/** A page of the menu, as the command palette lists it. */
export interface MenuPage {
  label: string;
  to: string;
}

/** The words of a label, for telling whether two labels name one thing. */
const wordsOf = (value: string): string =>
  value
    .toLowerCase()
    .replace(/&/g, ' and ')
    .replace(/[^\p{L}\p{N}]+/gu, ' ')
    .trim();

/** A path without its query or hash, and without a trailing slash. */
const pathnameOf = (path: string): string =>
  path.split(/[?#]/)[0].replace(/\/+$/, '') || '/';

/**
 * The page a link in a reply opens, when it is one: its path is a page of
 * the menu and its words name that page ("Titles & meta" → /seo/titles).
 * The model also writes made-up routes, and real routes under an action's
 * words ("Confirm generation" → /ai-visibility/contents); those return
 * null and go back to it as a follow-up.
 *
 * @param {string} href - Where the link points, a plugin route.
 * @param {string} label - The words it was written as.
 * @param {MenuPage[]} pages - The pages of the menu.
 * @returns {string | null} The route to open, query kept, or null.
 */
export function pageLinkTarget(
  href: string,
  label: string,
  pages: MenuPage[]
): string | null {
  if (!href.startsWith('/')) return null;
  const words: string = wordsOf(label);
  if (words === '') return null;
  const page: MenuPage | undefined = pages.find(
    candidate => pathnameOf(candidate.to) === pathnameOf(href)
  );
  if (!page) return null;
  const named: string = wordsOf(page.label);

  return named !== '' && (words === named || words.includes(named))
    ? href
    : null;
}