From 3f173d64683f35a30ffdf08aa990ee210998b0e2 Mon Sep 17 00:00:00 2001
From: Sipke Schoorstra <sipkeschoorstra@outlook.com>
Date: Wed, 17 Feb 2021 21:43:16 +0100
Subject: [PATCH] Implement unwinding of Switch activity

---
 .../Activities/ControlFlow/Switch/Switch.cs   | 40 ++++++++++++++++++-
 .../Elsa.Core/Services/ActivityActivator.cs   |  4 ++
 2 files changed, 42 insertions(+), 2 deletions(-)

diff --git a/src/core/Elsa.Core/Activities/ControlFlow/Switch/Switch.cs b/src/core/Elsa.Core/Activities/ControlFlow/Switch/Switch.cs
index dfd018389..4d0d060d3 100644
--- a/src/core/Elsa.Core/Activities/ControlFlow/Switch/Switch.cs
+++ b/src/core/Elsa.Core/Activities/ControlFlow/Switch/Switch.cs
@@ -1,9 +1,14 @@
 using System.Collections.Generic;
 using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
 using Elsa.ActivityResults;
 using Elsa.Attributes;
+using Elsa.Events;
 using Elsa.Services;
 using Elsa.Services.Models;
+using MediatR;
+using Newtonsoft.Json.Linq;
 
 // ReSharper disable once CheckNamespace
 namespace Elsa.Activities.ControlFlow
@@ -14,7 +19,7 @@ namespace Elsa.Activities.ControlFlow
         Description = "Evaluate multiple conditions and continue execution depending on the results.",
         Outcomes = new[] { OutcomeNames.Done }
     )]
-    public class Switch : Activity
+    public class Switch : Activity, INotificationHandler<ScopeEvicted>
     {
         [ActivityProperty(Hint = "The conditions to evaluate.")]
         public ICollection<SwitchCase> Cases { get; set; } = new List<SwitchCase>();
@@ -27,9 +32,29 @@ namespace Elsa.Activities.ControlFlow
             get => GetState<bool>();
             set => SetState(value);
         }
+        
+        public bool EnteredScope
+        {
+            get => GetState<bool>();
+            set => SetState(value);
+        }
 
         protected override IActivityExecutionResult OnExecute(ActivityExecutionContext context)
         {
+            if (!context.WorkflowInstance.Scopes.Contains(Id))
+            {
+                if (!EnteredScope)
+                {
+                    context.WorkflowInstance.Scopes.Push(Id);
+                    EnteredScope = true;
+                }
+                else
+                {
+                    EnteredScope = false;
+                    return Done();
+                }
+            }
+            
             if (Evaluated)
             {
                 Evaluated = false;
@@ -38,10 +63,21 @@ namespace Elsa.Activities.ControlFlow
             
             var matches = Cases.Where(x => x.Condition).Select(x => x.Name).ToList();
             var results = Mode == SwitchMode.MatchFirst ? matches.Any() ? new[] { matches.First() } : new string[0] : matches.ToArray();
-            var outcomes = new[] { OutcomeNames.Done }.Concat(results);
+            var outcomes = results;
             
             Evaluated = true;
             return Outcomes(outcomes);
         }
+
+        public Task Handle(ScopeEvicted notification, CancellationToken cancellationToken)
+        {
+            if (notification.EvictedScope.Type != nameof(Switch)) 
+                return Task.CompletedTask;
+            
+            var data = notification.WorkflowExecutionContext.WorkflowInstance.ActivityData.GetItem(notification.EvictedScope.Id, () => new JObject());
+            data.SetState(nameof(EnteredScope), false);
+            
+            return Task.CompletedTask;
+        }
     }
 }
\ No newline at end of file
diff --git a/src/core/Elsa.Core/Services/ActivityActivator.cs b/src/core/Elsa.Core/Services/ActivityActivator.cs
index 64eb039ea..be0f93ba2 100644
--- a/src/core/Elsa.Core/Services/ActivityActivator.cs
+++ b/src/core/Elsa.Core/Services/ActivityActivator.cs
@@ -34,11 +34,15 @@ namespace Elsa.Services
 
             if (IsReturningIfElse(activity))
                 return false;
+            
+            if (IsReturningSwitch(activity))
+                return false;
 
             return true;
         }
         
         private bool IsReturningComposite(IActivity activity) => activity is CompositeActivity && activity.Data.GetState<bool>(nameof(CompositeActivity.IsScheduled));
         private bool IsReturningIfElse(IActivity activity) => activity is IfElse && activity.Data.GetState<bool>(nameof(IfElse.EnteredScope));
+        private bool IsReturningSwitch(IActivity activity) => activity is Switch && activity.Data.GetState<bool>(nameof(Switch.EnteredScope));
     }
 }
\ No newline at end of file