class Rack::Protection::StrictTransport

def call(env)
  status, headers, body = @app.call(env)
  headers['Strict-Transport-Security'] ||= strict_transport
  [status, headers, body]
end

def strict_transport
  @strict_transport ||= begin
    strict_transport = 'max-age=' + options[:max_age].to_s
    strict_transport += '; includeSubDomains' if options[:include_subdomains]
    strict_transport += '; preload' if options[:preload]
    strict_transport.to_str
  end
end