fix: CursorPageIterator received items in revese order, add more te…

…sts for it

README.md

@@ -205,18 +205,21 @@ console.log(me);
 ## Pagination
 
 To simplify the process of paginating through the results, we provide a
-`PageIterator` class.
+`PageIterator` and `CursorPageIterator` classes.
 
 ```ts
 import { getPlaylistTracks, SpotifyClient } from "@soundify/web-api";
 import { PageIterator } from "@soundify/web-api/pagination";
 
-const client = new SpotifyClient("YOUR_ACCESS_TOKEN", {
-	waitForRateLimit: true,
-});
+const client = new SpotifyClient("YOUR_ACCESS_TOKEN");
 
 const playlistIter = new PageIterator(
-	(opts) => getPlaylistTracks(client, "37i9dQZEVXbMDoHDwVN2tF", opts),
+	(offset) => getPlaylistTracks(client, "37i9dQZEVXbMDoHDwVN2tF", {
+		// you can find the max limit for specific endpoint
+		// in spotify docs or in the jsdoc comments of this property
+		limit: 50,  
+		offset,
+	}),
 );
 
 // iterate over all tracks in the playlist
@@ -227,6 +230,41 @@ for await (const track of playlistIter) {
 // or collect all tracks into an array
 const allTracks = await playlistIter.collect();
 console.log(allTracks.length);
+
+// Want to get the last 100 items? No problem
+const lastHundredTracks = new PageIterator(
+	(offset) => getPlaylistTracks(
+		client, 
+		"37i9dQZEVXbMDoHDwVN2tF", 
+		{ limit: 50, offset }
+	),
+	{ initialOffset: -100 }, // this will work just as `Array.slice(-100)` 
+).collect();
+```
+
+```ts
+import { getFollowedArtists, SpotifyClient } from "@soundify/web-api";
+import { CursorPageIterator } from "@soundify/web-api/pagination";
+
+const client = new SpotifyClient("YOUR_ACCESS_TOKEN");
+
+// loop over all followed artists
+for await (const artist of new CursorPageIterator(
+	opts => getFollowedArtists(client, { limit: 50, after: opts.after })
+)) {
+	console.log(artist.name);
+}
+
+// or collect all followed artists into an array
+const artists = await new CursorPageIterator(
+	opts => getFollowedArtists(client, { limit: 50, after: opts.after })
+).collect();
+
+// get all followed artists starting from Radiohead
+const artists = await new CursorPageIterator(
+	opts => getFollowedArtists(client, { limit: 50, after: opts.after }),
+	{ initialAfter: "4Z8W4fKeB5YxbusRsdQVPb" } // let's start from Radiohead
+).collect();
 ```
 
 ## Other customizations

pagination.test.ts

@@ -128,3 +128,45 @@ Deno.test("CursorPageIterator: asyncIterator", async () => {
 		value: null,
 	});
 });
+
+Deno.test("CursorPageIterator: asyncIterator backwards", async () => {
+	const initialBefore = 30;
+	const cursorPageIterator = new CursorPageIterator((opts) => {
+		const limit = 20;
+
+		const beforeArtistIndex = mockArtists.findIndex((artist) =>
+			artist.id === opts.before
+		);
+		if (beforeArtistIndex === -1) {
+			throw new Error("Invalid cursor");
+		}
+
+		const lastIndex = beforeArtistIndex - limit - 1;
+		const hasPreviousPage = !(lastIndex < 0);
+
+		return Promise.resolve({
+			items: mockArtists.slice(
+				hasPreviousPage ? lastIndex : 0,
+				beforeArtistIndex,
+			),
+			next: hasPreviousPage ? "http://example.com" : null,
+			cursors: {
+				before: hasPreviousPage ? mockArtists.at(lastIndex)?.id : undefined,
+			},
+		});
+	}, { direction: "backward", initialBefore: initialBefore.toString() });
+
+	const iter = cursorPageIterator[Symbol.asyncIterator]();
+
+	for (let i = initialBefore - 1; i >= 0; i--) {
+		const result = await iter.next();
+		assertEquals(result, {
+			done: false,
+			value: mockArtists[i],
+		});
+	}
+	assertEquals(await iter.next(), {
+		done: true,
+		value: null,
+	});
+});

pagination.ts

@@ -115,7 +115,7 @@ export type CursorPageIteratorOptions<TDirection extends Direction> =
  * ```ts
  * // get the first 100 followed artists
  * const artists = await new CursorPageIterator(
- *   opts => getFollowedArtists(client, { limit: 50, after: opts.after})
+ *   opts => getFollowedArtists(client, { limit: 50, after: opts.after })
  * ).collect(100);
  * ```
  */
@@ -164,8 +164,14 @@ export class CursorPageIterator<
 				},
 			);
 
-			for (let i = 0; i < page.items.length; i++) {
-				yield page.items[i];
+			if (direction === "forward") {
+				for (let i = 0; i < page.items.length; i++) {
+					yield page.items[i];
+				}
+			} else {
+				for (let i = page.items.length - 1; i >= 0; i--) {
+					yield page.items[i];
+				}
 			}
 
 			if (!page.next) {