TPP - Roman Numerals.coffee

should = require 'should'

class ArabicToRoman

    constructor: -> 
        @CONVERSIONS = [
            {'roman': 'M', 'arabic': 1000},
            {'roman': 'CM', 'arabic': 900},
            {'roman': 'D', 'arabic': 500},
            {'roman': 'CD', 'arabic': 400},
            {'roman': 'C', 'arabic': 100},
            {'roman': 'XC', 'arabic': 90},
            {'roman': 'L', 'arabic': 50},
            {'roman': 'XL', 'arabic': 40},
            {'roman': 'X', 'arabic': 10},
            {'roman': 'IX', 'arabic': 9},
            {'roman': 'V', 'arabic': 5},
            {'roman': 'IV', 'arabic': 4},
            {'roman': 'I', 'arabic': 1}
        ]
    
    retrieve_partial_conversion: (arabic) ->
        return candidate for candidate in @CONVERSIONS when arabic >= candidate.arabic

    can_represent_in_roman: (arabic) -> arabic >= 1

    convert: (arabic, conversion = '') ->
        return conversion unless @can_represent_in_roman arabic

        partial_conversion = @retrieve_partial_conversion arabic
        return @convert(arabic - partial_conversion.arabic, conversion + partial_conversion.roman)

describe 'ArabicToRoman', ->

    before -> @converter = new ArabicToRoman

    it 'converts 0 to empty string', -> @converter.convert(0).should.eql('')

    it 'converts 1 to I', -> @converter.convert(1).should.eql('I')

    it 'converts 2 to II', -> @converter.convert(2).should.eql('II')

    it 'converts 4 to IV', -> @converter.convert(4).should.eql('IV')

    it 'converts 5 to V', -> @converter.convert(5).should.eql('V')
    
    it 'converts 6 to VI', -> @converter.convert(6).should.eql('VI')
        
    it 'converts 9 to IX', -> @converter.convert(9).should.eql('IX')

    it 'converts 10 to X', -> @converter.convert(10).should.eql('X')
    
    it 'converts 40 to XL', -> @converter.convert(40).should.eql('XL')

    it 'converts 50 to L', -> @converter.convert(50).should.eql('L')

    it 'converts 90 to XC', -> @converter.convert(90).should.eql('XC')
    
    it 'converts 100 to C', -> @converter.convert(100).should.eql('C')

    it 'converts 400 to CD', -> @converter.convert(400).should.eql('CD')
    
    it 'converts 500 to D', -> @converter.convert(500).should.eql('D')

    it 'converts 900 to CM', -> @converter.convert(900).should.eql('CM')

    it 'converts 1000 to M', -> @converter.convert(1000).should.eql('M')

    it 'converts 3888 to MMMDCCCLXXXVIII', -> @converter.convert(3888).should.eql('MMMDCCCLXXXVIII')