import { monotonicFactory } from "ulid";

const ULID_REGEX = /^[0-7][0-9A-HJKMNP-TV-Z]{25}$/;

// Monotonic factory: guarantees that successive calls produce ULIDs that sort
// in creation order even within the same millisecond. This is important for
// tiebreakers that rely on ULID ordering (e.g. reverse-chronological lists).
const monotonicUlid = monotonicFactory();

/** Generate a monotonic ULID. */
export function createUlid(): string {
  return monotonicUlid();
}

/** Validate a ULID string. */
export function isUlid(value: string): boolean {
  return ULID_REGEX.test(value);
}

/**
 * Assert a value is a ULID, throwing a clear error otherwise.
 * Used by the server to reject malformed IDs at the boundary.
 */
export function assertUlid(value: string): void {
  if (!isUlid(value)) {
    throw new Error(`Invalid ULID: ${value}`);
  }
}