#!/usr/bin/env ruby

require 'uri'
require 'net/http'
require 'json'

class CPIFetcher
  DEFAULT_CPI_SERIES_URL = 'http://api.bls.gov/publicAPI/v2/timeseries/data/CUUSA210SA0'.freeze
  attr_reader :url, :bls_token

  def initialize
    @url = URI(ENV['CPI_SERIES_URL'] || DEFAULT_CPI_SERIES_URL)
    @bls_token = ENV.fetch('BLS_TOKEN')
  end

  def cpi
    resp = fetch_raw_response

    return nil unless resp['Results']['series']

    data = resp['Results']['series'].first['data']
    data.sort! { |a, b| a['year'] <=> b['year'] }
    data.last['value']
  end

  private

  def fetch_raw_response
    res = Net::HTTP.start(url.hostname, url.port) do |http|
      http.request(build_request)
    end
    JSON.parse(res.body)
  end

  def build_request
    req = Net::HTTP::Get.new(url)
    req['Authorization'] = "token #{bls_token}"
    req
  end
end

if $PROGRAM_NAME == __FILE__
  puts CPIFetcher.new.cpi
  exit 0
end