;;;; 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 (turtle tordf)
  #:use-module (ice-9 match)
  #:use-module (ice-9 textual-ports)
  #:use-module (iri iri)
  #:use-module (turtle parser)
  #:use-module (srfi srfi-9)
  #:use-module (rdf rdf)
  #:export (turtle->rdf))

(define-record-type parser-state
  (make-parser-state base-uri namespaces bnode-labels cur-subject cur-predicate
                     cur-object blank-node-gen result)
  parser-state?
  (base-uri       parser-state-base-uri)
  (namespaces     parser-state-namespaces)
  (bnode-labels   parser-state-bnode-labels)
  (cur-subject    parser-state-cur-subject)
  (cur-predicate  parser-state-cur-predicate)
  (cur-object     parser-state-cur-object)
  (blank-node-gen parser-state-blank-node-gen)
  (result         parser-state-result))

(define* (update-parser-state
           state #:key (base-uri (parser-state-base-uri state))
                       (namespaces (parser-state-namespaces state))
                       (bnode-labels (parser-state-bnode-labels state))
                       (cur-subject (parser-state-cur-subject state))
                       (cur-predicate (parser-state-cur-predicate state))
                       (cur-object (parser-state-cur-object state))
                       (blank-node-gen (parser-state-blank-node-gen state))
                       (result (parser-state-result state)))
  (make-parser-state base-uri namespaces bnode-labels cur-subject cur-predicate
                     cur-object blank-node-gen result))

(define (create-generate-blank-node)
  (define num 0)
  (lambda ()
    (set! num (+ num 1))
    num))

(define (add-ns-to-state state ns iri)
  (update-parser-state state
    #:namespaces (cons (cons ns iri) (parser-state-namespaces state))))

(define (parse-string str)
  (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 (parse-iri iri state)
  (match iri
    (('iri ('prefixed-name ('pname-ln ('pname-ns ns) ('pn-local suffix))))
     `(("iri" . ,(string-append (assoc-ref (parser-state-namespaces state) ns)
                                suffix))
       ("state" . ,state)))
    (('iri ('prefixed-name ('pname-ln ('pname-ns ('pn-local suffix)))))
     `(("iri" . ,(string-append (assoc-ref (parser-state-namespaces state) "")
                                suffix))
       ("state" . ,state)))
    (('iri ('prefixed-name ('pname-ns ns)))
     `(("iri" . ,(assoc-ref (parser-state-namespaces state) ns))
       ("state" . ,state)))
    (('iri ('prefixed-name 'pname-ns))
     `(("iri" . ,(assoc-ref (parser-state-namespaces state) ""))
       ("state" . ,state)))
    (('iri 'iriref)
     `(("iri" . ,(resolve-iri (parser-state-base-uri state) ""))
       ("state" . ,state)))
    (('iri ('iriref iri ...))
     `(("iri" . ,(resolve-iri (parser-state-base-uri state) (parse-string iri)))
       ("state" . ,state)))))

(define (parse-verb verb state)
  (match verb
    ("a" `(("verb" . "http://www.w3.org/1999/02/22-rdf-syntax-ns#type")
           ("state" . ,state)))
    (('predicate iri)
     (let ((res (parse-iri iri state)))
       `(("verb" . ,(assoc-ref res "iri"))
         ("state" . ,(assoc-ref res "state")))))))

(define (parse-object object state)
  (match object
    (('rdf-literal ('string-pat (_ str ...)))
     (let ((object
             (make-rdf-literal (parse-string str)
                               "http://www.w3.org/2001/XMLSchema#string" #f)))
       (update-parser-state state
         #:cur-object object
         #:result
         (cons
           (make-rdf-triple
             (parser-state-cur-subject state)
             (parser-state-cur-predicate state)
             (make-rdf-literal str "http://www.w3.org/2001/XMLSchema#string" #f))
           (parser-state-result state)))))
    (('rdf-literal ('string-pat (_ str ...)) ("^^" iri))
     (let* ((res (parse-iri iri state))
            (iri (assoc-ref res "iri"))
            (state (assoc-ref res "state"))
            (object (make-rdf-literal (parse-string str) iri #f)))
       (update-parser-state state
         #:cur-object object
         #:result
         (cons
           (make-rdf-triple
             (parser-state-cur-subject state)
             (parser-state-cur-predicate state)
             object)
           (parser-state-result state)))))
    (('rdf-literal ('string-pat (_ 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
         #:cur-object object
         #:result
         (cons
           (make-rdf-triple
             (parser-state-cur-subject state)
             (parser-state-cur-predicate state)
             object)
           (parser-state-result state)))))
    (('numeric-literal ('decimal num))
     (let ((object
            (make-rdf-literal num "http://www.w3.org/2001/XMLSchema#decimal" #f)))
       (update-parser-state state
         #:cur-object object
         #:result
         (cons
           (make-rdf-triple
             (parser-state-cur-subject state)
             (parser-state-cur-predicate state)
             object)
           (parser-state-result state)))))
    (('numeric-literal ('integer int))
     (let ((object
           (make-rdf-literal int "http://www.w3.org/2001/XMLSchema#integer" #f)))
       (update-parser-state state
         #:cur-object object
         #:result
         (cons
           (make-rdf-triple
             (parser-state-cur-subject state)
             (parser-state-cur-predicate state)
             object)
           (parser-state-result state)))))
    (('numeric-literal ('double num))
     (let ((object
            (make-rdf-literal num "http://www.w3.org/2001/XMLSchema#double" #f)))
       (update-parser-state state
         #:cur-object object
         #:result
         (cons
           (make-rdf-triple
             (parser-state-cur-subject state)
             (parser-state-cur-predicate state)
             object)
           (parser-state-result state)))))
    (('boolean-literal bool)
     (let ((object
             (make-rdf-literal bool "http://www.w3.org/2001/XMLSchema#boolean" #f)))
       (update-parser-state state
         #:cur-object object
         #:result
         (cons
           (make-rdf-triple
             (parser-state-cur-subject state)
             (parser-state-cur-predicate state)
             object)
           (parser-state-result state)))))
    (('blank-node ('anon _))
     (let ((node ((parser-state-blank-node-gen state))))
       (update-parser-state state
         #:cur-object node
         #:result
         (cons
           (make-rdf-triple
             (parser-state-cur-subject state)
             (parser-state-cur-predicate state)
             node)
           (parser-state-result state)))))
    (('blank-node ('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
         #:cur-object node
         #:result
         (cons
           (make-rdf-triple
             (parser-state-cur-subject state)
             (parser-state-cur-predicate state)
             node)
           (parser-state-result state)))))
    (('blank-node-property-list ('predicate-object-list po ...))
     (let* ((node ((parser-state-blank-node-gen state)))
            (new-state (parse-predicate-object
                         po (update-parser-state state #:cur-subject node))))
       (update-parser-state new-state
         #:cur-object node
         #:cur-subject (parser-state-cur-subject state)
         #:cur-predicate (parser-state-cur-predicate state)
         #:result
         (cons
           (make-rdf-triple
             (parser-state-cur-subject state)
             (parser-state-cur-predicate state)
             node)
           (parser-state-result new-state)))))
    ('collection
     (let ((object "http://www.w3.org/1999/02/22-rdf-syntax-ns#nil"))
       (update-parser-state state
         #:cur-object object
         #:result
         (cons
           (make-rdf-triple
             (parser-state-cur-subject state)
             (parser-state-cur-predicate state)
             object)
           (parser-state-result state)))))
    (('collection objects ...)
     (let ((state (parse-collection objects state)))
       (update-parser-state state
         #:result
         (cons
           (make-rdf-triple
             (parser-state-cur-subject state)
             (parser-state-cur-predicate state)
             (parser-state-cur-object state))
           (parser-state-result state)))))
    (('iri _)
     (let* ((res (parse-iri object state))
            (iri (assoc-ref res "iri"))
            (state (assoc-ref res "state")))
       (update-parser-state state
         #:cur-object iri
         #:result
         (cons
           (make-rdf-triple
             (parser-state-cur-subject state)
             (parser-state-cur-predicate state)
             iri)
           (parser-state-result state)))))))

(define (parse-collection collection state)
  (let ((node ((parser-state-blank-node-gen state))))
    (let loop ((objects collection)
               (new-state
                 (update-parser-state state
                   #:cur-subject node
                   #:cur-predicate
                   "http://www.w3.org/1999/02/22-rdf-syntax-ns#first"))
               (previous-object #nil))
      (match objects
        ('()
         (update-parser-state new-state
           #:cur-object node
           #:cur-subject (parser-state-cur-subject state)
           #:cur-predicate (parser-state-cur-predicate state)
           #:result
           (cons
             (make-rdf-triple
               previous-object
               "http://www.w3.org/1999/02/22-rdf-syntax-ns#rest"
               "http://www.w3.org/1999/02/22-rdf-syntax-ns#nil")
             (parser-state-result new-state))))
        ((('object object) objects ...)
         (if (equal? previous-object #nil)
             (let ((new-state (parse-object object new-state)))
               (loop objects new-state node))
             (let* ((node ((parser-state-blank-node-gen new-state)))
                    (new-state
                      (update-parser-state new-state
                        #:cur-subject node))
                    (new-state (parse-object object new-state)))
               (loop
                 objects
                 (update-parser-state new-state
                   #:result
                   (cons
                     (make-rdf-triple
                       previous-object
                       "http://www.w3.org/1999/02/22-rdf-syntax-ns#rest"
                       node)
                     (parser-state-result new-state)))
                 node))))))))

(define (parse-object-list ol state)
  (let loop ((ol ol) (state state))
    (match ol
      ('() state)
      ((('object object) ol ...)
       (loop ol (parse-object object state)))
      ((ol)
       (loop ol state)))))

(define (parse-predicate-object po state)
  (let loop ((po po) (state state))
    (match po
      ((('verb verb) ('object-list ol ...) po)
       (let* ((verb (parse-verb verb state))
              (state (assoc-ref verb "state"))
              (verb (assoc-ref verb "verb"))
              (new-state (update-parser-state state #:cur-predicate verb))
              (res (parse-object-list ol new-state)))
         (loop po res)))
      ((('verb verb) ('object-list ol ...))
       (let* ((verb (parse-verb verb state))
              (state (assoc-ref verb "state"))
              (verb (assoc-ref verb "verb"))
              (new-state (update-parser-state state #:cur-predicate verb))
              (res (parse-object-list ol new-state)))
         res))
      (((('verb verb) ('object-list ol ...)) po ...)
       (let* ((verb (parse-verb verb state))
              (state (assoc-ref verb "state"))
              (verb (assoc-ref verb "verb"))
              (new-state (update-parser-state state #:cur-predicate verb))
              (res (parse-object-list ol new-state)))
         (loop po res)))
      ('() state)
      ((po)
       (loop po state)))))

(define (parse-subject s state)
  (match s
    (('iri _ ...)
     (let ((res (parse-iri s state)))
       `(("subject" . ,(assoc-ref res "iri"))
         ("state" . ,(assoc-ref res "state")))))
    (('collection objects ...)
     (let ((res (parse-collection objects state)))
       `(("subject" . ,(parser-state-cur-object res))
         ("state" . ,res))))
    ('collection
     `(("subject" . "http://www.w3.org/1999/02/22-rdf-syntax-ns#nil")
       ("state" . ,state)))
    (('blank-node ('anon _))
     (let ((node ((parser-state-blank-node-gen state))))
       `(("subject" . ,node)
         ("state" . ,state))))
    (('blank-node ('blank-node-label label))
     (if (assoc-ref (parser-state-bnode-labels state) label)
         `(("subject" . ,(assoc-ref (parser-state-bnode-labels state) label))
           ("state" . ,state))
         (let ((node ((parser-state-blank-node-gen state))))
           `(("subject" . ,node)
             ("state" . ,(update-parser-state state
                           #:bnode-labels
                           (cons
                             (cons label node)
                             (parser-state-bnode-labels state))))))))))

(define (parse-triples t state)
  (match t
    ((('subject subject) ('predicate-object-list predicate-object ...))
     (let* ((res (parse-subject subject state))
            (subject (assoc-ref res "subject"))
            (state (assoc-ref res "state"))
            (state (update-parser-state state
                    #:cur-subject subject)))
       (parse-predicate-object predicate-object state)))
    ((('blank-node-property-list ('predicate-object-list po ...))
      ('predicate-object-list predicate-object ...))
     (let* ((subject ((parser-state-blank-node-gen state)))
            (new-state (parse-predicate-object
                         po (update-parser-state state #:cur-subject subject))))
       (parse-predicate-object predicate-object new-state)))
    ((('blank-node-property-list ('predicate-object-list po ...)))
     (let* ((subject ((parser-state-blank-node-gen state))))
       (parse-predicate-object po (update-parser-state state
                                    #:cur-subject subject))))))

(define (parse-turtle-doc parse-tree state)
  (let loop ((parse-tree parse-tree) (state state))
    (match parse-tree
      ('() (parser-state-result state))
      ((('prefix-id ('pname-ns ns) ('iriref iri ...)) parse-tree ...)
       (loop parse-tree
             (add-ns-to-state
               state ns (resolve-iri (parser-state-base-uri state)
                                     (parse-string iri)))))
      ((('prefix-id ('pname-ns ('iriref iri ...))) parse-tree ...)
       (loop parse-tree
             (add-ns-to-state
               state "" (resolve-iri (parser-state-base-uri state)
                                     (parse-string iri)))))
      ((('sparql-prefix ('pname-ns ns) ('iriref iri ...)) parse-tree ...)
       (loop parse-tree
             (add-ns-to-state
               state ns (resolve-iri (parser-state-base-uri state)
                                     (parse-string iri)))))
      ((('sparql-prefix ('pname-ns ('iriref iri ...))) parse-tree ...)
       (loop parse-tree
             (add-ns-to-state
               state "" (resolve-iri (parser-state-base-uri state)
                                     (parse-string iri)))))
      ((('base ('iriref iri ...)) parse-tree ...)
       (loop parse-tree
             (update-parser-state
               state #:base-uri (resolve-iri (parser-state-base-uri state)
                                             (parse-string iri)))))
      ((('sparql-base ('iriref iri ...)) parse-tree ...)
       (loop parse-tree
             (update-parser-state
               state #:base-uri (resolve-iri (parser-state-base-uri state)
                                             (parse-string iri)))))
      ((('triples t ...) parse-tree ...)
       (let ((res (parse-triples t state)))
         (loop parse-tree (parse-triples t state))))
      ;; otherwise, it's a single element, not a list of statements
      (((? symbol? _) _ ...) (loop (list parse-tree) state)))))

(define (tordf parse-tree base)
  (define state
    (make-parser-state base '() '() #f #f #f (create-generate-blank-node) '()))
  (parse-turtle-doc parse-tree state))

(define (turtle->rdf str-or-file base)
  (define str
    (cond
      ((file-exists? str-or-file) (call-with-input-file str-or-file get-string-all))
      ((string? str-or-file) str-or-file)))
      
  (let ((parse-tree (parse-turtle str)))
    (tordf parse-tree base)))