add-shortening.js

/*
 * Create a shortening and return the shorturl if successful. Returns null if
 * the shorturl already exists and is not the requested shortening, or if the
 * longurl already has a random shortening and this shortening is also random.
 *
 * May throw other db errors.
 */
const addShortening = async (shortUrl, longUrl, isRandom) => {
  let addShorteningQuery = 'INSERT INTO shortenings (shorturl, longurl, israndom) VALUES ($1, $2, $3)';
  try {
    await pool.query(addShorteningQuery, [shortUrl, longUrl, isRandom]);
    return shortUrl;
  } catch (e) {
    if (e.constraint === 'shortenings_pkey') {
        // shortUrl is in the database, this is only okay if the longurl is identical
        return (await getLongUrl(shortUrl)) === longUrl ? shortUrl : null;
    } else if (e.constraint === 'random_shortening_constraint') {
        // can't add two random urls for one longurl
        return null;
    }
    // some other error
    throw e;
  }
}