--- /dev/null
+;;; fmt.el --- -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2023 John Turner
+
+;; Author: John Turner <notroot@gentoo-pc>
+
+;; This program is free software; you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; This program is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with this program. If not, see <https://www.gnu.org/licenses/>.
+
+(defgroup fmt nil
+ "Format buffers using external programs such as rustfmt.")
+
+(defcustom fmt-executable nil
+ "Formatter executable to use for formatting a buffer."
+ :local t
+ :type '(string)
+ :group 'fmt)
+
+(defcustom fmt-args nil
+ "Args to use when running fmt-executable."
+ :local t
+ :type '(repeat string)
+ :group 'fmt)
+
+(defun fmt--init-output-buffer (name)
+ (with-current-buffer (get-buffer-create name)
+ (erase-buffer)
+ (current-buffer)))
+
+(defun fmt--wait-for-processes (processes)
+ (cl-loop for process in processes
+ do (cl-loop while (accept-process-output process))))
+
+(defun fmt-process-current-buffer ()
+ (let* ((stdout-buffer (fmt--init-output-buffer "*fmt stdout*"))
+ (stderr-buffer (fmt--init-output-buffer "*fmt stderr*"))
+ (stderr (make-pipe-process
+ :name (format "%s stderr" fmt-executable)
+ :buffer stderr-buffer
+ :sentinel 'ignore
+ :noquery t))
+ (process (make-process
+ :name fmt-executable
+ :buffer stdout-buffer
+ :command (cons fmt-executable fmt-args)
+ :sentinel 'ignore
+ :noquery t
+ :connection-type 'pipe
+ :stderr stderr)))
+ (process-send-region process (point-min) (point-max))
+ (process-send-eof process)
+ (cons process stderr)))
+
+(defun fmt-current-buffer ()
+ (interactive)
+ (pcase-let ((`(,process . ,stderr) (fmt-process-current-buffer)))
+ (fmt--wait-for-processes (list process stderr))
+ (if (zerop (process-exit-status process))
+ (replace-buffer-contents (process-buffer process))
+ (message "%s failed with exit status %s. See %s for output."
+ fmt-executable
+ (process-exit-status process)
+ (process-buffer stderr)))))
+
+(provide 'fmt)
+;;; fmt.el ends here