#!/usr/bin/env perl

use strict;
use warnings;
use feature qw(say);

use Text::CSV;
my $csv = Text::CSV->new({ sep_char => ',' });

my $outfile = 'resolvers.csv';
open(my $fh, '>', $outfile) or die "Cannot create $outfile, $!\n";

my $file = $ARGV[0] or die "Need to get CSV file on the command line\n";
open(my $data, '<', $file) or die "Could not open '$file' $!\n";

my $linenumber = 0;
while (my $line = <$data>) {
  chomp $line;
  $linenumber += 1;
  if ($linenumber < 2) {
    print "$linenumber: Resolver address\n";
    print $fh "$line\n";
    } elsif ($csv->parse($line)) {
      my @fields = $csv->fields();
      # NOT IP6 AND (ends in :53, :443, :2053 ,:5353 OR ends like IP4)
      if ($fields[10] !~ m/^\[/ and ($fields[10] =~ m/:443$|:2053$|:5353$|:53$/ or $fields[10] =~ m/\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}$/)) {
            print "$linenumber: $fields[10]\n";
            print $fh "$line\n"
        }
    } else {
        # be quiet
    }
}
close $fh or die "Error in closing the file ", __FILE__, " $!\n";