;;; tutorial.el --- tutorial for Emacs

;; Copyright (C) 2006 Free Software Foundation, Inc.

;; Maintainer: FSF
;; Keywords: help, internal

;; 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 2, 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; see the file COPYING.  If not, write to the
;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
;; Boston, MA 02110-1301, USA.


;;; Commentary:

;; Code for running the Emacs tutorial.


;;; History:

;; File was created 2006-08.


;;; Code:

(defun tutorial--detailed-help (button)
  "Give detailed help about changed keys."
  (with-output-to-temp-buffer (help-buffer)
    (help-setup-xref (list #'tutorial--detailed-help button)
                     (interactive-p))
    (with-current-buffer (help-buffer)
      (let* ((tutorial-buffer (button-get button 'tutorial-buffer))
             (tutorial-arg    (button-get button 'tutorial-arg))
             (changed-keys (with-current-buffer tutorial-buffer
                             (tutorial--find-changed-keys))))
        ;;(insert (format "some help: %s, %s" (bufferp tutorial-buffer) tutorial-buffer))

        (when changed-keys
          (insert
           "The following key bindings used in the tutorial had been changed
from Emacs default in the " (buffer-name tutorial-buffer) " buffer:\n\n" )
          (let ((frm "   %-9s %-27s %-11s %s\n"))
            (insert (format frm "Key" "Standard Binding" "Is Now On" "Remark")))
          (dolist (tk changed-keys)
            (let* ((def-fun     (nth 1 tk))
                   (key         (nth 0 tk))
                   (def-fun-txt (nth 2 tk))
                   (where       (nth 3 tk))
                   (remark      (nth 4 tk))
                   (rem-fun (command-remapping def-fun))
                   (key-txt (key-description key))
                   (key-fun (with-current-buffer tutorial-buffer (key-binding key)))
                   tot-len)
              (unless (eq def-fun key-fun)
                ;; Insert key binding description:
                (insert "   " key-txt " ")
                (setq tot-len (length key-txt))
                (when (> 9 tot-len)
                  (insert (make-string (- 9 tot-len) ? ))
                  (setq tot-len 9))
                ;; Insert a link describing the old binding:
                (insert-button def-fun-txt
                               'value def-fun
                               'action
                               (lambda(button) (interactive)
                                 (describe-function
                                  (button-get button 'value)))
                               'follow-link t)
                (setq tot-len (+ tot-len (length def-fun-txt)))
                (when (> 36 tot-len)
                  (insert (make-string (- 36 tot-len) ? )))
                (when (listp where)
                  (setq where "list"))
                ;; Tell where the old binding is now:
                (insert (format " %-11s " where))
                ;; Insert a link with more information, for example
                ;; current binding and keymap or information about
                ;; cua-mode replacements:
                (insert-button (car remark)
                               'action
                               (lambda(b) (interactive)
                                 (let ((value (button-get b 'value)))
                                   (tutorial--describe-nonstandard-key value)))
                               'value (cdr remark)
                               'follow-link t)
                (insert "\n")))))

        ;; Viper turns itself off in the tutorial buffer by
        ;; default. Explain this and add some more information
        ;; about it:
        (when (and (boundp 'viper-mode)
                   (with-current-buffer tutorial-buffer
                     viper-mode))
          (insert "\n   Information About Viper\n")
          (cond
           ((with-current-buffer tutorial-buffer
              (eq viper-current-state 'emacs-state))
            (insert "
   You have enabled Viper mode, but in the tutorial buffer Viper
   mode is currently turned off.  You can however turn it on if
   you want to.  This may enable you to see what key bindings
   that Viper conflicts with:\n     ")
            (insert-button " Turn on Viper in tutorial! "
                           'action
                           (lambda(b) (interactive)
                             (let ((arg (button-get b 'tutorial-arg))
                                   (buf (button-get b 'tutorial-buffer)))
                               (with-current-buffer buf
                                 (viper-mode)
                                 (set-buffer-modified-p t))
                               (help-with-tutorial arg t)))
                           'tutorial-arg tutorial-arg
                           'tutorial-buffer tutorial-buffer
                           'follow-link t
                           'face 'custom-button
                           'mouse-face 'custom-button-mouse))
           (t
            (insert "
   You have enabled Viper mode in the tutorial buffer.  Some of
   the changed key bindings above depends on the Viper state.
   When you started the tutorial the Viper state was ")
            (cond
             ((eq viper-current-state 'vi-state)
              (insert "vi."))
             (t
              (insert "some insert state.")))
            (insert "\n     ")
            (insert-button " Turn off Viper in tutorial! "
                           'action
                           (lambda(b) (interactive)
                             (let ((arg (button-get b 'tutorial-arg))
                                   (buf (button-get b 'tutorial-buffer)))
                               (kill-buffer buf)
                               (help-with-tutorial arg t)))
                           'tutorial-arg tutorial-arg
                           'tutorial-buffer tutorial-buffer
                           'follow-link t
                           'face 'custom-button
                           'mouse-face 'custom-button-mouse)
            (insert "  ")
            (cond
             ((eq viper-current-state 'vi-state)
              (insert-button " Restart tutorial in Viper insert state! "
                             'action
                             (lambda(b) (interactive)
                               (let ((arg (button-get b 'tutorial-arg))
                                     (buf (button-get b 'tutorial-buffer)))
                                 (with-current-buffer buf
                                   (viper-insert nil)
                                   (set-buffer-modified-p t))
                                 (help-with-tutorial arg t)))
                             'tutorial-arg tutorial-arg
                             'tutorial-buffer tutorial-buffer
                             'follow-link t
                             'face 'custom-button
                             'mouse-face 'custom-button-mouse))
             ((not (eq viper-current-state 'vi-state))
              (insert-button " Restart tutorial in Viper vi state! "
                             'action
                             (lambda(b) (interactive)
                               (let ((arg (button-get b 'tutorial-arg))
                                     (buf (button-get b 'tutorial-buffer)))
                                 (with-current-buffer buf
                                   (let ((cmd
                                          (cond ((eq viper-current-state 'vi-state)
                                                 'viper-ESC)
                                                ((eq viper-current-state 'insert-state)
                                                 'viper-exit-insert-state)
                                                ((eq viper-current-state 'replace-state)
                                                 'viper-replace-state-exit-cmd)
                                                (t 'viper-change-state-to-vi)
                                                )))
                                     (call-interactively cmd)
                                     (set-buffer-modified-p t))
                                   (help-with-tutorial arg t))))
                             'tutorial-arg tutorial-arg
                             'tutorial-buffer tutorial-buffer
                             'follow-link t
                             'face 'custom-button
                             'mouse-face 'custom-button-mouse)))))
          (insert "\n   If you want to learn Viper keys please see the ")
          (insert-button "Viper manual"
                         'action
                         (lambda(button) (interactive)
                           (info-other-window "(viper)")
                           (message "Type C-x 0 to close the new window"))
                         'follow-link t)
          (insert ".\n")

          (insert "
It is legitimate to change key bindings, but changed bindings do not
correspond to what the tutorial says.  (See also " )
          (insert-button "Key Binding Conventions"
                         'action
                         (lambda(button) (interactive)
                           (info-other-window
                            "(elisp) Key Binding Conventions")
                           (message "Type C-x 0 to close the new window"))
                         'follow-link t)
          (insert ".)\n\n")
          (print-help-return-message)
          )))))

(defun tutorial--describe-nonstandard-key (value)
  "Give more information about a changed key binding.
This is used in `help-with-tutorial'.  The information includes
the key sequence that no longer has a default binding, the
default binding and the current binding.  It also tells in what
keymap the new binding has been done and how to access the
function in the default binding from the keyboard.

For `cua-mode' key bindings that try to combine CUA key bindings
with default Emacs bindings information about this is shown.

VALUE should have either of these formats:

  \(cua-mode)
  \(current-binding KEY-FUN DEF-FUN KEY WHERE)

Where
  KEY         is a key sequence whose standard binding has been changed
  KEY-FUN     is the actual binding for KEY
  DEF-FUN     is the standard binding of KEY
  WHERE       is a text describing the key sequences to which DEF-FUN is
              bound now (or, if it is remapped, a key sequence
              for the function it is remapped to)"
  (with-output-to-temp-buffer (help-buffer)
    (help-setup-xref (list #'tutorial--describe-nonstandard-key value)
                     (interactive-p))
    (with-current-buffer (help-buffer)
      (insert
       "Your Emacs customizations override the default binding for this key:"
       "\n\n")
      (let ((inhibit-read-only t))
        (cond
         ((eq (car value) 'cua-mode)
          (insert
           "CUA mode is enabled.

When CUA mode is enabled, you can use C-z, C-x, C-c, and C-v to
undo, cut, copy, and paste in addition to the normal Emacs
bindings.  The C-x and C-c keys only do cut and copy when the
region is active, so in most cases, they do not conflict with the
normal function of these prefix keys.

If you really need to perform a command which starts with one of
the prefix keys even when the region is active, you have three
options:
- press the prefix key twice very quickly (within 0.2 seconds),
- press the prefix key and the following key within 0.2 seconds, or
- use the SHIFT key with the prefix key, i.e. C-S-x or C-S-c."))
         ((eq (car value) 'current-binding)
          (let ((cb    (nth 1 value))
                (db    (nth 2 value))
                (key   (nth 3 value))
                (where (nth 4 value))
                map
                (maps (current-active-maps))
                mapsym)
            ;; Look at the currently active keymaps and try to find
            ;; first the keymap where the current binding occurs:
            (while maps
              (let* ((m (car maps))
                     (mb (lookup-key m key t)))
                (setq maps (cdr maps))
                (when (eq mb cb)
                  (setq map m)
                  (setq maps nil))))
            ;; Now, if a keymap was found we must found the symbol
            ;; name for it to display to the user.  This can not
            ;; always be found since all keymaps does not have a
            ;; symbol pointing to them, but here they should have
            ;; that:
            (when map
              (mapatoms (lambda (s)
                          (and
                           ;; If not already found
                           (not mapsym)
                           ;; and if s is a keymap
                           (and (boundp s)
                                (keymapp (symbol-value s)))
                           ;; and not the local symbol map
                           (not (eq s 'map))
                           ;; and the value of s is map
                           (eq map (symbol-value s))
                           ;; then save this value in mapsym
                           (setq mapsym s)))))
            (insert "The default Emacs binding for the key "
                    (key-description key)
                    " is the command `")
            (insert (format "%s" db))
            (insert "'.  "
                    "However, your customizations have rebound it to the command `")
            (insert (format "%s" cb))
            (insert "'.")
            (when mapsym
              (insert "  (For the more advanced user:"
                      " This binding is in the keymap `"
                      (format "%s" mapsym)
                      "'.)"))
            (if (string= where "")
                (unless (keymapp db)
                  (insert "\n\nYou can use M-x "
                          (format "%s" db)
                          " RET instead."))
              (insert "\n\nWith you current key bindings"
                      " you can use the key "
                      where
                      " to get the function `"
                      (format "%s" db)
                      "'."))
            )
          (fill-region (point-min) (point)))))
      (print-help-return-message))))

(defconst tutorial--default-keys
  (let (
        ;; On window system suspend Emacs is replaced in the
        ;; default keymap so honor this here.
        (suspend-emacs (if window-system
                           'iconify-or-deiconify-frame
                         'suspend-emacs)))
    `(
      ;; These are not mentioned but are basic:
      (ESC-prefix [27])
      (Control-X-prefix [?\C-x])
      (mode-specific-command-prefix [?\C-c])

      (save-buffers-kill-emacs [?\C-x ?\C-c])


      ;; * SUMMARY
      (scroll-up [?\C-v])
      (scroll-down [?\M-v])
      (recenter [?\C-l])


      ;; * BASIC CURSOR CONTROL
      (forward-char [?\C-f])
      (backward-char [?\C-b])

      (forward-word [?\M-f])
      (backward-word [?\M-b])

      (next-line [?\C-n])
      (previous-line [?\C-p])

      (move-beginning-of-line [?\C-a])
      (move-end-of-line [?\C-e])

      (backward-sentence [?\M-a])
      (forward-sentence [?\M-e])


      (beginning-of-buffer [?\M-<])
      (end-of-buffer [?\M->])

      (universal-argument [?\C-u])


      ;; * WHEN EMACS IS HUNG
      (keyboard-quit [?\C-g])


      ;; * DISABLED COMMANDS
      (downcase-region [?\C-x ?\C-l])


      ;; * WINDOWS
      (delete-other-windows [?\C-x ?1])
      ;; C-u 0 C-l
      ;; Type CONTROL-h k CONTROL-f.


      ;; * INSERTING AND DELETING
      ;; C-u 8 * to insert ********.

      (delete-backward-char [backspace])
      (delete-char [?\C-d])

      (backward-kill-word [(meta backspace)])
      (kill-word [?\M-d])

      (kill-line [?\C-k])
      (kill-sentence [?\M-k])

      (set-mark-command [?\C-@])
      (set-mark-command [?\C- ])
      (kill-region [?\C-w])
      (yank [?\C-y])
      (yank-pop [?\M-y])


      ;; * UNDO
      (advertised-undo [?\C-x ?u])
      (advertised-undo [?\C-x ?u])


      ;; * FILES
      (find-file [?\C-x ?\C-f])
      (save-buffer [?\C-x ?\C-s])


      ;; * BUFFERS
      (list-buffers [?\C-x ?\C-b])
      (switch-to-buffer [?\C-x ?b])
      (save-some-buffers [?\C-x ?s])


      ;; * EXTENDING THE COMMAND SET
      ;; C-x	Character eXtend.  Followed by one character.
      (execute-extended-command [?\M-x])

      ;; C-x C-f		Find file
      ;; C-x C-s		Save file
      ;; C-x s		Save some buffers
      ;; C-x C-b		List buffers
      ;; C-x b		Switch buffer
      ;; C-x C-c		Quit Emacs
      ;; C-x 1		Delete all but one window
      ;; C-x u		Undo


      ;; * MODE LINE
      (describe-mode [?\C-h ?m])

      (set-fill-column [?\C-x ?f])
      (fill-paragraph [?\M-q])


      ;; * SEARCHING
      (isearch-forward [?\C-s])
      (isearch-backward [?\C-r])


      ;; * MULTIPLE WINDOWS
      (split-window-vertically [?\C-x ?2])
      (scroll-other-window [?\C-\M-v])
      (other-window [?\C-x ?o])
      (find-file-other-window [?\C-x ?4 ?\C-f])


      ;; * RECURSIVE EDITING LEVELS
      (keyboard-escape-quit [27 27 27])


      ;; * GETTING MORE HELP
      ;; The most basic HELP feature is C-h c
      (describe-key-briefly [?\C-h ?c])
      (describe-key [?\C-h ?k])


      ;; * MORE FEATURES
      ;; F10


      ;; * CONCLUSION
      ;;(iconify-or-deiconify-frame [?\C-z])
      (,suspend-emacs [?\C-z])
      ))
  "Default Emacs key bindings that the tutorial depends on.")

(defun tutorial--sort-keys (left right)
  "Sort predicate for use with `tutorial--default-keys'.
This is a predicate function to `sort'.

The sorting is for presentation purpose only and is done on the
key sequence.

LEFT and RIGHT are the elements to compare."
  (let ((x (append (cadr left)  nil))
        (y (append (cadr right) nil)))
    ;; Skip the front part of the key sequences if they are equal:
    (while (and x y
                (listp x) (listp y)
                (equal (car x) (car y)))
      (setq x (cdr x))
      (setq y (cdr y)))
    ;; Try to make a comparision that is useful for presentation (this
    ;; could be made nicer perhaps):
    (let ((cx (car x))
          (cy (car y)))
      ;;(message "x=%s, y=%s;;;; cx=%s, cy=%s" x y cx cy)
      (cond
       ;; Lists? Then call this again
       ((and cx cy
             (listp cx)
             (listp cy))
        (tutorial--sort-keys cx cy))
       ;; Are both numbers? Then just compare them
       ((and (wholenump cx)
             (wholenump cy))
        (> cx cy))
       ;; Is one of them a number? Let that be bigger then.
       ((wholenump cx)
        t)
       ((wholenump cy)
        nil)
       ;; Are both symbols? Compare the names then.
       ((and (symbolp cx)
             (symbolp cy))
        (string< (symbol-name cy)
                 (symbol-name cx)))
       ))))

(defun tutorial--find-changed-keys ()
  "Find the key bindings that have changed.
Check if the default Emacs key bindings that the tutorial depends
on have been changed.

Return a list with the keys that have been changed.  The element
of this list have the following format:

  \(list KEY DEF-FUN DEF-FUN-TXT WHERE REMARK)

Where
  KEY         is a key sequence whose standard binding has been changed
  DEF-FUN     is the standard binding of KEY
  DEF-FUN-TXT is a short descriptive text for DEF-FUN
  WHERE       is a text describing the key sequences to which DEF-FUN is
              bound now (or, if it is remapped, a key sequence
              for the function it is remapped to)
  REMARK      is a list with info about rebinding. It has either of these
              formats:

                \(TEXT cua-mode)
                \(TEXT current-binding KEY-FUN DEF-FUN KEY WHERE)

              Here TEXT is a link text to show to the user.  The
              rest of the list is used to show information when
              the user clicks the link.

              KEY-FUN is the actual binding for KEY."
  (let (changed-keys
        (default-keys (sort tutorial--default-keys
                            'tutorial--sort-keys)))
    (dolist (kdf default-keys)
      ;; The variables below corresponds to those with the same names
      ;; described in the doc string.
      (let* ((key     (nth 1 kdf))
             (def-fun (nth 0 kdf))
             (def-fun-txt (format "%s" def-fun))
             (rem-fun (command-remapping def-fun))
             (key-fun (key-binding key))
             (where (where-is-internal (if rem-fun rem-fun def-fun))))
        (if where
            (progn
              (setq where (key-description (car where)))
              (when (and (< 10 (length where))
                         (string= (substring where 0 (length "<menu-bar>"))
                                  "<menu-bar>"))
                (setq where "The menus")))
          (setq where ""))
        (setq remark nil)
        (unless
            (cond ((eq key-fun def-fun)
                   ;; No rebinding, return t
                   t)
                  ((eq key-fun (command-remapping def-fun))
                   ;; Just a remapping, return t
                   t)
                  ;; cua-mode specials:
                  ((and cua-mode
                        (or (and
                             (equal key [?\C-v])
                             (eq key-fun 'cua-paste))
                            (and
                             (equal key [?\C-z])
                             (eq key-fun 'undo))))
                   (setq remark (list "cua-mode, more info" 'cua-mode))
                   nil)
                  ((and cua-mode
                        (or
                         (and (eq def-fun 'ESC-prefix)
                              (equal key-fun
                                     `(keymap
                                       (118 . cua-repeat-replace-region))))
                         (and (eq def-fun 'mode-specific-command-prefix)
                              (equal key-fun
                                     '(keymap
                                       (timeout . copy-region-as-kill))))
                         (and (eq def-fun 'Control-X-prefix)
                              (equal key-fun
                                     '(keymap (timeout . kill-region))))))
                   (setq remark (list "cua-mode replacement" 'cua-mode))
                   (cond
                    ((eq def-fun 'mode-specific-command-prefix)
                     (setq def-fun-txt "\"C-c prefix\""))
                    ((eq def-fun 'Control-X-prefix)
                     (setq def-fun-txt "\"C-x prefix\""))
                    ((eq def-fun 'ESC-prefix)
                     (setq def-fun-txt "\"ESC prefix\"")))
                   (setq where "Same key")
                   nil)
                  ;; viper-mode specials:
                  ((and (boundp 'viper-mode)
                        viper-mode
                        (eq viper-current-state 'vi-state)
                        (or (and (eq def-fun 'isearch-forward)
                                 (eq key-fun 'viper-isearch-forward))
                            (and (eq def-fun 'isearch-backward)
                                 (eq key-fun 'viper-isearch-backward))))
                   ;; These bindings works as the default bindings,
                   ;; return t
                   t)
                  ((when normal-erase-is-backspace
                     (or (and (equal key [C-delete])
                              (equal key-fun 'kill-word))
                         (and (equal key [C-backspace])
                              (equal key-fun 'backward-kill-word))))
                   ;; This is the strange handling of C-delete and
                   ;; C-backspace, return t
                   t)
                  (t
                   ;; This key has indeed been rebound. Put information
                   ;; in `remark' and return nil
                   (setq remark
                         (list "more info" 'current-binding
                               key-fun def-fun key where))
                   nil))
          (add-to-list 'changed-keys
                       (list key def-fun def-fun-txt where remark)))))
    changed-keys))

(defun tutorial--display-changes (changed-keys arg)
  "Display changes to some default key bindings.
If some of the default key bindings that the tutorial depends on
have been changed then display the changes in the tutorial buffer
with some explanatory links.

CHANGED-KEYS should be a list in the format returned by
`tutorial--find-changed-keys'."
  (when (or changed-keys
            (and (boundp 'viper-mode)
                 viper-mode))
    ;; Need the custom button face for viper buttons:
    (when (and (boundp 'viper-mode)
               viper-mode)
      (require 'cus-edit))
    (goto-char tutorial--point-before-chkeys)
    (let ((start (point))
          end
          (tab-map (let ((map (make-sparse-keymap)))
                     (define-key map [tab] 'forward-button)
                     (define-key map [(shift tab)] 'backward-button)
                     (define-key map [(meta tab)] 'backward-button)
                     map)))
      (insert "
 NOTICE: One of the main purposes of the tutorial is that You
 should be able to learn some important Emacs default key
 bindings.  However when you started the tutorial some key
 bindings used in the tutorial had been changed from Emacs
 default. Those key bindings have been marked below. [")
      (insert-button "Details"
                     'tutorial-buffer
                     (current-buffer)
                     'tutorial-arg arg
                     'action
                     'tutorial--detailed-help
                     'follow-link t
                     'face '(:inherit link :background "yellow"))
      (insert "]\n\n" )
      (when changed-keys
        (dolist (tk changed-keys)
          (let* ((def-fun     (nth 1 tk))
                 (key         (nth 0 tk))
                 (def-fun-txt (nth 2 tk))
                 (where       (nth 3 tk))
                 (remark      (nth 4 tk))
                 (rem-fun (command-remapping def-fun))
                 (key-txt (key-description key))
                 (key-fun (key-binding key))
                 tot-len)
            (unless (eq def-fun key-fun)
              ;; Mark the key in the tutorial text
              (unless (string= "Same key" where)
                (let ((here (point))
                      (key-desc (key-description key)))
                  (while (search-forward key-desc nil t)
                    (put-text-property (match-beginning 0)
                                       (match-end 0)
                                       'face '(:background "yellow"))
                    (forward-line)
                    (let ((s (concat
                              "** The key "
                              key-desc
                              " has been rebound, but you can use "
                              where " instead ["))
                          (start (point))
                          end)
                      (insert s)
                      (insert-button "Explain"
                                   'action
                                   (lambda(button) (interactive)
                                     (goto-char (point-min)))
                                   'follow-link t
                                   'help-echo
                                   "Click to go to explanation at top of buffer"
                                   'face '(:inherit 'link :background "yellow"))
                      (insert "] **")
                      (setq end (point))
                      (insert "\n")
                      (put-text-property start end 'local-map tab-map)
                      (put-text-property start end
                                         'face '(:background "yellow" :foreground "#c00"))
                      (put-text-property start end 'read-only t)))
                  (goto-char here)))))))


      (setq end (point))
      ;; Make the area with information about change key
      ;; bindings stand out:
      (put-text-property start end
                         'face
                         ;; The default warning face does not
                         ;;look good in this situation. Instead
                         ;;try something that could be
                         ;;recognized from warnings in normal
                         ;;life:
                         ;; 'font-lock-warning-face
                         (list :background "yellow" :foreground "#c00"))
      ;; Make it possible to use Tab/S-Tab between fields in
      ;; this area:
      (put-text-property start end 'local-map tab-map)
      (setq tutorial--point-after-chkeys (point-marker))
      ;; Make this area read-only:
      (put-text-property start end 'read-only t))))

(defvar tutorial--point-before-chkeys 0
  "Point before display of key changes.")
(make-variable-buffer-local 'tutorial--point-before-chkeys)
(defvar tutorial--point-after-chkeys 0
  "Point after display of key changes.")
(make-variable-buffer-local 'tutorial--point-after-chkeys)

(defvar tutorial--lang nil
  "Tutorial language.")
(make-variable-buffer-local 'tutorial--lang)

(defun tutorial--saved-dir ()
  "Directory where to save tutorials."
  (expand-file-name ".emacstut" "~/"))

(defun tutorial--saved-file ()
  "File name in which to save tutorials."
  (let ((file-name tutorial--lang)
        (ext (file-name-extension tutorial--lang)))
    (when (or (not ext)
              (string= ext ""))
      (setq file-name (concat file-name ".tut")))
    (expand-file-name file-name (tutorial--saved-dir))))

(defun tutorial--save-tutorial ()
  "Save the tutorial buffer.
This saves the part of the tutorial before and after the area
showing changed keys.  It also saves the point position and the
position where the display of changed bindings was inserted."
  ;; Anything to save?
  (when (or (buffer-modified-p)
            (< 1 (point)))
    (let ((tutorial-dir (tutorial--saved-dir))
          save-err)
      ;; The tutorial is saved in a subdirectory in the user home
      ;; directory. Create this subdirectory first.
      (unless (file-directory-p tutorial-dir)
        (condition-case err
            (make-directory tutorial-dir nil)
          (error (setq save-err t)
                 (warn "Could not create directory %s: %s" tutorial-dir
                       (error-message-string err)))))
      ;; Make sure we have that directory.
      (if (file-directory-p tutorial-dir)
          (let ((tut-point (if (= 0 tutorial--point-after-chkeys)
                               ;; No area display changed keys
                               (point)
                             (if (< (point) tutorial--point-after-chkeys)
                                 (- (point))
                               (- (point) tutorial--point-after-chkeys))))
                (old-point (point))
                ;; Use a special undo list so that we easily can undo
                ;; the changes we make to the tutorial buffer.  This is
                ;; currently not needed since we now delete the buffer
                ;; after saving, but kept for possible future use of
                ;; this function.
                buffer-undo-list
                (inhibit-read-only t))
            ;; Delete the area displaying info about changed keys.
            (when (< 0 tutorial--point-after-chkeys)
              (delete-region tutorial--point-before-chkeys
                             tutorial--point-after-chkeys))
            ;; Put the value of point first in the buffer so we can
            ;; write it.
            (goto-char (point-min))
            (insert (number-to-string tut-point)
                    "\n"
                    (number-to-string (marker-position
                                       tutorial--point-before-chkeys))
                    "\n")
            (condition-case err
                (write-region nil nil (tutorial--saved-file))
              (error (setq save-err t)
                     (warn "Could not save tutorial to %s: %s"
                           (tutorial--saved-file)
                           (error-message-string err))))
            ;; Restore point
            ;; An error is raised here?? Is this a bug?
            (condition-case err
                (undo-only)
              (error nil))
            (goto-char old-point)
            (if save-err
                (message "Could not save tutorial state.")
              (message "Saved tutorial state.")))
        (message "Can't save tutorial: %s is not a directory"
                 tutorial-dir)))))

;;;###autoload
(defun help-with-tutorial (&optional arg dont-ask-for-revert)
  "Select the Emacs learn-by-doing tutorial.
If there is a tutorial version written in the language
of the selected language environment, that version is used.
If there's no tutorial in that language, `TUTORIAL' is selected.
With ARG, you are asked to choose which language.
If DONT-ASK-FOR-REVERT is non-nil the buffer is reverted without
any question when restarting the tutorial.

If any of the standard Emacs key bindings that are used in the
tutorial have been changed then an explanatory note about this is
shown in the beginning of the tutorial buffer.

When the tutorial buffer is killed the content and the point
position in the buffer is saved so that the tutorial may be
resumed later."
  (interactive "P")
  (let* ((lang (if arg
                   (let ((minibuffer-setup-hook minibuffer-setup-hook))
                     (add-hook 'minibuffer-setup-hook
                               'minibuffer-completion-help)
                     (read-language-name 'tutorial "Language: " "English"))
                 (if (get-language-info current-language-environment 'tutorial)
                     current-language-environment
                   "English")))
         (filename (get-language-info lang 'tutorial))
         ;; Choose a buffer name including the language so that
         ;; several languages can be tested simultaneously:
         (tut-buf-name (concat "TUTORIAL (" lang ")"))
         (old-tut-buf (get-buffer tut-buf-name))
         (old-tut-win (when old-tut-buf (get-buffer-window old-tut-buf t)))
         (old-tut-is-ok (when old-tut-buf
                          (not (buffer-modified-p old-tut-buf))))
         old-tut-file
         (old-tut-point 1))
    (setq tutorial--point-after-chkeys (point-min))
    ;; Try to display the tutorial buffer before asking to revert it.
    ;; If the tutorial buffer is shown in some window make sure it is
    ;; selected and displayed:
    (if old-tut-win
        (raise-frame
         (window-frame
          (select-window (get-buffer-window old-tut-buf t))))
      ;; Else, is there an old tutorial buffer? Then display it:
      (when old-tut-buf
        (switch-to-buffer old-tut-buf)))
    ;; Use whole frame for tutorial
    (delete-other-windows)
    ;; If the tutorial buffer has been changed then ask if it should
    ;; be reverted:
    (when (and old-tut-buf
               (not old-tut-is-ok))
      (setq old-tut-is-ok
            (if dont-ask-for-revert
                nil
              (not (y-or-n-p
                    "You have changed the Tutorial buffer.  Revert it? ")))))
    ;; (Re)build the tutorial buffer if it is not ok
    (unless old-tut-is-ok
      (switch-to-buffer (get-buffer-create tut-buf-name))
      (unless lang (error "Variable lang is nil"))
      (setq tutorial--lang lang)
      (setq old-tut-file (file-exists-p (tutorial--saved-file)))
      (let ((inhibit-read-only t))
        (erase-buffer))
      (message "Preparing tutorial ...") (sit-for 0)

      ;; Do not associate the tutorial buffer with a file. Instead use
      ;; a hook to save it when the buffer is killed.
      (setq buffer-auto-save-file-name nil)
      (add-hook 'kill-buffer-hook 'tutorial--save-tutorial nil t)

      ;; Insert the tutorial. First offer to resume last tutorial
      ;; editing session.
      (when dont-ask-for-revert
        (setq old-tut-file nil))
      (when old-tut-file
        (setq old-tut-file
              (y-or-n-p "Resume your last saved tutorial? ")))
      (if old-tut-file
          (progn
            (insert-file-contents (tutorial--saved-file))
            (goto-char (point-min))
            (setq old-tut-point
                  (string-to-number
                   (buffer-substring-no-properties
                    (line-beginning-position) (line-end-position))))
            (forward-line)
            (setq tutorial--point-before-chkeys
                  (string-to-number
                   (buffer-substring-no-properties
                    (line-beginning-position) (line-end-position))))
            (forward-line)
            (delete-region (point-min) (point))
            (goto-char tutorial--point-before-chkeys)
            (setq tutorial--point-before-chkeys (point-marker)))
        (insert-file-contents (expand-file-name filename data-directory))
        (forward-line)
        (setq tutorial--point-before-chkeys (point-marker)))
      (hack-local-variables)


      ;; Check if there are key bindings that may disturb the
      ;; tutorial.  If so tell the user.
      (let ((changed-keys (tutorial--find-changed-keys)))
        (tutorial--display-changes changed-keys arg))


      ;; Clear message:
      (unless dont-ask-for-revert
        (message "") (sit-for 0))


      (if old-tut-file
          ;; Just move to old point in saved tutorial.
          (let ((old-point
                 (if (> 0 old-tut-point)
                     (- old-tut-point)
                   (+ old-tut-point tutorial--point-after-chkeys))))
            (when (< old-point 1)
              (setq old-point 1))
            (goto-char old-point))
        (goto-char (point-min))
        (search-forward "\n<<")
        (beginning-of-line)
        ;; Convert the <<...>> line to the proper [...] line,
        ;; or just delete the <<...>> line if a [...] line follows.
        (cond ((save-excursion
                 (forward-line 1)
                 (looking-at "\\["))
               (delete-region (point) (progn (forward-line 1) (point))))
              ((looking-at "<<Blank lines inserted.*>>")
               (replace-match "[Middle of page left blank for didactic purposes.   Text continues below]"))
              (t
               (looking-at "<<")
               (replace-match "[")
               (search-forward ">>")
               (replace-match "]")))
        (beginning-of-line)
        (let ((n (- (window-height (selected-window))
                    (count-lines (point-min) (point))
                    6)))
          (if (< n 8)
              (progn
                ;; For a short gap, we don't need the [...] line,
                ;; so delete it.
                (delete-region (point) (progn (end-of-line) (point)))
                (newline n))
            ;; Some people get confused by the large gap.
            (newline (/ n 2))

            ;; Skip the [...] line (don't delete it).
            (forward-line 1)
            (newline (- n (/ n 2)))))
        (goto-char (point-min)))
      (setq buffer-undo-list nil)
      (set-buffer-modified-p nil))))

(provide 'tutorial)

;;; tutorial.el ends here