Split out separate component

osu.Game/Rulesets/UI/GameplaySampleTriggerSource.cs

@@ -0,0 +1,84 @@
+// 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.Linq;
+using osu.Framework.Allocation;
+using osu.Framework.Graphics;
+using osu.Framework.Graphics.Containers;
+using osu.Game.Audio;
+using osu.Game.Rulesets.Objects;
+using osu.Game.Skinning;
+
+namespace osu.Game.Rulesets.UI
+{
+    /// <summary>
+    /// A component which can trigger the most appropriate hit sound for a given point in time, based on the state of a <see cref="HitObjectContainer"/>
+    /// </summary>
+    public class GameplaySampleTriggerSource : CompositeDrawable
+    {
+        private readonly HitObjectContainer hitObjectContainer;
+
+        private int nextHitSoundIndex;
+
+        /// <summary>
+        /// The number of concurrent samples allowed to be played concurrently so that it feels better when spam-pressing a key.
+        /// </summary>
+        private const int max_concurrent_hitsounds = OsuGameBase.SAMPLE_CONCURRENCY;
+
+        private readonly Container<SkinnableSound> hitSounds;
+
+        [Resolved]
+        private DrawableRuleset drawableRuleset { get; set; }
+
+        public GameplaySampleTriggerSource(HitObjectContainer hitObjectContainer)
+        {
+            this.hitObjectContainer = hitObjectContainer;
+            InternalChildren = new Drawable[]
+            {
+                hitSounds = new Container<SkinnableSound>
+                {
+                    Name = "concurrent sample pool",
+                    RelativeSizeAxes = Axes.Both,
+                    Children = Enumerable.Range(0, max_concurrent_hitsounds).Select(_ => new SkinnableSound()).ToArray()
+                },
+            };
+        }
+
+        private ISampleInfo[] playableSampleInfo;
+
+        /// <summary>
+        /// Play the most appropriate hit sound for the current point in time.
+        /// </summary>
+        public void Play()
+        {
+            var nextObject =
+                hitObjectContainer.AliveObjects.FirstOrDefault(h => h.HitObject.StartTime > Time.Current)?.HitObject ??
+                // fallback to non-alive objects to find next off-screen object
+                // TODO: make lookup more efficient?
+                drawableRuleset.Objects.FirstOrDefault(h => h.StartTime > Time.Current) ??
+                drawableRuleset.Objects.LastOrDefault();
+
+            if (nextObject != null)
+            {
+                var hitSound = getNextSample();
+                playableSampleInfo = GetPlayableSampleInfo(nextObject);
+                hitSound.Samples = playableSampleInfo;
+                hitSound.Play();
+            }
+        }
+
+        protected virtual ISampleInfo[] GetPlayableSampleInfo(HitObject nextObject) =>
+            // TODO: avoid cast somehow?
+            nextObject.Samples.Cast<ISampleInfo>().ToArray();
+
+        private SkinnableSound getNextSample()
+        {
+            var hitSound = hitSounds[nextHitSoundIndex];
+
+            // round robin over available samples to allow for concurrent playback.
+            nextHitSoundIndex = (nextHitSoundIndex + 1) % max_concurrent_hitsounds;
+
+            return hitSound;
+        }
+    }
+}