;;;; 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 flattening)

  #:use-module (jsonld generate-blank-node-identifier)

  #:use-module (jsonld json)

  #:use-module (jsonld node-map-generation)

  #:export (flattening))

(define* (flattening element #:key ordered?)

  ;; 1

  (let ((node-map `(("@default" . ())))

        (default-graph '())

        (node-map-generation (get-node-map-generation

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

    ;; 2

    (set! node-map

      (assoc-ref (node-map-generation element node-map) "node-map"))

    ;; 3

    (set! default-graph (assoc-ref node-map "@default"))

    ;; 4

    (for-each-pair

      (lambda (graph-name graph)

        (unless (equal? graph-name "@default")

          ;; 4.1

          (unless (json-has-key? default-graph graph-name)

            (set! default-graph

              (alist-set default-graph graph-name `(("@id" . ,graph-name)))))

          ;; 4.2

          (let ((entry (assoc-ref default-graph graph-name))

                (graph-entry '()))

            ;; 4.3

            (set! entry

              (alist-set entry "@graph" '()))

            ;; 4.4

            (for-each-pair

              (lambda (id node)

                (unless (null?

                          (filter

                            (lambda (kv)

                              (not (equal? (car kv) "@id")))

                            node))

                  (set! graph-entry (cons node graph-entry))))

              (if ordered?

                  (alist-sort-by-key graph)

                  graph))

            (set! entry

              (alist-set entry "@graph" (list->array 1 (reverse graph-entry))))

            (set! default-graph

              (alist-set default-graph graph-name entry)))))

      (if ordered?

          (alist-sort-by-key node-map)

          node-map))

    ;; 5

    (let ((flattened '()))

      ;; 6

      (for-each-pair

        (lambda (id node)

          (unless (null? (filter (lambda (kv) (not (equal? (car kv) "@id")))

                                 node))

            (set! flattened (cons node flattened))))

        (if ordered?

            (alist-sort-by-key default-graph)

            default-graph))

      ;; 7

      (list->array 1 (reverse flattened)))))