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/CollectionExtensions.cs

@@ -0,0 +1,14 @@
+using System.Collections;
+
+namespace OptimizelySDK.Tests.OdpTests
+{
+    public static class CollectionTestExtensions
+    {
+        public static string[] ToKeyCollection(this ICollection keys)
+        {
+            var keyArray = new string[keys.Count];
+            keys.CopyTo(keyArray, 0);
+            return keyArray;
+        }
+    }
+}

OptimizelySDK.Tests/OdpTests/LruCacheTest.cs

@@ -0,0 +1,201 @@
+/* 
+ * 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.Collections.Generic;
+using System.Threading;
+
+namespace OptimizelySDK.Tests.OdpTests
+{
+    [TestFixture]
+    public class LruCacheTest
+    {
+        private readonly List<string> _segments1And2 = new List<string>
+        {
+            "segment1",
+            "segment2",
+        };
+
+        private readonly List<string> _segments3And4 = new List<string>
+        {
+            "segment3",
+            "segment4",
+        };
+
+        private readonly List<string> _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 itemKeys = cache.ReadCurrentCache().Keys.ToKeyCollection();
+            Assert.AreEqual("user1", itemKeys[0]);
+            Assert.AreEqual("user2", itemKeys[1]);
+            Assert.AreEqual("user3", itemKeys[2]);
+
+            Assert.AreEqual(_segments1And2, cache.Lookup("user1"));
+
+            itemKeys = cache.ReadCurrentCache().Keys.ToKeyCollection();
+            // Lookup should move user1 to bottom of the list and push up others.
+            Assert.AreEqual("user2", itemKeys[0]);
+            Assert.AreEqual("user3", itemKeys[1]);
+            Assert.AreEqual("user1", itemKeys[2]);
+
+            Assert.AreEqual(_segments3And4, cache.Lookup("user2"));
+
+            itemKeys = cache.ReadCurrentCache().Keys.ToKeyCollection();
+            // Lookup should move user2 to bottom of the list and push up others.
+            Assert.AreEqual("user3", itemKeys[0]);
+            Assert.AreEqual("user1", itemKeys[1]);
+            Assert.AreEqual("user2", itemKeys[2]);
+
+            Assert.AreEqual(_segments5And6, cache.Lookup("user3"));
+
+            itemKeys = cache.ReadCurrentCache().Keys.ToKeyCollection();
+            // Lookup should move user3 to bottom of the list and push up others.
+            Assert.AreEqual("user1", itemKeys[0]);
+            Assert.AreEqual("user2", itemKeys[1]);
+            Assert.AreEqual("user3", itemKeys[2]);
+        }
+
+        [Test]
+        public void ShouldReorderListOnSave()
+        {
+            var cache = new LruCache<List<string>>();
+
+            cache.Save("user1", _segments1And2);
+            cache.Save("user2", _segments3And4);
+            cache.Save("user3", _segments5And6);
+
+            var itemKeys = cache.ReadCurrentCache().Keys.ToKeyCollection();
+            Assert.AreEqual("user1", itemKeys[0]);
+            Assert.AreEqual("user2", itemKeys[1]);
+            Assert.AreEqual("user3", itemKeys[2]);
+
+            cache.Save("user1", _segments1And2);
+
+            itemKeys = cache.ReadCurrentCache().Keys.ToKeyCollection();
+            // save should move user1 to bottom of the list and push up others.
+            Assert.AreEqual("user2", itemKeys[0]);
+            Assert.AreEqual("user3", itemKeys[1]);
+            Assert.AreEqual("user1", itemKeys[2]);
+
+            cache.Save("user2", _segments3And4);
+
+            itemKeys = cache.ReadCurrentCache().Keys.ToKeyCollection();
+            // save should move user2 to bottom of the list and push up others.
+            Assert.AreEqual("user3", itemKeys[0]);
+            Assert.AreEqual("user1", itemKeys[1]);
+            Assert.AreEqual("user2", itemKeys[2]);
+
+            cache.Save("user3", _segments5And6);
+
+            itemKeys = cache.ReadCurrentCache().Keys.ToKeyCollection();
+            // save should move user3 to bottom of the list and push up others.
+            Assert.AreEqual("user1", itemKeys[0]);
+            Assert.AreEqual("user2", itemKeys[1]);
+            Assert.AreEqual("user3", itemKeys[2]);
+        }
+
+        [Test]
+        public void ShouldHandleWhenCacheIsDisabled()
+        {
+            var cache = new LruCache<List<string>>(0, LruCache<object>.DEFAULT_TIMEOUT_SECONDS);
+
+            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>>(LruCache<object>.DEFAULT_MAX_SIZE, 1);
+
+            cache.Save("user1", _segments1And2);
+
+            Assert.AreEqual(_segments1And2, cache.Lookup("user1"));
+            Assert.AreEqual(1, cache.ReadCurrentCache().Count);
+
+            Thread.Sleep(1200);
+
+            Assert.IsNull(cache.Lookup("user1"));
+            Assert.AreEqual(0, cache.ReadCurrentCache().Count);
+        }
+
+        [Test]
+        public void ShouldHandleWhenCacheReachesMaxSize()
+        {
+            var cache = new LruCache<List<string>>(2, LruCache<object>.DEFAULT_TIMEOUT_SECONDS);
+
+            cache.Save("user1", _segments1And2);
+            cache.Save("user2", _segments3And4);
+            cache.Save("user3", _segments5And6);
+
+            Assert.AreEqual(2, cache.ReadCurrentCache().Count);
+
+            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.ReadCurrentCache().Count);
+
+            cache.Reset();
+
+            Assert.IsNull(cache.Lookup("user1"));
+            Assert.IsNull(cache.Lookup("user2"));
+            Assert.IsNull(cache.Lookup("user3"));
+
+            Assert.AreEqual(0, cache.ReadCurrentCache().Count);}
+    }
+}

OptimizelySDK.Tests/OptimizelySDK.Tests.csproj

@@ -80,6 +80,8 @@
     <Compile Include="DefaultErrorHandlerTest.cs" />
     <Compile Include="EntityTests\IntegrationTest.cs" />
     <Compile Include="EventTests\EventProcessorProps.cs" />
+    <Compile Include="OdpTests\CollectionExtensions.cs" />
+    <Compile Include="OdpTests\LruCacheTest.cs" />
     <Compile Include="OptimizelyConfigTests\OptimizelyConfigTest.cs" />
     <Compile Include="OptimizelyDecisions\OptimizelyDecisionTest.cs" />
     <Compile Include="OptimizelyJSONTest.cs" />
@@ -150,7 +152,6 @@
   <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/DateTimeExtension.cs

@@ -0,0 +1,30 @@
+/* 
+ * 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 System;
+
+namespace OptimizelySDK.Odp
+{
+    public static class DateTimeExtension
+    {
+        // Because we're only on .NET Framework 4.5
+        public static long ToUnixTimeMilliseconds(this DateTime dateTime)
+        {
+            var unixTimeStart = new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc);
+            return Convert.ToInt64(dateTime.Subtract(unixTimeStart).TotalMilliseconds);
+        }
+    }
+}

OptimizelySDK/Odp/ICache.cs

@@ -0,0 +1,25 @@
+/* 
+ * 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>
+    {
+        void Save(string key, T value);
+        T Lookup(string key);
+        void Reset();
+    }
+}