feat(casting): extract reusable next-episode helpers

utils/casting/episodes.ts

@@ -0,0 +1,38 @@
+/**
+ * Episode-list helpers for the casting player and the autoplay watcher.
+ */
+
+import type { Api } from "@jellyfin/sdk";
+import type {
+  BaseItemDto,
+  UserDto,
+} from "@jellyfin/sdk/lib/generated-client/models";
+import { getTvShowsApi } from "@jellyfin/sdk/lib/utils/api";
+
+/** The episode following `currentId` in `episodes`, or null if none / not found. */
+export const findNextEpisode = (
+  episodes: BaseItemDto[],
+  currentId: string | null | undefined,
+): BaseItemDto | null => {
+  const index = episodes.findIndex((e) => e.Id === currentId);
+  if (index < 0 || index + 1 >= episodes.length) return null;
+  return episodes[index + 1];
+};
+
+/**
+ * Fetch every episode of the series that owns the current episode.
+ * Mirrors the call previously inlined in `useCastEpisodes`: no season filter,
+ * and the same `userId` quirk (undefined when an access token is present, else
+ * the empty string) so the request payload stays byte-identical.
+ */
+export const fetchSeriesEpisodes = async (
+  api: Api,
+  _user: UserDto,
+  seriesId: string,
+): Promise<BaseItemDto[]> => {
+  const res = await getTvShowsApi(api).getEpisodes({
+    seriesId,
+    userId: api.accessToken ? undefined : "",
+  });
+  return res.data.Items ?? [];
+};