#!/usr/bin/perl -W
#
# lastmod.pl - A script which add the Last-Modified header to the specified HTML files
#
#	Copyright (C) 2006,2011 Bogdan 'bogdro' Drozdowski
#		(bogdandr AT op.pl, bogdro AT rudy.mif.pg.gda.pl)
#
#	Licence:
#	GNU General Public Licence v3
#
#	Last modified : 2011-12-18
#
#	Syntax:
#		./lastmod.pl xxx.html
#
# If the input filename is "-", standard input will be read and the result will
#	be written to the standard output.
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation; either version 3
# of the License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software Foudation:
#		Free Software Foundation
#		51 Franklin Street, Fifth Floor
#		Boston, MA 02110-1301
#		USA

use strict;
use warnings;

my ($outfname, $head, $lastmod);

if ( @ARGV == 0 ) {
	print "Syntax: $0 xxx.html\n";
	exit 1;
}

if ( $ARGV[0] !~ /\.htm/io ) {
	print "Syntax: $0 xxx.html\n";
	exit 1;
}

##########################################################
# opening the files

my $hin;
my $hout;

if ( !open ( $hin, $ARGV[0] ) ) {
#	$! is the error message
	print "$0: $ARGV[0]: $!\n";
	exit 2;
}

if ( $ARGV[0] eq '-' ) {
	$outfname = '-';
} else {
	# take only the filename
	($outfname = $ARGV[0]) =~ s/[\w\-\/\s]+\/([\w\-]+)/$1/;
	$outfname .= ".out";
}

if ( !open ( $hout, "> $outfname" ) ) {
	print "$0: $outfname: $!\n";
	close $hin;
	exit 3;
}

$head = 0;
$lastmod = 0;

my $datetime = gmtime;
$datetime =~ s/(\w+)\s+(\w+)\s+(\d+)\s+(\d{1,2}:\d{1,2}:\d{1,2})\s+(\d{4})(.*)/$1, $2 $3 $5 $4 $6/;
chop($datetime);

##########################################################
# processing:

while ( <$hin> ) {

	if ( !$head && /<head/io ) { $head = 1; }

	if ( !$head ) { print $hout $_; next; }

	if ( /Last-Modified/io && /http-equiv/io ) {

		s/content=".*"/content="$datetime GMT"/i;
		$lastmod = 1;
	}

	if ( /<\/head/io && !$lastmod ) {

		$_ = "<meta http-equiv=\"Last-Modified\" content=\"$datetime GMT\">\n$_";
	}

	print $hout $_;
}


##########################################################
# end

close $hout;
close $hin;

rename $outfname, $ARGV[0];