#!/usr/bin/perl
##############################################################################
# By BumbleBeeWare.com 2007
# zipcode distance calculator
# zipdistance.cgi
# reads database and calculates distance between 2 zipcodes
##############################################################################
# 
##############################################################################
print "Content-type: text/html\n\n";

# if direct access print form for zipcode fields
if($ENV{"REQUEST_METHOD"} ne "POST") {
print '<p align="center">To calculate the distance between 2 zipcodes
specify each zipcode.<br>
(US zipcodes only)</p>

<form action="zipdistance.cgi" method="POST">
    <div align="center"><center><table border="0" cellpadding="0"
    cellspacing="0">
        <tr>
            <td align="right">Zipcode 1:</td>
            <td><input type="text" size="5" maxlength="10"
            name="zip1"></td>
        </tr>
        <tr>
            <td align="right">Zipcode 2:</td>
            <td><input type="text" size="5" maxlength="10"
            name="zip2"></td>
        </tr>
        <tr>
            <td align="center" colspan="2"><input type="submit"
            name="submit" value="Calculate Distance"></td>
        </tr>
    </table>
    </center></div>
</form>';

exit;
}

# otherwise calculate the distance based on form inputs and datafile

# parse incoming form data
read(STDIN,$buffer,$ENV{'CONTENT_LENGTH'});
@pairs = split(/&/,$buffer);

foreach $pair (@pairs){
	($name,$value) = split(/=/,$pair);
	$value =~ tr/+/ /;
	$value =~ s/%([a-fA-F0-9][a-fA-F0-9])/pack("C", hex($1))/eg;
	$form{$name} = $value;
}


# open the datafile and get the latatude and logitude for each zipcode
open(FILE,"./zip_latlon.txt");
@zipdata = <FILE>;
close(FILE);

foreach $zipdata (@zipdata){
	
	$zipcode = "";
	$longitude = "";
	$latitude = "";
	
	chomp $zipdata;
	($zipcode, $longitude, $latitude) =split(/\|/,$zipdata);
	
	if ($form{'zip1'} eq "$zipcode"){
		$lat1 = $latitude;
		$lon1 = $longitude;}
		
	if ($form{'zip2'} eq "$zipcode"){
		$lat2 = $latitude;
		$lon2 = $longitude;}
					
}	


$distance = &great_circle_distance($lon1,$lat1,$lon2,$lat2);

print "The distance between $form{'zip1'} and $form{'zip2'} is: $distance miles.\n";
exit;


sub great_circle_distance {
	
	local($lon1,$lat1,$lon2,$lat2) = @_;

	# Convert all the degrees to radians
	$lat_1 = &deg_to_rad($lat1);
	$lon_1 = &deg_to_rad($lon1);
	$lat_2 = &deg_to_rad($lat2);
	$lon_2 = &deg_to_rad($lon2);

	# Find the deltas
	$delta_lat = $lat_2 - $lat_1;
	$delta_lon = $lon_2 - $lon_1;

	# Find the Great Circle distance
	$temp = sin($delta_lat/2.0)**2 + cos($lat_1) * cos($lat_2) * sin($delta_lon/2.0)**2;

	# EARTH_RADIUS = 3956

	$distance = 3956 * 2 * atan2(sqrt($temp),sqrt(1-$temp));

	return($distance);
}


# convert degrees to radians
sub deg_to_rad {
	
	local($deg_2) = @_;
	$radians = 0.0;
	$pi = atan2(1,1) * 4;
	$radians = $deg_2 * $pi/180.0;
	return($radians);
}