assign ids to html headers

this code feels like it could be way shorter and prettier

and it's broken for a few edge cases, here's some i can think of:
- it makes no attempt to ensure the ids that it assigns are unique on
  the page
- there might yet be weird characters inappropriate for an id that it
  uses anyway
- it doesn't make an attempt to limit the length of the id

but other than that it pretty much works

main.scm

@@ -139,6 +139,20 @@
         (hr)
         (footer (p "Generated by " (a (@ href "https://git.m455.casa/repo2html/") "repo2html")))))))
 
+(define (slugify tag inner)
+  (-> inner
+      (pre-post-order*
+       `(
+         (*text* . ,(lambda (trig str)
+                      (-> str
+                          (string-translate "/,:;\"[]{}()=+")
+                          (string-translate "ABCDEFGHIJKLMNOPQRSTUVWXYZ _." "abcdefghijklmnopqrstuvwxyz---")
+                          )))
+         ,@alist-conv-rules*))))
+
+(define (enumerate-tag tag inner)
+  `(,tag (@ (id ,(slugify tag inner))) ,inner))
+
 (define (in-git-directory?)
   (not (eof-object? (call-with-input-pipe "git rev-parse --git-dir" read-line))))
 
@@ -245,10 +259,19 @@
           (SXML->HTML
            (pre-post-order*
            (template-wrap->sxml filename sxml)
-           `((*text* . ,(lambda (trigger str)
-                         (if (equal? str (unspecified-value))
-                             ""
-                             ((alist-ref '*text* alist-conv-rules*) trigger str))))
+           `(;; assign all headings an id so you can link to them
+             (h1     . ,enumerate-tag)
+             (h2     . ,enumerate-tag)
+             (h3     . ,enumerate-tag)
+             (h4     . ,enumerate-tag)
+             (h5     . ,enumerate-tag)
+             ;; i'd expect this to be built-in, dunno why its needed
+             (*COMMENT* . ,(lambda (tag str) `("<!--" ,str "-->")))
+             ;; ignore #<unspecified> in tree
+             (*text* . ,(lambda (trigger str)
+                          (if (equal? str (unspecified-value))
+                              ""
+                              ((alist-ref '*text* alist-conv-rules*) trigger str))))
              ,@alist-conv-rules*))))))
 
     (create-directory html-repo-path #t)