group evenrhythms within a pattern

osu.Game.Rulesets.Taiko/Difficulty/Preprocessing/Rhythm/Data/EvenPatterns.cs

@@ -0,0 +1,55 @@
+// 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.Collections.Generic;
+using System.Linq;
+
+namespace osu.Game.Rulesets.Taiko.Difficulty.Preprocessing.Rhythm.Data
+{
+    /// <summary>
+    /// Represents <see cref="EvenHitObjects"/> grouped by their <see cref="EvenHitObjects.StartTime"/>'s interval.
+    /// </summary>
+    public class EvenPatterns : EvenRhythm<EvenHitObjects>
+    {
+        public EvenPatterns? Previous { get; private set; }
+
+        /// <summary>
+        /// The <see cref="EvenHitObjects.Interval"/> between children <see cref="EvenHitObjects"/> within this group.
+        /// If there is only one child, this will have the value of the first child's <see cref="EvenHitObjects.Interval"/>.
+        /// </summary>
+        public double ChildrenInterval => Children.Count > 1 ? Children[1].Interval : Children[0].Interval;
+
+        /// <summary>
+        /// The ratio of <see cref="ChildrenInterval"/> between this and the previous <see cref="EvenPatterns"/>. In the
+        /// case where there is no previous <see cref="EvenPatterns"/>, this will have a value of 1.
+        /// </summary>
+        public double IntervalRatio => ChildrenInterval / Previous?.ChildrenInterval ?? 1.0d;
+
+        public TaikoDifficultyHitObject FirstHitObject => Children[0].FirstHitObject;
+
+        public IEnumerable<TaikoDifficultyHitObject> AllHitObjects => Children.SelectMany(child => child.Children);
+
+        private EvenPatterns(EvenPatterns? previous, List<EvenHitObjects> data, ref int i)
+            : base(data, ref i, 5)
+        {
+            Previous = previous;
+
+            foreach (TaikoDifficultyHitObject hitObject in AllHitObjects)
+            {
+                hitObject.Rhythm.EvenPatterns = this;
+            }
+        }
+
+        public static void GroupPatterns(List<EvenHitObjects> data)
+        {
+            List<EvenPatterns> evenPatterns = new List<EvenPatterns>();
+
+            // Index does not need to be incremented, as it is handled within the EvenRhythm constructor.
+            for (int i = 0; i < data.Count;)
+            {
+                EvenPatterns? previous = evenPatterns.Count > 0 ? evenPatterns[^1] : null;
+                evenPatterns.Add(new EvenPatterns(previous, data, ref i));
+            }
+        }
+    }
+}