EU VAT rates in ruby (2020) + online fetcher to verify/update rates.

vat.rb

module VAT
  RATES = {
    "AT" => 20.0,
    "BE" => 21.0,
    "BG" => 20.0,
    "CY" => 19.0,
    "CZ" => 21.0,
    "DE" => 19.0,
    "DK" => 25.0,
    "EE" => 20.0,
    "ES" => 21.0,
    "FI" => 24.0,
    "FR" => 20.0,
    "GB" => 20.0, # not in online rates any more since Brexit
    "GR" => 24.0,
    "HR" => 25.0,
    "HU" => 27.0,
    "IE" => 23.0,
    "IT" => 22.0,
    "LT" => 21.0,
    "LU" => 17.0,
    "LV" => 21.0,
    "MT" => 18.0,
    "NL" => 21.0,
    "PL" => 23.0,
    "PT" => 23.0,
    "RO" => 19.0,
    "SE" => 25.0,
    "SI" => 22.0,
    "SK" => 20.0,
  }.freeze

  # updated twice a year - January & July
  def self.online_rates
    # https://github.com/VvanGemert/europe/blob/master/lib/europe/vat/rates.rb
    require 'rexml/document'
    require 'net/http'

    resp = Net::HTTP.get_response(URI.parse('https://europa.eu/youreurope/business/taxation/vat/vat-rules-rates/index_en.htm'))
    if resp.code.to_i == 200
      rates = {}
      data = resp.body.scan(%r{\<tbody\>(.*)\<\/tbody\>}m).first.first.strip
      xml = REXML::Document.new("<root>#{data}</root>")
      xml.first.elements.each('tr') do |result|
        next if result[3].nil?
        country = result[3].text.strip
        next if country == ""
        rate = result[5].text
        # converting to ISO 3166
        country = "GR" if country == "EL"
        rates[country] = rate.to_f if country
      end
      rates
    end
  rescue Errno::ECONNRESET
    nil
  end
end

vat_spec.rb

require 'rails_helper'

describe VAT do
  it "uses ISO 3166-1 code" do
    expect(VAT::RATES.keys).to match_array(ISO3166::Country.codes & VAT::RATES.keys)
    expect(VAT::RATES['GB']).to be > 15 # GB instead of UK
    expect(VAT::RATES['GR']).to be > 15 # GR instead of EL
  end

  it "matches countries gem rates" do
    ISO3166::Country.codes.each do |code|
      country = ISO3166::Country[code]
      if country.in_eu? || code == "GB"
        expect(VAT::RATES[code]).to eq country.vat_rates&.dig('standard')
      else # Only care about Europe so far
        expect(VAT::RATES[code]).to be_nil
      end
    end
  end

  it "matches online rates (+GB manually)", :requires_internet do
    WebMock.allow_net_connect!
    reference = VAT::online_rates
    skip "Couldn't fetch online rates" if reference.nil?
    expect(VAT::RATES).to eq(reference.merge("GB" => 20.0))
  end
end