# frozen_string_literal: true

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

class CPIFetcher
  def cpi
    resp = fetch_raw_response
    return nil unless resp['Results']['series']

    resp['Results']['series'].first['data']
  end

  def cpi_csv
    CSV.generate do |csv|
      csv << %w[year period period_name value]
      cpi.each do |rec|
        csv << %w[
          year period periodName value
        ].map { |k| rec.fetch(k) }
      end
    end
  end

  private def url
    @url ||= URI(ENV['CPI_SERIES_URL'] || File.join(
      'https://api.bls.gov',
      'publicAPI/v2/timeseries/data/'
    ))
  end

  private def series_id
    @series_id ||= ENV.fetch(
      'CPI_SERIES_ID', 'CUUR0200SA0'
    ).split(/[, ]/).map(&:strip).reject(&:empty?)
  end

  private def start_year
    @start_year ||= ENV.fetch('CPI_SERIES_START_YEAR', '2014')
  end

  private def end_year
    @end_year ||= ENV.fetch('CPI_SERIES_END_YEAR', Time.now.year.to_s)
  end

  private def bls_token
    @bls_token ||= ENV.fetch('BLS_TOKEN')
  end

  private def start_cpi_value(data)
    data = data.sort do |a, b|
      record_key(a) <=> record_key(b)
    end
    data.first.fetch('value')
  end

  private def record_key(record)
    "#{record['year']}.#{record['period']}"
  end

  private def latest_cpi_value(data)
    data.find { |d| d['latest'] == 'true' }.fetch('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::Post.new(url)
      .tap { |r| r['Authorization'] = "token #{bls_token}" }
      .tap { |r| r['Content-Type'] = 'application/json' }
      .tap { |r| r.body = JSON.generate(build_request_body) }
  end

  private def build_request_body
    {
      'seriesid' => series_id,
      'startyear' => start_year,
      'endyear' => end_year
    }
  end
end

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