#!/usr/bin/perl

use Math::BigFloat;

$principal=shift;
$interest=shift;
$years=shift;
$number_of_payments_per_year=shift;
$month=shift;
$year=shift;

if (! $principal) {$principal = 211000}
if (! $interest) {$interest = 5}
if (! $years) {$years = 15}
if (! $number_of_payments_per_year) {$number_of_payments_per_year = 12}
if (! $month) {$month="SEP"}
if (! $year) {$year=2003}

$number_of_payments_per_year = 12;
$total_number_of_payments = $years * $number_of_payments_per_year;

# Real, not percent.  E.G. if $interest=6 (ie 6%), then $interest_per_pay_period=0.005
$interest_per_pay_period = Math::BigFloat->new($interest);
$interest_per_pay_period /= 100*$number_of_payments_per_year;
# print "Rick, \$interest_per_pay_period=$interest_per_pay_period\n";

$total_number_of_payments=$years*$number_of_payments_per_year;

$magic_number = Math::BigFloat->new('1');
for (1 .. $total_number_of_payments) {$magic_number*=(1+$interest_per_pay_period)}

$foo1=Math::BigFloat->new($magic_number-1);
$foo1/=$magic_number;
$foo2=Math::BigFloat->new($principal);
$foo2*=$interest_per_pay_period;
$foo2/=$foo1;
# print "raw payment=$foo2\n";
# $foo2=($principal * $interest_per_pay_period / (($magic_number-1)/$magic_number));print "raw payment=$foo\n";
$monthly_payment = sprintf("%.2f",(0.006 + $principal * $interest_per_pay_period / (($magic_number-1)/$magic_number)));
# print "Rick, \$monthly_payment=$monthly_payment\n";

$printable_interest = $interest/100;
$printable_month = 'SEP';               #   When I got the loan.
$year = 2003;
 
%next_month = (JAN=>"FEB", FEB=>"MAR", MAR=>"APR", APR=>"MAY", MAY=>"JUN", JUN=>"JUL",
               JUL=>"AUG", AUG=>"SEP", SEP=>"OCT", OCT=>"NOV", NOV=>"DEC", DEC=>"JAN");
$payment_number = 0;
$interest_for_year = 0;
$years_this_page = 0;

print "\$$principal \@ $interest% interest for $years years ($monthly_payment monthly payments)\n\n";
for (1 .. $total_number_of_payments) {
  $payment_number++;
  if ($payment_number == 1 || ($month eq 'JAN' && $years_this_page == 5)) {
    print " PAYMENT               INTEREST  PRINCIPAL     NEW      YEAR'S\n";
    print " NUMBER   MONTH  YEAR   PAYMENT   PAYMENT   PRINCIPAL  INTEREST\n";
    print " -------  -----  ----  --------  ---------  ---------  --------\n";
    $years_this_page = 0;
  }
  $i = $principal * $interest_per_pay_period;
  $ii = sprintf("%.2f",$i);
  if ($ii - $i == .005) {$interest_payment = $ii - .01}
                   else {$interest_payment = $ii}
  $interest_for_year += $interest_payment;
  if ($monthly_payment > $interest_payment + $principal) {
    $principal_payment = $principal;
  } else {
    $principal_payment = $monthly_payment - $interest_payment;
  }
  $principal-=$principal_payment;
  if ($month eq 'JAN' || $month eq 'DEC' || $payment_number == 1) {
    $pm = "$month   $year  ";
  } else {
    $pm = "$month         ";
  }
  $line = sprintf("%6s     $pm %7.2f %10.2f %10.2f",$payment_number, $interest_payment, $principal_payment, $principal);
  if ($month eq 'DEC' || $principal == 0) {
    printf("$line %9.2f\n\n",$interest_for_year);
    $interest_for_year = 0;
  } else {
    print "$line\n";
  }
  $month = $next_month{$month};
  if ($month eq 'JAN') {
    $year++;
    $years_this_page++;
  }
  if ($principal == 0) {exit}
}