schedule-repayment.js

const fs = require('fs');
const Papa = require('papaparse');
const _ = require('lodash');

const pay_all_proportionally = (startLoans, emi) => {
  const loans = _.cloneDeep(startLoans);
  let total_outstanding = _.sumBy(loans, 'outstanding');
  let month = 0;
  while (total_outstanding > 0) {
    console.log(`month ${month} outstanding ${total_outstanding}`);
    _.forEach(loans, loan => {
      const part = (loan.outstanding / total_outstanding);
      const repay = _.round(emi * part);
      loan.outstanding -= repay;
      if (loan.outstanding > 0) {
        loan.outstanding += loan.principal * loan.mroi * .01;
      }
    })
    month++;
    total_outstanding = _.sumBy(loans, 'outstanding');
  }
}

const pay_by_high_rate_low_outstanding = (startLoans, emi) => {
  const loans = _.cloneDeep(startLoans);
  let total_outstanding = _.sumBy(loans, 'outstanding');
  let month = 0;
  while (total_outstanding > 0) {
    console.log(`month ${month} outstanding ${total_outstanding}`);
    const open_loans = _.filter(_.orderBy(loans, ['mroi', 'outstanding'], ['desc', 'asc']), l => l.outstanding);
    let available = emi;
    for (const loan of open_loans) {
      const need = loan.outstanding;
      const pay = _.min([need, available]);
      loan.outstanding -= pay;
      available -= pay;
    }
    _.forEach(open_loans, loan => {
      if (loan.outstanding > 0) {
        loan.outstanding += loan.principal * loan.mroi * .01;
      }
    })
    month++;
    total_outstanding = _.sumBy(loans, 'outstanding');
  }
}
const pay_by_low_rate = (startLoans, emi) => {
  const loans = _.cloneDeep(startLoans);
  let total_outstanding = _.sumBy(loans, 'outstanding');
  let month = 0;
  while (total_outstanding > 0) {
    console.log(`month ${month} outstanding ${total_outstanding}`);
    const open_loans = _.filter(_.orderBy(loans, ['mroi', 'outstanding'], ['asc', 'desc']), l => l.outstanding);
    let available = emi;
    for (const loan of open_loans) {
      const need = loan.outstanding;
      const pay = _.min([need, available]);
      loan.outstanding -= pay;
      available -= pay;
    }
    _.forEach(open_loans, loan => {
      if (loan.outstanding > 0) {
        loan.outstanding += loan.principal * loan.mroi * .01;
      }
    })
    month++;
    total_outstanding = _.sumBy(loans, 'outstanding');
  }
}
const pay_by_high_rate_high_outstanding = (startLoans, emi) => {
  const loans = _.cloneDeep(startLoans);
  let total_outstanding = _.sumBy(loans, 'outstanding');
  let month = 0;
  while (total_outstanding > 0) {
    console.log(`month ${month} outstanding ${total_outstanding}`);
    const open_loans = _.filter(_.orderBy(loans, ['mroi', 'outstanding'], ['desc', 'desc']), l => l.outstanding);
    let available = emi;
    for (const loan of open_loans) {
      const need = loan.outstanding;
      const pay = _.min([need, available]);
      loan.outstanding -= pay;
      available -= pay;
    }
    _.forEach(open_loans, loan => {
      if (loan.outstanding > 0) {
        loan.outstanding += loan.principal * loan.mroi * .01;
      }
    })
    month++;
    total_outstanding = _.sumBy(loans, 'outstanding');
  }
}
const pay_by_positive_rate_low_outstanding = (startLoans, emi) => {
  const loans = _.cloneDeep(startLoans);
  let total_outstanding = _.sumBy(loans, 'outstanding');
  let month = 0;
  while (total_outstanding > 0) {
    console.log(`month ${month} outstanding ${total_outstanding}`);
    const [positive_loans, zero_loans] = _.partition(loans, l => l.mroi > 0);
    const open_loans = _.filter([..._.orderBy(positive_loans, ['outstanding'], ['asc']), ...zero_loans], l => l.outstanding);
    let available = emi;
    for (const loan of open_loans) {
      const need = loan.outstanding;
      const pay = _.min([need, available]);
      loan.outstanding -= pay;
      available -= pay;
    }
    _.forEach(open_loans, loan => {
      if (loan.outstanding > 0) {
        loan.outstanding += loan.principal * loan.mroi * .01;
      }
    })
    month++;
    total_outstanding = _.sumBy(loans, 'outstanding');
  }
}
const algos = {
  a: pay_all_proportionally,
  b: pay_by_high_rate_low_outstanding,
  c: pay_by_high_rate_high_outstanding,
  d: pay_by_positive_rate_low_outstanding,
  e: pay_by_low_rate
}
const main = (algoText, installmentText) => {
  const installment = +installmentText;
  const { data: loans } = Papa.parse(fs.readFileSync('./loans.txt', 'utf8'), { header: true, dynamicTyping: true })
  
  if(!algoText) {
    console.log(`usage ${_.keys(algos).join('|')} emi_amount`);
    console.log(algos);
    return;
  }

  const algo = algos[algoText];
  algo(loans, installment);
}

main(...process.argv.slice(2));