/**
 * Tooling helpers for translation resources. Used by the repo-level
 * `pnpm i18n:check` script and its tests: every key must exist in every
 * language, in both directions.
 */

type TranslationTree = { [key: string]: string | TranslationTree };

/** Flattens {a:{b:"x"}} to ["a.b"]. */
export function translationKeys(tree: TranslationTree, prefix = ''): string[] {
  return Object.entries(tree).flatMap(([key, value]) => {
    const path = prefix ? `${prefix}.${key}` : key;
    return typeof value === 'string' ? [path] : translationKeys(value, path);
  });
}

/** Keys present in `reference` but missing in `candidate`. */
export function missingTranslationKeys(
  reference: TranslationTree,
  candidate: TranslationTree,
): string[] {
  const have = new Set(translationKeys(candidate));
  return translationKeys(reference).filter((key) => !have.has(key));
}