;;;; Copyright (C) 2020 Julien Lepiller <julien@lepiller.eu>

;;;; 

;;;; This library is free software; you can redistribute it and/or

;;;; modify it under the terms of the GNU Lesser General Public

;;;; License as published by the Free Software Foundation; either

;;;; version 3 of the License, or (at your option) any later version.

;;;; 

;;;; This library is distributed in the hope that it will be useful,

;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of

;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

;;;; Lesser General Public License for more details.

;;;; 

;;;; You should have received a copy of the GNU Lesser General Public

;;;; License along with this library; if not, write to the Free Software

;;;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

;;;; 

(define-module (jsonld generate-blank-node-identifier)

  #:use-module (jsonld json)

  #:export (get-generate-blank-node-identifier))

(define (get-generate-blank-node-identifier)

  (define identifier-map '())

  (define counter 0)

  (define* (generate-blank-node-identifier identifier)

      ;; 1

      (if (and (not (equal? identifier #nil))

               (json-has-key? identifier-map identifier))

       (assoc-ref identifier-map identifier)

       (let ((blank-node-identifier

               (string-append "_:b" (number->string counter))))

         (set! counter (+ counter 1))

         (unless (equal? identifier #nil)

           (set! identifier-map

             (alist-set identifier-map identifier blank-node-identifier)))

         blank-node-identifier)))

  generate-blank-node-identifier)