Set Route 53 record from local IP

.my53.yml

options:
  only_if: "192[.]168[.]4[.].*"
base:
  host: callum
  domain: office.example.net
aws:
  resource_id: SSS2222222
  access_key_id: SSSSSS44444444
  secret_access_key: "DSFKJNDS+++SSSSS2222222SDDS"

my53.rb

#!/usr/bin/env ruby

require 'fog'
require 'socket'
require 'yaml'

module Helpers
  def self.local_ip
    orig, Socket.do_not_reverse_lookup = Socket.do_not_reverse_lookup, true  # turn off reverse DNS resolution temporarily

    UDPSocket.open do |s|
      s.connect 'iinet.net.au', 1 # hit a local endpoint
      s.addr.last
    end
  ensure
    Socket.do_not_reverse_lookup = orig
  end

  def self.settings
    @settings = YAML.load_file(File.expand_path "~/.my53.yml") if defined?(@settings).nil?
    @settings
  end
end

module Execute
  def self.construct_dns
    Fog::DNS.new({ :provider => 'AWS', :aws_access_key_id => Helpers::settings['aws']['access_key_id'], :aws_secret_access_key => Helpers::settings['aws']['secret_access_key']})
  end

  def self.full_domain_name
    "#{Helpers::settings['base']['host']}.#{Helpers::settings['base']['domain']}."
  end

  def self.delete_and_set
    this_ip = Helpers::local_ip

    if Helpers::settings['options'].is_a?(Hash) && !(Helpers::settings['options']['only_if'].nil?)
      only_if = Helpers::settings['options']['only_if'].is_a?(Regexp) ? Helpers::settings['options']['only_if'] : Regexp.new(Helpers::settings['options']['only_if'])

      if only_if.match(this_ip).nil?
        return
      end
    end

    dns = construct_dns

    changes = []
    # see if the record exists so we can nuke it (it needs to match perfectly)
    current_state = dns.list_resource_record_sets Helpers::settings['aws']['resource_id']
    if current_state.respond_to?(:body)
      current_state.body["ResourceRecordSets"].each do |record|
        if record["Name"].eql?(full_domain_name)
          changes << {:action => "DELETE",
                      :name => record["Name"],
                      :type => record["Type"],
                      :ttl => record["TTL"],
                      :resource_records => record["ResourceRecords"]}
        end
      end
    end

    # build a new record
    changes << {:action => "CREATE",
                :name => full_domain_name,
                :type => "A",
                :ttl => 600,
                :resource_records => [this_ip]
                }

    dns.change_resource_record_sets Helpers::settings['aws']['resource_id'], changes
  end
end