From e31858693abbe3e5cb1336906c79e9a890002a4e Mon Sep 17 00:00:00 2001
From: "google-labs-jules[bot]"
 <161369871+google-labs-jules[bot]@users.noreply.github.com>
Date: Fri, 17 Jul 2026 20:48:32 +0000
Subject: [PATCH] Optimize WeightedRandom for IEnumerable by preventing
 multi-enumeration

Co-authored-by: johnstrand <11484777+johnstrand@users.noreply.github.com>
---
 BenchmarkDotNet.config                        |  0
 .../Extensions/CollectionExtensions.cs        | 31 +++++++++----------
 2 files changed, 15 insertions(+), 16 deletions(-)
 create mode 100644 BenchmarkDotNet.config

diff --git a/BenchmarkDotNet.config b/BenchmarkDotNet.config
new file mode 100644
index 0000000..e69de29
diff --git a/src/GameUtils/Extensions/CollectionExtensions.cs b/src/GameUtils/Extensions/CollectionExtensions.cs
index 7b76057..319315a 100644
--- a/src/GameUtils/Extensions/CollectionExtensions.cs
+++ b/src/GameUtils/Extensions/CollectionExtensions.cs
@@ -236,38 +236,37 @@ public static T WeightedRandom<T>(this IEnumerable<T> source, Func<T, float> wei
             return list[count - 1];
         }
 
-        var itemsTotalWeight = 0f;
-        var hasElements = false;
-        foreach (var item in source)
+        var array = source.ToArray();
+        int arrayCount = array.Length;
+        if (arrayCount == 0)
         {
-            hasElements = true;
-            itemsTotalWeight += weightSelector(item);
+            throw new InvalidOperationException("Sequence contains no elements.");
         }
 
-        if (!hasElements)
+        var arrayTotalWeight = 0f;
+        for (int i = 0; i < arrayCount; i++)
         {
-            throw new InvalidOperationException("Sequence contains no elements.");
+            arrayTotalWeight += weightSelector(array[i]);
         }
 
-        if (itemsTotalWeight <= 0)
+        if (arrayTotalWeight <= 0)
         {
             throw new InvalidOperationException("Total weight must be greater than zero.");
         }
 
-        var itemsTarget = (float)(Random.Shared.NextDouble() * itemsTotalWeight);
-        var itemsCumulative = 0f;
-        T lastItem = default!;
+        var arrayTarget = (float)(Random.Shared.NextDouble() * arrayTotalWeight);
+        var arrayCumulative = 0f;
 
-        foreach (var item in source)
+        for (int i = 0; i < arrayCount; i++)
         {
-            lastItem = item;
-            itemsCumulative += weightSelector(item);
-            if (itemsTarget <= itemsCumulative)
+            var item = array[i];
+            arrayCumulative += weightSelector(item);
+            if (arrayTarget <= arrayCumulative)
             {
                 return item;
             }
         }
 
-        return lastItem;
+        return array[arrayCount - 1];
     }
 }