support "backdrop" files as local movie fanart fallback

CHANGELOG.md

@@ -32,6 +32,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 - Add chapter `title` to filler expression
   - This can be used to include or exclude chapters with specific (case-insensitive) titles
   - E.g. `title == 'here'`, `title != 'not here'`, `title like '%here%'`
+- Local movie libraries: load fanart from `backdrop` files (created by Jellyfin)
 
 ### Changed
 - Disable automatic artwork database cleanup

ErsatzTV.Scanner.Tests/Core/Metadata/MovieFolderScannerTests.cs

@@ -511,6 +511,60 @@ public class MovieFolderScannerTests
             await _imageCache.Received(1).CopyArtworkToCache(fanArtPath, ArtworkKind.FanArt);
         }
 
+        [Test]
+        public async Task NewMovie_Statistics_And_FallbackMetadata_And_FanArt_Backdrop(
+            [ValueSource(typeof(LocalFolderScanner), nameof(LocalFolderScanner.VideoFileExtensions))]
+            string videoExtension,
+            [ValueSource(typeof(LocalFolderScanner), nameof(LocalFolderScanner.ImageFileExtensions))]
+            string imageExtension)
+        {
+            string moviePath = Path.Combine(
+                FakeRoot,
+                Path.Combine("Movie (2020)", $"Movie (2020){videoExtension}"));
+
+            string fanArtPath = Path.Combine(
+                Path.GetDirectoryName(moviePath) ?? string.Empty,
+                $"backdrop.{imageExtension}");
+
+            MovieFolderScanner service = GetService(
+                new FakeFileEntry(moviePath) { LastWriteTime = DateTime.Now },
+                new FakeFileEntry(fanArtPath) { LastWriteTime = DateTime.Now }
+            );
+            var libraryPath = new LibraryPath
+                { Id = 1, Path = FakeRoot, LibraryFolders = new List<LibraryFolder>() };
+
+            Either<BaseError, Unit> result = await service.ScanFolder(
+                libraryPath,
+                FFmpegPath,
+                FFprobePath,
+                0,
+                1,
+                CancellationToken.None);
+
+            result.IsRight.ShouldBeTrue();
+
+            await _movieRepository.Received(1).GetOrAdd(
+                Arg.Any<LibraryPath>(),
+                Arg.Any<LibraryFolder>(),
+                Arg.Any<string>(),
+                Arg.Any<CancellationToken>());
+            await _movieRepository.Received(1).GetOrAdd(
+                libraryPath,
+                Arg.Any<LibraryFolder>(),
+                moviePath,
+                Arg.Any<CancellationToken>());
+
+            await _localStatisticsProvider.Received(1).RefreshStatistics(
+                FFmpegPath,
+                FFprobePath,
+                Arg.Is<Movie>(i => i.MediaVersions.Head().MediaFiles.Head().Path == moviePath));
+
+            await _localMetadataProvider.Received(1).RefreshFallbackMetadata(
+                Arg.Is<Movie>(i => i.MediaVersions.Head().MediaFiles.Head().Path == moviePath));
+
+            await _imageCache.Received(1).CopyArtworkToCache(fanArtPath, ArtworkKind.FanArt);
+        }
+
         [Test]
         public async Task NewMovie_Statistics_And_FallbackMetadata_And_MovieNameFanArt(
             [ValueSource(typeof(LocalFolderScanner), nameof(LocalFolderScanner.VideoFileExtensions))]

ErsatzTV.Scanner/Core/Metadata/MovieFolderScanner.cs

@@ -381,26 +381,22 @@ public class MovieFolderScanner : LocalFolderScanner, IMovieFolderScanner
 
     private Option<string> LocateArtwork(Movie movie, ArtworkKind artworkKind)
     {
-        string segment = artworkKind switch
-        {
-            ArtworkKind.Poster => "poster",
-            ArtworkKind.FanArt => "fanart",
-            _ => throw new ArgumentOutOfRangeException(nameof(artworkKind))
-        };
-
         string path = movie.MediaVersions.Head().MediaFiles.Head().Path;
+        string fileName = Path.GetFileNameWithoutExtension(path);
         string folder = Path.GetDirectoryName(path) ?? string.Empty;
-        IEnumerable<string> possibleMoviePosters = ImageFileExtensions.Collect(ext =>
-                new[] { $"{segment}.{ext}", Path.GetFileNameWithoutExtension(path) + $"-{segment}.{ext}" })
-            .Map(f => Path.Combine(folder, f));
-        Option<string> result = possibleMoviePosters.Filter(p => _fileSystem.File.Exists(p)).HeadOrNone();
-        if (result.IsNone && artworkKind == ArtworkKind.Poster)
+
+        string[] segments = artworkKind switch
         {
-            IEnumerable<string> possibleFolderPosters = ImageFileExtensions.Collect(ext => new[] { $"folder.{ext}" })
-                .Map(f => Path.Combine(folder, f));
-            result = possibleFolderPosters.Filter(p => _fileSystem.File.Exists(p)).HeadOrNone();
-        }
+            ArtworkKind.Poster => ["poster", $"{fileName}-poster", "folder"],
+            ArtworkKind.FanArt => ["fanart", $"{fileName}-fanart", "backdrop"],
+            _ => throw new ArgumentOutOfRangeException(nameof(artworkKind))
+        };
 
-        return result;
+        return ImageFileExtensions
+            .Map(ext => segments.Map(segment => $"{segment}.{ext}"))
+            .Flatten()
+            .Map(f => Path.Combine(folder, f))
+            .Filter(s => _fileSystem.File.Exists(s))
+            .HeadOrNone();
     }
 }