Add ability to import files from a stream.

osu.Game/Database/ArchiveModelManager.cs

@@ -212,6 +212,14 @@ namespace osu.Game.Database
             return import;
         }
 
+        /// <summary>
+        /// Import one <typeparamref name="TModel"/> from a <see cref="Stream"/>.
+        /// </summary>
+        /// <param name="stream">The stream to import files from.</param>
+        /// <param name="filename">The filename of the archive being imported.</param>
+        public async Task Import(Stream stream, string filename)
+            => await Import(new ZipArchiveReader(stream, filename)); // we need to keep around the filename as some model managers (namely SkinManager) use the archive name to populate skin info
+
         /// <summary>
         /// Fired when the user requests to view the resulting import.
         /// </summary>

osu.Game/Database/ICanAcceptFiles.cs

@@ -2,6 +2,7 @@
 // See the LICENCE file in the repository root for full licence text.
 
 using System.Collections.Generic;
+using System.IO;
 using System.Threading.Tasks;
 
 namespace osu.Game.Database
@@ -17,6 +18,14 @@ namespace osu.Game.Database
         /// <param name="paths">The files which should be imported.</param>
         Task Import(params string[] paths);
 
+        /// <summary>
+        /// Import the specified stream.
+        /// </summary>
+        /// <param name="stream">The stream to import files from.</param>
+        /// <param name="filename">The filename of the archive being imported.</param>
+        /// <returns></returns>
+        Task Import(Stream stream, string filename);
+
         /// <summary>
         /// An array of accepted file extensions (in the standard format of ".abc").
         /// </summary>

osu.Game/OsuGameBase.cs

@@ -395,6 +395,17 @@ namespace osu.Game
             }
         }
 
+        public async Task Import(Stream stream, string filename)
+        {
+            var extension = Path.GetExtension(filename)?.ToLowerInvariant();
+
+            foreach (var importer in fileImporters)
+            {
+                if (importer.HandledExtensions.Contains(extension))
+                    await importer.Import(stream, Path.GetFileNameWithoutExtension(filename));
+            }
+        }
+
         public IEnumerable<string> HandledExtensions => fileImporters.SelectMany(i => i.HandledExtensions);
 
         protected override void Dispose(bool isDisposing)

osu.Game/Screens/Edit/Setup/ResourcesSection.cs

@@ -99,6 +99,8 @@ namespace osu.Game.Screens.Edit.Setup
             return Task.CompletedTask;
         }
 
+        Task ICanAcceptFiles.Import(Stream stream, string filename) => Task.CompletedTask;
+
         protected override void LoadComplete()
         {
             base.LoadComplete();