From 8a7690e13b74a91a1abe61575eb11ad1a56e43b9 Mon Sep 17 00:00:00 2001
From: Chomp <dev@dev.sp-tarkov.com>
Date: Fri, 25 Jul 2025 18:26:09 +0100
Subject: [PATCH] Improved performance of `GetRandomElement` when processing
 IEnnumerables

---
 .../SPTarkov.Server.Core/Helpers/BotHelper.cs |  4 ++--
 .../SPTarkov.Server.Core/Utils/RandomUtil.cs  | 20 ++++++++-----------
 UnitTests/Mock/MockRandomUtil.cs              |  8 ++++----
 3 files changed, 14 insertions(+), 18 deletions(-)

diff --git a/Libraries/SPTarkov.Server.Core/Helpers/BotHelper.cs b/Libraries/SPTarkov.Server.Core/Helpers/BotHelper.cs
index d28a08d9..a1fc26cf 100644
--- a/Libraries/SPTarkov.Server.Core/Helpers/BotHelper.cs
+++ b/Libraries/SPTarkov.Server.Core/Helpers/BotHelper.cs
@@ -226,7 +226,7 @@ public class BotHelper(
                 );
 
                 // Return a random string from names
-                return randomUtil.GetCollectionValue(chosenFactionDetails.FirstNames);
+                return randomUtil.GetRandomElement(chosenFactionDetails.FirstNames);
             }
 
             _pmcNameCache.TryAdd(cacheKey, matchingNames);
@@ -234,6 +234,6 @@ public class BotHelper(
             eligibleNames = matchingNames;
         }
 
-        return randomUtil.GetCollectionValue(eligibleNames);
+        return randomUtil.GetRandomElement(eligibleNames);
     }
 }
diff --git a/Libraries/SPTarkov.Server.Core/Utils/RandomUtil.cs b/Libraries/SPTarkov.Server.Core/Utils/RandomUtil.cs
index 49a681c9..2ac16cec 100644
--- a/Libraries/SPTarkov.Server.Core/Utils/RandomUtil.cs
+++ b/Libraries/SPTarkov.Server.Core/Utils/RandomUtil.cs
@@ -115,9 +115,9 @@ public class RandomUtil(ISptLogger<RandomUtil> _logger, ICloner _cloner)
     /// </summary>
     /// <param name="collection">The collection of strings to select a random value from.</param>
     /// <returns>A randomly selected string from the array.</returns>
-    public virtual T GetCollectionValue<T>(IEnumerable<T> collection)
+    public virtual T GetRandomElement<T>(IEnumerable<T> collection)
     {
-        // We can call `count` directly if it's a list
+        // Already a List
         if (collection is IList<T> list)
         {
             if (!list.Any())
@@ -128,13 +128,9 @@ public class RandomUtil(ISptLogger<RandomUtil> _logger, ICloner _cloner)
             return list[GetInt(0, list.Count - 1)];
         }
 
-        var count = collection.Count(); // Run query and count elements
-        if (count == 0)
-        {
-            throw new InvalidOperationException("Sequence contains no elements.");
-        }
-
-        return collection.ElementAt(GetInt(0, count - 1));
+        // Faster than Reservoir Sampling or calling collection.Count() and doing above
+        var toListedCollection = collection.ToList();
+        return toListedCollection[GetInt(0, toListedCollection.Count - 1)];
     }
 
     /// <summary>
@@ -147,7 +143,7 @@ public class RandomUtil(ISptLogger<RandomUtil> _logger, ICloner _cloner)
     public virtual TKey GetKey<TKey, TVal>(Dictionary<TKey, TVal> dictionary)
         where TKey : notnull
     {
-        return GetCollectionValue(dictionary.Keys);
+        return GetRandomElement(dictionary.Keys);
     }
 
     /// <summary>
@@ -160,7 +156,7 @@ public class RandomUtil(ISptLogger<RandomUtil> _logger, ICloner _cloner)
     public virtual TVal GetVal<TKey, TVal>(Dictionary<TKey, TVal> dictionary)
         where TKey : notnull
     {
-        return GetCollectionValue(dictionary.Values);
+        return GetRandomElement(dictionary.Values);
     }
 
     /// <summary>
@@ -467,7 +463,7 @@ public class RandomUtil(ISptLogger<RandomUtil> _logger, ICloner _cloner)
 
     public virtual T? GetArrayValue<T>(IEnumerable<T> list)
     {
-        return GetCollectionValue(list);
+        return GetRandomElement(list);
     }
 
     /// <summary>
diff --git a/UnitTests/Mock/MockRandomUtil.cs b/UnitTests/Mock/MockRandomUtil.cs
index 9ae204ca..c95fb485 100644
--- a/UnitTests/Mock/MockRandomUtil.cs
+++ b/UnitTests/Mock/MockRandomUtil.cs
@@ -47,7 +47,7 @@ public class MockRandomUtil(ISptLogger<RandomUtil> _logger, ICloner _cloner)
         return true;
     }
 
-    public override T GetCollectionValue<T>(IEnumerable<T> collection)
+    public override T GetRandomElement<T>(IEnumerable<T> collection)
     {
         if (!collection.Any())
         {
@@ -59,12 +59,12 @@ public class MockRandomUtil(ISptLogger<RandomUtil> _logger, ICloner _cloner)
 
     public override TKey GetKey<TKey, TVal>(Dictionary<TKey, TVal> dictionary)
     {
-        return GetCollectionValue(dictionary.Keys);
+        return GetRandomElement(dictionary.Keys);
     }
 
     public override TVal GetVal<TKey, TVal>(Dictionary<TKey, TVal> dictionary)
     {
-        return GetCollectionValue(dictionary.Values);
+        return GetRandomElement(dictionary.Values);
     }
 
     public override double GetNormallyDistributedRandomNumber(
@@ -125,7 +125,7 @@ public class MockRandomUtil(ISptLogger<RandomUtil> _logger, ICloner _cloner)
     public override T? GetArrayValue<T>(IEnumerable<T> list)
         where T : default
     {
-        return GetCollectionValue(list);
+        return GetRandomElement(list);
     }
 
     public override bool RollChance(double chance, double scale = 1)