#!/usr/bin/perl -w

use strict;
use warnings;
use RRDs;

my ($rrdfile, $srcrra, @dstrras) = @ARGV;
if (!defined $rrdfile) {
  die "usage: $0 </path/to/some.rrd> <source rra> <new rra> [ ... ]\n" .
      "e.g. to add both the MIN and AVERAGE rra to /var/db/eth0.rrd and " .
      "using the MAX rra as template::\n" .
      "$0 /var/db/eth0.rrd MAX MIN AVERAGE";
}

my $tmpfile = $rrdfile . ".xml";
my $tmpfile2 = $rrdfile . "2.xml";

RRDs::dump($rrdfile, $tmpfile);
my $err = RRDs::error;
die "cannot dump $rrdfile: $err" if $err;

open(SRC, $tmpfile) || die "cannot open $tmpfile: $!";
open(DST, ">$tmpfile2") || die "cannot open $tmpfile2: $!";

my $state = 0;
my @buffer;
while (<SRC>) {
  print DST;
  push @buffer, $_ if ($state == 2);
  $state = 2 if ($state && /\<cf\>$srcrra\<\/cf\>/);
  $state = 1 if /\<rra\>/;
  if (/\<\/rra\>/) {
    if ($state == 2) {
      foreach my $line(@dstrras) {
        print DST '<rra><cf>', $line, '</cf>';
        foreach (@buffer) {
          print DST;
        }
      }
    }
    $state = 0;
    @buffer = ();
  }
}

close(DST);
close(SRC);

rename($rrdfile, "$rrdfile.old") || die "cannot rename $rrdfile to $rrdfile.old: $!";

RRDs::restore($tmpfile2, $rrdfile);
$err = RRDs::error;
die "cannot restore $rrdfile from $tmpfile2: $err" if $err;

foreach ($tmpfile, $tmpfile2) {
  unlink($_) || warn "cannot remove $_: $!";
}