fix block playout build crash from empty collections (#2395)

CHANGELOG.md

@@ -23,6 +23,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
   - ETV will set this automatically when it has permission
   - When ETV does not have permission, startup will fail with logged instructions on how to configure MySql
 - Fix scaling anamorphic content in locales that don't use period as a decimal separator (e.g. `,`)
+- Block schedules: fix playout build crash when empty collection uses random playback order
 
 ### Changed
 - **BREAKING CHANGE**: change how `Scripted Schedule` system works

ErsatzTV.Core.Tests/Scheduling/RandomizedContentTests.cs

@@ -13,12 +13,12 @@ public class RandomizedContentTests
 
     private const int KnownSeed = 22295;
 
-    private readonly List<int> _expected = new()
-    {
+    private readonly List<int> _expected =
+    [
         5, 7, 7, 8, 6, 7, 8, 9, 10, 7, 5, 1, 7, 2, 5, 6, 1, 4, 5, 6, 4, 5, 1, 6, 5, 7, 1, 3, 9, 9, 9, 3,
         3, 2, 3, 4, 5, 6, 9, 3, 6, 9, 7, 1, 2, 10, 3, 8, 3, 8, 8, 3, 1, 5, 4, 3, 6, 4, 6, 2, 9, 8, 3, 1, 8, 5,
         1, 8, 2, 1, 1, 5, 5, 5, 3, 5, 8, 10, 4, 8, 7, 3, 3, 4, 4, 9, 2, 8, 8, 10, 8, 4, 3, 10, 7, 8, 9, 9
-    };
+    ];
 
     private CancellationToken _cancellationToken;
 

ErsatzTV.Core/Scheduling/RandomizedMediaCollectionEnumerator.cs

@@ -24,10 +24,17 @@ public class RandomizedMediaCollectionEnumerator : IMediaCollectionEnumerator
         State = new CollectionEnumeratorState { Seed = state.Seed };
         // we want to move at least once so we start with a random item and not the first
         // because _index defaults to 0
-        while (State.Index <= state.Index)
+        if (State.Index == state.Index)
         {
             MoveNext();
         }
+        else
+        {
+            while (State.Index <= state.Index)
+            {
+                MoveNext();
+            }
+        }
     }
 
     public void ResetState(CollectionEnumeratorState state) =>
@@ -41,6 +48,11 @@ public class RandomizedMediaCollectionEnumerator : IMediaCollectionEnumerator
 
     public void MoveNext()
     {
+        if (_mediaItems.Count == 0)
+        {
+            return;
+        }
+
         _index = _random.Next() % _mediaItems.Count;
         State.Index++;
     }

ErsatzTV.Core/Scheduling/RandomizedRotatingMediaCollectionEnumerator.cs

@@ -48,10 +48,17 @@ public class RandomizedRotatingMediaCollectionEnumerator : IMediaCollectionEnume
         State = new CollectionEnumeratorState { Seed = state.Seed };
         // we want to move at least once so we start with a random item and not the first
         // because _index defaults to 0
-        while (State.Index <= state.Index)
+        if (State.Index == state.Index)
         {
             MoveNext();
         }
+        else
+        {
+            while (State.Index <= state.Index)
+            {
+                MoveNext();
+            }
+        }
     }
 
     public void ResetState(CollectionEnumeratorState state) =>
@@ -66,6 +73,11 @@ public class RandomizedRotatingMediaCollectionEnumerator : IMediaCollectionEnume
     public void MoveNext()
     {
         var groups = _groupMedia.Keys.ToList();
+        if (groups.Count == 0)
+        {
+            return;
+        }
+
         int nextRandom = _random.Next();
 
         int groupNumber = nextRandom % groups.Count;