CBS-Mobile-App/src/modules/deposit/utils/depositCalculators.ts

import type {
  DepositAccount,
  DepositInterestPayoutType,
  DepositStatus,
} from '../../../types/app';

const MS_PER_DAY = 1000 * 60 * 60 * 24;

const clamp = (value: number, min: number, max: number) =>
  Math.min(Math.max(value, min), max);

export const calculateFixedDepositMaturity = (
  principal: number,
  annualRate: number,
  tenureMonths: number,
  payoutType: DepositInterestPayoutType = 'cumulative',
) => {
  if (principal <= 0 || annualRate <= 0 || tenureMonths <= 0) {
    return 0;
  }

  const years = tenureMonths / 12;

  if (payoutType === 'non-cumulative') {
    return principal + principal * (annualRate / 100) * years;
  }

  const quarterlyRate = annualRate / 100 / 4;
  const periods = years * 4;

  return principal * Math.pow(1 + quarterlyRate, periods);
};

export const calculateRecurringDepositMaturity = (
  monthlyInstallment: number,
  annualRate: number,
  tenureMonths: number,
) => {
  if (monthlyInstallment <= 0 || annualRate <= 0 || tenureMonths <= 0) {
    return 0;
  }

  const monthlyRate = annualRate / 100 / 12;
  let maturityAmount = 0;

  for (let month = 0; month < tenureMonths; month += 1) {
    maturityAmount += monthlyInstallment * Math.pow(1 + monthlyRate, tenureMonths - month);
  }

  return maturityAmount;
};

export const getDepositCanonicalStatus = (
  deposit: Pick<DepositAccount, 'status' | 'maturityDate'>,
  now = new Date(),
): DepositStatus => {
  if (deposit.status === 'closed') {
    return 'closed';
  }

  return new Date(deposit.maturityDate).getTime() <= now.getTime() ? 'matured' : 'active';
};

export const getDaysUntilMaturity = (maturityDate: string, now = new Date()) => {
  const diff = new Date(maturityDate).getTime() - now.getTime();

  return Math.ceil(diff / MS_PER_DAY);
};

export const isDepositNearMaturity = (
  deposit: Pick<DepositAccount, 'status' | 'maturityDate'>,
  now = new Date(),
) => {
  const daysUntilMaturity = getDaysUntilMaturity(deposit.maturityDate, now);

  return getDepositCanonicalStatus(deposit, now) === 'active' && daysUntilMaturity <= 7;
};

export const getDepositProgress = (
  startDate: string,
  maturityDate: string,
  now = new Date(),
) => {
  const start = new Date(startDate).getTime();
  const maturity = new Date(maturityDate).getTime();
  const current = now.getTime();

  if (maturity <= start) {
    return 1;
  }

  return clamp((current - start) / (maturity - start), 0, 1);
};

export const calculatePrematureClosureAmount = (
  deposit: Pick<
    DepositAccount,
    'kind' | 'principalAmount' | 'monthlyInstallment' | 'interestRate' | 'startDate' | 'maturityDate' | 'maturityAmount' | 'prematurePenaltyRate' | 'status'
  >,
  now = new Date(),
) => {
  const canonicalStatus = getDepositCanonicalStatus(deposit, now);

  if (canonicalStatus === 'closed') {
    return {
      penaltyAmount: 0,
      netAmount: deposit.maturityAmount,
    };
  }

  if (canonicalStatus === 'matured') {
    return {
      penaltyAmount: 0,
      netAmount: deposit.maturityAmount,
    };
  }

  const elapsedMonths = Math.max(
    1,
    Math.round((now.getTime() - new Date(deposit.startDate).getTime()) / (MS_PER_DAY * 30)),
  );

  const currentValue =
    deposit.kind === 'fd'
      ? calculateFixedDepositMaturity(
          deposit.principalAmount,
          deposit.interestRate,
          elapsedMonths,
          'non-cumulative',
        )
      : calculateRecurringDepositMaturity(
          deposit.monthlyInstallment ?? 0,
          deposit.interestRate,
          elapsedMonths,
        );
  const investedBase =
    deposit.kind === 'fd'
      ? deposit.principalAmount
      : (deposit.monthlyInstallment ?? 0) * elapsedMonths;

  const penaltyAmount = currentValue * ((deposit.prematurePenaltyRate ?? 0) / 100);

  return {
    penaltyAmount,
    netAmount: Math.max(currentValue - penaltyAmount, investedBase * 0.9),
  };
};