AlbumQuery and ArtistQuery types on MusicService

src/music_service.ts

@@ -38,31 +38,35 @@ export type Album = {
 };
 
 export type Paging = {
-  _index?: number;
-  _count?: number;
+  _index: number;
+  _count: number;
 };
 
 export type Result<T> = {
-  results: T[],
-  total: number
-}
+  results: T[];
+  total: number;
+};
 
 export function slice2<T>({ _index, _count }: Paging) {
-  const i0 = _index || 0;
-  const i1 = _count ? i0 + _count : undefined;
-  return (things: T[]): [T[], number] => [things.slice(i0, i1), things.length]
+  return (things: T[]): [T[], number] => [
+    things.slice(_index, _index + _count),
+    things.length,
+  ];
 }
 
-export const asResult = <T>([results, total]: [T[], number]) => ({ results, total })
+export const asResult = <T>([results, total]: [T[], number]) => ({
+  results,
+  total,
+});
+
+export type ArtistQuery = Paging
+
+export type AlbumQuery = Paging & {
+  artistId?: string
+}
 
 export interface MusicLibrary {
-  artists({ _index, _count }: Paging): Promise<Result<Artist>>;
+  artists(q: ArtistQuery): Promise<Result<Artist>>;
   artist(id: string): Artist;
-  albums({
-    artistId,
-    _index,
-    _count,
-  }: {
-    artistId?: string;
-  } & Paging): Promise<Result<Album>>;
+  albums(q: AlbumQuery): Promise<Result<Album>>;
 }