jsonからcsvに変換してみる

2019-09-13 追記: 逆バージョンもやってみた。

---

久々に再帰とか使った。

def json_to_csv(src_json_path, out_csv_path)
  data = JSON.parse(IO.read(src_json_path))
  @result = {}
  recursive_parse('', data)

  header = @result.keys.join(",")
  body = @result.values.join(",")

  open(out_csv_path,'w') do |f|
    f.puts(header)
    # 改行を空白に置換
    f.puts(body.gsub("\n", " "))
  end
end

def recursive_parse(chain_key, obj)
  if obj.class == Hash
    obj.each { |k,v| recursive_parse(chain_key + "|" + k.to_s , v )}
  elsif obj.class == Array
    obj.each_with_index { |v, idx| recursive_parse(chain_key + "|[" + idx.to_s + "]", v)}
  else
    @result[chain_key] = obj
  end
end

json_to_csv('./tmp/test_data.json', './tmp/out.csv')

戻す方はなんか長くなったのでクラスにしてしまった。

# frozen_string_literal: true

# reCreate json from csv
class CsvToJson
  require 'json'

  EMPTY_VAR_NAME = '@empty_json_hash'
  COPIED_VAR_NAME = '@copied_json_hash'

  def csv_to_json(src_csv_path, out_json_path)
    @empty_json_hash = {}

    File.open(src_csv_path, 'r') do |f|
      @header = f.gets.chomp
      @bodies = f.each_line.inject([]) { |res, line| res << line.chomp }
    end
    header_to_json_object(@header)

    @bodies.each_with_index do |body, idx|
      @copied_json_hash = @empty_json_hash.dup
      values_into_json_object(@header, body)

      File.open(renamed_path(out_json_path, idx), 'w') do |f|
        f.puts JSON.pretty_generate(@copied_json_hash)
      end
    end
  end

  private

  def renamed_path(path, idx)
    File.dirname(path) + "/#{idx}_" + File.basename(path)
  end

  def header_to_json_object(line)
    object_define_list = line.split(',')
    object_define_list.each { |item| recursive_parse_define_string(item, 0) }
  end

  def make_tree(items, var_name)
    items.inject(var_name) { |res, i| res + (/\[|\]/ =~ i ? i : "[\"#{i}\"]") }
  end

  def suffix(target)
    /\[|\]/ =~ target ? ' = []' : ' = {}'
  end

  def recursive_parse_define_string(item, depth)
    buffer = item.split('|').reject(&:empty?)
    current = make_tree(buffer[0..depth], EMPTY_VAR_NAME)
    next_index = depth + 1

    # element at bottom. so exit this method
    return eval(current + " = ''") if next_index == buffer.length

    eval(current + suffix(buffer[next_index])) unless eval(current)

    recursive_parse_define_string(item, next_index)
  end

  def values_into_json_object(header, body)
    headers = header.split(',')
    bodies = body.split(',')

    headers.each_with_index do |item, idx|
      buffer = item.split('|').reject(&:empty?)
      eval(make_tree(buffer, COPIED_VAR_NAME) + ' = ' + "\"#{bodies[idx]}\"")
    end
  end
end

CsvToJson.new.csv_to_json('./tmp/out.csv', './tmp/out.json')