;;; ws-mode.el --- WordStar emulation mode for GNU Emacs -*- lexical-binding: t -*-

;; Copyright (C) 1991, 2001-2023 Free Software Foundation, Inc.

;; Author: Juergen Nickelsen <nickel@cs.tu-berlin.de>
;; Version: 0.7
;; Keywords: emulations
;; Obsolete-since: 24.5

;; 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 provides emulation of WordStar with a minor mode.

;;; Code:

(defgroup wordstar nil
  "WordStar emulation within Emacs."
  :prefix "wordstar-"
  :prefix "ws-"
  :group 'emulations)

(defcustom wordstar-mode-lighter " WordStar"
  "Lighter shown in the modeline for `wordstar' mode."
  :type 'string)

(defvar wordstar-C-k-map
  (let ((map (make-keymap)))
    (define-key map " " ())
    (define-key map "0" #'ws-set-marker-0)
    (define-key map "1" #'ws-set-marker-1)
    (define-key map "2" #'ws-set-marker-2)
    (define-key map "3" #'ws-set-marker-3)
    (define-key map "4" #'ws-set-marker-4)
    (define-key map "5" #'ws-set-marker-5)
    (define-key map "6" #'ws-set-marker-6)
    (define-key map "7" #'ws-set-marker-7)
    (define-key map "8" #'ws-set-marker-8)
    (define-key map "9" #'ws-set-marker-9)
    (define-key map "b" #'ws-begin-block)
    (define-key map "\C-b" #'ws-begin-block)
    (define-key map "c" #'ws-copy-block)
    (define-key map "\C-c" #'ws-copy-block)
    (define-key map "d" #'save-buffers-kill-emacs)
    (define-key map "\C-d" #'save-buffers-kill-emacs)
    (define-key map "f" #'find-file)
    (define-key map "\C-f" #'find-file)
    (define-key map "h" #'ws-show-markers)
    (define-key map "\C-h" #'ws-show-markers)
    (define-key map "i" #'ws-indent-block)
    (define-key map "\C-i" #'ws-indent-block)
    (define-key map "k" #'ws-end-block)
    (define-key map "\C-k" #'ws-end-block)
    (define-key map "p" #'ws-print-block)
    (define-key map "\C-p" #'ws-print-block)
    (define-key map "q" #'kill-emacs)
    (define-key map "\C-q" #'kill-emacs)
    (define-key map "r" #'insert-file)
    (define-key map "\C-r" #'insert-file)
    (define-key map "s" #'save-some-buffers)
    (define-key map "\C-s" #'save-some-buffers)
    (define-key map "t" #'ws-mark-word)
    (define-key map "\C-t" #'ws-mark-word)
    (define-key map "u" #'ws-exdent-block)
    (define-key map "\C-u" #'keyboard-quit)
    (define-key map "v" #'ws-move-block)
    (define-key map "\C-v" #'ws-move-block)
    (define-key map "w" #'ws-write-block)
    (define-key map "\C-w" #'ws-write-block)
    (define-key map "x" #'save-buffers-kill-emacs)
    (define-key map "\C-x" #'save-buffers-kill-emacs)
    (define-key map "y" #'ws-delete-block)
    (define-key map "\C-y" #'ws-delete-block)
    map))

(defvar wordstar-C-o-map
  (let ((map (make-keymap)))
    (define-key map " " ())
    (define-key map "c" #'wordstar-center-line)
    (define-key map "\C-c" #'wordstar-center-line)
    (define-key map "b" #'switch-to-buffer)
    (define-key map "\C-b" #'switch-to-buffer)
    (define-key map "j" #'justify-current-line)
    (define-key map "\C-j" #'justify-current-line)
    (define-key map "k" #'kill-buffer)
    (define-key map "\C-k" #'kill-buffer)
    (define-key map "l" #'list-buffers)
    (define-key map "\C-l" #'list-buffers)
    (define-key map "m" #'auto-fill-mode)
    (define-key map "\C-m" #'auto-fill-mode)
    (define-key map "r" #'set-fill-column)
    (define-key map "\C-r" #'set-fill-column)
    (define-key map "\C-u" #'keyboard-quit)
    (define-key map "wd" #'delete-other-windows)
    (define-key map "wh" #'split-window-right)
    (define-key map "wo" #'other-window)
    (define-key map "wv" #'split-window-below)
    map))

(defvar wordstar-C-q-map
  (let ((map (make-keymap)))
    (define-key map " " ())
    (define-key map "0" #'ws-find-marker-0)
    (define-key map "1" #'ws-find-marker-1)
    (define-key map "2" #'ws-find-marker-2)
    (define-key map "3" #'ws-find-marker-3)
    (define-key map "4" #'ws-find-marker-4)
    (define-key map "5" #'ws-find-marker-5)
    (define-key map "6" #'ws-find-marker-6)
    (define-key map "7" #'ws-find-marker-7)
    (define-key map "8" #'ws-find-marker-8)
    (define-key map "9" #'ws-find-marker-9)
    (define-key map "a" #'ws-query-replace)
    (define-key map "\C-a" #'ws-query-replace)
    (define-key map "b" #'ws-goto-block-begin)
    (define-key map "\C-b" #'ws-goto-block-begin)
    (define-key map "c" #'end-of-buffer)
    (define-key map "\C-c" #'end-of-buffer)
    (define-key map "d" #'end-of-line)
    (define-key map "\C-d" #'end-of-line)
    (define-key map "f" #'ws-search)
    (define-key map "\C-f" #'ws-search)
    (define-key map "k" #'ws-goto-block-end)
    (define-key map "\C-k" #'ws-goto-block-end)
    (define-key map "l" #'ws-undo)
    (define-key map "\C-l" #'ws-undo)
    ;; (define-key map "p" #'ws-last-cursorp)
    ;; (define-key map "\C-p" #'ws-last-cursorp)
    (define-key map "r" #'beginning-of-buffer)
    (define-key map "\C-r" #'beginning-of-buffer)
    (define-key map "s" #'beginning-of-line)
    (define-key map "\C-s" #'beginning-of-line)
    (define-key map "\C-u" #'keyboard-quit)
    (define-key map "w" #'ws-last-error)
    (define-key map "\C-w" #'ws-last-error)
    (define-key map "y" #'ws-kill-eol)
    (define-key map "\C-y" #'ws-kill-eol)
    (define-key map "\177" #'ws-kill-bol)
    map))

(defvar wordstar-mode-map
  (let ((map (make-keymap)))
    (define-key map "\C-a" #'backward-word)
    (define-key map "\C-b" #'fill-paragraph)
    (define-key map "\C-c" #'scroll-up-command)
    (define-key map "\C-d" #'forward-char)
    (define-key map "\C-e" #'previous-line)
    (define-key map "\C-f" #'forward-word)
    (define-key map "\C-g" #'delete-char)
    (define-key map "\C-h" #'backward-char)
    (define-key map "\C-i" #'indent-for-tab-command)
    (define-key map "\C-j" #'help-for-help)
    (define-key map "\C-k" wordstar-C-k-map)
    (define-key map "\C-l" #'ws-repeat-search)
    (define-key map "\C-n" #'open-line)
    (define-key map "\C-o" wordstar-C-o-map)
    (define-key map "\C-p" #'quoted-insert)
    (define-key map "\C-q" wordstar-C-q-map)
    (define-key map "\C-r" #'scroll-down-command)
    (define-key map "\C-s" #'backward-char)
    (define-key map "\C-t" #'kill-word)
    (define-key map "\C-u" #'keyboard-quit)
    (define-key map "\C-v" #'overwrite-mode)
    (define-key map "\C-w" #'scroll-down-line)
    (define-key map "\C-x" #'next-line)
    (define-key map "\C-y" #'kill-complete-line)
    (define-key map "\C-z" #'scroll-up-line)
    map))

;; wordstar-C-j-map not yet implemented
(defvar wordstar-C-j-map nil)

;;;###autoload
(define-minor-mode wordstar-mode
  "Minor mode with WordStar-like key bindings.

BUGS:
 - Help menus with WordStar commands (C-j just calls help-for-help)
   are not implemented
 - Options for search and replace
 - Show markers (C-k h) is somewhat strange
 - Search and replace (C-q a) is only available in forward direction

No key bindings beginning with ESC are installed, they will work
Emacs-like."
  :group 'wordstar
  :lighter wordstar-mode-lighter
  :keymap wordstar-mode-map)

(defun turn-on-wordstar-mode ()
  (when (and (not (minibufferp))
             (not wordstar-mode))
    (wordstar-mode 1)))

(define-globalized-minor-mode global-wordstar-mode wordstar-mode
  turn-on-wordstar-mode)

(defun wordstar-center-paragraph ()
  "Center each line in the paragraph at or after point.
See `wordstar-center-line' for more info."
  (interactive)
  (save-excursion
    (forward-paragraph)
    (or (bolp) (newline 1))
    (let ((end (point)))
      (backward-paragraph)
      (wordstar-center-region (point) end))))

(defun wordstar-center-region (from to)
  "Center each line starting in the region.
See `wordstar-center-line' for more info."
  (interactive "r")
  (if (> from to)
      (let ((tem to))
	(setq to from from tem)))
  (save-excursion
    (save-restriction
      (narrow-to-region from to)
      (goto-char from)
      (while (not (eobp))
	(wordstar-center-line)
	(forward-line 1)))))

(defun wordstar-center-line ()
  "Center the line point is on, within the width specified by `fill-column'.
This means adjusting the indentation to match
the distance between the end of the text and `fill-column'."
  (interactive)
  (save-excursion
    (let (line-length)
      (beginning-of-line)
      (delete-horizontal-space)
      (end-of-line)
      (delete-horizontal-space)
      (setq line-length (current-column))
      (beginning-of-line)
      (indent-to
       (+ left-margin
	  (/ (- fill-column left-margin line-length) 2))))))

;;;;;;;;;;;
;; wordstar special variables:

(defvar ws-marker-0 nil "Position marker 0 in WordStar mode.")
(defvar ws-marker-1 nil "Position marker 1 in WordStar mode.")
(defvar ws-marker-2 nil "Position marker 2 in WordStar mode.")
(defvar ws-marker-3 nil "Position marker 3 in WordStar mode.")
(defvar ws-marker-4 nil "Position marker 4 in WordStar mode.")
(defvar ws-marker-5 nil "Position marker 5 in WordStar mode.")
(defvar ws-marker-6 nil "Position marker 6 in WordStar mode.")
(defvar ws-marker-7 nil "Position marker 7 in WordStar mode.")
(defvar ws-marker-8 nil "Position marker 8 in WordStar mode.")
(defvar ws-marker-9 nil "Position marker 9 in WordStar mode.")

(defvar ws-block-begin-marker nil "Beginning of \"Block\" in WordStar mode.")
(defvar ws-block-end-marker nil "End of \"Block\" in WordStar mode.")

(defvar ws-search-string nil "String of last search in WordStar mode.")
(defvar ws-search-direction t
  "Direction of last search in WordStar mode.  t if forward, nil if backward.")

(defvar ws-last-cursorposition nil
  "Position before last search etc. in WordStar mode.")

(defvar ws-last-errormessage nil
  "Last error message issued by a WordStar mode function.")

;;;;;;;;;;;
;; wordstar special functions:

(defun ws-error (string)
  "Report error of a WordStar special function.
Error message is saved in `ws-last-errormessage' for recovery
with C-q w."
  (setq ws-last-errormessage string)
  (error string))

(defun ws-begin-block ()
  "In WordStar mode: Set block begin marker to current cursor position."
  (interactive)
  (setq ws-block-begin-marker (point-marker))
  (message "Block begin marker set"))

(defun ws-show-markers ()
  "In WordStar mode: Show block markers."
  (interactive)
  (if (or ws-block-begin-marker ws-block-end-marker)
      (save-excursion
	(if ws-block-begin-marker
	    (progn
	      (goto-char ws-block-begin-marker)
	      (message "Block begin marker")
	      (sit-for 2))
	  (message "Block begin marker not set")
	  (sit-for 2))
	(if ws-block-end-marker
	    (progn
	      (goto-char ws-block-end-marker)
	      (message "Block end marker")
	      (sit-for 2))
	  (message "Block end marker not set"))
	(message ""))
    (message "Block markers not set")))

(defun ws-indent-block ()
  "In WordStar mode: Indent block (not yet implemented)."
  (interactive)
  (ws-error "Indent block not yet implemented"))

(defun ws-end-block ()
  "In WordStar mode: Set block end marker to current cursor position."
  (interactive)
  (setq ws-block-end-marker (point-marker))
  (message "Block end marker set"))

(defun ws-print-block ()
  "In WordStar mode: Print block."
  (interactive)
  (message "Don't do this. Write block to a file (C-k w) and print this file"))

(defun ws-mark-word ()
  "In WordStar mode: Mark current word as block."
  (interactive)
  (save-excursion
    (forward-word 1)
    (sit-for 1)
    (ws-end-block)
    (forward-word -1)
    (sit-for 1)
    (ws-begin-block)))

(defun ws-exdent-block ()
  "I don't know what this (C-k u) should do."
  (interactive)
  (ws-error "This won't be done -- not yet implemented"))

(defun ws-move-block ()
  "In WordStar mode: Move block to current cursor position."
  (interactive)
  (if (and ws-block-begin-marker ws-block-end-marker)
      (progn
	(kill-region ws-block-begin-marker ws-block-end-marker)
	(yank)
	(save-excursion
	  (goto-char (region-beginning))
	  (setq ws-block-begin-marker (point-marker))
	  (goto-char (region-end))
	  (setq ws-block-end-marker (point-marker))))
    (ws-error (cond (ws-block-begin-marker "Block end marker not set")
		    (ws-block-end-marker "Block begin marker not set")
		    (t "Block markers not set")))))

(defun ws-write-block ()
  "In WordStar mode: Write block to file."
  (interactive)
  (if (and ws-block-begin-marker ws-block-end-marker)
      (let ((filename (read-file-name "Write block to file: ")))
	(write-region ws-block-begin-marker ws-block-end-marker filename))
    (ws-error (cond (ws-block-begin-marker "Block end marker not set")
		    (ws-block-end-marker "Block begin marker not set")
		    (t "Block markers not set")))))


(defun ws-delete-block ()
  "In WordStar mode: Delete block."
  (interactive)
  (if (and ws-block-begin-marker ws-block-end-marker)
      (progn
	(kill-region ws-block-begin-marker ws-block-end-marker)
	(setq ws-block-end-marker nil)
	(setq ws-block-begin-marker nil))
    (ws-error (cond (ws-block-begin-marker "Block end marker not set")
		    (ws-block-end-marker "Block begin marker not set")
		    (t "Block markers not set")))))

(defun ws-goto-block-begin ()
  "In WordStar mode: Go to block begin marker."
  (interactive)
  (if ws-block-begin-marker
      (progn
	(setq ws-last-cursorposition (point-marker))
	(goto-char ws-block-begin-marker))
    (ws-error "Block begin marker not set")))

(defun ws-search (string)
  "In WordStar mode: Search string, remember string for repetition."
  (interactive "sSearch for: ")
  (message "Forward (f) or backward (b)")
  (let ((direction
	 (read-char)))
    (cond ((equal (upcase direction) ?F)
	   (setq ws-search-string string)
	   (setq ws-search-direction t)
	   (setq ws-last-cursorposition (point-marker))
	   (search-forward string))
	  ((equal (upcase direction) ?B)
	   (setq ws-search-string string)
	   (setq ws-search-direction nil)
	   (setq ws-last-cursorposition (point-marker))
	   (search-backward string))
	  (t (keyboard-quit)))))

(defun ws-goto-block-end ()
  "In WordStar mode: Go to block end marker."
  (interactive)
  (if ws-block-end-marker
      (progn
	(setq ws-last-cursorposition (point-marker))
	(goto-char ws-block-end-marker))
    (ws-error "Block end marker not set")))

(defun ws-undo ()
  "In WordStar mode: Undo and give message about undoing more changes."
  (interactive)
  (undo)
  (message "Repeat C-q l to undo more changes"))

(defun ws-goto-last-cursorposition ()
  "In WordStar mode: Go to position before last search."
  (interactive)
  (if ws-last-cursorposition
      (progn
	(setq ws-last-cursorposition (point-marker))
	(goto-char ws-last-cursorposition))
    (ws-error "No last cursor position available")))

(defun ws-last-error ()
  "In WordStar mode: repeat last error message.
This will only work for errors raised by WordStar mode functions."
  (interactive)
  (if ws-last-errormessage
      (message "%s" ws-last-errormessage)
    (message "No WordStar error yet")))

(defun ws-kill-eol ()
  "In WordStar mode: Kill to end of line (like WordStar, not like Emacs)."
  (interactive)
  (let ((p (point)))
    (end-of-line)
    (kill-region p (point))))

(defun ws-kill-bol ()
  "In WordStar mode: Kill to beginning of line (like WordStar, not like Emacs)."
  (interactive)
  (let ((p (point)))
    (beginning-of-line)
    (kill-region (point) p)))

(defun kill-complete-line ()
  "Kill the complete line."
  (interactive)
  (beginning-of-line)
  (if (eobp) (error "End of buffer"))
  (let ((beg (point)))
    (forward-line 1)
    (kill-region beg (point))))

(defun ws-repeat-search ()
  "In WordStar mode: Repeat last search."
  (interactive)
  (setq ws-last-cursorposition (point-marker))
  (if ws-search-string
      (if ws-search-direction
	  (search-forward ws-search-string)
	(search-backward ws-search-string))
    (ws-error "No search to repeat")))

(defun ws-query-replace (from to)
  "In WordStar mode: Search string, remember string for repetition."
  (interactive "sReplace: \n\
sWith: " )
  (setq ws-search-string from)
  (setq ws-search-direction t)
  (setq ws-last-cursorposition (point-marker))
  (query-replace from to))

(defun ws-copy-block ()
  "In WordStar mode: Copy block to current cursor position."
  (interactive)
  (if (and ws-block-begin-marker ws-block-end-marker)
      (progn
	(copy-region-as-kill ws-block-begin-marker ws-block-end-marker)
	(yank)
	(save-excursion
	  (goto-char (region-beginning))
	  (setq ws-block-begin-marker (point-marker))
	  (goto-char (region-end))
	  (setq ws-block-end-marker (point-marker))))
    (ws-error (cond (ws-block-begin-marker "Block end marker not set")
		    (ws-block-end-marker "Block begin marker not set")
		    (t "Block markers not set")))))

(defmacro ws-set-marker (&rest indices)
  (let (n forms)
    (while indices
      (setq n (pop indices))
      (push `(defun ,(intern (format "ws-set-marker-%d" n)) ()
               ,(format "In WordStar mode: Set marker %d to current cursor position" n)
               (interactive)
               (setq ,(intern (format "ws-marker-%d" n)) (point-marker))
               (message ,(format "Marker %d set" n)))
            forms))
    `(progn ,@(nreverse forms))))

(ws-set-marker 0 1 2 3 4 5 6 7 8 9)

(defmacro ws-find-marker (&rest indices)
  (let (n forms)
    (while indices
      (setq n (pop indices))
      (push `(defun ,(intern (format "ws-find-marker-%d" n)) ()
               ,(format "In WordStar mode: Go to marker %d." n)
               (interactive)
               (if ,(intern (format "ws-marker-%d" n))
                   (progn (setq ws-last-cursorposition (point-marker))
                          (goto-char ,(intern (format "ws-marker-%d" n))))
                 (ws-error ,(format "Marker %d not set" n))))
            forms))
    `(progn ,@(nreverse forms))))

(ws-find-marker 0 1 2 3 4 5 6 7 8 9)

(provide 'ws-mode)

;;; ws-mode.el ends here
