How to reverse a string selected in evil visual mode? - string

Question

I'm using Spacemacs, trying to write a function to reverse the string selected in evil visual mode. Here's what I get so far:
(defun fengqi/string-reverse (beg end)
(interactive)
(let ((string-to-reverse (buffer-substring-no-properties beg end)))
(message string-to-reverse beg end))
;; (delete-region beg end)
;; (insert (string-reverse string-to-reverse))
)
Obviously it doesn't work. How do I
get the selected region?
replace it with what I want?
I have read Enter Beg End parameters automatically in Evil-Visual-Mode, it's helpful, but I still don't how to do it.
To answer some questions in the comment:
When I was searching for some solutions, in this blog I found the function string-reverse. I tried in *ielm* buffer and it worked.
What I want is a function to reverse the string selected in evil visual mode.

Answer 1

I recently made some progress, and still there's some problem need to tackle.
The text selected in evil visual mode actually don't seem to be different from native emacs selections. What I missed is to pass the right code character to interactive, which should be r.
According to this blog, I now use search-forward and replace-match to replace the string.
And now the function looks like this:
(defun fengqi/string-reverse (beg end)
(interactive "r")
(save-restriction
(narrow-to-region beg end)
(let ((string-to-reverse (buffer-substring-no-properties (point-min) (point-max))))
(message string-to-reverse)
(goto-char (point-min))
(search-forward string-to-reverse)
(replace-match (string-reverse string-to-reverse)))))
But there's still a bug I don't know the reason. When the first character of the selected text is in upper case, this function doesn't work well:
For Abcde I expect the result to be edcbA, but instead I get EdcbA, which I don't see why.

Answer 2

Here is another implemention:
(defun ar-reverse-at-point (&optional beg end)
"Replace a string or region at point by result of ‘reverse’.
Works at any string detected at position, unless
optional BEG as start and
optional END as end are given as arguments or
an active region is set deliberately"
(interactive "*")
(let* ((pps (parse-partial-sexp (point-min) (point)))
;; (save-excursion (cadr (ar-beginning-of-string-atpt)))
(beg (cond (beg)
((use-region-p)
(region-beginning))
((and (nth 8 pps)(nth 3 pps))
(goto-char (nth 8 pps))
(point))))
;; (copy-marker (cdr (ar-end-of-string-atpt)))
(end (cond (end)
((use-region-p)
(copy-marker (region-end)))
((and (nth 8 pps)(nth 3 pps))
(forward-sexp)
(copy-marker (point)))))
(erg (buffer-substring beg end)))
(when (and beg end)
(delete-region beg end)
(insert (reverse erg)))))