auth.rb

module Hobby
  module Auth
    def self.[] *users
      Module.new do
        define_singleton_method :included do |app|
          users.each do |user|
            app.define_singleton_method user.downcase do |route|
              action = route.action
              route.action = -> do
                if user = (user.find_by_token request.headers['Authorization'])
                  instance_exec &action
                else
                  response.status = 403
                end
              end
            end
          end
        end
      end
    end
  end
end # Ends should be optional. Block nesting can be infered from two-space indent.