package com.cedarsoft.business.calc.roi;
import com.cedarsoft.business.Money;
import com.cedarsoft.business.MutableMoney;
import com.cedarsoft.business.calc.TimeSystem;
import com.cedarsoft.business.payment.DefaultPayment;
import com.cedarsoft.business.payment.Payment;
import org.jetbrains.annotations.NotNull;
import org.joda.time.LocalDate;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
/**
* Calculates the PAngV 2000.
*/
public class PAngV2000Calculator {
@NotNull
public static final Money TARGET_DELTA = new Money( 0.005 );
public static final double INITIAL_RATE_GUESS = 0.5;
public static final double MIN_CHANGE = 0.000004;
/**
* The payments
*/
private final List<Payment> payments = new ArrayList<Payment>();
/**
* The base date for the calculation
*/
@NotNull
private final LocalDate baseDate;
/**
* Creates a new pang calculator for the given base date
*
* @param baseDate the base date
*/
public PAngV2000Calculator( @NotNull LocalDate baseDate ) {
this.baseDate = baseDate;
}
/**
* Adds a (default) payment.
*
* @param amount the amount
* @param date the date
*/
public void addPayment( @NotNull Money amount, @NotNull LocalDate date ) {
addPayment( new DefaultPayment( amount, date ) );
}
/**
* Adds a payment
*
* @param payment the payment
*/
public void addPayment( @NotNull Payment payment ) {
payments.add( payment );
}
/**
* Adds the given payments
*
* @param additionalPayments the payments
*/
public void addPayments( @NotNull Collection<? extends Payment> additionalPayments ) {
this.payments.addAll( additionalPayments );
}
/**
* Returns the amount of the payments
*
* @return the amount of payments
*/
@NotNull
public Money getPaymentsAmount() {
MutableMoney amount = new MutableMoney();
for ( Payment payment : payments ) {
amount.plus( payment.getAmount() );
}
return amount.getMoney();
}
/**
* Returns the payments
*
* @return
*/
@NotNull
public List<? extends Payment> getPayments() {
return Collections.unmodifiableList( payments );
}
/**
* Calculates the PangV
*
* @return the PangV
*/
@NotNull
public PangV calculate() {
if ( payments.size() < 2 ) {
return PangV.NULL;
}
MutableMoney sum = new MutableMoney();
for ( Payment payment : payments ) {
sum.plus( payment.getAmount() );
}
boolean sumPositive = sum.getEstimatedValue() > 0;
//test it using bisection
double actualGuess;
if ( sumPositive ) {
actualGuess = -INITIAL_RATE_GUESS;
} else {
actualGuess = INITIAL_RATE_GUESS;
}
int counter = 0;
Money actualValue = Money.BIG;
while ( actualValue.abs().isGreaterThan( TARGET_DELTA ) ) {
double change = INITIAL_RATE_GUESS / Math.pow( 2, counter );
if ( change < MIN_CHANGE ) {
return new PangV( actualGuess, actualValue, counter, sum.immutable() );
}
//modify guess
if ( !sumPositive ^ actualValue.isGreaterThan( Money.ZERO ) ) {
actualGuess += change;
} else {
actualGuess -= change;
}
actualValue = calculateCashValue( actualGuess );
counter++;
}
return new PangV( actualGuess, actualValue, counter, sum.immutable() );
}
/**
* Calculates the cash value for all payments
*
* @param rate the rate
* @return the cash value for all payments
*/
@NotNull
public Money calculateCashValue( double rate ) {
MutableMoney cashValue = new MutableMoney();
for ( Payment payment : payments ) {
cashValue.plus( calulateCashValue( baseDate, payment, rate ) );
}
return cashValue.immutable();
}
/**
* Calculates the cash value of a payment for a given rate.
* The base for this calculation is a year with 365 days
*
* @param payment
* @param rate the rate
* @return the value
*/
@NotNull
public static Money calulateCashValue( @NotNull LocalDate base, @NotNull Payment payment, double rate ) {
double years = TimeSystem.BANK_304_365.calculateYears( base, payment.getDate() );
double divider = Math.pow( 1 + rate, years );
return payment.getAmount().divide( divider );
}
}