#!/usr/bin/perl
#   MailTrim.pl 1.6 2004-10-19 15:08:29-04 support Exp

sub Usage;
sub TrimMail;

use Getopt::Std;
getopts("n:k:vdT") || Usage;

# loop through the file(s) presented
for $file (@ARGV) {
	TrimMail($file);
}

exit 0;

# TrimMail - delete dup or excess mail messages in a file

sub TrimMail
{
	my ($filename) = $_[0];
	my (@msgs) = ();
	my ($Nmsgs, $inhead, $save_len, $first_msg) = (0,0,0,0);
	my ($som_loc, $last_som);

	unless (open(MFILE, "+<$filename")) {
		print STDERR "Skipping file $filename, can't open: $!\n";
		return;
	}
	flock(MFILE, 2) || die "Lock failed: $!";
	print STDERR "File $filename opened and locked\n" if $opt_v;

	$som_loc = 0;
	while (<MFILE>) {
		if (m/^From /) {
			# this is the start of a message, save the length if needed
			if ($save_len) {
				$msgs[$Nmsgs]{len} = $last_som - $som_loc;
				$save_len = 0;
				$Nmsgs++;
			}
			$som_loc = $last_som;
			$inhead = 1;
		} elsif ($inhead) {
			if (m/^\s*$/) {
				# end of the header
				$inhead = 0;
			} elsif (m/^Message-ID: (<[^>]+>)/i) {
				# save the Message-ID
				$MID = $1;
				if (defined $msgdata{$MID}) {
					print STDERR "Dup MID: $MID\n" if ($opt_v);
				} else {
					# save the starting loc
					$msgs[$Nmsgs]{start} = $som_loc;
					$save_len = 1;
					$msgs[$Nmsgs]{MID} = $MID;
					$msgdata{$MID} = $Nmsgs;
				}
			}
		}
		$last_som = tell(MFILE);
	}

	# handle the last message
	if ($save_len) {
		$msgs[$Nmsgs]{len} = $last_som - $som_loc;
		$Nmsgs++;
	}

	if ($opt_d) {
		print STDERR "Found $Nmsgs unique messages\n";
		for ($n = 0; $n < $Nmsgs; $n++) {
			printf STDERR "%03d %10d %7d\n", $n, $msgs[$n]{start}, $msgs[$n]{len};
		}
	}

	# find the starting message number
	if ($opt_n) {
		# limit the number of messages
		$first_msg = ( $opt_n < $Nmsgs ? $Nmsgs - $opt_n : 0 );
	} elsif ($opt_k) {
		# limit file size
		$save_len = 0;
		$first_msg = $Nmsgs;
		while ($first_msg && ($save_len+$msgs[$first_msg-1]{len}) <= (1024*$opt_k)) {
			$save_len += $msgs[--$first_msg]{len};
			printf STDERR "%03d %10d\n", $first_msg, $save_len if $opt_d;
		}
	}
	print STDERR "  First msg: $first_msg\n" if $opt_v;

	# now output the data
	if ($opt_T) {
		# truncate the file in place - DANGEROUS!!
	} else {
		unless (open(OFILE, ">$filename.NEW")) {
			warn "Didn't do file $filename, can't create copy: $!";
			close MFILE;
			return;
		}
		while ($first_msg < $Nmsgs) {
			seek(MFILE, $msgs[$first_msg]{start}, 0);
			read(MFILE, $text, $msgs[$first_msg]{len});
			print OFILE $text;
			$first_msg++;
		}
		close MFILE;
		close OFILE;

		# swap the files
		if (!link($filename, "$filename.OLD")) {
			print STDERR "$filename.NEW created\n"
			. "Unable to link $file to $filename.OLD\n";
		} elsif (!rename("$filename.NEW", $filename)) {
			print STDERR "$filename renamed to $filename.OLD\n"
			. "Unable to rename $filename.NEW to $filename\n";
		} elsif (!unlink "$filename.OLD") {
			print STDERR "Unlink of $filename.OLD failed: $!\n"
			. "file $filename has been truncated correctly\n";
		} else {
			print STDERR "  file $filename processing complete\n" if $opt_v;
		}
	}
}
# Usage - describe this program

sub Usage
{
	my $Rev = '1.6 (2004-10-19 15:08:29-04)';

	print STDERR "MailTrim v${Rev}\n"
	. "\n"
	. "  Trim a mail folder file to limit size or number of messages\n"
	. "\n"
	. "Usage\n"
	. "  MailTrim [ options ] file\n"
	. "  MailTrim [ options ] file1 [ file2 [ file3 [ ... fileN ] ] ]\n"
	. "\n"
	. "  The mail format file or files listed will be truncated as needed\n"
	. "  to limit the size by number of messages or size.\n"
	. "\n"
	. "Options\n"
	. "  -nXX    Limit the folder to the XX most recent messages\n"
	. "  -kXX    Limit the folder size to at most XX kilobytes\n"
	. "  -v      Output some progress reports on stdout\n"
	. "\n"
	. "Known limitations\n"
	. "  If the folder is modified by another program while MailTrim is\n"
	. "  running, results are undefined and data may be lost. The file is\n"
	. "  locked during truncation, but on some systems the locking may be\n"
	. "  advisory or ignored by ill-behaved programs\n"
	. "\n";

	exit 1;
}