Implement osu!mania auto replay generation.

osu.Game.Rulesets.Mania/Replays/ManiaAutoGenerator.cs

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+// Copyright (c) 2007-2017 ppy Pty Ltd <contact@ppy.sh>.
+// Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
+
+using System;
+using System.Linq;
+using osu.Game.Beatmaps;
+using osu.Game.Rulesets.Mania.Objects;
+using osu.Game.Rulesets.Objects.Types;
+using osu.Game.Rulesets.Replays;
+using osu.Game.Users;
+
+namespace osu.Game.Rulesets.Mania.Replays
+{
+    internal class ManiaAutoGenerator : AutoGenerator<ManiaHitObject>
+    {
+        private readonly int availableColumns;
+
+        public ManiaAutoGenerator(Beatmap<ManiaHitObject> beatmap, int availableColumns)
+            : base(beatmap)
+        {
+            this.availableColumns = availableColumns;
+
+            Replay = new Replay { User = new User { Username = @"Autoplay" } };
+        }
+
+        protected Replay Replay;
+
+        public override Replay Generate()
+        {
+            double[] holdEndTimes = new double[availableColumns];
+            for (int i = 0; i < availableColumns; i++)
+                holdEndTimes[i] = double.NegativeInfinity;
+
+            // Notes are handled row-by-row
+            foreach (var objGroup in Beatmap.HitObjects.GroupBy(h => h.StartTime))
+            {
+                double groupTime = objGroup.Key;
+
+                int activeColumns = 0;
+
+                // Get the previously held-down active columns
+                for (int i = 0; i < availableColumns; i++)
+                {
+                    if (holdEndTimes[i] > groupTime)
+                        activeColumns |= 1 << i;
+                }
+
+                // Add on the group columns, keeping track of the held notes for the next rows
+                foreach (var obj in objGroup)
+                {
+                    var holdNote = obj as HoldNote;
+                    if (holdNote != null)
+                        holdEndTimes[obj.Column] = Math.Max(holdEndTimes[obj.Column], holdNote.EndTime);
+
+                    activeColumns |= 1 << obj.Column;
+                }
+
+                Replay.Frames.Add(new ReplayFrame(groupTime, activeColumns, null, ReplayButtonState.None));
+
+                // Add the release frames. We can't do this with the loop above because we need activeColumns to be fully populated
+                foreach (var obj in objGroup.GroupBy(h => (h as IHasEndTime)?.EndTime ?? h.StartTime + 1).OrderBy(h => h.Key))
+                {
+                    var groupEndTime = obj.Key;
+
+                    int activeColumnsAtEnd = 0;
+                    for (int i = 0; i < availableColumns; i++)
+                    {
+                        if (holdEndTimes[i] > groupEndTime)
+                            activeColumnsAtEnd |= 1 << i;
+                    }
+
+                    Replay.Frames.Add(new ReplayFrame(groupEndTime, activeColumnsAtEnd, 0, ReplayButtonState.None));
+                }
+            }
+
+            Replay.Frames = Replay.Frames
+                                  // Pick the maximum activeColumns for all frames at the same time
+                                  .GroupBy(f => f.Time)
+                                  .Select(g => new ReplayFrame(g.First().Time, g.Max(gf => gf.MouseX), 0, ReplayButtonState.None))
+                                  .OrderBy(f => f.Time)
+                                  .ToList();
+
+            return Replay;
+        }
+    }
+}