;;; toggle-light-dark-theme.el -- Toggle dark and light theme  -*- lexical-binding: t -*-
;;
;; Copyright (C) 2020 Free Software Foundation, Inc.
;;
;; Author: Caio Henrique <caio.hcs0@gmail.com>
;; Maintainer: emacs-devel@gnu.org
;; Keywords: faces
;; Package: emacs

;; This file is part of GNU Emacs.

;; GNU Emacs 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.

;; GNU Emacs 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 GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.

;;; Commentary:

;; This file provides a function to toggle between a light and a dark
;; theme, the two themes can be specified with customize-option, the
;; function is added to the menu bar.

;;; Code:

(defgroup toggle-light-dark-theme nil
  "Toggle light dark theme"
  :group 'faces)

(defun toggle-light-dark-theme--custom-choices (theme)
  "Used to create the choice widget options of the
toggle-light-dark-theme custom variables."
  `(const :tag ,(symbol-name theme) ,theme))

(defcustom toggle-light-dark-theme-light-theme 'modus-operandi
  "The light theme used by the function `toggle-light-dark-theme'."
  :group 'toggle-light-dark-theme
  :type `(choice ,@(mapcar #'toggle-light-dark-theme--custom-choices
			   (custom-available-themes))))

(defcustom toggle-light-dark-theme-dark-theme 'tango-dark
  "The dark theme used by the function `toggle-light-dark-theme'."
  :group 'toggle-light-dark-theme
  :type `(choice ,@(mapcar #'toggle-light-dark-theme--custom-choices
			   (custom-available-themes))))

(defvar toggle-light-dark-theme--current-theme 'light)

;;;###autoload
(defun toggle-light-dark-theme ()
  "Disables all custom enabled themes and then toggles between a
light and a dark theme, which are the values of the variables
`toggle-light-dark-theme-light-theme' and
`toggle-light-dark-theme-dark-theme'."
  (interactive)
  (mapc #'disable-theme custom-enabled-themes)
  (cond ((eq toggle-light-dark-theme--current-theme 'light)
	 (load-theme toggle-light-dark-theme-dark-theme)
	 (setq toggle-light-dark-theme--current-theme 'dark))
	(t
	 (load-theme toggle-light-dark-theme-light-theme)
	 (setq toggle-light-dark-theme--current-theme 'light))))

(provide 'toggle-light-dark-theme)

;;; toggle-light-dark-theme.el ends here