toggl-beer-calculator.js

const WALTER_PRICE = 0.53,
  TARE_PRICE = 0.08;

const tareMoney = (bottles) => {
  return TARE_PRICE * bottles;
};

const round = (f) => {
  return Math.round(f * Math.pow(10, 2)) / Math.pow(10, 2);
};

const getNumWalters = async(money) => {
  var ret = [0, 0];
  // calculates the amount of beer
  ret[0] = Math.floor(money / WALTER_PRICE);
  // calculates the money left ( including the tare money )
  ret[1] = round(money - ret[0] * WALTER_PRICE + tareMoney(ret[0]));
  return ret;
};

const calculate = async(initialMoney) => {
  // gets the amount of beer based on the initial money
  let nextIteration = await getNumWalters(initialMoney);
  let totalWalters = nextIteration[0];

  // while there is money left we should get more beers
  while (nextIteration[1] > WALTER_PRICE) {
    nextIteration = await getNumWalters(nextIteration[1]);
    // adds to the total of beers
    totalWalters += nextIteration[0];
  }

  return {totalWalters: totalWalters, moneyLeft: nextIteration[1]};
}

module.exports = calculate;