Define the concept of patterns + additional comments.

osu.Game.Rulesets.Mania/Beatmaps/Patterns/PatternGenerator.cs

@@ -0,0 +1,89 @@
+// 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 osu.Game.Beatmaps;
+using osu.Game.Rulesets.Mania.Objects;
+using osu.Game.Rulesets.Objects;
+
+namespace osu.Game.Rulesets.Mania.Beatmaps.Patterns
+{
+    /// <summary>
+    /// Generator to create a pattern <see cref="Pattern"/> from a hit object.
+    /// </summary>
+    internal abstract class PatternGenerator
+    {
+        /// <summary>
+        /// The number of columns available to create the pattern.
+        /// </summary>
+        protected readonly int AvailableColumns;
+
+        /// <summary>
+        /// The last pattern.
+        /// </summary>
+        protected readonly Pattern PreviousPattern;
+
+        /// <summary>
+        /// The hit object to create the pattern for.
+        /// </summary>
+        protected readonly HitObject HitObject;
+       
+        /// <summary>
+        /// The beatmap which <see cref="HitObject"/> is a part of.
+        /// </summary>
+        protected readonly Beatmap Beatmap;
+
+        protected PatternGenerator(HitObject hitObject, Beatmap beatmap, Pattern previousPattern)
+        {
+            PreviousPattern = previousPattern;
+            HitObject = hitObject;
+            Beatmap = beatmap;
+
+            AvailableColumns = (int)Math.Round(beatmap.BeatmapInfo.Difficulty.CircleSize);
+        }
+
+        /// <summary>
+        /// Generates the pattern for <see cref="HitObject"/>, filled with hit objects.
+        /// </summary>
+        /// <returns>The <see cref="Pattern"/> containing the hit objects.</returns>
+        public abstract Pattern Generate();
+
+        /// <summary>
+        /// Constructs and adds a note to a pattern.
+        /// </summary>
+        /// <param name="pattern">The pattern to add to.</param>
+        /// <param name="originalObject">The original hit object (used for samples).</param>
+        /// <param name="column">The column to add the note to.</param>
+        /// <param name="startTime">The start time of the note.</param>
+        /// <param name="endTime">The end time of the note (set to <paramref name="startTime"/> for a non-hold note).</param>
+        /// <param name="siblings">The number of children alongside this note (these will not be generated, but are used for volume calculations).</param>
+        protected void AddToPattern(Pattern pattern, HitObject originalObject, int column, double startTime, double endTime, int siblings = 1)
+        {
+            ManiaHitObject newObject;
+
+            if (startTime == endTime)
+            {
+                newObject = new Note
+                {
+                    StartTime = startTime,
+                    Samples = originalObject.Samples,
+                    Column = column
+                };
+            }
+            else
+            {
+                newObject = new HoldNote
+                {
+                    StartTime = startTime,
+                    Samples = originalObject.Samples,
+                    Column = column,
+                    Duration = endTime - startTime
+                };
+            }
+
+            // Todo: Consider siblings and write sample volumes (probably at ManiaHitObject level)
+
+            pattern.Add(newObject);
+        }
+    }
+}