Consolidate LRU factory logic (#479)

Author: bitfaster

BitFaster.Caching/Lru/Builder/AsyncConcurrentLruBuilder.cs

@@ -16,13 +16,7 @@ internal AsyncConcurrentLruBuilder(LruInfo<K> info)
         ///<inheritdoc/>
         public override IAsyncCache<K, V> Build()
         {
-            return info switch
-            {
-                LruInfo<K> i when i.WithMetrics && !i.TimeToExpireAfterWrite.HasValue => new ConcurrentLru<K, V>(info.ConcurrencyLevel, info.Capacity, info.KeyComparer),
-                LruInfo<K> i when i.WithMetrics && i.TimeToExpireAfterWrite.HasValue => new ConcurrentTLru<K, V>(info.ConcurrencyLevel, info.Capacity, info.KeyComparer, info.TimeToExpireAfterWrite.Value),
-                LruInfo<K> i when i.TimeToExpireAfterWrite.HasValue => new FastConcurrentTLru<K, V>(info.ConcurrencyLevel, info.Capacity, info.KeyComparer, info.TimeToExpireAfterWrite.Value),
-                _ => new FastConcurrentLru<K, V>(info.ConcurrencyLevel, info.Capacity, info.KeyComparer),
-            };
+            return LruFactory<K, V>.CreateConcurrent(this.info) as IAsyncCache<K, V>;
         }
     }
 }

BitFaster.Caching/Lru/ConcurrentLruBuilder.cs

@@ -40,24 +40,7 @@ internal ConcurrentLruBuilder(LruInfo<K> info)
         ///<inheritdoc/>
         public override ICache<K, V> Build()
         {
-            if (info.TimeToExpireAfterWrite.HasValue && info.TimeToExpireAfterAccess.HasValue)
-                Throw.InvalidOp("Specifying both ExpireAfterWrite and ExpireAfterAccess is not supported.");
-
-            return info switch
-            {
-                LruInfo<K> i when i.WithMetrics && !i.TimeToExpireAfterWrite.HasValue && !i.TimeToExpireAfterAccess.HasValue => new ConcurrentLru<K, V>(info.ConcurrencyLevel, info.Capacity, info.KeyComparer),
-                LruInfo<K> i when i.WithMetrics && i.TimeToExpireAfterWrite.HasValue && !i.TimeToExpireAfterAccess.HasValue => new ConcurrentTLru<K, V>(info.ConcurrencyLevel, info.Capacity, info.KeyComparer, info.TimeToExpireAfterWrite.Value),
-                LruInfo<K> i when i.TimeToExpireAfterWrite.HasValue && !i.TimeToExpireAfterAccess.HasValue => new FastConcurrentTLru<K, V>(info.ConcurrencyLevel, info.Capacity, info.KeyComparer, info.TimeToExpireAfterWrite.Value),
-                LruInfo<K> i when i.WithMetrics && !i.TimeToExpireAfterWrite.HasValue && i.TimeToExpireAfterAccess.HasValue => CreateExpireAfterAccess<TelemetryPolicy<K, V>>(info),
-                LruInfo<K> i when !i.TimeToExpireAfterWrite.HasValue && i.TimeToExpireAfterAccess.HasValue => CreateExpireAfterAccess<NoTelemetryPolicy<K, V>>(info),
-                _ => new FastConcurrentLru<K, V>(info.ConcurrencyLevel, info.Capacity, info.KeyComparer),
-            };
-        }
-
-        private static ICache<K, V> CreateExpireAfterAccess<TP>(LruInfo<K> info) where TP : struct, ITelemetryPolicy<K, V>
-        {
-            return new ConcurrentLruCore<K, V, LongTickCountLruItem<K, V>, AfterAccessLongTicksPolicy<K, V>, TP>(
-                info.ConcurrencyLevel, info.Capacity, info.KeyComparer, new AfterAccessLongTicksPolicy<K, V>(info.TimeToExpireAfterAccess.Value), default);
+            return LruFactory<K, V>.CreateConcurrent(this.info);
         }
     }
 }

BitFaster.Caching/Lru/LruFactory.cs

@@ -0,0 +1,38 @@
+using System.Linq.Expressions;
+using BitFaster.Caching.Lru.Builder;
+
+namespace BitFaster.Caching.Lru
+{
+    /// <summary>
+    /// Factory class for creating ConcurrentLru variants.
+    /// </summary>
+    internal static class LruFactory<K, V>
+    {
+        /// <summary>
+        /// Creates a ConcurrentLru instance based on the provided LruInfo.
+        /// </summary>
+        /// <param name="info">The LruInfo</param>
+        /// <returns>A ConcurrentLru</returns>
+        internal static ICache<K, V> CreateConcurrent(LruInfo<K> info)
+        {
+            if (info.TimeToExpireAfterWrite.HasValue && info.TimeToExpireAfterAccess.HasValue)
+                Throw.InvalidOp("Specifying both ExpireAfterWrite and ExpireAfterAccess is not supported.");
+
+            return (info.WithMetrics, info.TimeToExpireAfterWrite.HasValue, info.TimeToExpireAfterAccess.HasValue) switch
+            {
+                (true, false, false) => new ConcurrentLru<K, V>(info.ConcurrencyLevel, info.Capacity, info.KeyComparer),
+                (true, true, false) => new ConcurrentTLru<K, V>(info.ConcurrencyLevel, info.Capacity, info.KeyComparer, info.TimeToExpireAfterWrite.Value),
+                (false, true, false) => new FastConcurrentTLru<K, V>(info.ConcurrencyLevel, info.Capacity, info.KeyComparer, info.TimeToExpireAfterWrite.Value),
+                (true, false, true) => CreateExpireAfterAccess<TelemetryPolicy<K, V>>(info),
+                (false, false, true) => CreateExpireAfterAccess<NoTelemetryPolicy<K, V>>(info),
+                _ => new FastConcurrentLru<K, V>(info.ConcurrencyLevel, info.Capacity, info.KeyComparer),
+            };
+        }
+
+        private static ICache<K, V> CreateExpireAfterAccess<TP>(LruInfo<K> info) where TP : struct, ITelemetryPolicy<K, V>
+        {
+            return new ConcurrentLruCore<K, V, LongTickCountLruItem<K, V>, AfterAccessLongTicksPolicy<K, V>, TP>(
+                info.ConcurrencyLevel, info.Capacity, info.KeyComparer, new AfterAccessLongTicksPolicy<K, V>(info.TimeToExpireAfterAccess.Value), default);
+        }
+    }
+}