Implement beatmap ruleset selector

osu.Game/Overlays/BeatmapSet/BeatmapRulesetSelector.cs

@@ -0,0 +1,50 @@
+// 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 osu.Framework.Graphics;
+using osu.Framework.Graphics.Containers;
+using osu.Framework.Graphics.UserInterface;
+using osu.Game.Beatmaps;
+using osu.Game.Rulesets;
+using osuTK;
+using System.Linq;
+
+namespace osu.Game.Overlays.BeatmapSet
+{
+    public class BeatmapRulesetSelector : RulesetSelector
+    {
+        private BeatmapSetInfo beatmapSet;
+
+        public BeatmapSetInfo BeatmapSet
+        {
+            get => beatmapSet;
+            set
+            {
+                if (value == beatmapSet)
+                    return;
+
+                beatmapSet = value;
+
+                foreach (BeatmapRulesetTabItem tab in TabContainer.TabItems)
+                    tab.SetBeatmaps(beatmapSet?.Beatmaps.FindAll(b => b.Ruleset.Equals(tab.Value)));
+
+                var firstRuleset = beatmapSet?.Beatmaps.OrderBy(b => b.Ruleset.ID).FirstOrDefault()?.Ruleset;
+                SelectTab(TabContainer.TabItems.FirstOrDefault(t => t.Value.Equals(firstRuleset)));
+            }
+        }
+
+        public BeatmapRulesetSelector()
+        {
+            AutoSizeAxes = Axes.Both;
+            TabContainer.Spacing = new Vector2(10, 0);
+        }
+
+        protected override TabItem<RulesetInfo> CreateTabItem(RulesetInfo value) => new BeatmapRulesetTabItem(value);
+
+        protected override TabFillFlowContainer CreateTabFlow() => new TabFillFlowContainer
+        {
+            Direction = FillDirection.Horizontal,
+            AutoSizeAxes = Axes.Both,
+        };
+    }
+}