Rakefile

#!/usr/bin/env rake
# frozen_string_literal: true

require 'bundler/gem_tasks'

desc '郵便番号のデータを作成/更新する'
task :create_zip_code_data do
  require 'csv'
  require 'jp_prefecture'

  file_name = 'ken_all_utf8.csv'

  # download files
  `curl -O https://www.post.japanpost.jp/zipcode/dl/kogaki/zip/ken_all.zip`
  `unzip ken_all.zip`
  `iconv -f sjis -t utf-8 ken_all.csv > #{file_name}`
  `rm ken_all.zip`
  `rm ken_all.csv`

  zips = []

  # read CSV
  CSV.foreach(file_name, headers: false) { |line| zips << [line[2], line[6]] }

  # create sorted list of zips -> prefecture_code
  zips = zips
         .collect { |zip, prefecture| [zip.to_i, JpPrefecture::Prefecture.find(name: prefecture).code] }
         .sort { |x, y| x[0] <=> y[0] }

  # prepare calculation
  ranged_zips = []
  current = [zips.first[0], zips.first[0], zips.first[1]]

  # calculate the zip ranges of each prefecture
  zips.each do |zip, code|
    if current[2] == code
      current[1] = zip
    else
      ranged_zips << current
      current = [zip, zip, code]
    end
  end

  # add last prefecture
  ranged_zips << current

  # create prefecture hash
  prefectures_to_zip = {}

  ranged_zips.each do |r0, r1, code|
    prefectures_to_zip[code] ||= []
    prefectures_to_zip[code] << [r0, r1]
  end

  prefectures_to_zip = Hash[*prefectures_to_zip.sort.flatten(1)]
  # save result
  File.open('data/zip.yml', 'w') do |file|
    file.write "# { prefecture_code: [[from_zip_1, to_zip_1], [from_zip_2, to_zip_2], ...], ... }\n"
    file.write "# Last updated: #{Time.now.utc}\n"
    file.write prefectures_to_zip.to_yaml
  end

  # delete temporary file
  `rm #{file_name}`
end