实现数据库级联删除

internal/repository/library.go

@@ -78,8 +78,41 @@ func (r *LibraryRepository) UpdatePath(id int, path string) error {
 }
 
 func (r *LibraryRepository) Delete(id int) error {
-	_, err := r.db.Exec("DELETE FROM libraries WHERE id = ?", id)
-	return err
+	tx, err := r.db.Begin()
+	if err != nil {
+		return err
+	}
+	defer tx.Rollback()
+
+	// Delete the library — CASCADE removes media_files and songs automatically
+	_, err = tx.Exec("DELETE FROM libraries WHERE id = ?", id)
+	if err != nil {
+		return err
+	}
+
+	// Clean up orphan albums (no songs reference them)
+	_, err = tx.Exec(`
+		DELETE FROM albums WHERE id NOT IN (
+			SELECT DISTINCT album_id FROM songs WHERE album_id IS NOT NULL
+		)
+	`)
+	if err != nil {
+		return err
+	}
+
+	// Clean up orphan artists (no songs and no albums reference them)
+	_, err = tx.Exec(`
+		DELETE FROM artists WHERE id NOT IN (
+			SELECT DISTINCT artist_id FROM songs WHERE artist_id IS NOT NULL
+			UNION
+			SELECT DISTINCT artist_id FROM albums WHERE artist_id IS NOT NULL
+		)
+	`)
+	if err != nil {
+		return err
+	}
+
+	return tx.Commit()
 }
 
 func (r *LibraryRepository) GetSongsByLibraryWithDetails(libraryID int) ([]SongDetail, error) {