Add support for dual stages (keycoop) and score multiplier

osu.Game.Rulesets.Mania/Beatmaps/ManiaBeatmap.cs

@@ -21,13 +21,20 @@ public class ManiaBeatmap : Beatmap<ManiaHitObject>
         /// </summary>
         public int TotalColumns => Stages.Sum(g => g.Columns);
 
+        /// <summary>
+        /// The total number of columns that were present in this <see cref="ManiaBeatmap"/> before any user adjustments.
+        /// </summary>
+        public readonly int OriginalTotalColumns;
+
         /// <summary>
         /// Creates a new <see cref="ManiaBeatmap"/>.
         /// </summary>
         /// <param name="defaultStage">The initial stages.</param>
-        public ManiaBeatmap(StageDefinition defaultStage)
+        /// <param name="originalTotalColumns">The total number of columns present before any user adjustments. Defaults to the total columns in <paramref name="defaultStage"/>.</param>
+        public ManiaBeatmap(StageDefinition defaultStage, int? originalTotalColumns = null)
         {
             Stages.Add(defaultStage);
+            OriginalTotalColumns = originalTotalColumns ?? defaultStage.Columns;
         }
 
         public override IEnumerable<BeatmapStatistic> GetStatistics()

osu.Game.Rulesets.Mania/Beatmaps/ManiaBeatmapConverter.cs

@@ -28,6 +28,8 @@ public class ManiaBeatmapConverter : BeatmapConverter<ManiaHitObject>
         public bool Dual;
         public readonly bool IsForCurrentRuleset;
 
+        private int originalTargetColumns;
+
         // Internal for testing purposes
         internal FastRandom Random { get; private set; }
 
@@ -65,6 +67,8 @@ public ManiaBeatmapConverter(IBeatmap beatmap, Ruleset ruleset)
                 else
                     TargetColumns = Math.Max(4, Math.Min((int)roundedOverallDifficulty + 1, 7));
             }
+
+            originalTargetColumns = TargetColumns;
         }
 
         public override bool CanConvert() => Beatmap.HitObjects.All(h => h is IHasXPosition);
@@ -81,7 +85,7 @@ protected override Beatmap<ManiaHitObject> ConvertBeatmap(IBeatmap original, Can
 
         protected override Beatmap<ManiaHitObject> CreateBeatmap()
         {
-            beatmap = new ManiaBeatmap(new StageDefinition { Columns = TargetColumns });
+            beatmap = new ManiaBeatmap(new StageDefinition { Columns = TargetColumns }, originalTargetColumns);
 
             if (Dual)
                 beatmap.Stages.Add(new StageDefinition { Columns = TargetColumns });

osu.Game.Rulesets.Mania/Difficulty/ManiaDifficultyAttributes.cs

@@ -8,5 +8,6 @@ namespace osu.Game.Rulesets.Mania.Difficulty
     public class ManiaDifficultyAttributes : DifficultyAttributes
     {
         public double GreatHitWindow;
+        public double ScoreMultiplier;
     }
 }

osu.Game.Rulesets.Mania/Difficulty/ManiaDifficultyCalculator.cs

@@ -47,6 +47,7 @@ protected override DifficultyAttributes CreateDifficultyAttributes(IBeatmap beat
                 Mods = mods,
                 // Todo: This int cast is temporary to achieve 1:1 results with osu!stable, and should be removed in the future
                 GreatHitWindow = (int)(hitWindows.WindowFor(HitResult.Great)) / clockRate,
+                ScoreMultiplier = getScoreMultiplier(beatmap, mods),
                 MaxCombo = beatmap.HitObjects.Sum(h => h is HoldNote ? 2 : 1),
                 Skills = skills
             };
@@ -93,12 +94,44 @@ protected override Mod[] DifficultyAdjustmentMods
                     new ManiaModKey3(),
                     new ManiaModKey4(),
                     new ManiaModKey5(),
+                    new MultiMod(new ManiaModKey5(), new ManiaModDualStages()),
                     new ManiaModKey6(),
+                    new MultiMod(new ManiaModKey6(), new ManiaModDualStages()),
                     new ManiaModKey7(),
+                    new MultiMod(new ManiaModKey7(), new ManiaModDualStages()),
                     new ManiaModKey8(),
+                    new MultiMod(new ManiaModKey8(), new ManiaModDualStages()),
                     new ManiaModKey9(),
+                    new MultiMod(new ManiaModKey9(), new ManiaModDualStages()),
                 }).ToArray();
             }
         }
+
+        private double getScoreMultiplier(IBeatmap beatmap, Mod[] mods)
+        {
+            double scoreMultiplier = 1;
+
+            foreach (var m in mods)
+            {
+                switch (m)
+                {
+                    case ManiaModNoFail _:
+                    case ManiaModEasy _:
+                    case ManiaModHalfTime _:
+                        scoreMultiplier *= 0.5;
+                        break;
+                }
+            }
+
+            var maniaBeatmap = (ManiaBeatmap)beatmap;
+            int diff = maniaBeatmap.TotalColumns - maniaBeatmap.OriginalTotalColumns;
+
+            if (diff > 0)
+                scoreMultiplier *= 0.9;
+            else if (diff < 0)
+                scoreMultiplier *= 0.9 + 0.04 * diff;
+
+            return scoreMultiplier;
+        }
     }
 }