dividends.js

import BigNumber from 'bignumber.js';
import moment from 'moment';

const defaultDecimalPlaces = 10;

const findApplicableSplitsAgainstDividendYear = (dividendYear, splits) => {
  const formattedDividendYear = Number(moment(dividendYear).format('X'));

  return splits.reduce((acc, split) => {
    const formattedExDate = Number(moment(split.exDate).format('X'));

    return formattedExDate > formattedDividendYear ?
      [
        ...acc,
        split.ratio
      ] :
      acc;
  }, []);
}

const applySplitsRatiosToMatchingDividendAmount = (dividendAmount, applicableSplits) => applicableSplits.reduce((acc, ratio) => {
  const amountWithAppliedSplitRatio = acc.multipliedBy(ratio);

  return amountWithAppliedSplitRatio;
}, dividendAmount);

export const adjustDividendAmountForSplits = (dividend, splits) => {
  const dividendAmount = new BigNumber(dividend.amount);
  const applicableSplits = findApplicableSplitsAgainstDividendYear(dividend.exDate, splits);

  const divAmountWithAppliedSplitRatios = applySplitsRatiosToMatchingDividendAmount(dividendAmount, applicableSplits);

  return divAmountWithAppliedSplitRatios.decimalPlaces(defaultDecimalPlaces).toNumber();
};