Function expandField

src/utils/cron.ts:31–77

(field: string, range: FieldRange)

// Supports: wildcard, N, star-slash-N (step), N-M (range), and comma-lists.
// Returns null if invalid.
function expandField(field: string, range: FieldRange): number[] | null {
  const { min, max } = range
  const out = new Set<number>()

  for (const part of field.split(',')) {
    // wildcard or star-slash-N
    const stepMatch = part.match(/^\*(?:\/(\d+))?$/)
    if (stepMatch) {
      const step = stepMatch[1] ? parseInt(stepMatch[1], 10) : 1
      if (step < 1) return null
      for (let i = min; i <= max; i += step) out.add(i)
      continue
    }

    // N-M or N-M/S
    const rangeMatch = part.match(/^(\d+)-(\d+)(?:\/(\d+))?$/)
    if (rangeMatch) {
      const lo = parseInt(rangeMatch[1]!, 10)
      const hi = parseInt(rangeMatch[2]!, 10)
      const step = rangeMatch[3] ? parseInt(rangeMatch[3], 10) : 1
      // dayOfWeek: accept 7 as Sunday alias in ranges (e.g. 5-7 = Fri,Sat,Sun → [5,6,0])
      const isDow = min === 0 && max === 6
      const effMax = isDow ? 7 : max
      if (lo > hi || step < 1 || lo < min || hi > effMax) return null
      for (let i = lo; i <= hi; i += step) {
        out.add(isDow && i === 7 ? 0 : i)
      }
      continue
    }

    // plain N
    const singleMatch = part.match(/^\d+$/)
    if (singleMatch) {
      let n = parseInt(part, 10)
      // dayOfWeek: accept 7 as Sunday alias → 0
      if (min === 0 && max === 6 && n === 7) n = 0
      if (n < min || n > max) return null
      out.add(n)
      continue
    }

    return null
  }

  if (out.size === 0) return null
  return Array.from(out).sort((a, b) => a - b)
}

/**
 * Parse a 5-field cron expression into expanded number arrays.