session-desktop/ts/components/conversation/ExpireTimer.tsx

import React, { useCallback, useState } from 'react';

import { getTimerBucketIcon } from '../../util/timer';

// tslint:disable-next-line: no-submodule-imports
import useInterval from 'react-use/lib/useInterval';
import styled, { CSSProperties } from 'styled-components';
import { SessionIcon } from '../icon/SessionIcon';

const ExpireTimerBucket = styled.div`
  font-size: var(--font-size-xs);
  line-height: 16px;
  letter-spacing: 0.3px;
  text-transform: uppercase;
  user-select: none;
  color: var(--text-primary-color);
`;

type Props = {
  expirationLength: number; // should be in milliseconds
  expirationTimestamp: number | null;
  style: CSSProperties;
};

export const ExpireTimer = (props: Props) => {
  const { expirationLength, expirationTimestamp, style } = props;

  const initialTimeLeft = Math.max(Math.round(((expirationTimestamp || 0) - Date.now()) / 1000), 0);
  const [timeLeft, setTimeLeft] = useState(initialTimeLeft);

  const update = useCallback(() => {
    if (expirationTimestamp) {
      const newTimeLeft = Math.max(Math.round((expirationTimestamp - Date.now()) / 1000), 0);
      if (newTimeLeft !== timeLeft) {
        setTimeLeft(newTimeLeft);
      }
    }
  }, [expirationTimestamp, timeLeft, setTimeLeft]);

  const updateFrequency = 500;
  useInterval(update, updateFrequency);

  if (!(expirationLength && expirationTimestamp)) {
    return null;
  }

  const expireTimerColor = 'var(--primary-text-color)';

  const bucket = getTimerBucketIcon(expirationTimestamp, expirationLength);

  return (
    <ExpireTimerBucket style={style}>
      <SessionIcon iconType={bucket} iconSize="tiny" iconColor={expireTimerColor} />
    </ExpireTimerBucket>
  );
};