一个把 wikitext 转换成 markdown 的 Emacs 函数

(defun wikitext-convert-all (&optional start end)
  "Convert simple wikitext to GFM markdown."

  (interactive
   (if (use-region-p)
       (list (region-beginning) (region-end))
     (list (point-min) (point-max))))

  (save-excursion
    (save-restriction
      (narrow-to-region start end)

      ;; --------------------------------------------------
      ;; 1. inline <code>
      ;; --------------------------------------------------
      (goto-char (point-min))
      (while (re-search-forward "<code>\\([^<\n]*\\)</code>" nil t)
        (replace-match (concat "`" (match-string 1) "`") t t))
      (goto-char (point-min))
      (while (re-search-forward "<code>" nil t)
        (replace-match "`"))
      (goto-char (point-min))
      (while (re-search-forward "</code>" nil t)
        (replace-match "`"))

      ;; --------------------------------------------------
      ;; 2. syntaxhighlight
      ;; --------------------------------------------------
      (goto-char (point-min))
      (while (re-search-forward "<syntaxhighlight\\s-+lang=[\"']\\([^\"']+\\)[\"'][^>]*>" nil t)
        (replace-match (concat "```" (match-string 1)) t t))
      (goto-char (point-min))
      (while (re-search-forward "</syntaxhighlight>" nil t)
        (replace-match "```"))

      ;; --------------------------------------------------
      ;; 3. 列表 # → *
      ;; --------------------------------------------------
      (let ((in-code-block nil))
        (goto-char (point-min))
        (while (not (eobp))
          (let ((line (thing-at-point 'line t)))
            (when (string-match "^```" line)
              (setq in-code-block (not in-code-block)))
            (unless in-code-block
              (beginning-of-line)
              (while (search-forward "#" (line-end-position) t)
                (replace-match "*"))))
          (forward-line 1)))

      ;; --------------------------------------------------
      ;; 4. headings
      ;; --------------------------------------------------
      (dolist (n '(6 5 4 3 2))
        (goto-char (point-min))
        (let ((pat (format "^=\\{%d\\}[ \t]*\\(.*?\\S-\\)[ \t]*=\\{%d\\}[ \t]*$" n n))
              (rep (concat (make-string n ?#) " \\1")))
          (while (re-search-forward pat nil t)
            (replace-match rep))))

      ;; --------------------------------------------------
      ;; 5. <del> -> ~~
      ;; --------------------------------------------------
      (goto-char (point-min))
      (while (re-search-forward "<del>" nil t)
        (replace-match "~~"))
      (goto-char (point-min))
      (while (re-search-forward "</del>" nil t)
        (replace-match "~~"))

      ;; --------------------------------------------------
      ;; 6. ---- -> ---
      ;; --------------------------------------------------
      (goto-char (point-min))
      (while (re-search-forward "^----[ \t]*$" nil t)
        (replace-match "---"))

      ;; --------------------------------------------------
      ;; 11-12. 行首 ; / : 处理
      ;; --------------------------------------------------
      (goto-char (point-min))
      (while (re-search-forward "^; \\(.*\\)$" nil t)
        (replace-match (concat "<strong>" (match-string 1) "</strong>") nil nil))
      (goto-char (point-min))
      (while (re-search-forward "^: \\(.*\\)$" nil t)
        (replace-match (match-string 1) nil nil))

      ;; --------------------------------------------------
      ;; 13. [[File:xxx]] -> ![xxx]()
      ;; --------------------------------------------------
      (goto-char (point-min))
      (while (re-search-forward
              "\\[\\[File:\\([^]|]+\\)\\.[a-zA-Z0-9]+[^]]*\\]\\]"
              nil t)
        (replace-match
         (format "![%s]()" (match-string 1))
         t t))

      (widen))))