#!/usr/bin/env ruby -w
#
# Time to party like it's roman_to_integer 'mcmxcix'
# "Learn to Program" by Chris Pine, p. 113

def roman_to_integer s
    roman_values = {
        'M' => 1000,
        'D' => 500,
        'C' => 100,
        'L' => 50,
        'X' => 10,
        'V' => 5,
        'I' => 1,
    }

    value = 0
    (0..(s.length - 1)).each do |i|
        c = s[i].chr
        if i < s.length - 1 && roman_values[c] < roman_values[s[i + 1].chr]
            value = value - roman_values[c]
        else
            value = value + roman_values[c]
        end
    end

    return value
end

test_values = [
	['I',       1],
	['II',      2],
	['III',     3],
	['IV',      4],
	['V',       5],
	['VI',      6],
	['VII',     7],
	['VIII',    8],
	['IX',      9],
	['X',       10],
	['XI',      11],
	['XII',     12],
	['XIII',    13],
	['XIV',     14],
	['XV',      15],
	['XVI',     16],
	['XVII',    17],
	['XVIII',   18],
	['XIX',     19],
	['XX',      20],
	['XXX',     30],
	['XL',      40],
	['L',       50],
	['LX',      60],
	['LXX',     70],
	['LXXX',    80],
	['XC',      90],
	['XCIX',    99],
	['C',       100],
	['CC',      200],
	['CD',      400],
	['D',       500],
	['CM',      900],
	['M',       1000],
	['MIX',     1009],
	['MCMXLV',  1945],
	['MCMXCIX', 1999],
	['MM',      2000],
	['MMM',     3000],
]

success = true
test_values.each do |roman, arabic|
	test = roman_to_integer roman
	if test != arabic
		puts "ERROR: #{roman} is #{test}, should be #{arabic}"
		success = false
	end
end

exit unless success

print "Roman number (or 'q' to quit): "
s = gets.chomp.upcase
while s != 'Q'
	puts "#{s}: #{roman_to_integer(s)}"
    print "Roman number (or 'q' to quit): "
    s = gets.chomp.upcase
end