feat: Added a generic LRUCache interface and a default implementation

.editorconfig

@@ -13,7 +13,7 @@ tab_width = 4
 
 # New line preferences
 end_of_line = crlf
-insert_final_newline = false
+insert_final_newline = true
 
 #### .NET Coding Conventions ####
 

OptimizelySDK.Tests/OdpTests/LruCacheTest.cs

@@ -0,0 +1,213 @@
+/* 
+ * Copyright 2022, Optimizely
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+using NUnit.Framework;
+using OptimizelySDK.Odp;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading;
+
+namespace OptimizelySDK.Tests.OdpTests
+{
+    public class LruCacheTest
+    {
+        private List<string> _segments1And2;
+        private List<string> _segments3And4;
+        private List<string> _segments5And6;
+
+        [SetUp]
+        public void SetUp()
+        {
+            _segments1And2 = new List<string>
+            {
+                "segment1",
+                "segment2",
+            };
+            _segments3And4 = new List<string>
+            {
+                "segment3",
+                "segment4",
+            };
+            _segments5And6 = new List<string>
+            {
+                "segment5",
+                "segment6",
+            };
+        }
+
+        [Test]
+        public void ShouldCreateSaveAndLookupOneItem()
+        {
+            var cache = new LruCache<string>();
+            Assert.IsNull(cache.Lookup("key1"));
+
+            cache.Save("key1", "value1");
+            Assert.AreEqual("value1", cache.Lookup("key1"));
+        }
+
+        [Test]
+        public void ShouldSaveAndLookupMultipleItems()
+        {
+            var cache = new LruCache<List<string>>();
+
+            cache.Save("user1", _segments1And2);
+            cache.Save("user2", _segments3And4);
+            cache.Save("user3", _segments5And6);
+
+            var cacheKeys = cache._readCurrentCacheKeys();
+
+            Assert.AreEqual("user3", cacheKeys[0]);
+            Assert.AreEqual("user2", cacheKeys[1]);
+            Assert.AreEqual("user1", cacheKeys[2]);
+
+            // Lookup should move user1 to top of the list and push down others.
+            Assert.AreEqual(_segments1And2, cache.Lookup("user1"));
+
+            cacheKeys = cache._readCurrentCacheKeys();
+            Assert.AreEqual("user1", cacheKeys[0]);
+            Assert.AreEqual("user3", cacheKeys[1]);
+            Assert.AreEqual("user2", cacheKeys[2]);
+
+            // Lookup should move user2 to the beginning of the list and push others.
+            Assert.AreEqual(_segments3And4, cache.Lookup("user2"));
+
+            cacheKeys = cache._readCurrentCacheKeys();
+            Assert.AreEqual("user2", cacheKeys[0]);
+            Assert.AreEqual("user1", cacheKeys[1]);
+            Assert.AreEqual("user3", cacheKeys[2]);
+
+            // Lookup moves user3 to top and pushes others down.
+            Assert.AreEqual(_segments5And6, cache.Lookup("user3"));
+
+            cacheKeys = cache._readCurrentCacheKeys();
+            Assert.AreEqual("user3", cacheKeys[0]);
+            Assert.AreEqual("user2", cacheKeys[1]);
+            Assert.AreEqual("user1", cacheKeys[2]);
+        }
+
+        [Test]
+        public void ShouldReorderListOnSave()
+        {
+            var cache = new LruCache<List<string>>();
+
+            cache.Save("user1", _segments1And2);
+            cache.Save("user2", _segments3And4);
+            cache.Save("user3", _segments5And6);
+
+            var cacheKeys = cache._readCurrentCacheKeys();
+
+            // last added should be at the top of the list
+            Assert.AreEqual("user3",cacheKeys[0]);
+            Assert.AreEqual("user2",cacheKeys[1]);
+            Assert.AreEqual("user1" ,cacheKeys[2]);
+
+            // save should move user1 to the top of the list and push down others.
+            cache.Save("user1", _segments1And2);
+
+            cacheKeys = cache._readCurrentCacheKeys();
+            Assert.AreEqual("user1",cacheKeys[0]);
+            Assert.AreEqual("user3",cacheKeys[1]);
+            Assert.AreEqual("user2",cacheKeys[2]);
+
+            // save user2 should bring it to the top and push down others.
+            cache.Save("user2", _segments3And4);
+
+            cacheKeys = cache._readCurrentCacheKeys();
+            Assert.AreEqual("user2",cacheKeys[0]);
+            Assert.AreEqual("user1",cacheKeys[1]);
+            Assert.AreEqual("user3",cacheKeys[2]);
+
+            // saving user3 again should return to the original insertion order.
+            cache.Save("user3", _segments5And6);
+
+            cacheKeys = cache._readCurrentCacheKeys();
+            Assert.AreEqual("user3",cacheKeys[0]);
+            Assert.AreEqual("user2",cacheKeys[1]);
+            Assert.AreEqual("user1" ,cacheKeys[2]);
+        }
+
+        [Test]
+        public void ShouldHandleWhenCacheIsDisabled()
+        {
+            var cache = new LruCache<List<string>>(maxSize: 0);
+
+            cache.Save("user1", _segments1And2);
+            cache.Save("user2", _segments3And4);
+            cache.Save("user3", _segments5And6);
+
+            Assert.IsNull(cache.Lookup("user1"));
+            Assert.IsNull(cache.Lookup("user2"));
+            Assert.IsNull(cache.Lookup("user3"));
+        }
+
+        [Test]
+        public void ShouldHandleWhenItemsExpire()
+        {
+            var cache = new LruCache<List<string>>(itemTimeout: TimeSpan.FromSeconds(1));
+
+            cache.Save("user1", _segments1And2);
+
+            Assert.AreEqual(_segments1And2, cache.Lookup("user1"));
+            Assert.AreEqual(1, cache._readCurrentCacheKeys().Length);
+
+            Thread.Sleep(1200);
+
+            Assert.IsNull(cache.Lookup("user1"));
+            Assert.AreEqual(0, cache._readCurrentCacheKeys().Length);
+        }
+
+        [Test]
+        public void ShouldHandleWhenCacheReachesMaxSize()
+        {
+            var cache = new LruCache<List<string>>(maxSize: 2);
+
+            cache.Save("user1", _segments1And2);
+            cache.Save("user2", _segments3And4);
+            cache.Save("user3", _segments5And6);
+
+            Assert.AreEqual(2, cache._readCurrentCacheKeys().Length);
+
+            Assert.AreEqual(_segments5And6, cache.Lookup("user3"));
+            Assert.AreEqual(_segments3And4, cache.Lookup("user2"));
+            Assert.IsNull(cache.Lookup("user1"));
+        }
+
+        [Test]
+        public void ShouldHandleWhenCacheIsReset()
+        {
+            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"));
+
+            Assert.AreEqual(3, cache._readCurrentCacheKeys().Length);
+
+            cache.Reset();
+
+            Assert.IsNull(cache.Lookup("user1"));
+            Assert.IsNull(cache.Lookup("user2"));
+            Assert.IsNull(cache.Lookup("user3"));
+
+            Assert.AreEqual(0, cache._readCurrentCacheKeys().Length);
+        }
+    }
+}

OptimizelySDK.Tests/OptimizelySDK.Tests.csproj

@@ -80,6 +80,7 @@
     <Compile Include="DefaultErrorHandlerTest.cs" />
     <Compile Include="EntityTests\IntegrationTest.cs" />
     <Compile Include="EventTests\EventProcessorProps.cs" />
+    <Compile Include="OdpTests\LruCacheTest.cs" />
     <Compile Include="OptimizelyConfigTests\OptimizelyConfigTest.cs" />
     <Compile Include="OptimizelyDecisions\OptimizelyDecisionTest.cs" />
     <Compile Include="OptimizelyJSONTest.cs" />
@@ -150,7 +151,6 @@
   <ItemGroup>
     <Service Include="{82A7F48D-3B50-4B1E-B82E-3ADA8210C358}" />
   </ItemGroup>
-  <ItemGroup />
   <Import Project="$(MSBuildBinPath)\Microsoft.CSharp.targets" />
   <!-- To modify your build process, add your task inside one of the targets below and uncomment it.
        Other similar extension points exist, see Microsoft.Common.targets.

OptimizelySDK/Odp/ICache.cs

@@ -0,0 +1,26 @@
+/* 
+ * Copyright 2022, Optimizely
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+namespace OptimizelySDK.Odp
+{
+    public interface ICache<T> 
+        where T : class
+    {
+        void Save(string key, T value);
+        T Lookup(string key);
+        void Reset();
+    }
+}