;; Copyright (c) 2003-2005 Edward Marco Baringer
;; All rights reserved. 
;; 
;; Redistribution and use in source and binary forms, with or without
;; modification, are permitted provided that the following conditions are
;; met:
;; 
;;  - Redistributions of source code must retain the above copyright
;;    notice, this list of conditions and the following disclaimer.
;; 
;;  - Redistributions in binary form must reproduce the above copyright
;;    notice, this list of conditions and the following disclaimer in the
;;    documentation and/or other materials provided with the distribution.
;; 
;;  - Neither the name of Edward Marco Baringer, nor BESE, nor the names
;;    of its contributors may be used to endorse or promote products
;;    derived from this software without specific prior written permission.
;; 
;; THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
;; "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
;; LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
;; A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT
;; OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
;; SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
;; LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
;; DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
;; THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
;; (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
;; OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.


(in-package :org.unknownlamer.ucw-im)

(defclass aux-slots-mixin ()
   ((%aux-slots
     :initform (make-hash-table :test #'eq))
    (%aux-slots-order :reader aux-slots
                      :initform nil)))

(defmethod slot-missing
            ((class t)
             (obj aux-slots-mixin)
             slot-name operation &optional new-value)
  (with-slots (%aux-slots %aux-slots-order)
      obj
   (ecase operation
     (slot-value
      (multiple-value-bind (value present-p)
                          (gethash slot-name %aux-slots)
        (if present-p value
            (slot-unbound class obj slot-name))))

     (setf
      (unless (nth-value 1 (gethash slot-name %aux-slots))
        (setf %aux-slots-order (nconc %aux-slots-order (list slot-name))))
      (setf (gethash slot-name %aux-slots) new-value))

     (slot-boundp
      (nth-value 1 (gethash slot-name %aux-slots)))

     (slot-makunbound
      (setf %aux-slots-order (delete slot-name %aux-slots-order))
      (remhash slot-name %aux-slots)))))