module MongoMapper
  module Plugins
    module Timestamps
      module ClassMethods
        def timestamps!
          key :created_at, Time
          key :updated_at, Time
          class_eval { before_save :update_timestamps }
        end
      end
      
      module InstanceMethods
        def update_timestamps
          now = Time.now.utc
          self[:created_at] = now if new? && !created_at?
          self[:updated_at] = now
        end
      end
    end
  end
end