#!/usr/bin/perl

#checks for valid email address
#usage validemail <file containing email addresses>

use warnings;
use strict;
use Email::Valid::Loose;
use Net::DNS;
use Parallel::ForkManager;
use Fcntl qw/:flock :seek/;

my $pm=new Parallel::ForkManager(20);
my $resolver=Net::DNS::Resolver->new();
my $addrfile = $ARGV[0] || die
"Usage validemail <file containing email addresses>
Will return two files: goodmails.csv and badmails.csv.
If these files exits already they will be deleted.
";
my ($is_valid, $host, $x, @mx, $add, @adds);

#custom words that make emails invalid to you
my @custom = qw/
        postmaster
        webmaster
/;

my $regex = join "|", @custom;
$regex = qr/$regex/;

open (EMAILS, "$addrfile");

#remove troublesome windows /r characters
#and leading whitespace
 while (<EMAILS>){
        $_ =~ s/\015//;
    $_ =~ s/^\s*//;
        chomp $_;
    push @adds, $_;
}
close (EMAILS);

#warning, I will delete existing files
open (BADADDR, ">badmails.csv") || die;
open (GOODADDR, ">goodmails.csv") || die;

#remove custom regexes
$x = 0;
while ($x <= $#adds){
    if ($adds[$x] =~ m/$regex/){
        splice @adds, $x, 1;
    }else{
        $x++;
    }
}

foreach $add (@adds){ 
    
    $pm->start and next;

        #if email is invalid move on
        if (!defined(Email::Valid::Loose->address($add))){
            writeaddr(*BADADDR, $add); #address is bad
            $pm->finish;
        }

        #if email is valid get domain name 
        $is_valid = Email::Valid::Loose->address($add);
        if ($is_valid =~ m/\@(.*)$/) {
            $host = $1;
        }
        $is_valid="";
        
        # perform dsn lookup to check domain
        @mx=mx($resolver, $host);

        if (@mx) {
            writeaddr(*GOODADDR, $add); #address is good
            }else{
            writeaddr(*BADADDR, $add); #address is bad
        }
       
    $pm->finish;
}

$pm->wait_all_children;

close (BADADDR);
close (GOODADDR);

sub writeaddr{
    my $FH = $_[0];
    my $address = $_[1];
    flock $FH, LOCK_EX or die "Flock failed: $!\n";
    seek  $FH, 0, 2 or die "Seek failed: $!\n";
    print $FH "$address\n";
    flock $FH, LOCK_UN or die "unFlock failed: $!\n";
}