import { DateTime } from 'luxon';

const DEFAULT_TIMEZONE = 'Etc/UTC';

const currentBrowserTimezone = (): string => {
  return Intl.DateTimeFormat().resolvedOptions().timeZone;
};

const now = (timezone: string = DEFAULT_TIMEZONE): number => {
  return DateTime.fromMillis(DateTime.now().toMillis(), { zone: timezone }).toMillis();
};

const fromNow = (millis: number | string, timezone = DEFAULT_TIMEZONE): number => {
  if (typeof millis === 'string') millis = Number(millis);
  return now(timezone) + millis;
};

const date = (millis: number | string, timezone = DEFAULT_TIMEZONE): DateTime => {
  if (typeof millis === 'string') millis = Number(millis);
  return DateTime.fromMillis(millis, { zone: timezone });
};

/**
 * https://moment.github.io/luxon/#/formatting?id=table-of-tokens
 */
const format = (millis: number | string, format: string = 'DD', timezone: string = DEFAULT_TIMEZONE): string => {
  if (typeof millis === 'string') millis = Number(millis);
  return date(millis, timezone).toFormat(format);
};

const ago = (millis: number | string, timezone: string = DEFAULT_TIMEZONE): string => {
  const now = DateTime.fromMillis(DateTime.now().toMillis(), { zone: timezone });
  const inputDate = date(millis);
  const diff = now.diff(inputDate, ['years', 'months', 'days', 'hours', 'minutes', 'seconds']);
  const diffRounded = diff.toObject();

  if (diffRounded.years) {
    return `${Math.floor(diffRounded.years)} year${diffRounded.years > 1 ? 's' : ''} ago`;
  } if (diffRounded.months) {
    return `${Math.floor(diffRounded.months)} month${diffRounded.months > 1 ? 's' : ''} ago`;
  } if (diffRounded.days) {
    return `${Math.floor(diffRounded.days)} day${diffRounded.days > 1 ? 's' : ''} ago`;
  } if (diffRounded.hours) {
    return `${Math.floor(diffRounded.hours)} hour${diffRounded.hours > 1 ? 's' : ''} ago`;
  } if (diffRounded.minutes) {
    return `${Math.floor(diffRounded.minutes)} minute${diffRounded.minutes > 1 ? 's' : ''} ago`;
  }
  return `${Math.floor(diffRounded.seconds || 0)} second${diffRounded.seconds || 0 > 1 ? 's' : ''} ago`;
};

const TimeUtil = {
  currentBrowserTimezone,
  now,
  fromNow,
  date,
  format,
  ago,
};

export default TimeUtil;