[emacs-berlin] Slugify function in elisp?

[Christian Tietze]

Sharing that as an attachment didn't work so well in the archives, sorry.

Here's the elisp pasted directly:

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(defun ct/slug (title)
  "Return the slug of TITLE."
  (let ((slug-trim-chars '(;; Combining Diacritical Marks https://www.unicode.org/charts/PDF/U0300.pdf
                           768 ; U+0300 COMBINING GRAVE ACCENT
                           769 ; U+0301 COMBINING ACUTE ACCENT
                           770 ; U+0302 COMBINING CIRCUMFLEX ACCENT
                           771 ; U+0303 COMBINING TILDE
                           772 ; U+0304 COMBINING MACRON
                           774 ; U+0306 COMBINING BREVE
                           775 ; U+0307 COMBINING DOT ABOVE
                           776 ; U+0308 COMBINING DIAERESIS
                           777 ; U+0309 COMBINING HOOK ABOVE
                           778 ; U+030A COMBINING RING ABOVE
                           779 ; U+030B COMBINING DOUBLE ACUTE ACCENT
                           780 ; U+030C COMBINING CARON
                           795 ; U+031B COMBINING HORN
                           803 ; U+0323 COMBINING DOT BELOW
                           804 ; U+0324 COMBINING DIAERESIS BELOW
                           805 ; U+0325 COMBINING RING BELOW
                           807 ; U+0327 COMBINING CEDILLA
                           813 ; U+032D COMBINING CIRCUMFLEX ACCENT BELOW
                           814 ; U+032E COMBINING BREVE BELOW
                           816 ; U+0330 COMBINING TILDE BELOW
                           817 ; U+0331 COMBINING MACRON BELOW
                           )))
    (cl-flet* ((nonspacing-mark-p (char) (memq char slug-trim-chars))
               (strip-nonspacing-marks (s) (ucs-normalize-NFC-string
                                            (apply #'string
                                                   (seq-remove #'nonspacing-mark-p
                                                               (ucs-normalize-NFD-string s)))))
               (cl-replace (title pair) (replace-regexp-in-string (car pair) (cdr pair) title)))
      (let* ((pairs `(("[^[:alnum:][:digit:]]" . "-") ;; convert anything not alphanumeric
                      ("__*" . "_")                   ;; remove sequential underscores
                      ("--*" . "-")                   ;; remove sequential dashes
                      ("^-+" . "")                    ;; remove starting dashes
                      ("-+$" . "")))                  ;; remove ending dashes
             (slug (-reduce-from #'cl-replace (strip-nonspacing-marks title) pairs)))
        (downcase slug)))))
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