import { EMPTY, Observable, expand, map, of, takeLast } from 'rxjs';
import { CursorPage } from '../../app/core/services/saas-platform.service';

export function findCursorPageItem<T extends { id: string }>(
  loadPage: (cursor: string) => Observable<CursorPage<T>>,
  id: string,
): Observable<T | null> {
  const target = id.trim();
  if (!target) return of(null);
  return loadPage('').pipe(
    expand((page) => (
      page.items.some((item) => item.id === target) || !page.nextCursor
        ? EMPTY
        : loadPage(page.nextCursor)
    )),
    takeLast(1),
    map((page) => page.items.find((item) => item.id === target) ?? null),
  );
}