cryptofiat.rb

#!/usr/bin/env ruby

require 'net/http'
require 'json'

def get_json(url)
  uri = URI(url)
  JSON.parse(Net::HTTP.get uri)
end

def get_asset_eur(asset)
  uri = URI("https://api.cryptonator.com/api/ticker/#{asset}-EUR")
  get_json(uri)["ticker"]["price"].to_f
end

def get_eur_to_fiat(fiat)
  case fiat
  when "EUR"
    1.0
  else
    fixer = get_json "http://api.fixer.io/latest?symbols=#{fiat}"
    fixer["rates"][fiat].to_f
  end
end

#
# main script
#

from_asset = ARGV.shift.upcase
to_fiat = ARGV.shift.upcase
amount = ARGV.shift.to_f

converted = amount * get_asset_eur(from_asset) * get_eur_to_fiat(to_fiat)
puts "#{amount} #{from_asset} is #{converted} #{to_fiat}"