From 334f8ad77f3dce407b28cfeb75183288c5631a00 Mon Sep 17 00:00:00 2001
From: Md Junaed Hossain <169046794+junaed-optimizely@users.noreply.github.com>
Date: Mon, 22 Sep 2025 23:46:34 +0600
Subject: [PATCH] [FSSDK-11159] lru cache impl update

---
 OptimizelySDK.Tests/OdpTests/LruCacheTest.cs | 108 +++++++++++++++++++
 OptimizelySDK/Odp/LruCache.cs                |  12 +++
 2 files changed, 120 insertions(+)

diff --git a/OptimizelySDK.Tests/OdpTests/LruCacheTest.cs b/OptimizelySDK.Tests/OdpTests/LruCacheTest.cs
index 426240c5..2ff8071d 100644
--- a/OptimizelySDK.Tests/OdpTests/LruCacheTest.cs
+++ b/OptimizelySDK.Tests/OdpTests/LruCacheTest.cs
@@ -208,5 +208,113 @@ public void ShouldHandleWhenCacheIsReset()
 
             Assert.AreEqual(0, cache.CurrentCacheKeysForTesting().Length);
         }
+
+        [Test]
+        public void ShouldHandleRemoveNonExistentKey()
+        {
+            var cache = new LruCache<List<string>>();
+            cache.Save("user1", _segments1And2);
+            cache.Save("user2", _segments3And4);
+
+            // Remove a key that doesn't exist
+            cache.Remove("user3");
+
+            // Existing keys should still be there
+            Assert.AreEqual(_segments1And2, cache.Lookup("user1"));
+            Assert.AreEqual(_segments3And4, cache.Lookup("user2"));
+        }
+
+        [Test]
+        public void ShouldHandleRemoveExistingKey()
+        {
+            var cache = new LruCache<List<string>>();
+
+            cache.Save("user1", _segments1And2);
+            cache.Save("user2", _segments3And4);
+            cache.Save("user3", _segments5And6);
+
+            Assert.AreEqual(_segments1And2, cache.Lookup("user1"));
+            Assert.AreEqual(_segments3And4, cache.Lookup("user2"));
+            Assert.AreEqual(_segments5And6, cache.Lookup("user3"));
+
+            cache.Remove("user2");
+
+            Assert.AreEqual(_segments1And2, cache.Lookup("user1"));
+            Assert.IsNull(cache.Lookup("user2"));
+            Assert.AreEqual(_segments5And6, cache.Lookup("user3"));
+        }
+
+        [Test]
+        public void ShouldHandleRemoveFromZeroSizedCache()
+        {
+            var cache = new LruCache<List<string>>(0);
+
+            cache.Save("user1", _segments1And2);
+            cache.Remove("user1");
+
+            Assert.IsNull(cache.Lookup("user1"));
+            Assert.AreEqual(0, cache.CurrentCacheKeysForTesting().Length);
+        }
+
+        [Test]
+        public void ShouldHandleRemoveAndAddBack()
+        {
+            var cache = new LruCache<List<string>>();
+
+            cache.Save("user1", _segments1And2);
+            cache.Save("user2", _segments3And4);
+            cache.Save("user3", _segments5And6);
+
+            // Remove user2 and add it back with different data
+            cache.Remove("user2");
+            cache.Save("user2", _segments1And2);
+
+            Assert.AreEqual(_segments1And2, cache.Lookup("user1"));
+            Assert.AreEqual(_segments1And2, cache.Lookup("user2"));
+            Assert.AreEqual(_segments5And6, cache.Lookup("user3"));
+
+            Assert.AreEqual(3, cache.CurrentCacheKeysForTesting().Length);
+        }
+
+        [Test]
+        public void ShouldHandleThreadSafetyWithRemove()
+        {
+            var cache = new LruCache<string>(100);
+
+            for (int i = 1; i <= 100; i++)
+            {
+                cache.Save($"key{i}", $"value{i}");
+            }
+
+            var threads = new List<Thread>();
+
+            for (int i = 1; i <= 50; i++)
+            {
+                int localI = i; // Capture variable for closure
+                var thread = new Thread(() => cache.Remove($"key{localI}"));
+                threads.Add(thread);
+                thread.Start();
+            }
+
+            // Wait for all threads to complete
+            foreach (var thread in threads)
+            {
+                thread.Join();
+            }
+
+            for (int i = 1; i <= 100; i++)
+            {
+                if (i <= 50)
+                {
+                    Assert.IsNull(cache.Lookup($"key{i}"), $"key{i} should be removed");
+                }
+                else
+                {
+                    Assert.AreEqual($"value{i}", cache.Lookup($"key{i}"), $"key{i} should still exist");
+                }
+            }
+
+            Assert.AreEqual(50, cache.CurrentCacheKeysForTesting().Length);
+        }
     }
 }
diff --git a/OptimizelySDK/Odp/LruCache.cs b/OptimizelySDK/Odp/LruCache.cs
index bf1af65a..45b9be5d 100644
--- a/OptimizelySDK/Odp/LruCache.cs
+++ b/OptimizelySDK/Odp/LruCache.cs
@@ -165,6 +165,18 @@ public void Reset()
             }
         }
 
+        /// <summary>
+        /// Remove the element associated with the provided key from the cache
+        /// </summary>
+        /// <param name="key">Key of element to remove from the cache</param>
+        public void Remove(string key)
+        {
+            lock (_mutex)
+            {
+                _cache.Remove(key);
+            }
+        }
+
         /// <summary>
         /// Wrapping class around a generic value stored in the cache
         /// </summary>