fix(jellyfin): honor AlbumIds filter on /Items

Feishin fetches an album's tracks with AlbumIds=<id>&IncludeItemTypes=Audio&Recursive=true, but the /Items handler never read the AlbumIds parameter, so the request degenerated into the entire library sorted by album: every track (with MediaSources, when requested) was counted and streamed for what should be one album's worth of songs — very slow on large libraries, and wrong results. Parse AlbumIds like GenreIds (comma-separated and repeated spellings, hex-decoded) and filter songs through a new filter.ByAlbumID helper, keeping the album_id column knowledge in the filter package.

server/filter/filters.go

@@ -189,6 +189,11 @@ func ByGenreID(genreIds []string) Sqlizer {
 	return genreTagFilter(Eq{"value": genreIds})
 }
 
+// ByAlbumID matches media files belonging to any of the given albums.
+func ByAlbumID(albumIds []string) Sqlizer {
+	return Eq{"album_id": albumIds}
+}
+
 // ArtistsByGenreID matches artists credited as album artist on an album with any of the given
 // genre tag ids. Non-correlated semi-join: the correlated EXISTS form rescans albums per artist row.
 func ArtistsByGenreID(genreIds []string) Sqlizer {

server/jellyfin/e2e/browsing_test.go

@@ -179,6 +179,27 @@ var _ = Describe("Browsing", func() {
 		})
 	})
 
+	// Feishin fetches an album's tracks with AlbumIds=<albumId>&IncludeItemTypes=Audio&Recursive=true.
+	Describe("album filtering (AlbumIds)", func() {
+		It("filters songs by AlbumIds", func() {
+			q := queryResult(get("/Items?IncludeItemTypes=Audio&Recursive=true&AlbumIds=" + enc(albumID("Abbey Road"))))
+			Expect(names(q.Items)).To(ConsistOf("Come Together", "Something"))
+			Expect(q.TotalRecordCount).To(Equal(2))
+		})
+
+		It("matches any of multiple comma-separated AlbumIds", func() {
+			q := queryResult(get("/Items?IncludeItemTypes=Audio&Recursive=true&AlbumIds=" + enc(albumID("Abbey Road")) + "," + enc(albumID("IV"))))
+			Expect(names(q.Items)).To(ConsistOf("Come Together", "Something", "Stairway To Heaven"))
+			Expect(q.TotalRecordCount).To(Equal(3))
+		})
+
+		It("returns nothing for an unknown album id", func() {
+			q := queryResult(get("/Items?IncludeItemTypes=Audio&Recursive=true&AlbumIds=" + enc("no-such-album")))
+			Expect(q.Items).To(BeEmpty())
+			Expect(q.TotalRecordCount).To(Equal(0))
+		})
+	})
+
 	// Finamp's genre screen sends ParentId=<libraryId> (scoping) plus GenreIds=<genreId>.
 	Describe("genre filtering (GenreIds)", func() {
 		lib1 := enc("1")

server/jellyfin/items.go

@@ -221,6 +221,7 @@ type itemsQuery struct {
 	artistId         string
 	contributingOnly bool
 	genreIds         []string
+	albumIds         []string
 }
 
 // parseItemsQuery also resolves the entity types (inferring them from the parent when
@@ -243,6 +244,8 @@ func (api *Router) parseItemsQuery(ctx context.Context, r *http.Request) itemsQu
 		parentId: dto.DecodeID(p.StringOr("parentid", "")),
 		// Finamp's genre screen sends ParentId=<libraryId> for scoping plus GenreIds for the genre.
 		genreIds: decodedQueryIDs(r, "genreids"),
+		// Feishin fetches an album's tracks with AlbumIds instead of ParentId.
+		albumIds: decodedQueryIDs(r, "albumids"),
 	}
 	// An artist's page filters by artist, not ParentId: Finamp sends ParentId=<libraryId> for scoping
 	// plus AlbumArtistIds/ArtistIds/contributingArtistIds for the artist.
@@ -528,6 +531,9 @@ func (api *Router) listSongs(ctx context.Context, opts model.QueryOptions, q ite
 	default:
 		filters = append(filters, notMissing)
 	}
+	if len(q.albumIds) > 0 {
+		filters = append(filters, filter.ByAlbumID(q.albumIds))
+	}
 	if len(q.genreIds) > 0 {
 		filters = append(filters, filter.ByGenreID(q.genreIds))
 	}