[Future to Next] Fallback Lib change (#2012)

* [Part 1, lib change in future branch] Add fallback event support  (#1875)

* add fallback events in lib

* update with new design

* fix warning

* fix warning

* fix issue

* fix indentation

* remove dll

* fix comments

* fix warning

* fix as comments

* fix after discussion

* fix comments

* remove extra line

* fix as comment

* [Lib] Fallback lib change (#1976)

* simplify lib change

* fix as comments

* fix as comments

* fix as comments

* fix merge error

Author: DingmaomaoBJTU

lib/csharp/microsoft.bot.builder.skills/Microsoft.Bot.Builder.Skills.Tests/Mocks/MockSkillTransport.cs

@@ -6,34 +6,34 @@
 
 namespace Microsoft.Bot.Builder.Skills.Tests.Mocks
 {
-	public class MockSkillTransport : ISkillTransport
-	{
-		private Activity _activityForwarded;
+    public class MockSkillTransport : ISkillTransport
+    {
+        private Activity _activityForwarded;
 
 		public Task CancelRemoteDialogsAsync(SkillManifest skillManifest, IServiceClientCredentials serviceClientCredentials, ITurnContext turnContext)
 		{
 			return Task.CompletedTask;
 		}
 
-		public void Disconnect()
-		{
-		}
+        public void Disconnect()
+        {
+        }
 
-		public Task<bool> ForwardToSkillAsync(SkillManifest skillManifest, IServiceClientCredentials serviceClientCredentials, ITurnContext dialogContext, Activity activity, Action<Activity> tokenRequestHandler = null)
+		public Task<bool> ForwardToSkillAsync(SkillManifest skillManifest, IServiceClientCredentials serviceClientCredentials, ITurnContext dialogContext, Activity activity, Action<Activity> tokenRequestHandler = null, Action<Activity> fallbackHandler = null)
 		{
 			_activityForwarded = activity;
 
-			return Task.FromResult(true);
-		}
+            return Task.FromResult(true);
+        }
 
-		public bool CheckIfSkillInvoked()
-		{
-			return _activityForwarded != null;
-		}
+        public bool CheckIfSkillInvoked()
+        {
+            return _activityForwarded != null;
+        }
 
-		public void VerifyActivityForwardedCorrectly(Action<Activity> assertion)
-		{
-			assertion(_activityForwarded);
-		}
-	}
+        public void VerifyActivityForwardedCorrectly(Action<Activity> assertion)
+        {
+            assertion(_activityForwarded);
+        }
+    }
 }

lib/csharp/microsoft.bot.builder.skills/Microsoft.Bot.Builder.Skills.Tests/SkillDialogTest.cs

@@ -7,7 +7,7 @@ namespace Microsoft.Bot.Builder.Skills.Tests
     internal class SkillDialogTest : SkillDialog
     {
         public SkillDialogTest(SkillManifest skillManifest, IServiceClientCredentials serviceClientCredentials, IBotTelemetryClient telemetryClient, UserState userState, ISkillTransport skillTransport = null)
-            : base(skillManifest, serviceClientCredentials, telemetryClient, userState, null, skillTransport)
+            : base(skillManifest, serviceClientCredentials, telemetryClient, userState, null, null, skillTransport)
         {
         }
     }

lib/csharp/microsoft.bot.builder.skills/Microsoft.Bot.Builder.Skills/ISkillIntentRecognizer.cs

@@ -0,0 +1,14 @@
+using System;
+using System.Threading.Tasks;
+using Microsoft.Bot.Builder.Dialogs;
+using Microsoft.Bot.Builder.Skills.Models.Manifest;
+
+namespace Microsoft.Bot.Builder.Skills
+{
+    public interface ISkillIntentRecognizer
+    {
+        Func<DialogContext, Task<string>> RecognizeSkillIntentAsync { get; }
+
+        bool ConfirmIntentSwitch { get; }
+    }
+}

lib/csharp/microsoft.bot.builder.skills/Microsoft.Bot.Builder.Skills/ISkillTransport.cs

@@ -8,7 +8,7 @@ namespace Microsoft.Bot.Builder.Skills
 {
     public interface ISkillTransport
     {
-        Task<bool> ForwardToSkillAsync(SkillManifest skillManifest, IServiceClientCredentials serviceClientCredentials, ITurnContext dialogContext, Activity activity, Action<Activity> tokenRequestHandler = null);
+        Task<bool> ForwardToSkillAsync(SkillManifest skillManifest, IServiceClientCredentials serviceClientCredentials, ITurnContext dialogContext, Activity activity, Action<Activity> tokenRequestHandler = null, Action<Activity> fallbackHandler = null);
 
         Task CancelRemoteDialogsAsync(SkillManifest skillManifest, IServiceClientCredentials serviceClientCredentials, ITurnContext turnContext);
 

lib/csharp/microsoft.bot.builder.skills/Microsoft.Bot.Builder.Skills/Models/SkillEvents.cs

@@ -3,5 +3,7 @@
     public class SkillEvents
     {
         public const string CancelAllSkillDialogsEventName = "skill/cancelallskilldialogs";
+        public const string FallbackEventName = "skill/fallbackrequest";
+        public const string FallbackHandledEventName = "skill/fallbackhandled";
     }
 }

lib/csharp/microsoft.bot.builder.skills/Microsoft.Bot.Builder.Skills/SkillCallingRequestHandler.cs

@@ -3,6 +3,7 @@
 using System.Text;
 using System.Threading;
 using System.Threading.Tasks;
+using Microsoft.Bot.Builder.Skills.Models;
 using Microsoft.Bot.Builder.Skills.Protocol;
 using Microsoft.Bot.Builder.Solutions;
 using Microsoft.Bot.Schema;
@@ -18,13 +19,20 @@ public class SkillCallingRequestHandler : RequestHandler
         private readonly ITurnContext _turnContext;
         private readonly IBotTelemetryClient _botTelemetryClient;
         private readonly Action<Activity> _tokenRequestHandler;
+        private readonly Action<Activity> _fallbackRequestHandler;
         private readonly Action<Activity> _handoffActivityHandler;
 
-        public SkillCallingRequestHandler(ITurnContext turnContext, IBotTelemetryClient botTelemetryClient, Action<Activity> tokenRequestHandler = null, Action<Activity> handoffActivityHandler = null)
+        public SkillCallingRequestHandler(
+            ITurnContext turnContext,
+            IBotTelemetryClient botTelemetryClient,
+            Action<Activity> tokenRequestHandler = null,
+            Action<Activity> fallbackRequestHandler = null,
+            Action<Activity> handoffActivityHandler = null)
         {
             _turnContext = turnContext ?? throw new ArgumentNullException(nameof(turnContext));
             _botTelemetryClient = botTelemetryClient;
             _tokenRequestHandler = tokenRequestHandler;
+            _fallbackRequestHandler = fallbackRequestHandler;
             _handoffActivityHandler = handoffActivityHandler;
 
             var routes = new RouteTemplate[]
@@ -54,6 +62,19 @@ public SkillCallingRequestHandler(ITurnContext turnContext, IBotTelemetryClient
                                             throw new ArgumentNullException("TokenRequestHandler", "Skill is requesting for token but there's no handler on the calling side!");
                                         }
                                     }
+                                    else if (activity.Type == ActivityTypes.Event && activity.Name == SkillEvents.FallbackEventName)
+                                    {
+                                        if (_fallbackRequestHandler != null)
+                                        {
+                                            _fallbackRequestHandler(activity);
+
+                                             return new ResourceResponse();
+                                        }
+                                        else
+                                        {
+                                            throw new ArgumentNullException("FallbackRequestHandler", "Skill is asking for fallback but there is no handler on the calling side!");
+                                        }
+                                    }
                                     else if (activity.Type == ActivityTypes.EndOfConversation)
                                     {
                                         if (_handoffActivityHandler != null)