;;; spray.el --- a speed reading mode

;; Copyright (C) 2014 Ian Kelling <ian@iankelling.org>

;; 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 2 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, write to the Free Software
;; Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA

;; Maintainer: Ian Kelling <ian@iankelling.org>
;; Author: Ian Kelling <ian@iankelling.org>
;; Author: zk_phi
;; Created: 18 Jun 2014
;; Version: 0.0.2
;; URL: https://github.com/ian-kelling/spray
;; Keywords: convenience

;;; Commentary:

;; For speed reading, or just more enjoyable reading. Narrows the buffer to show
;; one word at a time. Adjust speed / pause as needed.
;; 
;; Download from Melpa or put this script into a "load-path"ed directory, and
;; load it in your init file:

;;   (require 'spray)

;; Then you may run spray with "M-x spray-mode". Binding some keys may
;; also be useful.

;;   (global-set-key (kbd "<f6>") 'spray-mode)

;; In spray-mode buffers, following commands are available.

;; - =spray-start/stop= (SPC) ::
;; pause or resume spraying

;; - =spray-backward-word= (h, <left>) ::
;; pause and back to the last word

;; - =spray-forward-word= (l, <right>) ::
;; inverse of =spray-backward-word=

;; - =spray-faster= (f) ::
;; increases speed

;; - =spray-slower= (s) ::
;; decreases speed

;; - =spray-quit= (q, <return>) ::
;; quit =spray-mode=

;; You may customize spray by modifying following items:

;; - [Variable] spray-wpm
;; - [Variable] spray-height
;; - [Variable] spray-margin-top
;; - [Variable] spray-margin-left
;; - [Variable] spray-ramp
;; - [Keymap] spray-mode-map
;; - [Face] spray-base-face
;; - [Face] spray-accent-face

;; Readme.org from the package repository has some additional information:
;; A gif screencast.
;; Algorithm specification.
;; Comparison with similar projects.

;;; Known bugs:

;; repeated words are indistinguishable, for example
;; "going, going, gone" reads like going, gone, with a slight delay.
;;
;; sentences (like this) should trigger a pause for ( and )

;;; Change Log:

;; 0.0.0 test release
;; 0.0.1 add spray-set-margins
;; 0.0.2 margin options, speed control, better quit

;;; Code:

(require 'face-remap)

;; * customizable vars

(defcustom spray-wpm 400
  "Words per minute"
  :group 'spray
  :type 'integer)

(defcustom spray-height 400
  "Height of characters"
  :group 'spray
  :type 'integer)

(defcustom spray-margin-top 1
  "Character margin at top of buffer. Characters are as big as
  spray text characters."
  :group 'spray
  :type 'integer)

(defcustom spray-margin-left 1
  "Character margin at left of buffer. Characters are as big as
  spray text characters."
  :group 'spray
  :type 'integer)

(defcustom spray-ramp 2
  "Initial words before ramping up to full speed. Pauses for
this multiple of wpm on the first word,
decreasing by one for each subsequent word."
  :group 'spray
  :type 'integer)

(defcustom spray-unsupported-minor-modes
  '(buffer-face-mode smartparens-mode highlight-symbol-mode)
  "Minor modes to toggle off when in spray mode."
  :group 'spray
  :type '(list symbol))


;; * faces

(defface spray-base-face
  '((t (:inherit default)))
  "Face for non-accent characters."
  :group 'spray)

(defface spray-accent-face
  '((t (:foreground "red" :inherit spray-base-face)))
  "Face for accent character."
  :group 'spray)


;; keymap

(defvar spray-mode-map
  (let ((km (make-sparse-keymap)))
    (define-key km (kbd "SPC") 'spray-start/stop)
    (define-key km (kbd "h") 'spray-backward-word)
    (define-key km (kbd "l") 'spray-forward-word)
    (define-key km (kbd "<left>") 'spray-backward-word)
    (define-key km (kbd "<right>") 'spray-forward-word)
    (define-key km (kbd "f") 'spray-faster)
    (define-key km (kbd "s") 'spray-slower)
    (define-key km (kbd "q") 'spray-quit)
    (define-key km (kbd "<return>") 'spray-quit)
    (define-key km [remap forward-char] 'spray-forward-word)
    (define-key km [remap backward-char] 'spray-backward-word)
    (define-key km [remap forward-word] 'spray-forward-word)
    (define-key km [remap backward-word] 'spray-backward-word)
    (define-key km [remap keyboard-quit] 'spray-quit)
    km)
  "keymap for spray-mode buffers")


;; * internal vars

(defvar spray--margin-string "")
(defvar spray--base-overlay nil)
(defvar spray--accent-overlay nil)
(defvar spray--running nil)
(defvar spray--first-words 0)
(defvar spray--initial-delay 0)
(defvar spray--delay 0)
(defvar spray--saved-cursor-type nil)
(defvar spray--saved-restriction nil)
(defvar spray--saved-minor-modes nil)

;; * utility functions

(defun spray-set-margins ()
  "Setup spray--margin-string"
  (setq spray--margin-string
        (concat (make-string spray-margin-top 10) ;; 10 = ascii newline
                (make-string spray-margin-left 32)))) ;; 32 = ascii space

;; * the mode

;;;###autoload
(define-minor-mode spray-mode
  "spray mode"
  :init nil
  :keymap spray-mode-map
  (cond (spray-mode
         (setq spray--base-overlay (make-overlay (point-min) (point-max))
               spray--accent-overlay (make-overlay 0 0)
               spray--saved-cursor-type cursor-type
               spray--saved-restriction (and (buffer-narrowed-p)
                                             (cons (point-min) (point-max))))
         (dolist (mode spray-unsupported-minor-modes)
           (when (and (boundp mode) (eval mode))
             (funcall mode -1)
             (push mode spray--saved-minor-modes)))
         (setq cursor-type nil)
         (let ((buffer-face-mode-face `(:height ,spray-height)))
           (buffer-face-mode 1))
         (overlay-put spray--base-overlay 'priority 100)
         (overlay-put spray--base-overlay 'face 'spray-base-face)
         (overlay-put spray--accent-overlay 'priority 101)
         (overlay-put spray--accent-overlay 'face 'spray-accent-face)
         (spray-start))
        (t
         (spray-stop)
         (delete-overlay spray--accent-overlay)
         (delete-overlay spray--base-overlay)
         (buffer-face-mode -1)
         (if spray--saved-restriction
             (narrow-to-region (car spray--saved-restriction)
                               (cdr spray--saved-restriction))
           (widen))
         (setq cursor-type spray--saved-cursor-type)
         (dolist (mode spray--saved-minor-modes)
           (funcall mode 1))
         (setq spray--saved-minor-modes nil))))

(defun spray-quit ()
  "Exit spray mode."
  (interactive)
  (spray-mode -1))

(defun spray--word-at-point ()
  (skip-chars-backward "^\s\t\n—")
  (let* ((beg (point))
         (len (+ (skip-chars-forward "^\s\t\n—") (skip-chars-forward "—")))
         (end (point))
         (accent (+ beg (cl-case len
                       ((1) 1)
                       ((2 3 4 5) 2)
                       ((6 7 8 9) 3)
                       ((10 11 12 13) 4)
                       (t 5)))))
    ;; this fairly obfuscated, using magic numbers to store state
    ;; it would be nice to sometime patch this so it is more readable.
    ;; for greater than 9 length, we display for twice as long
    ;; for some punctuation, we display a blank
    (setq spray--delay (+ (if (> len 9) 1 0)
                          (if (looking-at "\n[\s\t\n]") 3 0)
                          (cl-case (char-before)
                            ((?. ?! ?\? ?\;) 3)
                            ((?, ?: ?—) 1)
                            (t 0))))
    (move-overlay spray--accent-overlay (1- accent) accent)
    (move-overlay spray--base-overlay beg end)
    (spray-set-margins)
    (overlay-put spray--base-overlay 'before-string
                 (concat spray--margin-string
                         (make-string (- 5 (- accent beg)) ?\s)))
    (narrow-to-region beg end)))

(defun spray--update ()
  (cond ((not (zerop spray--initial-delay))
         (setq spray--initial-delay (1- spray--initial-delay)))
        ((not (zerop spray--delay))
         (setq spray--delay (1- spray--delay))
         (when (= spray--delay 2)
           (narrow-to-region (point) (point))))
        (t
         (widen)
         (if (eobp)
             (spray-mode -1)
           (when (not (zerop spray--first-words))
             (setq spray--initial-delay spray--first-words)
             (setq spray--first-words (1- spray--first-words)))
           (skip-chars-forward "\s\t\n—")
           (spray--word-at-point)))))

;; * interactive commands

(defun spray-start/stop ()
  "Toggle pause/unpause spray."
  (interactive)
  (or (spray-stop) (spray-start)))

(defun spray-stop ()
  "Pause spray.
Returns t if spray was unpaused."
  (interactive)
  (prog1 spray--running
    (when spray--running
      (cancel-timer spray--running)
      (setq spray--running nil))))

(defun spray-start ()
  "Start / resume spray."
  (interactive)
  (setq spray--first-words spray-ramp)
  (setq spray--running
        (run-with-timer 0 (/ 60.0 spray-wpm) 'spray--update)))

(defun spray-forward-word ()
  (interactive)
  (spray-stop)
  (widen)
  (skip-chars-forward "\s\t\n—")
  (spray--word-at-point))

(defun spray-backward-word ()
  (interactive)
  (spray-stop)
  (widen)
  (skip-chars-backward "^\s\t\n—")
  (skip-chars-backward "\s\t\n—")
  (spray--word-at-point))

(defun spray-faster ()
  "Increases speed.

Increases the wpm (words per minute) parameter. See the variable
`spray-wpm'."
  (interactive)
  (spray-inc-wpm 20))

(defun spray-slower ()
  "Decreases speed.

Decreases the wpm (words per minute) parameter. See the variable
`spray-wpm'."
  (interactive)
  (spray-inc-wpm -20))

(defun spray-inc-wpm (delta)
  (let ((was-running spray--running))
    (spray-stop)
    (when (< 10 (+ spray-wpm delta))
      (setq spray-wpm (+ spray-wpm delta)))
    (and was-running (spray-backward-word))
    (message "spray wpm: %d" spray-wpm)
    (when was-running
      (spray-start))))

;; * provide

(provide 'spray)

;;; spray.el ends here