From 89418ccb92b9389d3442be2af128c593fa362acc Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Hugo=20H=C3=B6rnquist?= <hugo@lysator.liu.se>
Date: Wed, 12 Aug 2020 15:34:55 +0200
Subject: Calendar names now encoded with modified base64

---
 module/html/util.scm | 31 +++++++++++++++++++++++++++++--
 1 file changed, 29 insertions(+), 2 deletions(-)

(limited to 'module/html/util.scm')

diff --git a/module/html/util.scm b/module/html/util.scm
index 36b1d929..edbcf756 100644
--- a/module/html/util.scm
+++ b/module/html/util.scm
@@ -1,10 +1,37 @@
 (define-module (html util)
+  :use-module ((util base64)
+               :select (base64encode base64decode))
   :use-module (util))
 
+;;; @var{html-attr} & @var{html-unattr} used to just strip any
+;;; attributes not valid in css. That allowed a human reader to
+;;; quickly see what data it was. The downside was that it was one
+;;; way. The new base64 based system supports both an encode and a
+;;; decode without problem.
+;;;
+;;; The encoded string substitutes { + => å, / => ä, = => ö } to be
+;;; valid CSS selector names.
+
 ;; Retuns an HTML-safe version of @var{str}.
 (define-public (html-attr str)
-  (define cs (char-set-adjoin char-set:letter+digit #\- #\_))
-  (string-filter (lambda (c) (char-set-contains? cs c)) str))
+  (string-map (lambda (c)
+                (case c
+                  ((#\+) #\å)
+                  ((#\/) #\ä)
+                  ((#\=) #\ö)
+                  (else c)))
+              (base64encode str)))
+
+(define-public (html-unattr str)
+  (base64decode
+    (string-map (lambda (c)
+                  (case c
+                    ((#\å) #\+)
+                    ((#\ä) #\/)
+                    ((#\ö) #\=)
+                    (else c)))
+                str)))
+
 
 (define-public (date-link date)
   ((@ (datetime) date->string) date "~Y-~m-~d"))
-- 
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