module ActiveUtils::RequiresParameters

def requires!(hash, *params)
  params.each do |param|
    if param.is_a?(Array)
      raise ArgumentError.new("Missing required parameter: #{param.first}") unless hash.has_key?(param.first)
      valid_options = param[1..-1]
      raise ArgumentError.new("Parameter: #{param.first} must be one of #{valid_options.to_sentence(:words_connector => 'or')}") unless valid_options.include?(hash[param.first])
    else
      raise ArgumentError.new("Missing required parameter: #{param}") unless hash.has_key?(param)
    end
  end
end