;;;; 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 list-to-rdf)

  #:use-module (iri iri)

  #:use-module (jsonld deserialize-jsonld)

  #:use-module (jsonld json)

  #:use-module (jsonld object-to-rdf)

  #:use-module (rdf rdf)

  #:export (list-to-rdf))

(define* (list-to-rdf generate-blank-node rdf-direction lst list-triples)

  (let ((result json-null))

    (if (null? lst)

        ;; 1

        (set! result (rdf-iri "nil"))

        ;; 2

        (let ((bnodes (map

                        (lambda _

                          (blank-node->rdf-blank-node (generate-blank-node json-null)))

                        lst)))

          ;; 3

          (let loop ((bnodes bnodes) (lst lst))

            (unless (null? bnodes)

              ;; 3.2

              (let* ((subject (car bnodes))

                     (item (car lst))

                     (rest (cdr bnodes))

                     (rest (if (null? rest) (rdf-iri "nil") (car rest)))

                     (res (object-to-rdf generate-blank-node rdf-direction

                                         item '()))

                     (object (assoc-ref res "result"))

                     (embedded-triples (assoc-ref res "list-triples")))

                ;; 3.3

                (unless (json-null? object)

                  (set! list-triples

                    (cons (make-rdf-triple subject (rdf-iri "first") object)

                          list-triples)))

                ;; 3.4

                (set! list-triples

                  (cons (make-rdf-triple subject (rdf-iri "rest") rest)

                        list-triples))

                ;; 3.5

                (set! list-triples

                  (append list-triples embedded-triples)))

              (loop (cdr bnodes) (cdr lst))))

          ;; 4

          (if (null? bnodes)

              (set! result (rdf-iri "nil"))

              (set! result (car bnodes)))))

    `(("result" . ,result)

      ("list-triples" . ,list-triples))))