// atproto timestamp identifiers: 53 bits of microseconds and a 10-bit clock id, as sortable base32.

const ALPHABET = "234567abcdefghijklmnopqrstuvwxyz";
const CLOCK_ID = BigInt(Math.floor(Math.random() * 1024));

export const TID_PATTERN = /^[234567abcdefghij][234567abcdefghijklmnopqrstuvwxyz]{12}$/;

let last = 0;

export function tid(now = Date.now()): string {
  last = Math.max(now * 1000, last + 1);
  let n = (BigInt(last) << 10n) | CLOCK_ID;
  let out = "";
  for (let i = 0; i < 13; i++, n >>= 5n) out = ALPHABET[Number(n & 31n)] + out;
  return out;
}