;;;; Copyright (C) 2019, 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 value-expansion)

  #:use-module (jsonld context)

  #:use-module (jsonld iri-expansion)

  #:use-module (jsonld json)

  #:use-module (jsonld options)

  #:use-module (ice-9 match)

  #:use-module (srfi srfi-1)

  #:use-module (web uri)

  #:export (value-expansion))

(define* (value-expansion active-context active-property value

                          #:key (options (new-jsonld-options)))

  "Expand a value.  This is an implementation of the value expansion algorithm

defined in the JsonLD API specification.

See @url{https://www.w3.org/TR/json-ld-api/#value-expansion}."

  (let* ((definition (term-definition-ref active-context active-property))

         (type-mapping

           (if (term-definition? definition)

               (term-definition-type definition)

               #f))

         (language-mapping

           (if (term-definition? definition)

               (term-definition-language definition)

               #f))

         (direction-mapping

           (if (term-definition? definition)

               (term-definition-direction definition)

               #f)))

    (cond

      ;; 1

      ((and (string? value)

            (equal? type-mapping "@id"))

        (let ((result (iri-expansion active-context value

                                     #:document-relative? #t

                                     #:options options)))

          `(("@id" . ,(assoc-ref result "iri")))))

      ;; 2

      ((and (string? value)

            (equal? type-mapping "@vocab"))

        (let ((result (iri-expansion active-context value

                                     #:document-relative? #t

                                     #:vocab? #t

                                     #:options options)))

          `(("@id" . ,(assoc-ref result "iri")))))

      (else

        ;; 3

        (let ((result `(("@value" . ,value))))

          ;; 4

          (when (and type-mapping (not (member type-mapping '("@id" "@vocab" "@none"))))

            (set! result (alist-set result "@type" type-mapping)))

          ;; 5

          (when (string? value)

            (let* ((language (or language-mapping (active-context-language active-context)))

                   (direction (or direction-mapping (active-context-direction active-context))))

              (when (equal? language-mapping #nil)

                (set! language #nil))

              (when (equal? direction-mapping #nil)

                (set! direction #nil))

              (when language

                (set! result (alist-set result "@language" language)))

              (when direction

                (set! result (alist-set result "@direction" direction)))))

          ;; 6

          result)))))