#!/usr/bin/env ruby
# Plugin to monitor Room Alert 11E environmental units.
# Requires ruby and the ruby SNMP library.
#
# Written by Phil Gold <phil_g@pobox.com>.
#
# Usage: Copy or link into /etc/munin/node.d/.  End word can be either
#        "temperature" or "humidity".
#
# Parameters:
#
# 	config   (required)
# 	autoconf (optional - used by munin-config)
#
# Config variables:
#
#       units     - DNS names of environmental units
#       community - Community to use to access the Room Alert unit
#                   Defaults to 'public'.
#       variables of the form label_<unit>_<num>, where dots and dashes in the
#         unit names are replaced with underscores - labels for specific sensors
#         in the unit.
#         e.g. env.label_192_168_1_115_2 Main Unit
#
# Example config:
#
#       [room_alert_*]
#       env.units unit1.example.com unit2.example.com
#       env.community private
#       env.label_unit1_example_com_2 Main Unit
#       env.label_unit1_example_com_3 Rack 2 Sensor

require 'snmp'

base_oid = 'enterprises.20916.1.3.1'

case $0.match('[^_]+$')[0]
when 'temperature'
  subchannel = 1
  name = 'temperature'
  label = '°C'
  letter = 't'
when 'humidity'
  subchannel = 3
  name = 'humidity'
  label = '% Relative Humidity'
  letter = 'h'
else
  exit 1
end

def is_vb_valid(vb, subchannel)
  (vb.name[-1] == 0 and vb.name[-2] == subchannel and vb.value > 1)
end

def field_name(unit, vb, letter)
  clean_unit = unit.gsub(/[.-]/, '_')
  sensor = vb.name[-3].to_s
  "#{clean_unit}_#{letter}#{sensor}"
end

def label(unit, vb)
  clean_unit = unit.gsub(/[.-]/, '_')
  sensor = vb.name[-3].to_s
  label = "#{unit} " + (ENV["label_#{clean_unit}_#{sensor}"] || "sensor #{sensor}")
end

units = (ENV['units'] || '').split(/\s+/)
community = ENV['community'] || 'public'

case ARGV[0]
when 'autoconf'
  puts 'no'
  exit 0
when 'config'
  puts "graph_title Room Alert 11E units (#{name} probes)"
  puts "graph_vlabel #{label}"
  puts 'graph_category sensors'
  puts 'graph_args --lower-limit 0 --upper-limit 100' if name == 'humidity'
  units.each do |unit|
    SNMP::Manager.open(Host: unit,
                       Community: community,
                       Version: :SNMPv1) do |manager|
      manager.walk(base_oid) do |vb|
        next unless is_vb_valid(vb, subchannel)

        puts "#{field_name(unit, vb, letter)}.label #{label(unit, vb)}"
      end
    end
  end
  exit 0
end

units.each do |unit|
  SNMP::Manager.open(Host: unit,
                     Community: community,
                     Version: :SNMPv1) do |manager|
    manager.walk(base_oid) do |vb|
      next unless is_vb_valid(vb, subchannel)

      puts "#{field_name(unit, vb, letter)}.value #{vb.value.to_f / 100}"
    end
  end
end