Initial structure

osu.Game/Collections/CollectionManager.cs

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+// 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;
+using System.Collections.Generic;
+using System.IO;
+using System.Threading.Tasks;
+using osu.Framework.Logging;
+using osu.Framework.Platform;
+using osu.Game.Beatmaps;
+using osu.Game.IO.Legacy;
+
+namespace osu.Game.Collections
+{
+    public class CollectionManager
+    {
+        private const string import_from_stable_path = "collection.db";
+
+        private readonly BeatmapManager beatmaps;
+
+        public CollectionManager(BeatmapManager beatmaps)
+        {
+            this.beatmaps = beatmaps;
+        }
+
+        /// <summary>
+        /// Set a storage with access to an osu-stable install for import purposes.
+        /// </summary>
+        public Func<Storage> GetStableStorage { private get; set; }
+
+        /// <summary>
+        /// This is a temporary method and will likely be replaced by a full-fledged (and more correctly placed) migration process in the future.
+        /// </summary>
+        public Task ImportFromStableAsync()
+        {
+            var stable = GetStableStorage?.Invoke();
+
+            if (stable == null)
+            {
+                Logger.Log("No osu!stable installation available!", LoggingTarget.Information, LogLevel.Error);
+                return Task.CompletedTask;
+            }
+
+            if (!stable.ExistsDirectory(import_from_stable_path))
+            {
+                // This handles situations like when the user does not have a Skins folder
+                Logger.Log($"No {import_from_stable_path} folder available in osu!stable installation", LoggingTarget.Information, LogLevel.Error);
+                return Task.CompletedTask;
+            }
+
+            return Task.Run(async () => await Import(GetStableImportPaths(GetStableStorage()).Select(f => stable.GetFullPath(f)).ToArray()));
+        }
+
+        private List<BeatmapCollection> readCollection(Stream stream)
+        {
+            var result = new List<BeatmapCollection>();
+
+            using (var reader = new SerializationReader(stream))
+            {
+                reader.ReadInt32(); // Version
+
+                int collectionCount = reader.ReadInt32();
+                result.Capacity = collectionCount;
+
+                for (int i = 0; i < collectionCount; i++)
+                {
+                    var collection = new BeatmapCollection { Name = reader.ReadString() };
+
+                    int mapCount = reader.ReadInt32();
+                    collection.Beatmaps.Capacity = mapCount;
+
+                    for (int j = 0; j < mapCount; j++)
+                    {
+                        string checksum = reader.ReadString();
+
+                        var beatmap = beatmaps.QueryBeatmap(b => b.MD5Hash == checksum);
+                        if (beatmap != null)
+                            collection.Beatmaps.Add(beatmap);
+                    }
+                }
+            }
+
+            return result;
+        }
+    }
+
+    public class BeatmapCollection
+    {
+        public string Name;
+
+        public readonly List<BeatmapInfo> Beatmaps = new List<BeatmapInfo>();
+    }
+}