// A guest login's clock. That is the whole difference between a guest and an account: it
// can do everything, until it can't, so what the console has to show is how long is left.
import { useEffect, useState } from 'react'

// fmtLeft says how long is left, in the roundest terms that are still honest.
export function fmtLeft(ms: number): string {
  const min = Math.floor(ms / 60000)
  if (min >= 120) return `${Math.floor(min / 60)} h ${min % 60} min`
  if (min >= 1) return `${min} min`
  return 'under a minute'
}

// useTimeLeft is the milliseconds until `until`, re-rendering the caller every 15 seconds so
// the number keeps up. 0 when there is no expiry, which is every normal account.
export function useTimeLeft(until?: string): number {
  const [, tick] = useState(0)
  const active = !!until
  useEffect(() => {
    if (!active) return
    const t = setInterval(() => tick((n) => n + 1), 15000)
    return () => clearInterval(t)
  }, [active])
  return until ? Math.max(0, new Date(until).getTime() - Date.now()) : 0
}