+(defconst lurk-url-regex
+ (rx (:
+ (group (+ alpha))
+ "://"
+ (group (or (+ (any alnum "." "-"))
+ (+ (any alnum ":"))))
+ (opt (group (: ":" (+ digit))))
+ (opt (group (: "/"
+ (opt
+ (* (any alnum "-/.,#:%=&_?~@"))
+ (any alnum "-/#:%=&_~@")))))))
+ "Imperfect regex used to find URLs in plain text.")
+
+(defun lurk-click-url (button)
+ (browse-url (button-get button 'url)))
+
+(defun lurk-buttonify-urls (&rest strings)
+ "Turn substrings which look like urls in STRING into clickable buttons."
+ (with-temp-buffer
+ (apply #'insert strings)
+ (goto-char (point-min))
+ (while (re-search-forward lurk-url-regex nil t)
+ (let ((url (match-string 0)))
+ (make-text-button (match-beginning 0)
+ (match-end 0)
+ 'action #'lurk-click-url
+ 'url url
+ 'follow-link t
+ 'face 'button
+ 'help-echo "Open URL in browser.")))
+ (buffer-string)))
+
+(defun lurk-add-formatting (string)
+ (with-temp-buffer
+ (insert string)
+ (goto-char (point-min))
+ (let ((bold nil)
+ (italics nil)
+ (underline nil)
+ (strikethrough nil)
+ (prev-point (point)))
+ (while (re-search-forward (rx (any "\x02\x1D\x1F\x1E")) nil t)
+ (let ((beg (+ (match-beginning 0) 1)))
+ (if bold
+ (add-face-text-property prev-point beg '(:weight bold)))
+ (if italics
+ (add-face-text-property prev-point beg '(:slant italic)))
+ (if underline
+ (add-face-text-property prev-point beg '(:underline t)))
+ (if strikethrough
+ (add-face-text-property prev-point beg '(:strike-through t)))
+ (pcase (match-string 0)
+ ("\x02" (setq bold (not bold)))
+ ("\x1D" (setq italics (not italics)))
+ ("\x1F" (setq underline (not underline)))
+ ("\x1E" (setq strikethrough (not strikethrough))))
+ (delete-region (match-beginning 0) (match-end 0))
+ (setq prev-point (point)))))
+ (buffer-string)))
+
+