jabber-feature-neg.el

   1 ;; jabber-feature-neg.el - Feature Negotiation by JEP-0020
   2
   3 ;; Copyright (C) 2002, 2003, 2004 - tom berger - object@intelectronica.net
   4 ;; Copyright (C) 2003, 2004 - Magnus Henoch - mange@freemail.hu
   5
   6 ;; This file is a part of jabber.el.
   7
   8 ;; This program is free software; you can redistribute it and/or modify
   9 ;; it under the terms of the GNU General Public License as published by
  10 ;; the Free Software Foundation; either version 2 of the License, or
  11 ;; (at your option) any later version.
  12
  13 ;; This program is distributed in the hope that it will be useful,
  14 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 ;; GNU General Public License for more details.
  17
  18 ;; You should have received a copy of the GNU General Public License
  19 ;; along with this program; if not, write to the Free Software
  20 ;; Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  21
  22 (require 'jabber-disco)
  23 (require 'cl)
  24
  25 (add-to-list 'jabber-advertised-features "http://jabber.org/protocol/feature-neg")
  26
  27 (defun jabber-fn-parse (xml-data type)
  28   "Parse a Feature Negotiation request, return alist representation.
  29 XML-DATA should have one child element, <x/>, in the jabber:x:data
  30 namespace.
  31
  32 TYPE is either 'request or 'response.
  33
  34 Returned alist has field name as key, and value is a list of offered
  35 alternatives."
  36   (let ((x (car (jabber-xml-get-children xml-data 'x))))
  37     (unless (and x
  38                  (string= (jabber-xml-get-attribute x 'xmlns) "jabber:x:data"))
  39       (jabber-signal-error "modify" 'bad-request "Malformed Feature Negotiation"))
  40
  41     (let (alist
  42           (fields (jabber-xml-get-children x 'field)))
  43       (dolist (field fields)
  44         (let ((var (jabber-xml-get-attribute field 'var))
  45               (value (car (jabber-xml-get-children field 'value)))
  46               (options (jabber-xml-get-children field 'option)))
  47           (setq alist (cons
  48                        (cons var
  49                              (cond
  50                               ((eq type 'request)
  51                                (mapcar #'(lambda (option)
  52                                            (car (jabber-xml-node-children
  53                                                  (car (jabber-xml-get-children
  54                                                        option 'value)))))
  55                                        options))
  56                               ((eq type 'response)
  57                                (jabber-xml-node-children value))
  58                               (t
  59                                (error "Incorrect Feature Negotiation type: %s" type))))
  60                        alist))))
  61       ;; return alist
  62       alist)))
  63
  64 (defun jabber-fn-encode (alist type)
  65   "Transform a feature alist into an <x/> node int the jabber:x:data namespace.
  66 Note that this is not the reverse of `jabber-fn-parse'.
  67
  68 TYPE is either 'request or 'response."
  69   (let ((requestp (eq type 'request)))
  70     `(x ((xmlns . "jabber:x:data")
  71          (type . ,(if requestp "form" "submit")))
  72          ,@(mapcar #'(lambda (field)
  73                        `(field
  74                          ((type . "list-single")
  75                           (var . ,(car field)))
  76                          ,@(if requestp
  77                                 (mapcar
  78                                  #'(lambda (option)
  79                                      `(option nil (value nil ,option)))
  80                                  (cdr field))
  81                               (list `(value nil ,(cadr field))))))
  82                    alist))))
  83
  84 (defun jabber-fn-intersection (mine theirs)
  85   "Find values acceptable to both parties.
  86
  87 MINE and THEIRS are alists, as returned by `jabber-fn-parse'.
  88
  89 An alist is returned, where the keys are the negotiated variables,
  90 and the values are lists containing the preferred option.  If
  91 negotiation is impossible, an error is signalled.  The errors are as
  92 specified in JEP-0020, and not necessarily the ones of higher-level
  93 protocols."
  94
  95   (let ((vars (mapcar #'car mine))
  96         (their-vars (mapcar #'car theirs)))
  97
  98     ;; are the same variables being negotiated?
  99     (sort vars 'string-lessp)
 100     (sort their-vars 'string-lessp)
 101     (let ((mine-but-not-theirs (set-difference vars their-vars :test 'string=))
 102           (theirs-but-not-mine (set-difference their-vars vars :test 'string=)))
 103       (when mine-but-not-theirs
 104         (jabber-signal-error "modify" 'not-acceptable (car mine-but-not-theirs)))
 105       (when theirs-but-not-mine
 106         (jabber-signal-error "cancel" 'feature-not-implemented (car theirs-but-not-mine))))
 107
 108       (let (alist)
 109         (dolist (var vars)
 110           (let ((my-options (cdr (assoc var mine)))
 111                 (their-options (cdr (assoc var theirs))))
 112             (let ((common-options (intersection my-options their-options :test 'string=)))
 113               (if common-options
 114                   ;; we have a match; but which one to use?
 115                   ;; the first one will probably work
 116                   (setq alist
 117                         (cons (list var (car common-options))
 118                               alist))
 119                 ;; no match
 120                 (jabber-signal-error "modify" 'not-acceptable var)))))
 121         alist)))
 122
 123 (provide 'jabber-feature-neg)
 124
 125 ;;; arch-tag: 65b2cdcc-7a5f-476b-a613-84ec8e590186