Implement preview track playback

osu.Game/Beatmaps/Drawables/Cards/Buttons/PlayButton.cs

@@ -1,25 +1,43 @@
 // 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.
 
+#nullable enable
+
+using System.Collections.Generic;
 using osu.Framework.Allocation;
 using osu.Framework.Bindables;
+using osu.Framework.Extensions.IEnumerableExtensions;
 using osu.Framework.Graphics;
+using osu.Framework.Graphics.Containers;
 using osu.Framework.Graphics.Sprites;
+using osu.Game.Audio;
 using osu.Game.Graphics;
 using osu.Game.Graphics.Containers;
+using osu.Game.Graphics.UserInterface;
 using osuTK;
 
 namespace osu.Game.Beatmaps.Drawables.Cards.Buttons
 {
     public class PlayButton : OsuHoverContainer
     {
+        public IBindable<double> Progress => progress;
+        private readonly BindableDouble progress = new BindableDouble();
+
         public BindableBool Playing { get; } = new BindableBool();
 
-        private readonly BeatmapSetInfo beatmapSetInfo;
+        private readonly IBeatmapSetInfo beatmapSetInfo;
+
+        protected override IEnumerable<Drawable> EffectTargets => icon.Yield();
 
         private readonly SpriteIcon icon;
+        private readonly LoadingSpinner loadingSpinner;
 
-        public PlayButton(BeatmapSetInfo beatmapSetInfo)
+        [Resolved]
+        private PreviewTrackManager previewTrackManager { get; set; } = null!;
+
+        private PreviewTrack? previewTrack;
+
+        public PlayButton(IBeatmapSetInfo beatmapSetInfo)
         {
             this.beatmapSetInfo = beatmapSetInfo;
 
@@ -34,6 +52,10 @@ namespace osu.Game.Beatmaps.Drawables.Cards.Buttons
                     Icon = FontAwesome.Solid.Play,
                     Size = new Vector2(14)
                 },
+                loadingSpinner = new LoadingSpinner
+                {
+                    Size = new Vector2(14)
+                }
             };
 
             Action = () => Playing.Toggle();
@@ -49,12 +71,72 @@ namespace osu.Game.Beatmaps.Drawables.Cards.Buttons
         {
             base.LoadComplete();
 
-            Playing.BindValueChanged(_ => updateState(), true);
+            Playing.BindValueChanged(updateState, true);
         }
 
-        private void updateState()
+        protected override void Update()
         {
-            icon.Icon = Playing.Value ? FontAwesome.Solid.Stop : FontAwesome.Solid.Play;
+            base.Update();
+
+            if (Playing.Value && previewTrack != null && previewTrack.TrackLoaded)
+                progress.Value = previewTrack.CurrentTime / previewTrack.Length;
+            else
+                progress.Value = 0;
+        }
+
+        private void updateState(ValueChangedEvent<bool> playing)
+        {
+            icon.Icon = playing.NewValue ? FontAwesome.Solid.Stop : FontAwesome.Solid.Play;
+
+            if (!playing.NewValue)
+            {
+                stopPreview();
+                return;
+            }
+
+            if (previewTrack == null)
+            {
+                toggleLoading(true);
+                LoadComponentAsync(previewTrack = previewTrackManager.Get(beatmapSetInfo), onPreviewLoaded);
+            }
+            else
+                tryStartPreview();
+        }
+
+        private void stopPreview()
+        {
+            toggleLoading(false);
+            Playing.Value = false;
+            previewTrack?.Stop();
+        }
+
+        private void onPreviewLoaded(PreviewTrack loadedPreview)
+        {
+            // another async load might have completed before this one.
+            // if so, do not make any changes.
+            if (loadedPreview != previewTrack)
+                return;
+
+            AddInternal(loadedPreview);
+            toggleLoading(false);
+
+            loadedPreview.Stopped += () => Schedule(() => Playing.Value = false);
+
+            if (Playing.Value)
+                tryStartPreview();
+        }
+
+        private void tryStartPreview()
+        {
+            if (previewTrack?.Start() == false)
+                Playing.Value = false;
+        }
+
+        private void toggleLoading(bool loading)
+        {
+            Enabled.Value = !loading;
+            icon.FadeTo(loading ? 0 : 1, BeatmapCard.TRANSITION_DURATION, Easing.OutQuint);
+            loadingSpinner.State.Value = loading ? Visibility.Visible : Visibility.Hidden;
         }
     }
 }