utils.js

const fs = require('promise-fs');
const fetch = require('node-fetch');
const envPath = require('find-config')('.env');

// dotenv is trying to read .env from the path which calls utils.js, so the path is NOT relative to utils.js
require('dotenv').config({ path: envPath });

/**
 * Try to figure out the date to use
 * @returns {*[]}
 */
const guessDate = () => {
  // If no date is specified, try to guess the date from the path of the calling file
  let [, year, day] = process.cwd().match(/(\d{4})\/(\d{1,2})$/) || [];

  if (day && day.startsWith('0')) {
    day = day.substr(1);
  }

  // In case we still don't have a date try to guess it from today's day
  const today = new Date();
  if (!year) {
    const month = today.getMonth();
    year = today.getFullYear();
    // If we are not in december, let's assume that it is last years puzzle we are interested in
    if (month < 11) {
      year -= 1;
    }
  }

  if (!day) {
    day = today.getDate();
  }

  return [year, day];
};

const getRemoteData = ({ year, day } = {}) => {
  if (!year && !day) {
    [year, day] = guessDate();
  }

  const session = process.env.SESSION;
  if (!session) {
    throw new Error(`No session id specified. 
    Please update your .env file with your session id from the cookie at adventofcode.com`);
  }
  const url = `https://adventofcode.com/${year}/day/${day}/input`;
  const headers = {
    cookie: `session=${session}`,
  };

  return fetch(url, { headers }).then((res) => res.text());
};

const getData = async () => {
  const fileName = 'input.txt';
  try {
    return await fs.readFile(fileName, 'ascii');
  } catch (err) {
    if (process.env.JEST_WORKER_ID === undefined) {
      console.log('No local input file found. Calling adventofcode.com');
      const content = await getRemoteData();
      await fs.writeFile(fileName, content);
      return content;
    }
    throw new Error('Trying to download data when running Jest');
  }
};

const getRows = () => getData().then((data) => data.trim().split('\n'));
const getRow = () => getRows().then((data) => data[0]);
const getNumberRows = () => getRows().then((data) => data.map(Number));

const clone = (object) => JSON.parse(JSON.stringify(object));
const grouped = (arr, groupSize) =>
  arr.reduce((acc, item, index) => {
    // eslint-disable-next-line no-unused-expressions
    index % groupSize === 0 ? acc.push([item]) : acc[acc.length - 1].push(item);
    return acc;
  }, []);
const minBy = (cb) => (a, b) => (cb(b) < cb(a) ? b : a);
const groupRows = (rows) =>
  rows.reduce(
    (acc, row) => {
      // eslint-disable-next-line no-unused-expressions
      row ? acc[acc.length - 1].push(row) : acc.push([]);
      return acc;
    },
    [[]],
  );

const minInArray = (arr) => Math.min(...arr);
const maxInArray = (arr) => Math.max(...arr);

module.exports = {
  getRow,
  getRows,
  getNumberRows,
  clone,
  grouped,
  minBy,
  minInArray,
  maxInArray,
  groupRows,
};