Software Craftsmanship Barcelona 2013 - Transformation Priority Premise [Roman Numerals Kata]

RomanNumerals.coffee

should = require 'should'

class ArabicToRomanConversions

    conversions: 
        [
            { arabic: 1, roman: 'I'},
            { arabic: 4, roman: 'IV'},
            { arabic: 5, roman: 'V'},
            { arabic: 9, roman: 'IX'},
            { arabic: 10, roman: 'X'},
            { arabic: 40, roman: 'XL'},
            { arabic: 50, roman: 'L'},
            { arabic: 90, roman: 'XC'},
            { arabic: 100, roman: 'C'},
            { arabic: 400, roman: 'CD'},
            { arabic: 500, roman: 'D'},
            { arabic: 900, roman: 'CM'}
            { arabic: 1000, roman: 'M'}
        ]

    lookup_conversion: (arabic) ->    
        for conversion in @conversions
            partial_conversion = conversion if conversion.arabic <= arabic
        partial_conversion

class ArabicToRoman

    constructor: (@dictionary) ->

    cant_convert: (arabic) -> arabic < 1

    convert: (arabic, roman = '') ->
        return roman if @cant_convert arabic
        
        partial_conversion = @dictionary.lookup_conversion arabic
        arabic_remaining = arabic - partial_conversion.arabic
        roman += partial_conversion.roman

        @convert arabic_remaining, roman

describe 'RomanNumerals', ->

    before -> @roman_converter = new ArabicToRoman(new ArabicToRomanConversions)

    it 'for 1 it should return I', -> @roman_converter.convert(1).should.eql 'I'

    it 'for 2 it should return II', -> @roman_converter.convert(2).should.eql 'II'

    it 'for 3 it should return III', -> @roman_converter.convert(3).should.eql 'III'

    it 'for 4 it should return IV', -> @roman_converter.convert(4).should.eql 'IV'

    it 'for 5 it should return V', -> @roman_converter.convert(5).should.eql 'V'

    it 'for 9 it should return IX', -> @roman_converter.convert(9).should.eql 'IX'

    it 'for 10 it should return X', -> @roman_converter.convert(10).should.eql 'X'

    it 'for 40 it should return XL', -> @roman_converter.convert(40).should.eql 'XL'

    it 'for 50 it should return L', -> @roman_converter.convert(50).should.eql 'L'

    it 'for 90 it should return XC', -> @roman_converter.convert(90).should.eql 'XC'
    
    it 'for 100 it should return C', -> @roman_converter.convert(100).should.eql 'C'

    it 'for 400 it should return CD', -> @roman_converter.convert(400).should.eql 'CD'

    it 'for 500 it should return D', -> @roman_converter.convert(500).should.eql 'D'

    it 'for 900 it should return CM', -> @roman_converter.convert(900).should.eql 'CM'

    it 'for 1000 it should return M', -> @roman_converter.convert(1000).should.eql 'M'