Add SeasonalBackgroundLoader and SeasonalBackground

osu.Game/Graphics/Backgrounds/SeasonalBackgroundLoader.cs

@@ -0,0 +1,68 @@
+// 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;
+using JetBrains.Annotations;
+using osu.Framework.Allocation;
+using osu.Framework.Graphics;
+using osu.Framework.Graphics.Textures;
+using osu.Framework.Utils;
+using osu.Game.Online.API;
+using osu.Game.Online.API.Requests;
+using osu.Game.Online.API.Requests.Responses;
+
+namespace osu.Game.Graphics.Backgrounds
+{
+    [LongRunningLoad]
+    public class SeasonalBackgroundLoader : Component
+    {
+        private List<APISeasonalBackground> backgrounds = new List<APISeasonalBackground>();
+        private int current;
+
+        [BackgroundDependencyLoader]
+        private void load(IAPIProvider api)
+        {
+            var request = new GetSeasonalBackgroundsRequest();
+            request.Success += response =>
+            {
+                backgrounds = response.Backgrounds ?? backgrounds;
+                current = RNG.Next(0, backgrounds.Count);
+            };
+
+            api.PerformAsync(request);
+        }
+
+        public SeasonalBackground LoadBackground(string fallbackTextureName)
+        {
+            string url = null;
+
+            if (backgrounds.Any())
+            {
+                current = (current + 1) % backgrounds.Count;
+                url = backgrounds[current].Url;
+            }
+
+            return new SeasonalBackground(url, fallbackTextureName);
+        }
+    }
+
+    [LongRunningLoad]
+    public class SeasonalBackground : Background
+    {
+        private readonly string url;
+        private readonly string fallbackTextureName;
+
+        public SeasonalBackground([CanBeNull] string url, string fallbackTextureName = @"Backgrounds/bg1")
+        {
+            this.url = url;
+            this.fallbackTextureName = fallbackTextureName;
+        }
+
+        [BackgroundDependencyLoader]
+        private void load(LargeTextureStore textures)
+        {
+            Sprite.Texture = textures.Get(url) ?? textures.Get(fallbackTextureName);
+        }
+    }
+}