use strict;
use warnings;
use feature 'say';

# verify a message
use Mail::DKIM::Verifier;
use Mail::DKIM::ARC::Verifier;
use Time::Piece;
use Time::Seconds;

my $separator = "_______________________________\n";
my $indent = "     ";

# create a verifier object
my $dkim = Mail::DKIM::Verifier->new();
my $arc = Mail::DKIM::ARC::Verifier->new();
 
my $filename = shift or die "$0 FILENAME\n";
open FILE, '<', $filename or die "$!\n";

while (<FILE>)
{
    # remove local line terminators
    chomp;
    s/\015$//;
 
    # use SMTP line terminators
    $dkim->PRINT("$_\015\012");
}
$dkim->CLOSE;

open FILE, '<', $filename or die "Could not open '$filename'\n";

while (<FILE>)
{
    # remove local line terminators
    chomp;
    s/\015$//;

    # use SMTP line terminators
    $arc->PRINT("$_\015\012");
}
$arc->CLOSE;

my $email = $dkim->message_originator->address; 
say "$separator";
say "From $email";
say "";
 
# what is the result of the DKIM verify?
my $dkim_result = $dkim->result_detail;
say "DKIM result = $dkim_result";
say "$separator";

open FILE, '<', $filename or die "Could not open '$filename'\n";
my $header = "";
my $dkim_string = "";
my $found_dkim = 0;
my $found_domkey = 0;
my $finite_loop = 20;
my $loop_counter = 0;
my $substr = "";
my $substr2 = "";
my $tstring = "";
my $xstring = "";
my $sstring = "";
my $time_t = "";
my $time_x = "";
my $slength = 0;
my $time_diff = "";
my $found_t = 0; 
my $found_x = 0;

my @all_signatures = $dkim->signatures;
# there might be multiple signatures, what is the result per signature?
foreach my $signature ($dkim->signatures)
{
    say 'DKIM signature identity: ' . $signature->identity;
    say 'DKIM verify result: ' . $signature->result_detail;
	say "";
	
	while (my $line = <FILE>) {
	
		chomp $line;
		$line =~ tr/\t/ /;
		$line =~ s/^\s+//; # left trim
		$line =~ s/\s+$//; # right trim

		$dkim_string = "";
	
		if ($line =~ /^DKIM-Signature:/i) {
			$loop_counter = 0;
			$found_dkim = 1;

			while (1) {

				$substr = "bh=";
				if (index($line, $substr) != -1) {
					$dkim_string = $dkim_string . $line;
					last;
				}

				$substr = "b=";
				if (index($line, $substr) != -1) {
					$dkim_string = $dkim_string . $line;
					last;
				}

				$dkim_string = $dkim_string . $line;
				$line = <FILE>;
			
				chomp $line;
				$line =~ tr/\t/ /;
				$line =~ s/^\s+//; # left trim
				$line =~ s/\s+$//; # right trim
			
				$loop_counter++;
				if ($loop_counter == $finite_loop) {
					warn "Finite loop count of $finite_loop reached!";
					say "$dkim_string";
					last;
				}
			}
		}
	
		if ($line =~ /^DomainKey-Signature:/i) {
			$loop_counter = 0;
			$found_domkey = 1;

			while (1) {

				$substr = "bh=";
				if (index($line, $substr) != -1) {
					$dkim_string = $dkim_string . $line;
					last;
				}

				$substr = "b=";
				if (index($line, $substr) != -1) {
					$dkim_string = $dkim_string . $line;
					last;
				}

				$dkim_string = $dkim_string . $line;
				$line = <FILE>;
			
				chomp $line;
				$line =~ tr/\t/ /;
				$line =~ s/^\s+//; # left trim
				$line =~ s/\s+$//; # right trim
			
				$loop_counter++;
				if ($loop_counter == $finite_loop) {
					warn "Finite loop count of $finite_loop reached!";
					say "$dkim_string";
					last;
				}
			}
		}
	
		if ($found_domkey == 1)
		{
			$header = "DomainKey"; 
			parse_file_for ($header);
		}
		
		if ($found_domkey == 1) {
			$found_domkey = 0;
			say "$separator";
			last;
		}

		if ($found_dkim == 1)
		{
			$header = "DKIM"; 
			parse_file_for ($header);
		}

		if ($found_dkim == 1) {
			$found_dkim = 0;
			say "$separator";
			last;
		}
	}
}

# what is the result of the ARC verify?
my $arc_result = $arc->result_detail;
say "ARC  result = $arc_result";

my @all_arc_signatures = $arc->signatures;
# there might be multiple signatures, what is the result per signature?
foreach my $signature ($arc->signatures)
{
	say "";
    say $signature->prefix() . ' v=' . $signature->instance .
                                 ' ' . $signature->result_detail;
}

say "$separator";

foreach my $policy ($dkim->policies)
{
        my $policy_name = $policy->name;
        my $policy_result = $policy->apply($dkim);
        say "$policy_name policy result: $policy_result";
}

say "$separator";

sub parse_file_for {
	
	my $header = shift;

	if ($dkim_string =~ /d=[^ ]+;/) {
		$substr = "d=";
		$substr2 = ";";
		if (index($dkim_string, $substr) != -1) {
			$sstring=(substr($dkim_string,index($dkim_string, $substr)+2));
			$slength=index($sstring, $substr2);
			$sstring=substr($sstring,0,$slength);
			say $indent.$header." domain    $substr$sstring";
		}
	}
	
	if ($dkim_string =~ /s=[^ ]+;/) {
		$substr = "s=";
		$substr2 = ";";
		if (index($dkim_string, $substr) != -1) {
			$sstring=(substr($dkim_string,index($dkim_string, $substr)+2));
			$slength=index($sstring, $substr2);
			$sstring=substr($sstring,0,$slength);
			say $indent.$header." selector  $substr$sstring";
		}
	}

	if ($dkim_string =~ /t=[0123456789]+;/) {
		$substr = "t=";
		if (index($dkim_string, $substr) != -1) {
			$tstring=(substr($dkim_string,index($dkim_string, $substr)+2,10));
			$time_t = Time::Piece->gmtime($tstring);
			say $indent.$header." Timestamp $substr$tstring -> " . $time_t->strftime();
			$found_t = 1;
		}
	}
	
	if ($dkim_string =~ /x=[0123456789]+;/) {
		$substr = "x=";
		if (index($dkim_string, $substr) != -1) {
			$xstring=(substr($dkim_string,index($dkim_string, $substr)+2,10));
			$time_x = Time::Piece->gmtime($xstring);
			say $indent.$header." Expiry    $substr$xstring -> " . $time_x->strftime();
			$found_x = 1;
		}
	}
	
	if ($found_t == 1 && $found_x == 1) {
		$time_diff = $time_x - $time_t;
		say "\n".$indent."The time difference is " . $time_diff->pretty();
		$found_t = 0;
		$found_x = 0;
	}
	
	return 0;
}

close FILE