From 49b135580ba3d60b2f77dada99a1adc4c64ef9b2 Mon Sep 17 00:00:00 2001
From: Theodor Thornhill <theo@thornhill.no>
Date: Wed, 25 Jan 2023 21:04:00 +0100
Subject: [PATCH] Initial c-ts-mode-set-style attempt

---
 lisp/progmodes/c-ts-mode.el | 47 ++++++++++++++++++++++++++++++-------
 1 file changed, 38 insertions(+), 9 deletions(-)

diff --git a/lisp/progmodes/c-ts-mode.el b/lisp/progmodes/c-ts-mode.el
index 95f9001e0d..0585795f35 100644
--- a/lisp/progmodes/c-ts-mode.el
+++ b/lisp/progmodes/c-ts-mode.el
@@ -92,6 +92,25 @@ c-ts-mode-indent-offset
   :safe 'integerp
   :group 'c)
 
+(defun c-ts-mode--indent-style-setter (sym val)
+  "Custom setter for `c-ts-mode-set-style'."
+  (named-let loop ((res nil)
+                   (buffers (buffer-list)))
+    (if (null buffers)
+        (mapc (lambda (b)
+                (with-current-buffer b
+                  (set-default sym val)
+                  (setq-local treesit-simple-indent-rules
+                              (treesit--indent-rules-optimize
+                               (c-ts-mode--set-indent-style
+                                (if (eq major-mode 'c-ts-mode) 'c 'cpp))))))
+              res)
+      (let ((buffer (car buffers)))
+        (with-current-buffer buffer
+          (if (or (eq major-mode 'c-ts-mode) (eq major-mode 'c++-ts-mode))
+              (loop (append res (list buffer)) (cdr buffers))
+            (loop res (cdr buffers))))))))
+
 (defcustom c-ts-mode-indent-style 'gnu
   "Style used for indentation.
 
@@ -100,13 +119,27 @@ c-ts-mode-indent-style
 set instead.  This function is expected return a list that
 follows the form of `treesit-simple-indent-rules'."
   :version "29.1"
-  :type '(choice (symbol :tag "Gnu" 'gnu)
-                 (symbol :tag "K&R" 'k&r)
-                 (symbol :tag "Linux" 'linux)
-                 (symbol :tag "BSD" 'bsd)
+  :type '(choice (symbol :tag "Gnu" gnu)
+                 (symbol :tag "K&R" k&r)
+                 (symbol :tag "Linux" linux)
+                 (symbol :tag "BSD" bsd)
                  (function :tag "A function for user customized style" ignore))
+  :set #'c-ts-mode--indent-style-setter
   :group 'c)
 
+(defun c-ts-mode-set-style ()
+  (interactive)
+  (or (eq major-mode 'c-ts-mode) (eq major-mode 'c++-ts-mode)
+      (error "Buffer %s is not a c-ts-mode (c-ts-mode-set-style)"
+             (buffer-name)))
+  (c-ts-mode--indent-style-setter
+   'c-ts-mode-indent-style
+   (intern
+    (completing-read
+     "Select style: "
+     (mapcar #'car (c-ts-mode--indent-styles (if (eq major-mode 'c-ts-mode) 'c 'cpp)))
+     nil t nil nil "gnu"))))
+
 ;;; Syntax table
 
 (defvar c-ts-mode--syntax-table
@@ -255,11 +288,7 @@ c-ts-mode--set-indent-style
   (let ((style
          (if (functionp c-ts-mode-indent-style)
              (funcall c-ts-mode-indent-style)
-           (pcase c-ts-mode-indent-style
-             ('gnu   (alist-get 'gnu (c-ts-mode--indent-styles mode)))
-             ('k&r   (alist-get 'k&r (c-ts-mode--indent-styles mode)))
-             ('bsd   (alist-get 'bsd (c-ts-mode--indent-styles mode)))
-             ('linux (alist-get 'linux (c-ts-mode--indent-styles mode)))))))
+           (alist-get c-ts-mode-indent-style (c-ts-mode--indent-styles mode)))))
     `((,mode ,@style))))
 
 (defun c-ts-mode--top-level-label-matcher (node &rest _)
-- 
2.34.1