#!/usr/bin/perl
use strict;

my $VERSION = '0.11';

use Fcntl qw(:DEFAULT :flock :seek);
use Data::Dumper;

our %options;
map { my ($k, $v) = split '='; $options{$k} = $v; } @ARGV;
$options{trace} ||= 1;

our ($accept_list, $trace);

`echo $$ > /var/run/accept-recipient.pid`;

sub trace ($;$) { my ($m, $l) = @_; $l = 1 if not defined $l; warn "$m\n" if $options{trace} >= $l; return $m; }

our %file_tail = (
	name => '/var/log/mail',
	maxinterval => 10,
	interval => 5,
	adjustafter => 3,
	tail => -1,
	resetafter => 30,
);

trace "Calling tail_init";
tail_init();

$| = 1;

my (%user, %sender);

# Which users have ~/.accept-list files?
my $accept_list = exists $options{'accept-list'} ? $options{'accept-list'} : '.accept-list';
for ( glob "/home/*/$accept_list" ) {
	$user{ ( split '/' )[2] } = $_;
}

trace Dumper \%user;

while ( 'repeat forever' ) {

	$_ = tail_getline();

	my ($queue_id, $from, $to);
	if ( ($queue_id, $from) = /([\da-zA-Z]+): from=<([^@]+)@/o ) {
		next if $from =~ /\+spam-x/;
		$sender{ $queue_id } = $from;
	} elsif ( ($queue_id, $to) = /([\da-zA-Z]+): to=<([^>]+)>/o ) {
		if ( my $accept_list = $user{ $sender{ $queue_id } } ) {
			open ACCEPT_LIST, ">>$accept_list";
			print ACCEPT_LIST $to, "\n";
			close ACCEPT_LIST;
		}
	}
	
}

exit;


# Logfile-reading functions
# stolen from pop-before-smtp

sub tail_init {
	&tail_open;
	$::tail_buf = '';
	if ($file_tail{'tail'} >= 0) {
		if (defined sysseek(TAIL, -$file_tail{'tail'}*128, SEEK_END)) {
			&tail_getline; # dump partial line
		} else {
			sysseek(TAIL, 0, SEEK_SET);
		}
	}
}

sub tail_open {
	open(TAIL, $file_tail{'name'}) or die "Unable to open $file_tail{'name'}: $!";
	$::tail_inode = (stat(TAIL))[1];
}

sub tail_getline {
	while (1) {
		return $1 if $::tail_buf =~ s/^(.*\n)//;
		my $cnt = 1;
		my $slept = 0;
		my $i = $file_tail{'interval'};
		while (1) {
			last if sysread(TAIL, $::tail_buf, 2048, length($::tail_buf));
			sysseek(TAIL, 0, SEEK_CUR);
			if ($slept >= $file_tail{'resetafter'}) {
				$slept = 0;
				my $new_inode;
				foreach (1..5) {
					$new_inode = (stat($file_tail{'name'}))[1];
					last if $new_inode;
					sleep 2;
				}
				if ($::tail_inode != $new_inode) {
					&tail_open;
					$cnt = 1;
				}
			}
			if ($cnt % $file_tail{'adjustafter'} == 0) {
				$i += 2;
				$i = $file_tail{'maxinterval'} if $i > $file_tail{'maxinterval'};
			}
			sleep $i;
			$cnt++;
			$slept += $i;
		}
	}
}