Function parseCronExpression

src/utils/cron.ts:83–107

(expr: string)

 * Returns null if invalid or unsupported syntax.
 */
export function parseCronExpression(expr: string): CronFields | null {
  // Defensive against non-string input: ExecuteExtraTool passes raw params
  // through to validateInput without re-running the target tool's schema, so
  // a wrong field name (e.g. 'schedule' instead of 'cron') surfaces here as
  // undefined. Without this guard, .trim() below throws "undefined is not an
  // object" — every CronCreate call from ExecuteExtraTool fails identically.
  if (typeof expr !== 'string') return null
  const parts = expr.trim().split(/\s+/)
  if (parts.length !== 5) return null

  const expanded: number[][] = []
  for (let i = 0; i < 5; i++) {
    const result = expandField(parts[i]!, FIELD_RANGES[i]!)
    if (!result) return null
    expanded.push(result)
  }

  return {
    minute: expanded[0]!,
    hour: expanded[1]!,
    dayOfMonth: expanded[2]!,
    month: expanded[3]!,
    dayOfWeek: expanded[4]!,
  }
}

/**
 * Compute the next Date strictly after `from` that matches the cron fields,