quzhou.js

const fs = require("fs");
const { promisify } = require("util");
const pp = require("papaparse");

const readFile = promisify(fs.readFile);
const writeFile = promisify(fs.writeFile);

const mutateMemoForPerson = (memo, person, pricePerPerson, title) => {
  const maybeCouple = person.split("*");
  if (maybeCouple.length > 1) {
    return maybeCouple.map((subperson) =>
      mutateMemoForPerson(
        memo,
        subperson,
        pricePerPerson / maybeCouple.length,
        title
      )
    );
  }
  const previousPerson = memo[person] || { total: 0, expenses: [] };
  const nextPerson = {
    total: previousPerson.total + pricePerPerson,
    expenses: [...previousPerson.expenses, { title, pricePerPerson }],
  };
  memo[person] = nextPerson;
};

(async () => {
  try {
    const file = await readFile("./quzhou.csv");
    const {
      data: [, ...allExpenses],
    } = await pp.parse(file.toString());

    const pricedPerPerson = allExpenses.reduce((memo, current) => {
      const [title, priceString, personsString] = current;
      const personsBillable = personsString.split(", ");
      const price = parseInt(priceString);
      const pricePerPerson = price / personsBillable.length;
      for (const person of personsBillable) {
        mutateMemoForPerson(memo, person, pricePerPerson, title);
      }
      return memo;
    }, {});
    for (const [key, value] of Object.entries(pricedPerPerson)) {
      const template = `
Quzhou Expenses for ${key}

${value.expenses
  .map(({ title, pricePerPerson }) => `* ${title} CN¥${pricePerPerson})`)
  .join("\n")}

Total: CN¥${value.total}
      
      `;
      await writeFile(`people/${key}.txt`, template);
    }
  } catch (error) {
    console.log({ error });
  }
})();