#!perl

our $DATE = '2018-06-03'; # DATE
our $VERSION = '0.001'; # VERSION

use strict;
use warnings;
use Getopt::Long;

my %Opts = (
    format         => '%4d|',
    # XXX whether to add line number to empty lines
    # XXX starting line number
    # XXX line number increment (default 1)
);

sub parse_cmdline {
    my $res = GetOptions(
        'format|f'       => \$Opts{format},
        'version|v'      => sub {
            no warnings 'once';
            print "linenum version ", ($main::VERSION || "dev"), "\n";
            exit 0;
        },
        'help|h'           => sub {
            print <<USAGE;
Usage:
  linenum [OPTIONS]... [FILE]...
  linenum --version (or -v)
  linenum --help (or -h)
Options:
  --format, -f
For more details, see the manpage/documentation.
USAGE
            exit 0;
        },
    );
    exit 99 if !$res;
}

sub run {
    my $i = 0;
    while (<>) {
        $i++;
        my $linum;
        if (/\S/) {
            $linum = sprintf $Opts{format}, $i;
        } else {
            $linum = sprintf $Opts{format}, $i;
            $linum =~ s/(-?[0-9]+)/" " x length($1)/e;
        }
        print $linum, $_;
    }
}

# MAIN

parse_cmdline();
run();

1;
# ABSTRACT: Add line number to lines
# PODNAME: linenum

__END__

=pod

=encoding UTF-8

=head1 NAME

linenum - Add line number to lines

=head1 VERSION

This document describes version 0.001 of linenum (from Perl distribution App-linenum), released on 2018-06-03.

=head1 SYNOPSIS

 linenum [OPTION]... [FILE]...

=head1 DESCRIPTION

=head1 HOMEPAGE

Please visit the project's homepage at L<https://metacpan.org/release/App-linenum>.

=head1 SOURCE

Source repository is at L<https://github.com/perlancar/perl-App-linenum>.

=head1 BUGS

Please report any bugs or feature requests on the bugtracker website L<https://rt.cpan.org/Public/Dist/Display.html?Name=App-linenum>

When submitting a bug or request, please include a test-file or a
patch to an existing test-file that illustrates the bug or desired
feature.

=head1 SEE ALSO

L<String::LineNumber>

=head1 AUTHOR

perlancar <perlancar@cpan.org>

=head1 COPYRIGHT AND LICENSE

This software is copyright (c) 2018 by perlancar@cpan.org.

This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.

=cut
