feat: enable subscription logic for messengers

In order to help control traffic over the websocket, a subscription feature has been added:
* A config option, `enableMessengerSubscriptions` has been added
* When true, the MessengerBase class will assume that any message sent using the `PostStatusMessage` that has a valid client ID wants to send any subsequent unsolicited updates to that same client
* The client's ID will be added a list of subscribed client IDs
* Any subsequent messages sent using the `PostStatusMessage` methods that have a null clientId will ONLY be sent to subscribed clients
* When a client disconnects, it will be removed from the list of subscribed clients

This should cut down drastically on the traffic to the UI, especially when combined with requesting partial status updates from a device rather than the entire state.

src/PepperDash.Essentials.MobileControl.Messengers/Messengers/MessengerBase.cs

@@ -1,7 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
-using Newtonsoft.Json;
+using Crestron.SimplSharp.Net;
 using Newtonsoft.Json.Linq;
 using PepperDash.Core;
 using PepperDash.Core.Logging;
@@ -13,13 +13,26 @@ namespace PepperDash.Essentials.AppServer.Messengers
     /// <summary>
     /// Provides a messaging bridge
     /// </summary>
-    public abstract class MessengerBase : EssentialsDevice, IMobileControlMessenger
+    public abstract class MessengerBase : EssentialsDevice, IMobileControlMessengerWithSubscriptions
     {
         /// <summary>
         /// The device this messenger is associated with
         /// </summary>
         protected IKeyName _device;
 
+        /// <summary>
+        /// Enable subscriptions
+        /// </summary>
+        protected bool enableMessengerSubscriptions;
+
+        /// <summary>
+        /// List of clients subscribed to this messenger
+        /// </summary>
+        /// <remarks>
+        /// Unsoliciited feedback from a device in a messenger will ONLY be sent to devices in this subscription list. When a client disconnects, it's ID will be removed from the collection.
+        /// </remarks>
+        protected HashSet<string> SubscriberIds = new HashSet<string>();
+
         private readonly List<string> _deviceInterfaces;
 
         private readonly Dictionary<string, Action<string, JToken>> _actions = new Dictionary<string, Action<string, JToken>>();
@@ -93,6 +106,21 @@ namespace PepperDash.Essentials.AppServer.Messengers
             RegisterActions();
         }
 
+        /// <summary>
+        /// Register this messenger with appserver controller
+        /// </summary>
+        /// <param name="appServerController">Parent controller for this messenger</param>
+        /// <param name="enableMessengerSubscriptions">Enable subscriptions</param>
+        public void RegisterWithAppServer(IMobileControl appServerController, bool enableMessengerSubscriptions)
+        {
+            this.enableMessengerSubscriptions = enableMessengerSubscriptions;
+            AppServerController = appServerController ?? throw new ArgumentNullException("appServerController");
+
+            AppServerController.AddAction(this, HandleMessage);
+
+            RegisterActions();
+        }
+
         private void HandleMessage(string path, string id, JToken content)
         {
             // replace base path with empty string. Should leave something like /fullStatus
@@ -103,7 +131,7 @@ namespace PepperDash.Essentials.AppServer.Messengers
                 return;
             }
 
-            Debug.LogMessage(Serilog.Events.LogEventLevel.Debug, "Executing action for path {path}", this, path);
+            this.LogDebug("Executing action for path {path}", path);
 
             action(id, content);
         }
@@ -117,7 +145,6 @@ namespace PepperDash.Essentials.AppServer.Messengers
         {
             if (_actions.ContainsKey(path))
             {
-                //Debug.LogMessage(Serilog.Events.LogEventLevel.Verbose, $"Messenger {Key} already has action registered at {path}", this);
                 return;
             }
 
@@ -154,6 +181,52 @@ namespace PepperDash.Essentials.AppServer.Messengers
 
         }
 
+        /// <summary>
+        /// Add client to the susbscription list for unsolicited feedback
+        /// </summary>
+        /// <param name="clientId">Client ID to add</param>
+        protected void SubscribeClient(string clientId)
+        {
+            if (!enableMessengerSubscriptions)
+            {
+                this.LogWarning("Messenger subscriptions not enabled");
+                return;
+            }
+
+            if (SubscriberIds.Any(id => id == clientId))
+            {
+                this.LogVerbose("Client {clientId} already subscribed", clientId);
+                return;
+            }
+
+            SubscriberIds.Add(clientId);
+
+            this.LogDebug("Client {clientId} subscribed", clientId);
+        }
+
+        /// <summary>
+        /// Remove a client from the subscription list
+        /// </summary>
+        /// <param name="clientId">Client ID to remove</param>
+        public void UnsubscribeClient(string clientId)
+        {
+            if (!enableMessengerSubscriptions)
+            {
+                this.LogWarning("Messenger subscriptions not enabled");
+                return;
+            }
+
+            if (!SubscriberIds.Any(i => i == clientId))
+            {
+                this.LogVerbose("Client with ID {clientId} is not subscribed", clientId);
+                return;
+            }
+
+            SubscriberIds.RemoveWhere((i) => i == clientId);
+
+            this.LogInformation("Client with ID {clientId} unsubscribed", clientId);
+        }
+
         /// <summary>
         /// Helper for posting status message
         /// </summary>
@@ -228,11 +301,33 @@ namespace PepperDash.Essentials.AppServer.Messengers
         {
             try
             {
+                // Allow for legacy method to continue without subscriptions
+                if (!enableMessengerSubscriptions)
+                {
+                    AppServerController?.SendMessageObject(new MobileControlMessage { Type = !string.IsNullOrEmpty(type) ? type : MessagePath, ClientId = clientId, Content = content });
+                    return;
+                }
+
+                // handle subscription feedback
+                // If client is null or empty, this message is unsolicited feedback. Iterate through the subscriber list and send to all interested parties
+                if (string.IsNullOrEmpty(clientId))
+                {
+                    foreach (var client in SubscriberIds)
+                    {
+                        AppServerController?.SendMessageObject(new MobileControlMessage { Type = !string.IsNullOrEmpty(type) ? type : MessagePath, ClientId = client, Content = content });
+                    }
+
+                    return;
+                }
+
+                SubscribeClient(clientId);
+
                 AppServerController?.SendMessageObject(new MobileControlMessage { Type = !string.IsNullOrEmpty(type) ? type : MessagePath, ClientId = clientId, Content = content });
             }
             catch (Exception ex)
             {
-                Debug.LogMessage(ex, "Exception posting status message", this);
+                this.LogError("Exception posting status message: {message}", ex.Message);
+                this.LogDebug(ex, "Stack Trace: ");
             }
         }