#!/usr/bin/perl
my $MAIL_FROM = "kuri\@usupi.org";
my $FORWARD_FROM = "kakuu-no-address\@ezweb.ne.jp";
my $FORWARD_TO = "usu\@usupi.org";
my $SENDMAIL_CMD = "/usr/sbin/sendmail -oi $FORWARD_TO";
my $FORWARD_MAX_LINES = 10;

sub send_mail {
	my ($cmd, $message) = @_;
	if(open(MAIL, "|$cmd")) {
		print MAIL $message;
		close MAIL;
	} else {
		print STDERR "cannot open \"$SENDMAIL\".\n";
	}
	1;
}

### main

my $forward = 0;
my $message = "";
my $line = 0;
my ($from_parsing, $from_header) = (0, "");
my ($to_parsing, $to_header) = (0, "");
my ($cc_parsing, $cc_header) = (0, "");

# parse header
while (<>) {
	chop;
	last if /^\s*$/;
	if($from_parsing) {
		if(/^\s+(\S.*)$/) {
			$from_header .= " $1";
			next;
		} else {
			$message .= "Reply-To: $from_header\n";
			$forward = 1 if $from_header =~ /$FORWARD_FROM/;
			$from_parsing = 0;
		}
	} elsif($to_parsing) {
		if(/^\s+(\S.*)$/) {
			$to_header .= " $1";
		} else {
			$to_header .= "\n";
			$to_parsing = 0;
		}
	} elsif($cc_parsing) {
		if(/^\s+(\S.*)$/) {
			$cc_header .= " $1";
		} else {
			$cc_header .= "\n";
			$cc_parsing = 0;
		}
	}
	$forward = 1 if /^Subject:\s*KEITAI/;
	if(/^From:\s+(\S.*)$/) {
		$from_header = $1;
		$from_parsing = 1;
		$_ = "From: $MAIL_FROM";
	} elsif(/^To:/) {
		$to_header .= $_;
		$to_parsing = 1;
	} elsif(/^Cc:/) {
		$cc_header .= $_;
		$cc_parsing = 1;
	}
	$message .= "$_\n";
}
$message .= sprintf("\n%s%sFrom: %s\n\n",
	$to_header, $cc_header, $from_header);

# get content
while (<>) {
	$message .= $_;
	$line++;
}
exit 0 unless $forward && $line <= $FORWARD_MAX_LINES;

&send_mail($SENDMAIL_CMD, $message);
0;