Merge pull request #8444 from LittleEndu/select-recommended

Make beatmap carousel select recommended difficulties

osu.Game.Tests/Visual/SongSelect/TestSceneBeatmapCarousel.cs

@@ -54,6 +54,35 @@ private void load(RulesetStore rulesets)
             this.rulesets = rulesets;
         }
 
+        [Test]
+        public void TestRecommendedSelection()
+        {
+            loadBeatmaps();
+
+            AddStep("set recommendation function", () => carousel.GetRecommendedBeatmap = beatmaps => beatmaps.LastOrDefault());
+
+            // check recommended was selected
+            advanceSelection(direction: 1, diff: false);
+            waitForSelection(1, 3);
+
+            // change away from recommended
+            advanceSelection(direction: -1, diff: true);
+            waitForSelection(1, 2);
+
+            // next set, check recommended
+            advanceSelection(direction: 1, diff: false);
+            waitForSelection(2, 3);
+
+            // next set, check recommended
+            advanceSelection(direction: 1, diff: false);
+            waitForSelection(3, 3);
+
+            // go back to first set and ensure user selection was retained
+            advanceSelection(direction: -1, diff: false);
+            advanceSelection(direction: -1, diff: false);
+            waitForSelection(1, 2);
+        }
+
         /// <summary>
         /// Test keyboard traversal
         /// </summary>

osu.Game/Screens/Select/BeatmapCarousel.cs

@@ -48,6 +48,11 @@ public class BeatmapCarousel : CompositeDrawable, IKeyBindingHandler<GlobalActio
         /// </summary>
         public BeatmapSetInfo SelectedBeatmapSet => selectedBeatmapSet?.BeatmapSet;
 
+        /// <summary>
+        /// A function to optionally decide on a recommended difficulty from a beatmap set.
+        /// </summary>
+        public Func<IEnumerable<BeatmapInfo>, BeatmapInfo> GetRecommendedBeatmap;
+
         private CarouselBeatmapSet selectedBeatmapSet;
 
         /// <summary>
@@ -116,6 +121,7 @@ private void loadBeatmapSets(IEnumerable<BeatmapSetInfo> beatmapSets)
         private readonly Stack<CarouselBeatmap> randomSelectedBeatmaps = new Stack<CarouselBeatmap>();
 
         protected List<DrawableCarouselItem> Items = new List<DrawableCarouselItem>();
+
         private CarouselRoot root;
 
         public BeatmapCarousel()
@@ -579,7 +585,10 @@ private CarouselBeatmapSet createCarouselSet(BeatmapSetInfo beatmapSet)
                     b.Metadata = beatmapSet.Metadata;
             }
 
-            var set = new CarouselBeatmapSet(beatmapSet);
+            var set = new CarouselBeatmapSet(beatmapSet)
+            {
+                GetRecommendedBeatmap = beatmaps => GetRecommendedBeatmap?.Invoke(beatmaps)
+            };
 
             foreach (var c in set.Beatmaps)
             {

osu.Game/Screens/Select/Carousel/CarouselBeatmapSet.cs

@@ -16,6 +16,8 @@ public class CarouselBeatmapSet : CarouselGroupEagerSelect
 
         public BeatmapSetInfo BeatmapSet;
 
+        public Func<IEnumerable<BeatmapInfo>, BeatmapInfo> GetRecommendedBeatmap;
+
         public CarouselBeatmapSet(BeatmapSetInfo beatmapSet)
         {
             BeatmapSet = beatmapSet ?? throw new ArgumentNullException(nameof(beatmapSet));
@@ -28,6 +30,17 @@ public CarouselBeatmapSet(BeatmapSetInfo beatmapSet)
 
         protected override DrawableCarouselItem CreateDrawableRepresentation() => new DrawableCarouselBeatmapSet(this);
 
+        protected override CarouselItem GetNextToSelect()
+        {
+            if (LastSelected == null)
+            {
+                if (GetRecommendedBeatmap?.Invoke(Children.OfType<CarouselBeatmap>().Where(b => !b.Filtered.Value).Select(b => b.Beatmap)) is BeatmapInfo recommended)
+                    return Children.OfType<CarouselBeatmap>().First(b => b.Beatmap == recommended);
+            }
+
+            return base.GetNextToSelect();
+        }
+
         public override int CompareTo(FilterCriteria criteria, CarouselItem other)
         {
             if (!(other is CarouselBeatmapSet otherSet))

osu.Game/Screens/Select/Carousel/CarouselGroupEagerSelect.cs

@@ -90,11 +90,15 @@ private void attemptSelection()
             PerformSelection();
         }
 
+        protected virtual CarouselItem GetNextToSelect()
+        {
+            return Children.Skip(lastSelectedIndex).FirstOrDefault(i => !i.Filtered.Value) ??
+                   Children.Reverse().Skip(InternalChildren.Count - lastSelectedIndex).FirstOrDefault(i => !i.Filtered.Value);
+        }
+
         protected virtual void PerformSelection()
         {
-            CarouselItem nextToSelect =
-                Children.Skip(lastSelectedIndex).FirstOrDefault(i => !i.Filtered.Value) ??
-                Children.Reverse().Skip(InternalChildren.Count - lastSelectedIndex).FirstOrDefault(i => !i.Filtered.Value);
+            CarouselItem nextToSelect = GetNextToSelect();
 
             if (nextToSelect != null)
                 nextToSelect.State.Value = CarouselItemState.Selected;

osu.Game/Screens/Select/DifficultyRecommender.cs

@@ -0,0 +1,92 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using osu.Framework.Allocation;
+using osu.Framework.Bindables;
+using osu.Framework.Extensions.IEnumerableExtensions;
+using osu.Framework.Graphics;
+using osu.Game.Beatmaps;
+using osu.Game.Online.API;
+using osu.Game.Online.API.Requests;
+using osu.Game.Rulesets;
+
+namespace osu.Game.Screens.Select
+{
+    public class DifficultyRecommender : Component, IOnlineComponent
+    {
+        [Resolved]
+        private IAPIProvider api { get; set; }
+
+        [Resolved]
+        private RulesetStore rulesets { get; set; }
+
+        [Resolved]
+        private Bindable<RulesetInfo> ruleset { get; set; }
+
+        private readonly Dictionary<RulesetInfo, double> recommendedStarDifficulty = new Dictionary<RulesetInfo, double>();
+
+        [BackgroundDependencyLoader]
+        private void load()
+        {
+            api.Register(this);
+        }
+
+        /// <summary>
+        /// Find the recommended difficulty from a selection of available difficulties for the current local user.
+        /// </summary>
+        /// <remarks>
+        /// This requires the user to be online for now.
+        /// </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>
+        public BeatmapInfo GetRecommendedBeatmap(IEnumerable<BeatmapInfo> beatmaps)
+        {
+            if (recommendedStarDifficulty.TryGetValue(ruleset.Value, out var stars))
+            {
+                return beatmaps.OrderBy(b =>
+                {
+                    var difference = b.StarDifficulty - stars;
+                    return difference >= 0 ? difference * 2 : difference * -1; // prefer easier over harder
+                }).FirstOrDefault();
+            }
+
+            return null;
+        }
+
+        private void calculateRecommendedDifficulties()
+        {
+            rulesets.AvailableRulesets.ForEach(rulesetInfo =>
+            {
+                var req = new GetUserRequest(api.LocalUser.Value.Id, rulesetInfo);
+
+                req.Success += result =>
+                {
+                    // algorithm taken from https://github.com/ppy/osu-web/blob/e6e2825516449e3d0f3f5e1852c6bdd3428c3437/app/Models/User.php#L1505
+                    recommendedStarDifficulty[rulesetInfo] = Math.Pow((double)(result.Statistics.PP ?? 0), 0.4) * 0.195;
+                };
+
+                api.Queue(req);
+            });
+        }
+
+        public void APIStateChanged(IAPIProvider api, APIState state)
+        {
+            switch (state)
+            {
+                case APIState.Online:
+                    calculateRecommendedDifficulties();
+                    break;
+            }
+        }
+
+        protected override void Dispose(bool isDisposing)
+        {
+            base.Dispose(isDisposing);
+
+            api.Unregister(this);
+        }
+    }
+}

osu.Game/Screens/Select/SongSelect.cs

@@ -81,6 +81,8 @@ public abstract class SongSelect : OsuScreen, IKeyBindingHandler<GlobalAction>
 
         protected BeatmapCarousel Carousel { get; private set; }
 
+        private DifficultyRecommender recommender;
+
         private BeatmapInfoWedge beatmapInfoWedge;
         private DialogOverlay dialogOverlay;
 
@@ -109,6 +111,7 @@ private void load(AudioManager audio, DialogOverlay dialog, OsuColour colours, S
 
             AddRangeInternal(new Drawable[]
             {
+                recommender = new DifficultyRecommender(),
                 new ResetScrollContainer(() => Carousel.ScrollToSelected())
                 {
                     RelativeSizeAxes = Axes.Y,
@@ -156,6 +159,7 @@ private void load(AudioManager audio, DialogOverlay dialog, OsuColour colours, S
                                             RelativeSizeAxes = Axes.Both,
                                             SelectionChanged = updateSelectedBeatmap,
                                             BeatmapSetsChanged = carouselBeatmapsLoaded,
+                                            GetRecommendedBeatmap = recommender.GetRecommendedBeatmap,
                                         },
                                     }
                                 },