#!/usr/bin/perl -w

use CGI qw / :standard /;
use LWP::UserAgent;
use strict;

print header();


# use z to enter a zip and get the city and state
# use cs to enter the city, state and get all available zip codes for the area

my $query = 'z';


my $city = 'New York';
my $state = 'NY';
my $zip = '10001';
my $usps_form = 'http://www.usps.gov/cgi-bin/zip4/ctystzip2';


# prepare agent

my  $ua = LWP::UserAgent->new();
$ua->agent( 'AgentName/0.1 ' . $ua->agent );


# prepare request

my $req = HTTP::Request->new( POST => $usps_form );
$req->content_type( 'application/x-www-form-urlencoded' );

$req->content( "ctystzip=$city $state&Submit=Process" ) if $query eq 'cs';
$req->content( "ctystzip=$zip&Submit=Process" ) if $query eq 'z';


# process request

my $res = $ua->request( $req );


# process result

if ( $res->is_success ) {


    # city/state to zip query

    if ( $query eq 'cs'){

        my @zips = zip_from_city_state( $res->content );

        my $count = @zips;

        print p( "$count zip codes for $city, $state" ),
            blockquote ( join ( ", ", @zips ) );

    }


    # zip to city/state query

    elsif ( $query eq 'z' ){

        my $cs_aref = city_state_from_zip( $res->content );

        print p( "Cities listed for $zip:" ), '<BLOCKQUOTE>';
        print "$_->{'c'}, $_->{'s'}", br() foreach @$cs_aref;
        print '</BLOCKQUOTE>';

    }

    else {
        die 'Bad query.';
    }

}
else {

    warn 'USPS down, bad request, or no results.';

}

sub zip_from_city_state {

    my @zips;

    # there has to be a more efficient way to do this :)
    foreach ( split( /<BR>/i, ( split( m|</?PRE>|i, $_[0] ) )[1] ) ){

        my $zip =  substr( $_, 0, 5 );
        push @zips, $zip if $zip =~ /^\d{5,5}/;

    }

    return @zips;
}

sub city_state_from_zip {

    my ( $res, $cs_aref ) = ( shift, () );
    $res =~ s/<BR>/\n/gi;

    # there has to be a more efficient way to do this :)
    my @lines =
        split( "\n", ( split( /--+/, ( split( m|</?PRE>|i, $res ) )[1] ) )[1] );

    for my $line ( @lines ){

        my ( $city, $state ) = unpack( 'A27A2', $line );
        push @$cs_aref, { 'c' => $city, 's' => $state } if $city and $state;

    }

    return $cs_aref;

}