#!/usr/bin/env ruby
# frozen_string_literal: true

# See documentation at the end of this file.

require 'json'

# Munin uses "U" to mean "no value".
def replace_null(value)
  return 'U' if value.nil?

  value
end

if ARGV.length != 1 || ARGV.first != 'config'
  raise 'Error: plugin designed for the dirtyconfig protocol, must be run with the config argument'
end

sky = JSON.parse(`gpspipe --json --seconds 10 2> /dev/null | sed --quiet '/SKY/{p;q}'`)

puts <<~MUNIN
  multigraph gpsd_dop
  graph_title GPS dop
  graph_category gps
  xdop.label xdop
  ydop.label ydop
  vdop.label vdop
  tdop.label tdop
  hdop.label hdop
  gdop.label gdop
  pdop.label pdop
  xdop.info Longitudinal dilution of precision
  ydop.info Latitudinal dilution of precision
  vdop.info Vertical (altitude) dilution of precision
  tdop.info Time dilution of precision
  hdop.info Horizontal dilution of precision
  gdop.info Geometric (hyperspherical) dilution of precision, a combination of PDOP and TDOP
  pdop.info Position (spherical/3D) dilution of precision
  xdop.type GAUGE
  ydop.type GAUGE
  vdop.type GAUGE
  tdop.type GAUGE
  hdop.type GAUGE
  gdop.type GAUGE
  pdop.type GAUGE
  xdop.value #{replace_null(sky['xdop'])}
  ydop.value #{replace_null(sky['ydop'])}
  vdop.value #{replace_null(sky['vdop'])}
  tdop.value #{replace_null(sky['tdop'])}
  hdop.value #{replace_null(sky['hdop'])}
  gdop.value #{replace_null(sky['gdop'])}
  pdop.value #{replace_null(sky['pdop'])}

  multigraph gpsd_satellites
  graph_title GPS satellites
  graph_category gps
  nSat.min 0
  uSat.min 0
  nSat.label nSat
  uSat.label uSat
  nSat.info Number of satellites seen
  uSat.info Number of satellites used
  nSat.type GAUGE
  uSat.type GAUGE
  nSat.value #{replace_null(sky['nSat'])}
  uSat.value #{replace_null(sky['uSat'])}
MUNIN

__END__

=pod

=encoding utf8

=head1 NAME

gpsd - Munin plugin for graphing data from gpsd.

=head1 CONFIGURATION

No configuration needed.

=head1 NOTES

Requires the multigraph and dirtyconfig capabilities available in munin 2.0
and newer.

Developed and tested with gpsd 3.22.

=head1 AUTHOR

Copyright © 2022 Kenyon Ralph <kenyon@kenyonralph.com>

=head1 LICENSE

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, see L<https://www.gnu.org/licenses/>.

=cut