From dff865f335c8c4c70ed8b4ec7bf1975fc2f52440 Mon Sep 17 00:00:00 2001
From: Dean Herbert <pe@ppy.sh>
Date: Tue, 22 Dec 2020 14:12:02 +0900
Subject: [PATCH] Tidy up comments, code, and multiple linq enumeration

---
 osu.Game/OsuGame.cs                            | 18 ++++++------------
 .../Screens/Select/DifficultyRecommender.cs    |  2 ++
 2 files changed, 8 insertions(+), 12 deletions(-)

diff --git a/osu.Game/OsuGame.cs b/osu.Game/OsuGame.cs
index d2c27b766c..d76bd163e1 100644
--- a/osu.Game/OsuGame.cs
+++ b/osu.Game/OsuGame.cs
@@ -364,25 +364,19 @@ namespace osu.Game
 
                 // we might even already be at the song
                 if (Beatmap.Value.BeatmapSetInfo.Hash == databasedSet.Hash && (difficultyCriteria?.Invoke(Beatmap.Value.BeatmapInfo) ?? true))
-                {
                     return;
-                }
 
                 // Find beatmaps that match our predicate.
-                var beatmaps = databasedSet.Beatmaps.Where(b => difficultyCriteria?.Invoke(b) ?? true);
+                var beatmaps = databasedSet.Beatmaps.Where(b => difficultyCriteria?.Invoke(b) ?? true).ToList();
 
                 // Use all beatmaps if predicate matched nothing
-                if (!beatmaps.Any())
+                if (beatmaps.Count == 0)
                     beatmaps = databasedSet.Beatmaps;
 
-                // Try to select recommended beatmap
-                // This should give us a beatmap from current ruleset if there are any in our matched beatmaps
-                var selection = DifficultyRecommender.GetRecommendedBeatmap(beatmaps);
-                // Fallback if a difficulty can't be recommended, maybe we are offline
-                // First try to find a beatmap in current ruleset
-                selection ??= beatmaps.FirstOrDefault(b => b.Ruleset.Equals(Ruleset.Value));
-                // Otherwise use first beatmap
-                selection ??= beatmaps.First();
+                // Prefer recommended beatmap if recommendations are available, else fallback to a sane selection.
+                var selection = DifficultyRecommender.GetRecommendedBeatmap(beatmaps)
+                                ?? beatmaps.FirstOrDefault(b => b.Ruleset.Equals(Ruleset.Value))
+                                ?? beatmaps.First();
 
                 Ruleset.Value = selection.Ruleset;
                 Beatmap.Value = BeatmapManager.GetWorkingBeatmap(selection);
diff --git a/osu.Game/Screens/Select/DifficultyRecommender.cs b/osu.Game/Screens/Select/DifficultyRecommender.cs
index fa48316e9d..3b3fc812e6 100644
--- a/osu.Game/Screens/Select/DifficultyRecommender.cs
+++ b/osu.Game/Screens/Select/DifficultyRecommender.cs
@@ -4,6 +4,7 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using JetBrains.Annotations;
 using osu.Framework.Allocation;
 using osu.Framework.Bindables;
 using osu.Framework.Extensions.IEnumerableExtensions;
@@ -47,6 +48,7 @@ namespace osu.Game.Screens.Select
         /// </remarks>
         /// <param name="beatmaps">A collection of beatmaps to select a difficulty from.</param>
         /// <returns>The recommended difficulty, or null if a recommendation could not be provided.</returns>
+        [CanBeNull]
         public BeatmapInfo GetRecommendedBeatmap(IEnumerable<BeatmapInfo> beatmaps)
         {
             if (!recommendedStarDifficulty.Any())