import crypto from 'node:crypto';

const DAY = new Intl.DateTimeFormat('en-CA', { timeZone: 'Europe/Berlin', year: 'numeric', month: '2-digit', day: '2-digit' });

// Tagessalz nur im RAM; neu erzeugt, sobald sich der Kalendertag in Europe/Berlin ändert.
export function createSalt({ now = Date.now, random = () => crypto.randomBytes(32) } = {}) {
  let day = null;
  let salt = null;
  const current = () => {
    const d = DAY.format(now());
    if (d !== day) { day = d; salt = random(); }
    return salt;
  };
  const hmac = (s) => crypto.createHmac('sha256', current()).update(s).digest('hex');
  return {
    visitorId: (site, ip, ua) => hmac(`${site}|${ip}|${ua}`).slice(0, 16),
    rateKey: (site, ip) => hmac(`${site}|${ip}`),
  };
}