wip: event engine delegates exposed

Author: MikeDobrzan

src/Api/PubnubApi/EventEngine/Core/EffectDispatcher.cs

@@ -8,13 +8,17 @@ public class EffectDispatcher {
 		private readonly Dictionary<System.Type, IEffectHandler> effectInvocationHandlerMap =
 			new Dictionary<System.Type, IEffectHandler>();
 
+		public event System.Action<IEffectInvocation> OnEffectDispatch;
+
 		/// <summary>
 		/// Dispatch an invocation i.e. call a registered effect handler.
 		/// </summary>
 		public async Task Dispatch<T>(T invocation) where T : IEffectInvocation {
 			if (!effectInvocationHandlerMap.ContainsKey(invocation.GetType())) {
 				throw new ArgumentException($"No handler for {invocation.GetType().Name} found.");
 			}
+			
+			OnEffectDispatch?.Invoke(invocation);
 
 			if (invocation is IEffectCancelInvocation) {
 				await effectInvocationHandlerMap[invocation.GetType()].Cancel();

src/Api/PubnubApi/EventEngine/Core/Engine.cs

@@ -11,6 +11,25 @@ public abstract class Engine {
 		private Task currentTransitionLoop = Utils.EmptyTask;
 
 		private readonly IEffectInvocation[] emptyInvocationList = new IEffectInvocation[0];
+		
+		/// <summary>
+		/// Subscribe to receive notification on effect dispatch
+		/// </summary>
+		public event System.Action<IEffectInvocation> OnEffectDispatch
+		{
+			add => dispatcher.OnEffectDispatch += value;
+			remove => dispatcher.OnEffectDispatch -= value;
+		}
+
+		/// <summary>
+		/// Subscribe to receive notification on state transition
+		/// </summary>
+		public event System.Action<TransitionResult> OnStateTransition;
+
+		/// <summary>
+		/// Subscribe to receive notification on event being queued
+		/// </summary>
+		public event System.Action<IEvent> OnEventQueued;
 
 		public Engine() {
 			eventQueue.OnEventQueued += OnEvent;
@@ -22,12 +41,14 @@ public Engine() {
 
 		private async void OnEvent(EventQueue q)
 		{
+			OnEventQueued?.Invoke(q.Peek());
 			await currentTransitionLoop;
 			currentTransitionLoop = eventQueue.Loop(async e => currentState = await Transition(e));
 		}
 
 		private async Task<State> Transition(IEvent e) {
 			var stateInvocationPair = currentState.Transition(e);
+			OnStateTransition?.Invoke(stateInvocationPair);
 
 			if (stateInvocationPair is null) {
 				return currentState;

src/Api/PubnubApi/EventEngine/Core/EventQueue.cs

@@ -33,6 +33,14 @@ private IEvent Dequeue()
             }
         }
 
+        public IEvent Peek()
+        {
+            lock (lockObj)
+            {
+                return eventQueue.Peek();
+            }
+        }
+
         public async Task Loop<T>(System.Func<IEvent, Task<T>> function)
         {
             while (Count > 0)