metamask-extension/ui/app/pages/swaps/countdown-timer/countdown-timer.js

import React, { useState, useEffect, useContext, useRef } from 'react'
import PropTypes from 'prop-types'
import classnames from 'classnames'
import { Duration } from 'luxon'
import { I18nContext } from '../../../contexts/i18n'
import InfoTooltip from '../../../components/ui/info-tooltip'

const TIMER_BASE = 60000

// Return the mm:ss start time of the countdown timer.
// If time has elapsed between `timeStarted` the time current time,
// then that elapsed time will be subtracted from the timer before
// rendering
function getNewTimer (currentTime, timeStarted, timeBaseStart) {
  const timeAlreadyElapsed = currentTime - timeStarted
  return timeBaseStart - timeAlreadyElapsed
}

function decreaseTimerByOne (timer) {
  return Math.max(timer - 1000, 0)
}

function timeBelowWarningTime (timer, warningTime) {
  const [warningTimeMinutes, warningTimeSeconds] = warningTime.split(':')
  return timer <= ((Number(warningTimeMinutes) * 60) + Number(warningTimeSeconds)) * 1000
}

export default function CountdownTimer ({
  timeStarted,
  timeOnly,
  timerBase = TIMER_BASE,
  warningTime,
  labelKey,
  infoTooltipLabelKey,
}) {
  const t = useContext(I18nContext)
  const intervalRef = useRef()
  const initialTimeStartedRef = useRef()

  const [currentTime, setCurrentTime] = useState(() => Date.now())
  const [timer, setTimer] = useState(() => getNewTimer(currentTime, timeStarted, timerBase))

  useEffect(() => {
    if (intervalRef.current === undefined) {
      intervalRef.current = setInterval(() => {
        setTimer(decreaseTimerByOne)
      }, 1000)
    }

    return function cleanup () {
      clearInterval(intervalRef.current)
    }
  }, [])

  // Reset the timer that timer has hit '0:00' and the timeStarted prop has changed
  useEffect(() => {
    if (!initialTimeStartedRef.current) {
      initialTimeStartedRef.current = timeStarted || Date.now()
    }

    if (timer === 0 && timeStarted !== initialTimeStartedRef.current) {
      initialTimeStartedRef.current = timeStarted
      const newCurrentTime = Date.now()
      setCurrentTime(newCurrentTime)
      setTimer(getNewTimer(newCurrentTime, timeStarted, timerBase))

      clearInterval(intervalRef.current)
      intervalRef.current = setInterval(() => {
        setTimer(decreaseTimerByOne)
      }, 1000)
    }
  }, [timeStarted, timer, timerBase])

  const formattedTimer = Duration.fromMillis(timer).toFormat('m:ss')
  let time
  if (timeOnly) {
    time = <div className="countdown-timer__time">{formattedTimer}</div>
  } else if (labelKey) {
    time = t(labelKey, [<div key="countdown-time-1" className="countdown-timer__time">{formattedTimer}</div>])
  }

  return (
    <div className="countdown-timer">
      <div
        className={classnames('countdown-timer__timer-container', {
          'countdown-timer__timer-container--warning': warningTime && timeBelowWarningTime(timer, warningTime),
        })}
      >
        {time}
      </div>
      {
        !timeOnly && infoTooltipLabelKey
          ? (
            <InfoTooltip
              position="bottom"
              contentText={t(infoTooltipLabelKey)}
            />
          )
          : null
      }
    </div>
  )
}

CountdownTimer.propTypes = {
  timeStarted: PropTypes.number,
  timeOnly: PropTypes.bool,
  timerBase: PropTypes.number,
  warningTime: PropTypes.string,
  labelKey: PropTypes.string,
  infoTooltipLabelKey: PropTypes.string,
}