the longer it may take the to stop the monitor.
+        /// This value has no effect when the monitor is run via <see cref="AttachToPoller{T}"/>.
+        /// </remarks>
+        TimeSpan Timeout { get; set; }
+
+        /// <summary>
+        /// Raised whenever any monitored event fires.
+        /// </summary>
+        event EventHandler<NetMQMonitorEventArgs>? EventReceived;
+
+        /// <summary>
+        /// Occurs when a connection is made to a socket.
+        /// </summary>
+        event EventHandler<NetMQMonitorSocketEventArgs>? Connected;
+
+        /// <summary>
+        /// Occurs when a synchronous connection attempt failed, and its completion is being polled for.
+        /// </summary>
+        event EventHandler<NetMQMonitorErrorEventArgs>? ConnectDelayed;
+
+        /// <summary>
+        /// Occurs when an asynchronous connect / reconnection attempt is being handled by a reconnect timer.
+        /// </summary>
+        event EventHandler<NetMQMonitorIntervalEventArgs>? ConnectRetried;
+
+        /// <summary>
+        /// Occurs when a socket is bound to an address and is ready to accept connections.
+        /// </summary>
+        event EventHandler<NetMQMonitorSocketEventArgs>? Listening;
+
+        /// <summary>
+        /// Occurs when a socket could not bind to an address.
+        /// </summary>
+        event EventHandler<NetMQMonitorErrorEventArgs>? BindFailed;
+
+        /// <summary>
+        /// Occurs when a connection from a remote peer has been established with a socket's listen address.
+        /// </summary>
+        event EventHandler<NetMQMonitorSocketEventArgs>? Accepted;
+
+        /// <summary>
+        /// Occurs when a connection attempt to a socket's bound address fails.
+        /// </summary>
+        event EventHandler<NetMQMonitorErrorEventArgs>? AcceptFailed;
+
+        /// <summary>
+        /// Occurs when a connection was closed.
+        /// </summary>
+        event EventHandler<NetMQMonitorSocketEventArgs>? Closed;
+
+        /// <summary>
+        /// Occurs when a connection couldn't be closed.
+        /// </summary>
+        event EventHandler<NetMQMonitorErrorEventArgs>? CloseFailed;
+
+        /// <summary>
+        /// Occurs when the stream engine (TCP and IPC specific) detects a corrupted / broken session.
+        /// </summary>
+        event EventHandler<NetMQMonitorSocketEventArgs>? Disconnected;
+
+        /// <summary>
+        /// Add the monitor object to a NetMQPoller, register to <see cref="EventReceived"/> to be signalled on new events
+        /// </summary>
+        /// <param name="poller"></param>
+        /// <typeparam name="T"></typeparam>
+        /// <exception cref="ArgumentNullException"></exception>
+        /// <exception cref="InvalidOperationException"></exception>
+        void AttachToPoller<T>(T poller) where T : INetMQPoller;
+
+        /// <summary>
+        /// Remove the monitor object from attached poller
+        /// </summary>
+        void DetachFromPoller();
+
+        /// <summary>
+        /// Start monitor the socket, the method doesn't start a new thread and will block until the monitor poll is stopped
+        /// </summary>
+        /// <exception cref="InvalidOperationException">The Monitor must not have already started nor attached to a poller.</exception>
+        void Start();
+
+        /// <summary>
+        /// Start a background task for the monitoring operation.
+        /// </summary>
+        /// <returns></returns>
+        Task StartAsync();
+
+        /// <summary>
+        /// Stop monitoring. Blocks until monitoring completed.
+        /// </summary>
+        /// <exception cref="InvalidOperationException">If this monitor is attached to a poller you must detach it first and not use the stop method.</exception>
+        void Stop();
+    }
+}

src/NetMQ/Monitoring/NetMQMonitor.cs

@@ -17,7 +17,7 @@ namespace NetMQ.Monitoring
     ///   <item>Call <see cref="AttachToPoller{T}"/> and <see cref="DetachFromPoller()"/>.</item>
     /// </list>
     /// </remarks>
-    public class NetMQMonitor : IDisposable
+    public class NetMQMonitor : INetMQMonitor
     {
         private readonly NetMQSocket m_monitoringSocket;
         private readonly bool m_ownsMonitoringSocket;