currency_conversion

currency_conversion.rb

require 'test/unit'
extend Test::Unit::Assertions

CONVERSIONS = {
  'USD' => {
    'BRL' => 5,
    'AJU' => 3
  },
  'MXN' => { 'ARS' => 3 },
  'BRL' => { 'MXN' => 2, 'XXX' => 2 },
  'ARS' => { 'BPN' => 0.5, 'XXX' => 0.5 }
}

def convert(unit, origin_currency, conversion_currency)
  return -1 unless CONVERSIONS[origin_currency]
  
  rate = CONVERSIONS[origin_currency][conversion_currency]

  return rate * unit if rate

  CONVERSIONS[origin_currency].keys.each do |currency|
    rate_deep = convert(unit, currency, conversion_currency)
    return rate_deep * CONVERSIONS[origin_currency][currency] if rate_deep != -1
  end

  return -1
end

assert_equal convert(3, 'USD', 'BRL'), 15
assert_equal convert(3, 'USD', 'XD'), -1
assert_equal convert(3, 'XD', 'USD'), -1
assert_equal convert(3, 'USD', 'MXN'), 30
assert_equal convert(3, 'USD', 'ARS'), 90
assert_equal convert(3, 'USD', 'BPN'), 45
assert_equal convert(3, 'USD', 'XXX'), 30