Fix importing archives which are nested in a single folder within a zip

osu.Game.Tests/Beatmaps/IO/ImportBeatmapTest.cs

@@ -15,7 +15,10 @@
 using osu.Game.Beatmaps;
 using osu.Game.IO;
 using osu.Game.Tests.Resources;
+using SharpCompress.Archives;
 using SharpCompress.Archives.Zip;
+using SharpCompress.Common;
+using SharpCompress.Writers.Zip;
 
 namespace osu.Game.Tests.Beatmaps.IO
 {
@@ -135,7 +138,7 @@ public async Task TestRollbackOnFailure()
                     using (var zip = ZipArchive.Open(brokenOsz))
                     {
                         zip.AddEntry("broken.osu", brokenOsu, false);
-                        zip.SaveTo(outStream, SharpCompress.Common.CompressionType.Deflate);
+                        zip.SaveTo(outStream, CompressionType.Deflate);
                     }
 
                     // this will trigger purging of the existing beatmap (online set id match) but should rollback due to broken osu.
@@ -366,6 +369,51 @@ public async Task TestImportWhenFileOpen()
             }
         }
 
+        [Test]
+        public async Task TestImportNestedStructure()
+        {
+            using (HeadlessGameHost host = new CleanRunHeadlessGameHost("TestImportNestedStructure"))
+            {
+                try
+                {
+                    var osu = loadOsu(host);
+
+                    var temp = TestResources.GetTestBeatmapForImport();
+
+                    string extractedFolder = $"{temp}_extracted";
+                    string subfolder = Path.Combine(extractedFolder, "subfolder");
+
+                    Directory.CreateDirectory(subfolder);
+
+                    try
+                    {
+                        using (var zip = ZipArchive.Open(temp))
+                            zip.WriteToDirectory(subfolder);
+
+                        using (var zip = ZipArchive.Create())
+                        {
+                            zip.AddAllFromDirectory(extractedFolder);
+                            zip.SaveTo(temp, new ZipWriterOptions(CompressionType.Deflate));
+                        }
+
+                        var imported = await osu.Dependencies.Get<BeatmapManager>().Import(temp);
+
+                        ensureLoaded(osu);
+
+                        Assert.IsFalse(imported.Files.Any(f => f.Filename.Contains("subfolder")), "Files contain common subfolder");
+                    }
+                    finally
+                    {
+                        Directory.Delete(extractedFolder, true);
+                    }
+                }
+                finally
+                {
+                    host.Exit();
+                }
+            }
+        }
+
         public static async Task<BeatmapSetInfo> LoadOszIntoOsu(OsuGameBase osu, string path = null)
         {
             var temp = path ?? TestResources.GetTestBeatmapForImport();

osu.Game/Database/ArchiveModelManager.cs

@@ -11,6 +11,7 @@
 using Microsoft.EntityFrameworkCore;
 using osu.Framework;
 using osu.Framework.Extensions;
+using osu.Framework.Extensions.IEnumerableExtensions;
 using osu.Framework.IO.File;
 using osu.Framework.Logging;
 using osu.Framework.Platform;
@@ -481,12 +482,16 @@ private List<TFileModel> createFileInfos(ArchiveReader reader, FileStore files)
         {
             var fileInfos = new List<TFileModel>();
 
+            string prefix = reader.Filenames.GetCommonPrefix();
+            if (!(prefix.EndsWith("/") || prefix.EndsWith("\\")))
+                prefix = string.Empty;
+
             // import files to manager
             foreach (string file in reader.Filenames)
                 using (Stream s = reader.GetStream(file))
                     fileInfos.Add(new TFileModel
                     {
-                        Filename = FileSafety.PathStandardise(file),
+                        Filename = FileSafety.PathStandardise(file.Substring(prefix.Length)),
                         FileInfo = files.Add(s)
                     });