;;;; 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 term-selection)

  #:use-module (jsonld context)

  #:use-module (jsonld inverse-context-creation)

  #:use-module (jsonld json)

  #:export (term-selection))

(define* (term-selection active-context var containers type/language

                         preferred-values)

  ;; 1

  (when (json-null? (active-context-inverse-context active-context))

    (set! active-context

      (update-active-context active-context

                             #:inverse-context

                             (inverse-context-creation active-context))))

  (let ((container-map (assoc-ref (active-context-inverse-context active-context) var))

        (result json-null))

    ;; 4

    (for-each

      (lambda (container)

        ;; 4.1

        (when (json-has-key? container-map container)

          ;; 4.2

          (let* ((type/language-map (assoc-ref container-map container))

                 ;; 4.3

                 (value-map (assoc-ref type/language-map type/language)))

            (for-each

              (lambda (item)

                (when (json-has-key? value-map item)

                  (unless (not-null-or-false result)

                    (set! result (assoc-ref value-map item)))))

              preferred-values))))

      containers)

    ;; 5

    result))