module Doorkeeper::Models::Expirable

def expired?
  expires_in && Time.now > expired_time
end

def expired_time
  created_at + expires_in.seconds
end

def expires_in_seconds
  return nil if expires_in.nil?
  expires = (created_at + expires_in.seconds) - Time.now
  expires_sec = expires.seconds.round(0)
  expires_sec > 0 ? expires_sec : 0  
end