From 2a4948bb516435d11245256931eeb9cc0f562aba 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 | 45 +++++++++++++++++++++++++------------
 1 file changed, 31 insertions(+), 14 deletions(-)

diff --git a/lisp/progmodes/c-ts-mode.el b/lisp/progmodes/c-ts-mode.el
index 95f9001e0d..35f076b28d 100644
--- a/lisp/progmodes/c-ts-mode.el
+++ b/lisp/progmodes/c-ts-mode.el
@@ -92,7 +92,7 @@ c-ts-mode-indent-offset
   :safe 'integerp
   :group 'c)
 
-(defcustom c-ts-mode-indent-style 'gnu
+(defcustom c-ts-mode-indent-style "gnu"
   "Style used for indentation.
 
 The selected style could be one of GNU, K&R, LINUX or BSD.  If
@@ -100,13 +100,33 @@ 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 (string :tag "Gnu" "gnu")
+                 (string :tag "K&R" "k&r")
+                 (string :tag "Linux" "linux")
+                 (string :tag "BSD" "bsd")
                  (function :tag "A function for user customized style" ignore))
+  :set #'c-ts-mode--indent-style
   :group 'c)
 
+(defun c-ts-mode--indent-style (sym val)
+  "Custom setter for `c-ts-mode-indent-style'."
+  (set-default sym val))
+
+(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)))
+  (if-let ((mode (cond ((eq major-mode 'c-ts-mode) 'c)
+                       ((eq major-mode 'c++-ts-mode) 'cpp)
+                       (t nil)))
+           (choice (completing-read "Select style: " '("gnu" "k&r" "linux" "bsd"))))
+      (c-ts-mode--indent-style 'c-ts-mode-indent-style choice)
+    (kill-local-variable 'treesit-simple-indent-rules)
+    (setq-local treesit-simple-indent-rules
+                (treesit--indent-rules-optimize
+                 (c-ts-mode--set-indent-style mode)))))
+
 ;;; Syntax table
 
 (defvar c-ts-mode--syntax-table
@@ -224,19 +244,19 @@ c-ts-mode--indent-styles
            ((parent-is "do_statement") parent-bol c-ts-mode-indent-offset)
            ,@(when (eq mode 'cpp)
                `(((node-is "field_initializer_list") parent-bol ,(* c-ts-mode-indent-offset 2)))))))
-    `((gnu
+    `(("gnu"
        ;; Prepend rules to set highest priority
        ((match "while" "do_statement") parent 0)
        (c-ts-mode--top-level-label-matcher point-min 1)
        ,@common)
-      (k&r ,@common)
-      (linux
+      ("k&r" ,@common)
+      ("linux"
        ;; Reference:
        ;; https://www.kernel.org/doc/html/latest/process/coding-style.html,
        ;; and script/Lindent in Linux kernel repository.
        ((node-is "labeled_statement") point-min 0)
        ,@common)
-      (bsd
+      ("bsd"
        ((node-is "}") parent-bol 0)
        ((node-is "labeled_statement") parent-bol c-ts-mode-indent-offset)
        ((parent-is "labeled_statement") parent-bol c-ts-mode-indent-offset)
@@ -255,11 +275,8 @@ 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) nil nil #'equal))))
     `((,mode ,@style))))
 
 (defun c-ts-mode--top-level-label-matcher (node &rest _)
-- 
2.34.1