#!/usr/local/bin/perl
$args = $ENV{'QUERY_STRING'};
print "Content-type: text/html\n\n";

if (length($args) < 3)
{
print <<FullForm;
<title>How Long will it Last?</title>
<h3>How Long will it Last?</h3>
<p>
Here is a new twist on the mortgage calcuator. Here you tell how much
you want to spend each month, an interest rate and a loan amount, and
the computer tells you how long it will take you to pay it off!
<hr>
<form action="http://alfredo.wustl.edu/mort/loan.cgi">
<li><input type="text" name="abal" size="10" value="100000"> 
Beginning Balance of Loan
<li><input type="text" name="pay1" size="10" value="600"> 
Minimum Monthly payment
<li><input type="text" name="pay2" size="10" value="1200"> 
Maximum Monthly payment
<li><input type="text" name="intr" size="10" value="7.5"> 
annual percentage rate (%) (fixed loan)
<li><input type="submit" value="Calculate these values">
</form>
FullForm
}
else
{
  print "<title>Loan Length Estimations</title>\n";
  print "<h1>Loan Length Estimations</h1>\n";
  # Let's do the calculations!
  @va = split("&",$args);
  for ($i=0; $i<7; $i++) { @va[$i] = substr(@va[$i],5); }
  ($abal,$pay1,$pay2,$intr) = @va; 
  print "<h3>Inputs</h3>\n";
  print "<li>Beginning Balance of Loan: \$ $abal\n"; 
  print "<li>Minimum monthly payment : \$ $pay1\n"; 
  print "<li>Maximum monthly payment : \$ $pay2\n"; 
  print "<li>Annual interest rate: $intr % \n"; 
  print "<hr>\n";
  $intr = $intr/1200;  # convert to monthly

  for ($i=0; $i<2; $i++)
  {
    $mv = $abal; $mm = 0; $ti = 0;
    if ($i == 0)
    { $py = $pay1; $mt = "minimum"; }
    else
    { $py = $pay2; $mt = "maximum"; }
    while($mv > 0 && $mm < 1200)
    {
      $mi = $mv * $intr; $ti = $ti + $mi;
      $mv = $mv + $mi - $py; $mm++; 
    }
    print "<h3>Using the $mt payment it will take";
    printf("%5d months (%7.3f years) to pay off your loan</h3>\n",
		$mm, $mm/12);
    printf("<li> Total interest: \$ %9.2f (%9.2f average per month)\n",
		$ti, $ti/$mm);
  }
}