;;;; 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 (nquads tordf)

  #:use-module (ice-9 match)

  #:use-module (ice-9 textual-ports)

  #:use-module (iri iri)

  #:use-module (nquads parser)

  #:use-module (srfi srfi-9)

  #:use-module (rdf rdf)

  #:use-module (rdf utils)

  #:use-module (web uri)

  #:export (nquads->rdf))

(define-record-type parser-state

  (make-parser-state bnode-labels blank-node-gen result)

  parser-state?

  (bnode-labels   parser-state-bnode-labels)

  (blank-node-gen parser-state-blank-node-gen)

  (result         parser-state-result))

(define* (update-parser-state

           state #:key (bnode-labels (parser-state-bnode-labels state))

                       (blank-node-gen (parser-state-blank-node-gen state))

                       (result (parser-state-result state)))

  (make-parser-state bnode-labels blank-node-gen result))

(define (create-generate-blank-node)

  (define num 0)

  (lambda ()

    (set! num (+ num 1))

    num))

(define* (parse-string str #:optional for-iri?)

  (match str

    ((? string? str) str)

    ((component str ...)

     (match component

       ((? string? str1)

        (string-append str1 (parse-string str)))

       (('uchar n)

        (string-append (string (integer->char (string->number n 16)))

                       (parse-string str)))

       (('echar e)

        (string-append

          (match e

            ("\\t" "\t")

            ("\\b" "\b")

            ("\\n" "\n")

            ("\\r" "\r")

            ("\\f" "\f")

            ("\\\\" "\\")

            ("\\\"" "\"")

            ("\\'" "'"))

          (parse-string str)))))

    (() "")))

(define (valid-iri? iri)

  (and (not (string-any (ucs-range->char-set 0 33) iri))

       (not (string-any #\< iri))

       (not (string-any #\> iri))

       (string->uri iri)))

(define (parse-iri iri state)

  (match iri

    ('iriref ""

     (throw 'invalid-iri ""))

    (('iriref iri)

     (if (valid-iri? iri) iri (throw 'invalid-iri iri)))

    (('iriref iri ...)

     (let ((iri (parse-string iri)))

       (if (valid-iri? iri) iri (throw 'invalid-iri iri))))))

(define (parse-object object state)

  (match object

    (('literal ('string-literal-quote ("^^" iri)))

     (let* ((iri (parse-iri iri state))

            (object (make-rdf-literal "" iri #f)))

       (update-parser-state state

         #:result object)))

    (('literal ('string-literal-quote ('langtag lang)))

     (let ((object

           (make-rdf-literal

             ""

             "http://www.w3.org/1999/02/22-rdf-syntax-ns#langString"

             lang)))

       (update-parser-state state

         #:result object)))

    (('literal ('string-literal-quote str ...))

     (let ((object

             (make-rdf-literal (parse-string str)

                               "http://www.w3.org/2001/XMLSchema#string" #f)))

       (update-parser-state state

         #:result object)))

    (('literal ('string-literal-quote str ...) ("^^" iri))

     (let* ((iri (parse-iri iri state))

            (object (make-rdf-literal (parse-string str) iri #f)))

       (update-parser-state state

         #:result object)))

    (('literal ('string-literal-quote str ...) ('langtag lang))

     (let ((object

           (make-rdf-literal

             (parse-string str)

             "http://www.w3.org/1999/02/22-rdf-syntax-ns#langString"

             lang)))

       (update-parser-state state

         #:result object)))

    (('literal)

     (let ((object

           (make-rdf-literal

             ""

             "http://www.w3.org/1999/02/22-rdf-syntax-ns#string"

             #f)))

       (update-parser-state state

         #:result object)))

    (('blank-node-label label)

     (let* ((node

              (or (assoc-ref (parser-state-bnode-labels state) label)

                  ((parser-state-blank-node-gen state))))

            (state

              (if (assoc-ref (parser-state-bnode-labels state) label)

                  state

                  (update-parser-state state

                    #:bnode-labels

                    (cons

                      (cons label node)

                      (parser-state-bnode-labels state))))))

       (update-parser-state state

         #:bnode-labels

         (if (assoc-ref (parser-state-bnode-labels state) label)

             (parser-state-bnode-labels state)

             (cons (cons label node)

                   (parser-state-bnode-labels state)))

         #:result node)))

    (('iriref _ ...)

     (update-parser-state state

       #:result (parse-iri object state)))))

(define (parse-statement statement state)

  (match statement

    ((subject predicate object)

     (let* ((state (parse-object subject state))

            (subject (parser-state-result state))

            (state (parse-object predicate state))

            (predicate (parser-state-result state))

            (state (parse-object object state))

            (object (parser-state-result state)))

       (update-parser-state state

         #:result (cons "@default" (make-rdf-triple subject predicate object)))))

    ((subject predicate object graph-name)

     (let* ((state (parse-object subject state))

            (subject (parser-state-result state))

            (state (parse-object predicate state))

            (predicate (parser-state-result state))

            (state (parse-object object state))

            (object (parser-state-result state))

            (state (parse-object graph-name state))

            (graph-name (parser-state-result state)))

       (update-parser-state state

         #:result (cons graph-name (make-rdf-triple subject predicate object)))))))

(define (parse-nquads-doc parse-tree state)

  (let loop ((parse-tree parse-tree) (state state) (default-graph '())

                                     (named-graphs '()))

    (match parse-tree

      ('() (make-rdf-dataset default-graph named-graphs))

      ((('statement statement ...) parse-tree ...)

       (let* ((state (parse-statement statement state))

              (res (parser-state-result state))

              (graph-name (car res))

              (triple (cdr res)))

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

             (loop

               parse-tree

               state

               (cons triple default-graph)

               named-graphs)

             (loop

               parse-tree

               state

               default-graph

               (alist-set

                 named-graphs graph-name

                 (cons triple (or (assoc-ref named-graphs graph-name)'())))))))

      (('statement _ ...)

       (loop (list parse-tree) state default-graph named-graphs))

      (((parse-tree ...))

       (loop parse-tree state default-graph named-graphs)))))

(define (nquads->rdf str-or-file)

  (define str

    (cond ((port? str-or-file) (get-string-all str-or-file))

          ((string? str-or-file) str-or-file)))

  (let ((parse-tree (parse-nquads str)))

    (parse-nquads-doc

      parse-tree (make-parser-state '() (create-generate-blank-node) #f))))