// Fetches a chapter's raw text for building a study (the free Bible source). The Reader's "Save for
// offline" downloads go through the same address, so a saved book builds a study with no connection.
// Failures say what's wrong and what to do, instead of a generic error.
export async function fetchStudyChapter(translation, bookAbbrev, chapter, { signal } = {}) {
  const code = translation === 'NET' ? 'eng_net' : (translation || 'BSB');
  let res;
  try {
    res = await fetch(`https://bible.helloao.org/api/${code}/${bookAbbrev}/${chapter}.json`, { signal });
  } catch (err) {
    if (err?.name === 'AbortError') throw err;
    const offline = typeof navigator !== 'undefined' && navigator.onLine === false;
    throw new Error(offline
      ? "You're offline and this chapter isn't saved on this device. In the Reader, use Save for offline while connected."
      : 'Could not reach the Bible text. Check your connection and try again.', { cause: err });
  }
  if (res.status === 503) throw new Error("You're offline and this chapter isn't saved on this device. In the Reader, use Save for offline while connected.");
  if (!res.ok) throw new Error('Unable to load chapter.');
  return res.json();
}