algoritmo muy malo para obtener datos del ciclo menstrual

asyncGetPeriodInformation.js

export const EN_PERIODO = "EN PERIODO";
export const OVULANDO = "OVULANDO";
export const INFERTIL = "INFERTIL";

const getGetOrdinal = function(n) {
  var s = ["th", "st", "nd", "rd"],
    v = n % 100;
  return n + (s[(v - 20) % 10] || s[v] || s[0]);
};

const asyncGetPeriodInformation = (
  dateString,
  longMenstrualCycle,
  longPeriodDays
) =>
  new Promise((resolve, reject) => {
    if (
      !Number.isInteger(longPeriodDays) ||
      !Number.isInteger(longMenstrualCycle)
    ) {
      return reject({
        error: "longMenstrualCycle and longPeriodDays must be integers"
      });
    }
    if (
      !/^[0-9]{4}-(0[1-9]|1[0-2])-(0[1-9]|[1-2][0-9]|3[0-1])$/.test(dateString)
    ) {
      return reject({ error: "Date format is not valid" });
    }
    const DATE_STRING = dateString;
    const LMC = longMenstrualCycle; // LONG MENSTRUAL CYCLE
    const LPD = longPeriodDays; // LONG PERIOD DAYS
    const CD = new Date(); // Dia de hoy
    const LSTPD = new Date(DATE_STRING); // Se le resta el LPD Para tener el primer dia de sangrado
    if (LSTPD.getTime() > CD.getTime()) {
      return reject({ error: "Date more big than today" });
    }
    const getDaysBetween = (d1, d2) =>
      (d2.getTime() - d1.getTime()) / (1000 * 3600 * 24);
    const getCurrentPhase = (
      currentDate = CD,
      lastPeriodDayOfLastCycle = LSTPD,
      longMenstrualCycle = LMC,
      longPeriodDays = LPD
    ) => {
      const _lastPeriodDayOfLastCycle = lastPeriodDayOfLastCycle;

      const lastFirstDayInPeriod = new Date(
        _lastPeriodDayOfLastCycle.setDate(
          _lastPeriodDayOfLastCycle.getDate() - longPeriodDays
        )
      );

      const daysBetween = Math.floor(
        getDaysBetween(lastFirstDayInPeriod, currentDate)
      );

      return daysBetween <= longMenstrualCycle
        ? daysBetween
        : Math.floor(daysBetween % longMenstrualCycle);
    };

    const currentDayInCycle = getCurrentPhase();
    const lastDayOfFirstInfertil = LPD + 6;
    const lastDayOvulando = lastDayOfFirstInfertil + 6;
    let CURRENT_STATE = EN_PERIODO;
    for (let dia = 1; dia <= LMC; dia++) {
      if (dia <= LPD && currentDayInCycle === dia) {
        // en periodo
        break;
      } else if (
        dia > LPD &&
        dia <= lastDayOfFirstInfertil &&
        currentDayInCycle === dia
      ) {
        // dias infertiles
        CURRENT_STATE = INFERTIL;
        break;
      } else if (
        dia > lastDayOfFirstInfertil &&
        dia <= lastDayOvulando &&
        currentDayInCycle === dia
      ) {
        // ovulandito
        CURRENT_STATE = OVULANDO;
        break;
      } else if (dia > lastDayOvulando) {
        // dias infertiles
        CURRENT_STATE = INFERTIL;
        break;
      }
    }

    const cuantosDiasFaltanParaNuevoCiclo = (currentDay, cycleDays) => {
      return cycleDays - currentDay;
    };

    const getDaysLeftToOvulation = (currentDay, cycleDays) => {
      if (currentDay <= lastDayOfFirstInfertil) {
        return lastDayOfFirstInfertil - currentDay + 1;
      } else {
        return cuantosDiasFaltanParaNuevoCiclo(currentDay, cycleDays) + 11;
      }
    };

    const informationAbout = {
      daysLeftToNewCycle: cuantosDiasFaltanParaNuevoCiclo(
        currentDayInCycle,
        LMC
      )
    };

    if (CURRENT_STATE === EN_PERIODO) {
      informationAbout["periodOrdinalDay"] = getGetOrdinal(currentDayInCycle);
    }

    if (CURRENT_STATE === INFERTIL || CURRENT_STATE === EN_PERIODO) {
      informationAbout["daysLeftToOvulation"] = getDaysLeftToOvulation(
        currentDayInCycle,
        LMC
      );
    }

    return resolve({
      currentState: CURRENT_STATE,
      currentDay: currentDayInCycle,
      ...informationAbout
    });
  });

export default asyncGetPeriodInformation;