;;; transient-navigation.el --- Navigate with a transient mode  -*- lexical-binding: t; -*-

;; Copyright (C) 2014  Tom Willemse

;; Author: Tom Willemse <tom@ryuslash.org>
;; Keywords: convenience
;; Version: 1.0.0

;; 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 <http://www.gnu.org/licenses/>.

;;; Commentary:

;; Ease navigation by providing a minor mode that enables a transient
;; key map whenever certain navigation commands are specified.

;; The `transient-navigation-mode' and
;; `global-transient-navigation-mode' minor modes can be used to
;; enable this mode either locally or globally.

;; More keybindings can be added to your liking by using the
;; `transnav-make-transient' macro.  With this macro You can specify
;; the key to use while the transient keymap is enabled, which map you
;; would like to have activated and which function you would like it
;; to replace and put in the transient keymap.

;; Currently the variables `transient-C-navigation-map' and
;; `transient-M-navigation-map' are provided, which try to extend the
;; Control and Meta (Alt) prefixed navigation commands.  You can
;; easily add your own by creating a keymap and passing it as the MAP
;; parameter to `transnav-make-transient'.

;;; Code:

(defgroup transient-navigation nil
  "Customization group for the `transient-navigation' package."
  :group 'convenience)

(defcustom transient-navigation-cursor-color "#0074D9"
  "Color for the cursor when a transient navigation map is enabled.

A value of nil disables changing the color of the cursor when a
transient map is enabled."
  :group 'transient-navigation
  :type 'color)

(defcustom transient-navigation-cursor-type nil
  "The type of cursor to use when a transient map is enabled.

A value of nil disables changing the type of the cursor when a
transient map is enabled."
  :group 'transient-navigation)

(defvar transient-navigation-mode-map (make-sparse-keymap)
  "The keymap that will start all the trouble.

The original keybindings will be remapped to the ones enabling
the transient keymap.")
(defvar transient-C-navigation-map (make-sparse-keymap)
  "The keymap containing control-prefixed keys.")
(defvar transient-M-navigation-map (make-sparse-keymap)
  "The keymap containing meta-prefixed keys.")

(defmacro transnav-make-transient (key map func)
  "Bind KEY in MAP to FUNC with a transient map."
  (let* ((ofuncname (symbol-name func))
         (funcname (intern (concat "transient-" ofuncname))))
    `(progn
       (defun ,funcname (&rest args)
         (interactive)
         (ignore args)
         (call-interactively #',func)
         (let ((current-cursor-color (frame-parameter (selected-frame) 'cursor-color))
               (current-cursor-type cursor-type))
           (when transient-navigation-cursor-color
             (set-cursor-color transient-navigation-cursor-color))
           (when transient-navigation-cursor-type
             (setq cursor-type transient-navigation-cursor-type))
           (set-transient-map
            ,map t (lambda ()
                     (when transient-navigation-cursor-color
                       (set-cursor-color current-cursor-color))
                     (when transient-navigation-cursor-type
                       (setq cursor-type current-cursor-type))))))
       (define-key ,map (kbd ,key) #',func)
       (define-key transient-navigation-mode-map
         [remap ,func] #',funcname))))

(transnav-make-transient "f" transient-C-navigation-map forward-char)
(transnav-make-transient "b" transient-C-navigation-map backward-char)
(transnav-make-transient "n" transient-C-navigation-map next-line)
(transnav-make-transient "p" transient-C-navigation-map previous-line)
(transnav-make-transient "e" transient-C-navigation-map end-of-line)
(transnav-make-transient "a" transient-C-navigation-map beginning-of-line)

(transnav-make-transient "f" transient-M-navigation-map forward-word)
(transnav-make-transient "b" transient-M-navigation-map backward-word)
(transnav-make-transient "e" transient-M-navigation-map forward-sentence)
(transnav-make-transient "a" transient-M-navigation-map backward-sentence)

;;;###autoload
(define-minor-mode transient-navigation-mode
  "Remap certain navigation commands to ones with a transient map."
  nil nil transient-navigation-mode-map)

;;;###autoload
(define-globalized-minor-mode global-transient-navigation-mode
  transient-navigation-mode transient-navigation-mode)

(provide 'transient-navigation)
;;; transient-navigation.el ends here