Move lookup/storage/compute logic to base class (and consume in ScorePerformanceCache)

osu.Game/Database/MemoryCachingComponent.cs

@@ -2,6 +2,9 @@
 // See the LICENCE file in the repository root for full licence text.
 
 using System.Collections.Concurrent;
+using System.Threading;
+using System.Threading.Tasks;
+using JetBrains.Annotations;
 using osu.Framework.Graphics;
 
 namespace osu.Game.Database
@@ -12,6 +15,34 @@ namespace osu.Game.Database
     /// </summary>
     public abstract class MemoryCachingComponent<TLookup, TValue> : Component
     {
-        protected readonly ConcurrentDictionary<TLookup, TValue> Cache = new ConcurrentDictionary<TLookup, TValue>();
+        private readonly ConcurrentDictionary<TLookup, TValue> cache = new ConcurrentDictionary<TLookup, TValue>();
+
+        protected virtual bool CacheNullValues => true;
+
+        /// <summary>
+        /// Retrieve the cached value for the given <see cref="TLookup"/>.
+        /// </summary>
+        /// <param name="lookup">The lookup to retrieve.</param>
+        /// <param name="token">An optional <see cref="CancellationToken"/> to cancel the operation.</param>
+        protected async Task<TValue> GetAsync([NotNull] TLookup lookup, CancellationToken token = default)
+        {
+            if (cache.TryGetValue(lookup, out TValue performance))
+                return performance;
+
+            var computed = await ComputeValueAsync(lookup, token);
+
+            if (computed != null || CacheNullValues)
+                cache[lookup] = computed;
+
+            return computed;
+        }
+
+        /// <summary>
+        /// Called on cache miss to compute the value for the specified lookup.
+        /// </summary>
+        /// <param name="lookup">The lookup to retrieve.</param>
+        /// <param name="token">An optional <see cref="CancellationToken"/> to cancel the operation.</param>
+        /// <returns>The computed value.</returns>
+        protected abstract Task<TValue> ComputeValueAsync(TLookup lookup, CancellationToken token = default);
     }
 }

osu.Game/Scoring/ScorePerformanceCache.cs

@@ -15,28 +15,25 @@ namespace osu.Game.Scoring
     /// A component which performs and acts as a central cache for performance calculations of locally databased scores.
     /// Currently not persisted between game sessions.
     /// </summary>
-    public class ScorePerformanceCache : MemoryCachingComponent<ScorePerformanceCache.PerformanceCacheLookup, double>
+    public class ScorePerformanceCache : MemoryCachingComponent<ScorePerformanceCache.PerformanceCacheLookup, double?>
     {
         [Resolved]
         private BeatmapDifficultyCache difficultyCache { get; set; }
 
+        protected override bool CacheNullValues => false;
+
         /// <summary>
         /// Calculates performance for the given <see cref="ScoreInfo"/>.
         /// </summary>
         /// <param name="score">The score to do the calculation on. </param>
         /// <param name="token">An optional <see cref="CancellationToken"/> to cancel the operation.</param>
-        public Task<double?> CalculatePerformanceAsync([NotNull] ScoreInfo score, CancellationToken token = default)
+        public Task<double?> CalculatePerformanceAsync([NotNull] ScoreInfo score, CancellationToken token = default) =>
+            GetAsync(new PerformanceCacheLookup(score), token);
+
+        protected override async Task<double?> ComputeValueAsync(PerformanceCacheLookup lookup, CancellationToken token = default)
         {
-            var lookupKey = new PerformanceCacheLookup(score);
+            var score = lookup.ScoreInfo;
 
-            if (Cache.TryGetValue(lookupKey, out double performance))
-                return Task.FromResult((double?)performance);
-
-            return computePerformanceAsync(score, lookupKey, token);
-        }
-
-        private async Task<double?> computePerformanceAsync(ScoreInfo score, PerformanceCacheLookup lookupKey, CancellationToken token = default)
-        {
             var attributes = await difficultyCache.GetDifficultyAsync(score.Beatmap, score.Ruleset, score.Mods, token);
 
             // Performance calculation requires the beatmap and ruleset to be locally available. If not, return a default value.
@@ -46,31 +43,25 @@ namespace osu.Game.Scoring
             token.ThrowIfCancellationRequested();
 
             var calculator = score.Ruleset.CreateInstance().CreatePerformanceCalculator(attributes.Attributes, score);
-            var total = calculator?.Calculate();
 
-            if (total.HasValue)
+            return calculator?.Calculate();
-                Cache[lookupKey] = total.Value;
-
-            return total;
         }
 
         public readonly struct PerformanceCacheLookup
         {
-            public readonly string ScoreHash;
+            public readonly ScoreInfo ScoreInfo;
-            public readonly int LocalScoreID;
 
             public PerformanceCacheLookup(ScoreInfo info)
             {
-                ScoreHash = info.Hash;
+                ScoreInfo = info;
-                LocalScoreID = info.ID;
             }
 
             public override int GetHashCode()
             {
                 var hash = new HashCode();
 
-                hash.Add(ScoreHash);
+                hash.Add(ScoreInfo.Hash);
-                hash.Add(LocalScoreID);
+                hash.Add(ScoreInfo.ID);
 
                 return hash.ToHashCode();
             }