// Job ids are ULIDs: a 48-bit millisecond timestamp followed by 80 bits of
// randomness, Crockford base32-encoded to a fixed 26 chars. Two properties earn
// their keep on the /jobs screen:
//   1. Lexicographic order == chronological order, so the on-disk `.jobs`
//      directory can be sorted and paginated by filename alone.
//   2. The timestamp is recoverable from the id itself (jobIdTime), so listing a
//      page never has to stat/read every file to know when a job ran.
// Hand-rolled to avoid a dependency; strict within-millisecond monotonicity is
// not needed here (tie-break order between jobs sharing a ms is irrelevant).

// Crockford base32 (no I, L, O, U).
const ENCODING = "0123456789ABCDEFGHJKMNPQRSTVWXYZ";
const ENCODING_LEN = ENCODING.length; // 32
const TIME_LEN = 10; // 48 bits -> 10 base32 chars
const RANDOM_LEN = 16; // 80 bits -> 16 base32 chars

function encodeTime(now: number): string {
  let str = "";
  for (let i = TIME_LEN; i > 0; i--) {
    const mod = now % ENCODING_LEN;
    str = ENCODING[mod] + str;
    now = Math.floor(now / ENCODING_LEN);
  }
  return str;
}

function encodeRandom(): string {
  let str = "";
  for (let i = RANDOM_LEN; i > 0; i--) {
    str += ENCODING[Math.floor(Math.random() * ENCODING_LEN)];
  }
  return str;
}

export function ulid(now: number = Date.now()): string {
  return encodeTime(now) + encodeRandom();
}

// Decode the millisecond timestamp carried by a job id. Handles both id schemes
// so on-disk logs written before the ULID switch still sort/paginate correctly:
//   - Legacy `Date.now().toString(36)-<rand>` (contains a "-").
//   - ULID (26 chars, no "-"): the first 10 chars are the base32 timestamp.
// Returns 0 when the id is unparseable; callers fall back to the file mtime.
export function jobIdTime(id: string): number {
  const dash = id.indexOf("-");
  if (dash >= 0) {
    const t = parseInt(id.slice(0, dash), 36);
    return Number.isFinite(t) ? t : 0;
  }
  if (id.length < TIME_LEN) return 0;
  let time = 0;
  for (let i = 0; i < TIME_LEN; i++) {
    const idx = ENCODING.indexOf(id[i].toUpperCase());
    if (idx < 0) return 0;
    time = time * ENCODING_LEN + idx;
  }
  return time;
}