;; disfluid, implementation of the Solid specification
;; Copyright (C) 2021  Vivien Kraus

;; This program is free software: you can redistribute it and/or modify
;; it under the terms of the GNU Affero General Public License as
;; published by the Free Software Foundation, either version 3 of the
;; License, or (at your option) any later version.

;; This program 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 Affero General Public License for more details.

;; You should have received a copy of the GNU Affero General Public License
;; along with this program.  If not, see <https://www.gnu.org/licenses/>.

(define-module (webid-oidc serve)
  #:use-module (webid-oidc errors)
  #:use-module (webid-oidc fetch)
  #:use-module (webid-oidc web-i18n)
  #:use-module ((webid-oidc parameters) #:prefix p:)
  #:use-module (ice-9 optargs)
  #:use-module (ice-9 receive)
  #:use-module (ice-9 exceptions)
  #:use-module (rnrs bytevectors)
  #:use-module (web request)
  #:use-module (web response)
  #:use-module (web uri)
  #:use-module (rdf rdf)
  #:use-module (turtle fromrdf)
  #:use-module (nquads fromrdf)
  #:use-module (json)
  #:use-module (jsonld)
  #:declarative? #t
  #:export
  (

   &not-acceptable
   make-not-acceptable
   not-acceptable?
   not-acceptable-client-accepts
   not-acceptable-path
   not-acceptable-content-type
   
   convert
   ))

(define-exception-type
  &not-acceptable
  &external-error
  make-not-acceptable
  not-acceptable?
  (client-accepts not-acceptable-client-accepts)
  (path not-acceptable-path)
  (content-type not-acceptable-content-type))

(define (convert client-accepts server-name path content-type content)
  (let ((data-as-rdf
         (false-if-exception
          (parameterize
              ((p:anonymous-http-request
                (lambda _
                  (values (build-response
                           #:headers `((content-type ,content-type)))
                          content))))
            (fetch
             (build-uri (uri-scheme server-name)
                        #:userinfo (uri-userinfo server-name)
                        #:host (uri-host server-name)
                        #:port (uri-port server-name)
                        #:path path))))))
    (if client-accepts
        ;; Content negociation is asked
        (let try-satisfy ((accepts client-accepts))
          (if (null? accepts)
              (let ((final-message
                     (format #f (G_ "content negociation failed while serving a request"))))
                (raise-exception
                 (make-exception
                  (make-not-acceptable client-accepts path content-type)
                  (make-exception-with-message final-message))))
              (let ((request (car accepts)))
                (cond
                 ((or (eq? request content-type)
                      (eq? request '*/*))
                  (values content-type content))
                 ((and (eq? request 'text/turtle) data-as-rdf)
                  (values 'text/turtle
                          (rdf->turtle data-as-rdf)))
                 ((and (or (eq? request 'application/n-quads)
                           (eq? request 'text/x-nquads))
                       data-as-rdf)
                  (values request
                          (rdf->nquads
                           (make-rdf-dataset data-as-rdf '()))))
                 ((and (eq? request 'application/ld+json) data-as-rdf)
                  (values 'application/ld+json
                          (scm->json-string
                           (rdf->jsonld
                            (make-rdf-dataset data-as-rdf '())))))
                 ;; Add other conversion strategies here
                 (else
                  (try-satisfy (cdr accepts)))))))
        ;; Content negociation is unwanted
        (values content-type content))))