#!/usr/bin/perl -s

use strict;
use warnings;

our ($o, $even, $odd, $all);
my $output = $o || "out.pdf";
my $tmp    = "_${$}_";

$even ||= "0cm 0cm";
$odd  ||= "0cm 0cm";

if ($all) {
    $even = $odd = $all;
}
my $file = shift @ARGV;

my $info = `pdfinfo $file|grep Pages`;
$info =~ m!(\d+)!;
my $nrPages = $1;

open TEX, ">$tmp.tex" or die "Can't create temporary files\n";
print TEX texheader();
for my $p (1..$nrPages) {
    if ($p % 2 == 0) {
        ## Even
        print TEX "\\includepdf[offset=$even,pages=$p]{$file}\n";
    } else {
        ## Odd
        print TEX "\\includepdf[offset=$odd,pages=$p]{$file}\n";
    }
}
print TEX "\\end{document}\n";
close TEX;
`pdflatex -interaction=batchmode $tmp.tex`;
`mv $tmp.pdf $output`;

for (<$tmp*>) {
    print "unlinking $_\n";
	unlink $_;
}

sub texheader {
    return <<'EOT';
\documentclass[a4paper]{article}
\usepackage{pdfpages}
\begin{document}
EOT
}