calculateAverageBaseRate.ts

function averageBaseRate(
  leaseTerm: number,
  baseRate: number,
  escalationValue: number,
  opex: number,
  sizeSf: number,
  numOfFreeMonths: number,
  accumulateBaseRate: Function,
) {

  // variables
  let averageBaseRate = 0;

  // early return due to free duration
  if (leaseTerm <= numOfFreeMonths) {
    return 0;
  }

  // helper utils
  let round2digits = (num) => (Math.round(num * 100)) / 100;

  // in between a year
  if (numOfFreeMonths < leaseTerm && leaseTerm <= numOfFreeMonths + 11) {
    return round2digits((baseRate * (leaseTerm - numOfFreeMonths)) / leaseTerm);
  }

  // accumulator for base rate during yearly interval
  let accumulatorBaseRate = accumulateBaseRate(escalationValue);

  // over a year accumulation
  let totalBaseRent: number = 0;
  let totalBaseRentFirstYear: number = 0;
  let monthsToCalculate: number = 0;
  let shouldStartPeriod: boolean = false;

  if (numOfFreeMonths <= 12) {
    totalBaseRentFirstYear = (baseRate / 12) * sizeSf * (12 - numOfFreeMonths);
    monthsToCalculate = leaseTerm - 12;
    shouldStartPeriod = true;
    // console.log('totalBaseRentFirstYear = ' + totalBaseRentFirstYear)
  } else {
    totalBaseRentFirstYear = 0;
    monthsToCalculate = leaseTerm - numOfFreeMonths;
    shouldStartPeriod = false;
  }
  // console.log('monthsToCalculate = ' + monthsToCalculate)

  totalBaseRent = totalBaseRentFirstYear; // initial value for first fiscal year

  let accBaseRate: number = 0; // accumulator for base rate

  // next calculation is less than a year
  if (monthsToCalculate <= 12) {
    // this time, base rate is accumulated
    accBaseRate = !shouldStartPeriod ? baseRate : accumulatorBaseRate(baseRate);
    // console.log(accBaseRate)
    totalBaseRent += ( (accBaseRate/12) * sizeSf * monthsToCalculate );
  }
  // make interval calculation
  else {
    let intervalYear = parseInt(String(monthsToCalculate / 12));
    let remainMonths = monthsToCalculate - (12 * intervalYear);
    // console.log('intervalYear = ' + intervalYear)
    // console.log('remainMonths = ' + remainMonths)
    // console.log('shouldStartPeriod = ' + (shouldStartPeriod))

    // initial accumulate value of base rate
    accBaseRate = baseRate;
    for (let i = 0; i < Math.round(intervalYear); i++) {
      if (!shouldStartPeriod) {
        shouldStartPeriod = true
      } else {
        accBaseRate = (accumulatorBaseRate(accBaseRate))
      }
      totalBaseRent += (accBaseRate * sizeSf);
      // console.log('accBaseRate = ' + accBaseRate + ' | totalRent = ' + (accBaseRate * sizeSf))
    }
    if (remainMonths > 0) {
      accBaseRate = (accumulatorBaseRate(accBaseRate));
      totalBaseRent += ((accBaseRate / 12) * sizeSf * remainMonths);
      // console.log('accBaseRate = ' + accBaseRate + ' | totalRent = ' + ((accBaseRate / 12) * sizeSf * remainMonths))
    }
  }
  // console.log('totalBaseRent = ' + totalBaseRent)

  // calculate average base rate
  averageBaseRate = ((totalBaseRent / leaseTerm) / sizeSf) * 12;

  // round up to 2 decimal digits
  // return parseFloat(averageBaseRate.toFixed(2));
  return round2digits(averageBaseRate)

}



class RentCalculator {
  private calculator: {
    Percent: (leaseTerm, baseRate, escalationValue, opex, sizeSf, numOfFreeMonths) => number;
    Amount: (leaseTerm, baseRate, escalationValue, opex, sizeSf, numOfFreeMonths) => number;
    Flat: (leaseTerm, baseRate, escalationValue, opex, sizeSf, numOfFreeMonths) => number
  };

  constructor() {
    this.calculator = {
      'Flat':         this._calcFlat,
      'Percent':      this._calcPercent,
      'Amount':       this._calcAmount,
    }
  }

  calculateAverageBaseRent(leaseTerm, baseRate, escalationValue, escalationType, freeRentType, opex, sizeSf, numOfFreeMonths) {
    let calculator = this.calculator[escalationType];
    if (typeof calculator === 'undefined') {
      return 0;
    }

    return calculator(leaseTerm, baseRate, escalationValue, opex, sizeSf, numOfFreeMonths);
  }

  _calcFlat(leaseTerm, baseRate, escalationValue, opex, sizeSf, numOfFreeMonths) {
    const accumulateBaseRate = escalationValue => rate => rate;
    return averageBaseRate(leaseTerm, baseRate, escalationValue, opex, sizeSf, numOfFreeMonths, accumulateBaseRate);
  }

  _calcPercent(leaseTerm, baseRate, escalationValue, opex, sizeSf, numOfFreeMonths) {
    const accumulateBaseRate = escalationValue => rate => rate + rate * escalationValue / 100;
    return averageBaseRate(leaseTerm, baseRate, escalationValue, opex, sizeSf, numOfFreeMonths, accumulateBaseRate);
  }

  _calcAmount(leaseTerm, baseRate, escalationValue, opex, sizeSf, numOfFreeMonths) {
    const accumulateBaseRate = escalationValue => rate => rate + escalationValue;;
    return averageBaseRate(leaseTerm, baseRate, escalationValue, opex, sizeSf, numOfFreeMonths, accumulateBaseRate);
  }
}

export default RentCalculator;