// The feed's live YouTube search in the address bar (`?page=feed&yt=lofi&ytn=40`), so a search is a
// link and survives a reload. Only the term and how many results to gather: which source answers is
// the instance's setting at the moment the link opens (an admin may have switched it since), and that
// decides whether the search runs by itself (the free page scrape) or waits for a press (an API
// search spends 100 quota units, so nobody's reload or bookmark spends them unasked).

const YT_SEARCH_KEY = "yt";
const YT_COUNT_KEY = "ytn";
export const YT_SEARCH_KEYS = [YT_SEARCH_KEY, YT_COUNT_KEY] as const;

/** How many live-search results one fetch gathers; the first is the default, left out of the URL. */
export const YT_COUNTS = [20, 40, 60, 100] as const;
export const DEFAULT_YT_COUNT = YT_COUNTS[0];

/** The search a URL names, or null: a blank term names none (the search box never sends one). */
export function ytSearchFrom(params: URLSearchParams): string | null {
  return params.get(YT_SEARCH_KEY)?.trim() || null;
}

/** The result count a URL names; anything but one of the offered counts is the default. */
export function ytCountFrom(params: URLSearchParams): number {
  const n = Number(params.get(YT_COUNT_KEY));
  return (YT_COUNTS as readonly number[]).includes(n) ? n : DEFAULT_YT_COUNT;
}

/** The URL updates for a search (null = none): a default count clears its key. */
export function ytSearchParams(term: string | null, count: number): Record<string, string | null> {
  return {
    [YT_SEARCH_KEY]: term,
    [YT_COUNT_KEY]: term != null && count !== DEFAULT_YT_COUNT ? String(count) : null,
  };
}