module Sinatra::Helpers

=> Expires: Mon, 08 Jun 2009 08:50:17 GMT
=> Cache-Control: public, must-revalidate, max-age=60
expires 500, :public, :must_revalidate

"values" arguments are passed to the #cache_control helper:
indicating when the response should be considered "stale". The remaining
can be an integer number of seconds in the future or a Time object
Set the Expires header and Cache-Control/max-age directive. Amount

def expires(amount, *values)
  values << {} unless values.last.kind_of?(Hash)
  if amount.respond_to?(:to_time)
    max_age = amount.to_time - Time.now
    time = amount.to_time
  else
    max_age = amount
    time = Time.now + amount
  end
  values.last.merge!(:max_age => max_age)
  cache_control(*values)
  response['Expires'] = time.httpdate
end