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;;; Copyright © 2019 - 2020 Jakob L. Kreuze <zerodaysfordays@sdf.org>
;;;
;;; This program is free software; you can redistribute it and/or
;;; modify it under the terms of the GNU 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
;;; General Public License for more details.
;;;
;;; You should have received a copy of the GNU General Public License
;;; along with this program. If not, see
;;; <http://www.gnu.org/licenses/>.
(define-module (jakob utils sxml)
#:use-module (ice-9 match)
#:use-module (srfi srfi-1)
#:export (hyperlink
image
stylesheet
script
sanitize-subtree
rewrite-absolute-urls-as-relative))
;;;
;;; Utility procedures to aid in writing SXML by hand.
;;;
(define (hyperlink target text)
`(a (@ (href ,target)) ,text))
(define* (image file-name #:optional description)
(let ((src (string-append "/static/image/" file-name)))
(if description
`(img (@ (src ,src) (alt ,description) (title ,description)))
`(img (@ (src ,src))))))
(define (stylesheet file-name)
`(link (@ (rel "stylesheet") (href ,(format #f "/static/css/~a" file-name)))))
(define (script file-name)
(let ((src (string-append "/static/js/" file-name)))
`(script (@ (src ,src)))))
;;;
;;; A reader extension for implicitly-sanitized SXML trees.
;;;
(define (sanitize-subtree subtree)
"Remove `nil', `#f', and any unspecified elements from `sbtree'"
(if (list? subtree)
(map sanitize-subtree (remove (lambda (elt)
(or (unspecified? elt)
(eq? 'nil elt)
(eq? #f elt)))
subtree))
subtree))
(define (sxml-reader chr port)
"Read an SXML literal expression possibly containing unquote forms and
sanitize the resultant subtree."
`(sanitize-subtree ,(cons 'quasiquote (list (read port)))))
;; Install the reader extension when imported.
(read-hash-extend #\< sxml-reader)
(define (rewrite-absolute-urls-as-relative tree)
(match tree
(('a attrs body ...)
(if (assoc 'href (cdr attrs))
(let* ((url (car (assoc-ref (cdr attrs) 'href)))
(url (if (string-prefix? "https://jakob.space" url)
(string-drop url (string-length "https://jakob.space"))
url))
(url (if (string-prefix? "http://jakob.space" url)
(string-drop url (string-length "http://jakob.space"))
url))
(attrs `(@ (href ,url) ,@(filter (match-lambda
(('href _) #f)
(_ #t))
(cdr attrs)))))
`(a ,attrs ,@body))
tree))
((xs ...)
(map rewrite-absolute-urls-as-relative xs))
(elem elem)))
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