fix: enhance playlist path normalization for cross-library support

Signed-off-by: Deluan <deluan@navidrome.org>

core/playlists.go

@@ -233,7 +233,9 @@ func normalizePathForComparison(path string) string {
 	return strings.ToLower(norm.NFC.String(path))
 }
 
-// TODO This won't work for multiple libraries
+// normalizePaths converts playlist file paths to library-relative paths.
+// For relative paths, it resolves them to absolute paths first, then determines which
+// library they belong to. This allows playlists to reference files across library boundaries.
 func (s *playlists) normalizePaths(ctx context.Context, pls *model.Playlist, folder *model.Folder, lines []string) ([]string, error) {
 	libRegex, err := s.compileLibraryPaths(ctx)
 	if err != nil {
@@ -246,15 +248,21 @@ func (s *playlists) normalizePaths(ctx context.Context, pls *model.Playlist, fol
 		var filePath string
 
 		if folder != nil && !filepath.IsAbs(line) {
-			// For relative paths, resolve them to absolute first
+			// Two-step resolution for relative paths:
+			// 1. Resolve relative path to absolute path based on playlist location
+			//    Example: playlist at /music/playlists/test.m3u with line "../songs/abc.mp3"
+			//             resolves to /music/songs/abc.mp3
 			filePath = filepath.Join(folder.AbsolutePath(), line)
 			filePath = filepath.Clean(filePath)
-			// Try to find which library this resolved path belongs to
+
+			// 2. Determine which library this absolute path belongs to using regex matching
+			//    This allows playlists to reference files in different libraries
 			if libPath = libRegex.FindString(filePath); libPath == "" {
-				// If not found in regex, fallback to the playlist's library
+				// If regex doesn't match any library, check if it's in the playlist's library
 				libPath = folder.LibraryPath
-				// Verify the file is actually in a library by checking if we can get a relative path
-				if _, err := filepath.Rel(libPath, filePath); err != nil {
+				// Verify the file is actually in this library (reject paths with ..)
+				rel, err := filepath.Rel(libPath, filePath)
+				if err != nil || strings.HasPrefix(rel, "..") {
 					log.Warn(ctx, "Path in playlist not found in any library", "path", line, "line", idx)
 					continue
 				}

core/playlists_test.go

@@ -117,7 +117,7 @@ var _ = Describe("Playlists", func() {
 			var tmpDir, plsDir, songsDir string
 
 			BeforeEach(func() {
-				// Create temp directory structure once
+				// Create temp directory structure
 				tmpDir = GinkgoT().TempDir()
 				plsDir = tmpDir + "/playlists"
 				songsDir = tmpDir + "/songs"
@@ -160,8 +160,66 @@ var _ = Describe("Playlists", func() {
 				pls, err := ps.ImportFile(ctx, plsFolder, "test.m3u")
 				Expect(err).ToNot(HaveOccurred())
 				Expect(pls.Tracks).To(HaveLen(2))
+				Expect(pls.Tracks[0].Path).To(Equal("abc.mp3")) // From songsDir library
+				Expect(pls.Tracks[1].Path).To(Equal("def.mp3")) // From plsDir library
+			})
+
+			It("ignores paths that point outside all libraries", func() {
+				// Create a temporary playlist file with path outside libraries
+				plsContent := "#PLAYLIST:Outside Test\n../../outside.mp3\nabc.mp3"
+				plsFile := plsDir + "/test.m3u"
+				Expect(os.WriteFile(plsFile, []byte(plsContent), 0600)).To(Succeed())
+
+				plsFolder := &model.Folder{
+					ID:          "2",
+					LibraryID:   2,
+					LibraryPath: plsDir,
+					Path:        "",
+					Name:        "",
+				}
+
+				pls, err := ps.ImportFile(ctx, plsFolder, "test.m3u")
+				Expect(err).ToNot(HaveOccurred())
+				// Should only find abc.mp3, not outside.mp3
+				Expect(pls.Tracks).To(HaveLen(1))
 				Expect(pls.Tracks[0].Path).To(Equal("abc.mp3"))
-				Expect(pls.Tracks[1].Path).To(Equal("def.mp3"))
+			})
+
+			It("handles relative paths with multiple '../' components", func() {
+				// Create a nested structure: tmpDir/playlists/subfolder/test.m3u
+				subFolder := plsDir + "/subfolder"
+				Expect(os.Mkdir(subFolder, 0755)).To(Succeed())
+
+				// Create the media file in the subfolder directory
+				// The mock will return it as "def.mp3" relative to plsDir
+				ds.MockedMediaFile = &mockedMediaFileFromListRepo{
+					data: []string{
+						"abc.mp3", // From songsDir library
+						"def.mp3", // From plsDir library root
+					},
+				}
+
+				// From subfolder, ../../songs/abc.mp3 should resolve to songs library
+				// ../def.mp3 should resolve to plsDir/def.mp3
+				plsContent := "#PLAYLIST:Nested Test\n../../songs/abc.mp3\n../def.mp3"
+				plsFile := subFolder + "/test.m3u"
+				Expect(os.WriteFile(plsFile, []byte(plsContent), 0600)).To(Succeed())
+
+				// The folder: AbsolutePath = LibraryPath + Path + Name
+				// So for /playlists/subfolder: LibraryPath=/playlists, Path="", Name="subfolder"
+				plsFolder := &model.Folder{
+					ID:          "2",
+					LibraryID:   2,
+					LibraryPath: plsDir,
+					Path:        "",          // Empty because subfolder is directly under library root
+					Name:        "subfolder", // The folder name
+				}
+
+				pls, err := ps.ImportFile(ctx, plsFolder, "test.m3u")
+				Expect(err).ToNot(HaveOccurred())
+				Expect(pls.Tracks).To(HaveLen(2))
+				Expect(pls.Tracks[0].Path).To(Equal("abc.mp3")) // From songsDir library
+				Expect(pls.Tracks[1].Path).To(Equal("def.mp3")) // From plsDir library root
 			})
 		})
 	})