;;;; 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 iri-expansion)

  #:use-module (jsonld context)

  #:use-module (jsonld create-term-definition)

  #:use-module (jsonld download)

  #:use-module (jsonld iri)

  #:use-module (jsonld json)

  #:use-module (jsonld options)

  #:use-module (json)

  #:use-module (web uri)

  #:use-module (rnrs bytevectors)

  #:use-module (ice-9 match)

  #:use-module (srfi srfi-9)

  #:export (iri-expansion

            expand-key

            json-key-expanded-to?))

(define (expand-key active-context key)

  (assoc-ref

    (iri-expansion active-context key #:vocab? #t)

    "iri"))

(define (json-key-expanded-to? active-context element value)

  (and

    (json-object? element)

    (not

      (null?

        (filter

          (lambda (kv)

            (equal? value (expand-key active-context (car kv))))

          element)))))

(define* (iri-expansion active-context iri

                        #:key document-relative? vocab? (local-context '())

                              (defined '())

                              (options (new-jsonld-options)))

  "Expand an IRI.  This is an implementation of the IRI expansion algorithm 

defined in the JsonLD API specification."

  ;; 2

  (when (and (keyword-form? iri) (not (json-keyword? iri)))

    ;; Should give a warning and return null, we only return null without warning

    (set! iri #nil))

  ;; if not 1 or 2

  (unless (or (json-keyword? iri) (equal? iri #nil))

    ;; 3

    (when (and local-context (json-has-key? local-context iri))

      (let ((def (assoc-ref defined iri)))

        (unless (or (equal? def 'true) (equal? def #f))

          (let ((result (create-term-definition active-context local-context iri defined

                                                #:options options)))

            (set! active-context (assoc-ref result "active-context"))

            (set! defined (assoc-ref result "defined"))))))

    (cond

      ((not (string? iri))

       #t)

      ;; 4

      ((and (term-definition? (term-definition-ref active-context iri))

            (json-keyword?

              (term-definition-iri (term-definition-ref active-context iri))))

       (set! iri (term-definition-iri (term-definition-ref active-context iri))))

      ;; 5

      ((and vocab?

            (term-definition? (term-definition-ref active-context iri)))

       (set! iri (term-definition-iri (term-definition-ref active-context iri))))

      ;; 6

      ((and (not (equal? iri ""))

            (string-index (substring iri 1) #\:))

       ;; 6.1

       (let ((prefix (car (string-split iri #\:)))

             (suffix (string-join (cdr (string-split iri #\:)) ":")))

         (if (or (equal? prefix "_")

                 (and (> (string-length suffix) 1) (equal? (substring suffix 0 2) "//")))

           ;; 6.2

           (set! iri iri)

           (begin

             ;; 6.3

             (when (and (json-object? local-context)

                        (json-has-key? local-context prefix))

               (let ((def (assoc-ref defined prefix)))

                 (unless (or (equal? def 'true))

                   (let* ((result (create-term-definition active-context local-context prefix defined

                                                          #:options options)))

                     (set! active-context (assoc-ref result "active-context"))

                     (set! defined (assoc-ref result "defined"))))))

             ;; 6.4

             (if (and

                   (term-definition? (term-definition-ref active-context prefix))

                   (term-definition-iri (term-definition-ref active-context prefix))

                   (term-definition-prefix? (term-definition-ref active-context prefix)))

               (set! iri

                 (string-append (term-definition-iri

                                  (term-definition-ref active-context prefix))

                                suffix))

               ;; 6.5

               (cond

                 ((absolute-iri? iri)

                  (set! iri iri))

                 ;; 7

                 ((and vocab? (active-context-vocab active-context))

                  (set! iri (string-append (active-context-vocab active-context)

                                           iri)))

                 (else

                   (if (and document-relative? (not (equal? (active-context-base active-context) #nil)))

                       ;; 8

                       (set! iri (resolve-iri (or

                                                (active-context-base active-context)

                                                (jsonld-options-base options))

                                              iri))

                       ;; 9

                       (set! iri iri)))))))))

      ;; 7

      ((and vocab? (active-context-vocab active-context))

       (set! iri (string-append (active-context-vocab active-context)

                                iri)))

      (else

        (if (and document-relative? (not (equal? (active-context-base active-context) #nil)))

          ;; 8

          (set! iri (resolve-iri (or

                                   (active-context-base active-context)

                                   (jsonld-options-base options))

                                 iri))

          ;; 9

          (set! iri iri)))))

  ;; return an alist of potentially modified objects: iri (the return iri),

  ;; defined and active-context.

  `(("iri" . ,iri) ("active-context" . ,active-context) ("defined" . ,defined)))