freeCodeCamp/api-server/server/utils/user-stats.js

import compose from 'lodash/fp/compose';
import map from 'lodash/fp/map';
import sortBy from 'lodash/fp/sortBy';
import trans from 'lodash/fp/transform';
import last from 'lodash/fp/last';
import forEachRight from 'lodash/fp/forEachRight';
import moment from 'moment-timezone';
import { dayCount } from '../utils/date-utils';

const transform = trans.convert({ cap: false });

const hoursBetween = 24;
const hoursDay = 24;

export function prepUniqueDaysByHours(cals, tz = 'UTC') {

  let prev = null;

  // compose goes bottom to top (map > sortBy > transform)
  return compose(
    transform((data, cur, i) => {
      if (i < 1) {
        data.push(cur);
        prev = cur;
      } else if (
        moment(cur)
          .tz(tz)
          .diff(moment(prev).tz(tz).startOf('day'), 'hours')
        >= hoursDay
      ) {
        data.push(cur);
        prev = cur;
      }
    }, []),
    sortBy(e => e),
    map(ts => moment(ts).tz(tz).startOf('hours').valueOf())
  )(cals);
}

export function calcCurrentStreak(cals, tz = 'UTC') {

  let prev = last(cals);
  if (
    moment()
      .tz(tz)
      .startOf('day')
      .diff(moment(prev).tz(tz), 'hours')
    > hoursBetween
  ) {
    return 0;
  }
  let currentStreak = 0;
  let streakContinues = true;
  forEachRight(cur => {
    if (
      moment(prev)
        .tz(tz)
        .startOf('day')
        .diff(moment(cur).tz(tz), 'hours')
      <= hoursBetween
    ) {
      prev = cur;
      currentStreak++;
    } else {
      // current streak found
      streakContinues = false;
    }
    return streakContinues;
  })(cals);

  return currentStreak;
}

export function calcLongestStreak(cals, tz = 'UTC') {

  let tail = cals[0];
  const longest = cals.reduce((longest, head, index) => {
    const last = cals[index === 0 ? 0 : index - 1];
    // is streak broken
    if (moment(head).tz(tz).startOf('day').diff(moment(last).tz(tz), 'hours')
        > hoursBetween) {
      tail = head;
    }
    if (dayCount(longest, tz) < dayCount([head, tail], tz)) {
      return [head, tail];
    }
    return longest;
  }, [cals[0], cals[0]]);

  return dayCount(longest, tz);
}