# frozen_string_literal: true

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

class CPIFetcher
  DEFAULT_CPI_SERIES_URL = File.join(
    'https://api.bls.gov',
    'publicAPI/v2/timeseries/data/CUUSA210SA0'
  )
  private_constant :DEFAULT_CPI_SERIES_URL
  attr_reader :url, :bls_token
  private :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']

    last_cpi_value(resp['Results']['series'].first['data'])
  end

  private def last_cpi_value(data)
    data
      .sort { |a, b| a['year'] <=> b['year'] }
      .then { |d| d.last['value'] }
  end

  private def fetch_raw_response
    Net::HTTP.new(url.hostname, url.port)
      .tap { |h| h.use_ssl = true }
      .tap { |h| h.verify_mode = OpenSSL::SSL::VERIFY_PEER }
      .then { |h| JSON.parse(h.request(build_request).body) }
  end

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

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