Convert Kanji numerical to roman numerical

kanji_to_number.rb

# Encoding: UTF-8

module KanjiToNumber
  POS_FOR_DEN = {'十' => 1, '百' => 2, '千' => 3, '万' => 4}
  NUM_FOR_NUM = {'壱' => '1', '一' => '1', '１' => '1',
                 '弐' => '2', '二' => '2', '２' => '2',
                 '参' => '3', '三' => '3', '３' => '3',
                 '四' => '4', '４' => '4',
                 '五' => '5', '５' => '5',
                 '六' => '6', '６' => '6',
                 '七' => '7', '７' => '7',
                 '八' => '8', '８' => '8',
                 '九' => '9', '９' => '9',
                 '零' => '0', '〇' => '0', '０' => '0'}

  def self.convert(kanji)
    number = ''
    letters = kanji.chars.to_a.reverse

    letters.each_with_index do |letter, i|
      if NUM_FOR_NUM.has_key?(letter)
        number = "#{NUM_FOR_NUM[letter]}#{number}"
      elsif POS_FOR_DEN.has_key?(letter)
        add_one = (i == letters.size-1 || (i < letters.size-1 && POS_FOR_DEN.has_key?(letters[i+1])))
        add_zero = (i == 0 || i == letters.size-1)
        position = POS_FOR_DEN[letter] - (add_one || add_zero ? 1 : 0) + (add_zero ? 1 : 0)

        while number.length < position
          number = "0#{number}"
        end

        number = "1#{number}" if add_one
      end
    end

    number.to_i
  end

  # Another method, WIP
  DENS = %r{ [#{POS_FOR_DEN.keys.join}] }x
  NUMS = %r{ [#{NUM_FOR_NUM.keys.join}] }x
  MATCHER = %r{ (?<num> #{NUMS}+ )? (?<denom> #{DENS} ) }x
  def self.convert2(kanji)
    number = ''
    last_pos = 0

    puts MATCHER.inspect
    kanji.gsub!(MATCHER) do |md|
      puts "---"
      num = $1.nil? ? '一' : $1
      puts num

      denom = $2.nil? ? 0 : POS_FOR_DEN[$2]
      puts denom

      if number.length == 0
        number = '0' * (denom + num.length)
      end
      puts number

      conv_num = num.chars.to_a.collect { |n| NUM_FOR_NUM[n] }.join
      number[last_pos, (conv_num.length)] = conv_num
      last_pos = last_pos + conv_num.length

      ''
    end

    number.to_i
  end
  
end

require 'minitest/autorun'
class KanjiToNumberTest < MiniTest::Unit::TestCase
  def test_convert
    assert_equal 2012, KanjiToNumber.convert('二千十二')
    assert_equal 2012, KanjiToNumber.convert('二〇一二')
    assert_equal 2012, KanjiToNumber.convert('二〇一二')

    assert_equal 2222, KanjiToNumber.convert('二千二百二十二')
    assert_equal 2022, KanjiToNumber.convert('二千二十二')
    assert_equal 2002, KanjiToNumber.convert('二千二')
    assert_equal 2000, KanjiToNumber.convert('二千')
    assert_equal 1000, KanjiToNumber.convert('千')

    assert_equal 2220, KanjiToNumber.convert('二千二百二十')
    assert_equal 2200, KanjiToNumber.convert('二千二百')
    assert_equal 2002, KanjiToNumber.convert('二千二')

    assert_equal 1222, KanjiToNumber.convert('千二百二十二')
    assert_equal 222, KanjiToNumber.convert('二百二十二')
    assert_equal 122, KanjiToNumber.convert('百二十二')

    assert_equal 321, KanjiToNumber.convert('三二一')
    assert_equal 4321, KanjiToNumber.convert('四三二一')
    
    assert_equal 10001, KanjiToNumber.convert('万一')
    assert_equal 10001, KanjiToNumber.convert('一万一')
    assert_equal 240001, KanjiToNumber.convert('２４万一')
    assert_equal 11110, KanjiToNumber.convert('万千百十')
  end
end