Set up content negociation

To add support for new conversion strategies, edit serve.scm and fetch.scm.

1 files changed, 73 insertions, 0 deletions

diff --git a/src/scm/webid-oidc/serve.scm b/src/scm/webid-oidc/serve.scm
new file mode 100644
index 0000000..4f54495
--- /dev/null
+++ b/src/scm/webid-oidc/serve.scm
@@ -0,0 +1,73 @@
+;; webid-oidc, 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 (ice-9 optargs)
+  #:use-module (ice-9 receive)
+  #:use-module (ice-9 exceptions)
+  #:use-module (rnrs bytevectors)
+  #:use-module (web client)
+  #:use-module (web request)
+  #:use-module (web response)
+  #:use-module (web uri)
+  #:use-module (rdf rdf)
+  #:use-module (turtle fromrdf)
+  #:use-module (nquads fromrdf)
+  #:export
+  (
+   convert
+   ))
+
+(define (convert client-accepts server-name path content-type content)
+  (let ((data-as-rdf
+         (false-if-exception
+          (fetch
+           (build-uri (uri-scheme server-name)
+                      #:userinfo (uri-userinfo server-name)
+                      #:host (uri-host server-name)
+                      #:port (uri-port server-name)
+                      #:path path)
+           #:http-get
+           (lambda args
+             (values (build-response
+                      #:headers `((content-type ,content-type)))
+                     content))))))
+    (if client-accepts
+        ;; Content negociation is asked
+        (let try-satisfy ((accepts client-accepts))
+          (if (null? accepts)
+              (raise-exception (make-not-acceptable client-accepts path content-type))
+              (let ((request (caar 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 '()))))
+                 ;; Add other conversion strategies here
+                 (else
+                  (try-satisfy (cdr accepts)))))))
+        ;; Content negociation is unwanted
+        (values content-type content))))