// Convert a duration in seconds to a humanised string like "2h 13m" or "45m 12s".
// Returns "?" for non-finite or negative input so the UI never renders NaN/empty.
export function humaniseUptime(seconds: number | null | undefined): string {
  if (seconds == null || !Number.isFinite(seconds) || seconds < 0) return '?'

  const s = Math.floor(seconds)
  const days = Math.floor(s / 86400)
  const hours = Math.floor((s % 86400) / 3600)
  const minutes = Math.floor((s % 3600) / 60)
  const secs = s % 60

  if (days > 0) return `${days}d ${hours}h`
  if (hours > 0) return `${hours}h ${minutes}m`
  if (minutes > 0) return `${minutes}m ${secs}s`
  return `${secs}s`
}