#!/usr/bin/perl

use strict;
use warnings;

=head1 NAME

extractDS.px - Extract a single data-source from an RRD-file

=head1 SYNOPSYS

  extractDS.px -i input.rrd -s source_ds -o output.rrd -d destination_ds

=head1 DEPENDENCIES

extractDS.px requires Perl and the included L<Getopt::Long> module, as well as
the L<XML::Simple> module.

=cut

use Getopt::Long ('GetOptions');
use XML::Simple (qw(xml_in xml_out));
use Data::Dumper ();

our $InFile;
our $InDS;
our $OutFile;
our $OutDS;

GetOptions ("infile|i=s" => \$InFile,
	"inds|s=s" => \$InDS,
	"outfile|o=s" => \$OutFile,
	"outds|d=s" => \$OutDS) or exit (1);

if (!$InFile || !$OutFile || !$InDS || !$OutDS)
{
	print "$InFile $InDS $OutFile $OutDS\n";
	print STDERR "Usage: $0 -i <infile> -I <inds> -o <outfile> -O <outds>\n";
	exit (1);
}
if (!-f $InFile)
{
	print STDERR "Input file does not exist\n";
	exit (1);
}
if (-f $OutFile)
{
	print STDERR "Output file does exist\n";
	exit (1);
}

extract_ds ($InFile, $OutFile, $InDS, $OutDS);
exit (0);

{
my $ds_index = -1;
my $current_index = -1;
# state 0 == searching for DS index
# state 1 == parse RRA header
# state 2 == parse <ds> in RRA header
# state 3 == parse values
my $state = 0;
my $out_cache = '';
sub handle_line
{
	my $fh = shift;
	my $line = shift;

	if (!defined ($state))
	{
		$ds_index = -1;
		$current_index = -1;
		$state = 0;
		$out_cache = '';
	}

	if ($state == 0)
	{
		if ($line =~ m/<ds>/)
		{
			$out_cache = $line;
			$current_index++;
		}
		elsif ($line =~ m#<name>\s*([^<\s]+)\s*</name>#)
		{
			if ($1 eq $InDS)
			{
				$ds_index = $current_index;
				$out_cache .= "\t\t<name>$OutDS</name>\n";
			}
		}
		elsif ($line =~ m#</ds>#)
		{
			$out_cache .= $line;
			if ($ds_index == $current_index)
			{
				print $fh $out_cache;
			}
		}
		elsif ($line =~ m#<rra>#)
		{
			print $fh $line;
			$current_index = -1;
			$state = 1;
		}
		elsif ($current_index == -1)
		{
			print $fh $line;
		}
		else
		{
			$out_cache .= $line;
		}
	}
	elsif ($state == 1)
	{
		if ($line =~ m#<ds>#)
		{
			$current_index++;
			if ($current_index == $ds_index)
			{
				print $fh $line;
			}

			if ($line =~ m#</ds>#) { $state = 1; }
			else { $state = 2; }
		}
		elsif ($line =~ m#<database>#)
		{
			print $fh $line;
			$state = 3;
		}
		else
		{
			print $fh $line;
		}
	}
	elsif ($state == 2)
	{
		if ($current_index == $ds_index)
		{
			print STDERR $line;
			print $fh $line;
		}
		if ($line =~ m#</ds>#)
		{
			$state = 1;
		}
	}
	else
	{
		if ($line =~ m#</database>#)
		{
			print $fh $line;
			$current_index = -1;
			$state = 1;
		}
		else
		{
			my $line_begin = "\t\t";
			$current_index = 0;
			if ($line =~ m#(<!-- .*? -->)#)
			{
				$line_begin .= "$1 ";
			}

			while ($line =~ m#<v>\s*([^<\s]+)\s*</v>#)
			{
				my $value = $1;
				if ($current_index == $ds_index)
				{
					print $fh "$line_begin<row> <v>$value</v> </row>\n";
					last;
				}
				$current_index++;
			}
		}
	}
}} # handle_line

sub extract_ds
{
	my $in_file = shift;
	my $out_file = shift;
	my $in_ds = shift;
	my $out_ds = shift;

	my $in_fh;
	my $out_fh;

	open ($in_fh,  '-|', 'rrdtool', 'dump', $in_file) or die ("open (rrdtool): $!");
	open ($out_fh, '|-', 'rrdtool', 'restore', '-', $out_file) or die ("open (rrdtool): $!");

	while (my $line = <$in_fh>)
	{
		handle_line ($out_fh, $line);
	}

	close ($in_fh);
	close ($out_fh);
} # extract_ds

=head1 AUTHOR

Florian octo Forster E<lt>octo at verplant.orgE<gt>