;;; gametree.el --- manage game analysis trees in Emacs  -*- lexical-binding: t -*-

;; Copyright (C) 1997, 1999, 2001-2024 Free Software Foundation, Inc.

;; Author: Ian T Zimmerman <itz@rahul.net>
;; Created: Wed Dec 10 07:41:46 PST 1997
;; Keywords: games

;; 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 little hack has enabled me to keep track of my email chess
;;  games in Emacs.  For a long time I dreamt about writing a real,
;;  graphical tree editor; but, then the idea struck me, why do it
;;  graphically, when it can be done in Emacs? :-)  And in fact Emacs
;;  almost had what I needed out of the box, namely the powerful
;;  Outline mode.  This code is built entirely on Outline mode, it
;;  only adds two commands that I found indispensable when dealing
;;  with the special kind of trees that analysis trees comprise.

;;  The built-in documentation should be enough to explain the use,
;;  along with the following example (yes, this is a real game).

;;  *** 23. f4 ef 24. Nf3 Rf3 -/+
;;  25. Rf3 Qh2 26. Kh1 Qh1 27. Ke2 Qg2 -+
;;  ******* 25. gf3 Nce3 26. Qe2 Nf1 -/+
;;  27. Qe5 Ne5 28. Kf1 Nf3 -/+
;;  27. Kf1 Nh2 28. Kf2 Ng4 29. fg4 Rf8 30. Ke1 Qg3 31. Kd1 Rf2 -+

;;  Place the preceding in a scratch buffer, load this code, and do
;;  M-x gametree-mode.  Now place the cursor just after the `Nf3' and
;;  before the `Rf3' on the first line, and do C-c C-j.  The result is

;;  *** 23. f4 ef 24. Nf3
;;  ****** 24: Rf3 -/+
;;  25. Rf3 Qh2 26. Kh1 Qh1 27. Ke2 Qg2 -+
;;  ******* 25. gf3 Nce3 26. Qe2 Nf1 -/+
;;  27. Qe5 Ne5 28. Kf1 Nf3 -/+
;;  27. Kf1 Nh2 28. Kf2 Ng4 29. fg4 Rf8 30. Ke1 Qg3 31. Kd1 Rf2 -+

;;  Now you can add another subvariation on Black's 24th move: with
;;  the cursor still on the first line, do C-c C-v, and voila

;;  *** 23. f4 ef 24. Nf3
;;  24:
;;  ****** 24: Rf3 -/+
;;  25. Rf3 Qh2 26. Kh1 Qh1 27. Ke2 Qg2 -+
;;  ******* 25. gf3 Nce3 26. Qe2 Nf1 -/+
;;  27. Qe5 Ne5 28. Kf1 Nf3 -/+
;;  27. Kf1 Nh2 28. Kf2 Ng4 29. fg4 Rf8 30. Ke1 Qg3 31. Kd1 Rf2 -+

;;  and the cursor is positioned on the new line just after the move
;;  number, so you can start typing the new analysis.  That's it,
;;  quite simple.

;;  As of version 1.1, a simple score reducer has been implemented.
;;  As you type in leaf variations, you can add a numerical score tag
;;  to them with C-c ; . Then, with the cursor on a variation higher
;;  up in the tree, you can do C-c ^ and the program will compute the
;;  reduced score of the internal variation based on the scores of its
;;  children (which are recursively computed).  You can use any range
;;  of numbers you wish as scores, maybe -1000 to 1000 or 0 to 100,
;;  all that matters to the program is that higher means better for
;;  White, lower means better for Black.

;;; Code:

(require 'outline)

;;;; Configuration variables

(defgroup gametree nil
  "Manage game analysis trees in Emacs."
  :prefix "gametree-"
  :group 'games
  :version "20.3")

(defcustom gametree-half-ply-regexp (regexp-quote ":")
  "Matches ends of numbers of moves by the \"second\" player.
For instance, it is an almost universal convention in chess to postfix
numbers of moves by Black (if considered in isolation) by the ellipsis
\"...\".  This is NOT a good choice for this program, though, because it
conflicts with the use of ellipsis by Outline mode to denote collapsed
subtrees.  The author uses \":\" because it agrees nicely with a set of
LaTeX macros he uses for typesetting annotated games."
  :type 'regexp)

(defcustom gametree-full-ply-regexp (regexp-quote ".")
  "Matches ends of numbers of moves by the \"first\" player.
For instance, it is an almost universal convention in chess to postfix
numbers of moves by White (if considered in isolation) by the dot \".\"."
  :type 'regexp)

(defcustom gametree-half-ply-format "%d:"
  "Output format for move numbers of moves by the \"second\" player.
Has to contain \"%d\" to output the actual number."
  :type 'string)

(defcustom gametree-full-ply-format "%d."
  "Output format for move numbers of moves by the \"first\" player.
Has to contain \"%d\" to output the actual number."
  :type 'string)

(defcustom gametree-make-heading-function
  (lambda (level)
    (insert (make-string level ?*)))
  "A function of one numeric argument, LEVEL, to insert a heading at point.
You should change this if you change `outline-regexp'."
  :type 'function)

(defvar gametree-local-layout nil
  "A list encoding the layout (i.e. the show or hide state) of the file.
If Emacs notices a local variable specification of this variable in
the first line of the buffer while saving the buffer to the visited
file, the local value will be saved there and restored the next time
the file is visited (subject to the usual restriction via
`enable-local-variables'), and the layout will be set accordingly.")

(defcustom gametree-score-opener "{score="
  "The string which opens a score tag, and precedes the actual score."
  :type 'string)

(defcustom gametree-score-manual-flag "!"
  "String marking the line as manually (as opposed to automatically) scored."
  :type 'string)

(defcustom gametree-score-closer "}"
  "The string which closes a score tag, and follows the actual score."
  :type 'string)

(defcustom gametree-score-regexp
  (concat "[^\n\^M]*\\("
          (regexp-quote gametree-score-opener)
          "[ 	]*\\("
          (regexp-quote gametree-score-manual-flag)
          "[ 	]*\\)?\\([-+]?[0-9]+\\)"
          (regexp-quote gametree-score-closer)
          "[ 	]*\\)[\n\^M]")
  "Regular expression matching lines that guide the program in scoring.
Its third parenthetical group should match the actual score.  Its
first parenthetical group should match the entire score tag.  Its
second parenthetical group should be an optional flag that marks the
line as *manually* (as opposed to automatically) scored, which
prevents the program from recursively applying the scoring algorithm
on the subtree headed by the marked line, and makes it use the manual
score instead."
  :type 'regexp)

(defcustom gametree-default-score 0
  "Score to assume for branches lacking score tags."
  :type 'integer)

;;;; Helper functions

(defun gametree-prettify-heading ()
  "Insert/delete space between leading asterisks and heading text.
If the current variation is an internal node (i.e. starts with one or
more asterisks), ensure there's at least one space between the
asterisks and the text.  If on the other hand this is a leaf, there
should be no leading white space."
  (save-excursion
    (beginning-of-line 1)
    (if (re-search-forward (concat "\\=" outline-regexp) nil t)
        (if (not (looking-at "[ \t]+")) (insert " "))
      (delete-char (save-excursion (skip-chars-forward " \t"))))
    (if (re-search-forward (concat "\\=[ \t]*[1-9][0-9]*\\("
                                   gametree-full-ply-regexp "\\|"
                                   gametree-half-ply-regexp "\\)") nil t)
        (if (not (looking-at "[ \t]+")) (insert " ")
          (delete-char (1- (save-excursion (skip-chars-forward  " \t"))))))))

(defun gametree-looking-at-ply ()
  "Read and return the number of the ply under point."
  (if (eobp) 0
    (let ((boundary (concat "[ \t]*\\([1-9][0-9]*\\)\\("
                            gametree-full-ply-regexp "\\|"
                            gametree-half-ply-regexp "\\)"))
          (limit (line-beginning-position 1)))
      (if (looking-at boundary)
          (+ (* 2 (string-to-number (match-string 1)))
             (if (string-match gametree-half-ply-regexp (match-string 2)) 1 0))
        (save-excursion
          (re-search-backward boundary limit)
          (skip-chars-backward "0123456789")
          (1+ (* 2 (string-to-number
                    (buffer-substring (point) (match-end 1))))))))))

(defun gametree-current-branch-ply ()
  "Return the ply number of the first move of the current variation."
  (save-excursion
    (beginning-of-line 1)
    (re-search-forward (concat "\\=" outline-regexp) nil t)
    (gametree-looking-at-ply)))

(defsubst gametree-forward-line ()
  (re-search-forward "[\n\^M]" nil 'move))

(defun gametree-current-branch-depth ()
  "Return the depth of the current variation in the analysis tree.
This value is simply the outline heading level of the current line."
  (save-excursion
    (beginning-of-line 1)
    (if (looking-at outline-regexp)
        (outline-level) 0)))

(defun gametree-transpose-following-leaves ()
  "Move the current leaf variation behind all others on the same level."
  (let ((following-leaves
         (save-excursion
           (gametree-forward-line)
           (let ((p (point)))
             (while (and (not (eobp))
                         (= 0 (gametree-current-branch-depth)))
               (gametree-forward-line))
             (prog1 (buffer-substring p (point))
               (delete-region p (point)))))))
    (save-excursion
      (beginning-of-line 1)
      (insert following-leaves))))


;;;; Functions related to the task of saving and restoring current
;;;; outline layout

(defsubst gametree-show-children-and-entry ()
  (outline-show-children)
  (outline-show-entry))

(defun gametree-entry-shown-p ()
  (save-excursion
    (forward-line 1)
    (and (bolp) (not (eobp)) (not (looking-at outline-regexp)))))

(defun gametree-children-shown-p ()
  (save-excursion
    (ignore-errors
        (let ((depth (gametree-current-branch-depth)))
          (outline-next-visible-heading 1)
          (< depth (gametree-current-branch-depth))))))

(defun gametree-current-layout (depth &optional from-top-level)
  (let ((layout nil) (first-time t))
    (while (save-excursion
             (ignore-errors
               (or (and first-time from-top-level
                        (bolp) (looking-at outline-regexp))
                   (setq first-time nil)
                   (outline-next-visible-heading 1))
               (< depth (gametree-current-branch-depth))))
      (if (not first-time)
          (outline-next-visible-heading 1))
      (setq first-time nil)
      (if (not (gametree-children-shown-p))
          (setq layout
                (nconc layout
                       (if (gametree-entry-shown-p)
                           (list 'show-entry)
                         (list nil))))
        (setq layout (nconc layout (if (gametree-entry-shown-p)
                                       (list 'gametree-show-children-and-entry)
                                     (list 'show-children))))
        (let ((sub-layout
               (gametree-current-layout (gametree-current-branch-depth))))
          (setq layout (nconc layout (list sub-layout))))))
    layout))

(defun gametree-save-layout ()
  (save-excursion
    (goto-char (point-min))
    (setq gametree-local-layout (gametree-current-layout 0 t))))

(defun gametree-apply-layout (layout depth &optional from-top-level)
  (let ((first-time t))
    (while (and layout
                (save-excursion
                  (ignore-errors
                    (or (and first-time from-top-level
                             (bolp) (looking-at outline-regexp))
                        (setq first-time nil)
                        (outline-next-visible-heading 1))
                    (< depth (gametree-current-branch-depth)))))
      (if (not first-time)
          (outline-next-visible-heading 1))
      (setq first-time nil)
      (outline-hide-subtree)
      (if (nth 0 layout)
          (funcall (nth 0 layout)))
      (if (not (and (nth 1 layout) (listp (nth 1 layout))))
          (setq layout (cdr layout))
        (gametree-apply-layout (nth 1 layout)
                               (gametree-current-branch-depth))
        (setq layout (cdr (cdr layout)))))))

(defun gametree-restore-layout ()
  (save-excursion
    (goto-char (point-min))
    (gametree-apply-layout gametree-local-layout 0 t)))

(defun gametree-hack-file-layout ()
  (save-excursion
    (goto-char (point-min))
    (if (looking-at "[^\n]*-[^\n]*gametree-local-layout: \\([^;\n]*\\);")
        (progn
          (goto-char (match-beginning 1))
          (delete-region (point) (match-end 1))
          (let ((standard-output (current-buffer)))
            (princ gametree-local-layout))))))


;;;; Scoring functions

(defun gametree-current-branch-score ()
  "Return score of current variation according to its score tag.
When no score tag is present, use the value of `gametree-default-score'."
  (if (looking-at gametree-score-regexp)
      (string-to-number (match-string 3))
    gametree-default-score))

(defun gametree-compute-reduced-score ()
  "Return current internal node score computed recursively from subnodes.
Subnodes which have been manually scored are honored."
  (if (or
       (= 0 (gametree-current-branch-depth))
       (save-excursion (gametree-forward-line) (eobp))
       (and (looking-at gametree-score-regexp)
            (not (null (match-string 2)))))
      (gametree-current-branch-score)
    (let ((depth (gametree-current-branch-depth)))
      (save-excursion
        (gametree-forward-line)
        ;; the case of a leaf node has already been handled, so here I
        ;; know I am on the 1st line of the current subtree.  This can
        ;; be either a leaf child, or a subheading.
        (let ((running gametree-default-score)
              (minmax
               (if (= 0 (mod (gametree-current-branch-ply) 2))
                   'max 'min)))
          (while (and (not (eobp))
                      (= 0 (gametree-current-branch-depth))) ;handle leaves
            (setq running (funcall minmax running
                                   (gametree-current-branch-score)))
            (gametree-forward-line))
          (let ((done (and (not (eobp))
                           (< depth (gametree-current-branch-depth)))))
            (while (not done)           ;handle subheadings
              (setq running (funcall minmax running
                                     (gametree-compute-reduced-score)))
              (setq done (ignore-errors (outline-forward-same-level 1)))))
          running)))))

;;;; Commands

(defun gametree-insert-new-leaf (&optional at-depth)
  "Start a new leaf variation under the current branching point.
The new variation can later be split to be a branching point itself,
with \\[gametree-break-line-here].  If the point is currently on a
leaf variation, this command won't work; use \\[gametree-break-line-here]
on the current line first.

With a numeric arg AT-DEPTH, first go up the tree until a node of
depth AT-DEPTH or smaller is found."
  (interactive "*P")
  (if (zerop (gametree-current-branch-depth))
      (outline-up-heading 0))
  (if at-depth
      (while (> (gametree-current-branch-depth)
                (prefix-numeric-value at-depth))
        (outline-up-heading 1)))
  (beginning-of-line 1)
  (let ((parent-depth (gametree-current-branch-depth)))
    (outline-show-entry)
    (condition-case nil
        (outline-next-visible-heading 1)
      (error
       (goto-char (point-max))
       (if (not (bolp)) (insert "\n"))))
    (let ((starting-plies
           (if (> (gametree-current-branch-depth) parent-depth)
               (gametree-current-branch-ply)
             (save-excursion (forward-line -1)
                             (gametree-current-branch-ply)))))
      (goto-char (1- (point)))
      (insert "\n")
      (insert (format (if (= 0 (mod starting-plies 2))
                          gametree-full-ply-format
                        gametree-half-ply-format)
                      (/ starting-plies 2))))))

(defun gametree-break-line-here (&optional at-move)
  "Split the variation node at the point position.
This command works whether the current variation node is a leaf, or is
already branching at its end.  The new node is created at a level that
reflects the number of game plies between the beginning of the current
variation and the breaking point.

With a numerical argument AT-MOVE, split the variation before
White's AT-MOVEth move, or Black's if negative.  The last option will
only work of Black's moves are explicitly numbered, for instance
`1. e4 1: e5'."
  (interactive "*P")
  (if at-move (progn
          (end-of-line 1)
          (let ((limit (point)))
            (beginning-of-line 1)
            (re-search-forward
             (concat
              (regexp-quote
               (int-to-string (abs (prefix-numeric-value at-move))))
              (if (> at-move 0) gametree-full-ply-regexp
                gametree-half-ply-regexp)) limit))
          (goto-char (match-beginning 0))))
  (gametree-transpose-following-leaves)
  (let* ((pt (point-marker))
         (plies (gametree-current-branch-ply))
         (depth (gametree-current-branch-depth))
         (old-depth depth))
    (if (= depth 0)
        (progn
          (save-excursion
            (outline-previous-visible-heading 1)
            (setq depth
                  (let ((old-branch-ply
                         (condition-case nil
                             (gametree-current-branch-ply)
                           (error 0))))
                    (if (zerop old-branch-ply)
                        (1+ (gametree-current-branch-depth))
                      (+ (gametree-current-branch-depth)
                         (- plies old-branch-ply))))))
          (save-excursion
            (beginning-of-line 1)
            (funcall gametree-make-heading-function depth)
            (gametree-prettify-heading))))
    (save-excursion
      (if (not (looking-at (concat "[ \t]*[1-9][0-9]*\\("
                                   gametree-full-ply-regexp "\\|"
                                   gametree-half-ply-regexp "\\)")))
          (progn
            (insert (format (if (= 0 (mod (gametree-looking-at-ply) 2))
                                gametree-full-ply-format
                              gametree-half-ply-format)
                            (/ (gametree-looking-at-ply) 2)))
            (gametree-prettify-heading)
            (beginning-of-line 1)))
      (goto-char pt)
      (insert "\n")
      (if (not (= 0 old-depth))
          (funcall gametree-make-heading-function
                   (+ depth (- (gametree-current-branch-ply) plies))))
      (gametree-prettify-heading))))

(defun gametree-merge-line ()
  "Merges a variation with its only child.
Does *not* check if the variation has in fact a unique child; users beware."
  (interactive "*")
  (if (zerop (gametree-current-branch-depth))
      (outline-up-heading 0))
  (if (looking-at gametree-score-regexp)
      (delete-region (match-beginning 1) (match-end 1)))
  (end-of-line 1)
  (let ((prev-depth (save-excursion (forward-line 1)
                                    (gametree-current-branch-depth))))
    (delete-char (1+ prev-depth))
    (if (zerop prev-depth)
        (save-excursion
          (beginning-of-line 1)
          (delete-char (gametree-current-branch-depth))
          (gametree-prettify-heading)))))

(defun gametree-insert-score (score &optional auto)
  "Insert a score tag with value SCORE at the end of the current line.
If this line already has a score tag, just jump to it and alter it.
When called from a program, optional AUTO flag tells if the score is
being entered automatically (and thus should lack the manual mark)."
  (interactive "*P")
  (beginning-of-line 1)
  (if (looking-at gametree-score-regexp)
      (progn
        (goto-char (match-beginning 3))
        (if (and auto (not (null (match-string 2))))
            (delete-region (match-beginning 2) (match-end 2)))
        (if (not (null score))
            (delete-region (match-beginning 3) (match-end 3)))
        (if (and (not auto) (null (match-string 2)))
            (insert gametree-score-manual-flag)))
    (end-of-line 1)
    (if (= 0 (save-excursion (skip-chars-backward " \t")))
        (insert " "))
    (insert gametree-score-opener)
    (if (not auto) (insert gametree-score-manual-flag))
    (save-excursion (insert gametree-score-closer)))
  (if (not (null score))
      (save-excursion
        (insert (int-to-string (prefix-numeric-value score))))))

(defun gametree-compute-and-insert-score ()
  "Compute current node score, maybe recursively from subnodes.  Insert it.
Subnodes which have been manually scored are honored."
  (interactive "*")
  (let ((auto (not (and (looking-at gametree-score-regexp)
                        (not (null (match-string 2))))))
        (score (gametree-compute-reduced-score)))
    (gametree-insert-score score auto)))


(defun gametree-layout-to-register (register)
  "Store current tree layout in register REGISTER.
Use \\[gametree-apply-register-layout] to restore that configuration.
Argument is a character, naming the register.

Interactively, reads the register using `register-read-with-preview'."
  (interactive (list (register-read-with-preview "Layout to register: ")))
  (save-excursion
    (goto-char (point-min))
    (set-register register
                  (gametree-current-layout 0 t))))

(defun gametree-apply-register-layout (char)
  "Return to a tree layout stored in a register.
Argument is a character, naming the register.

Interactively, reads the register using `register-read-with-preview'."
  (interactive
   (progn
     (barf-if-buffer-read-only)
     (list (register-read-with-preview "Apply layout from register: "))))
  (save-excursion
    (goto-char (point-min))
    (gametree-apply-layout (get-register char) 0 t)))

(defun gametree-save-and-hack-layout ()
  "Save the current tree layout and hack the file local variable spec.
This function saves the current layout in `gametree-local-layout' and,
if a local file variable specification for this variable exists in the
buffer, it is replaced by the new value.  See the documentation for
`gametree-local-layout' for more information."
  (interactive)
  (gametree-save-layout)
  (let ((inhibit-read-only t))
    (gametree-hack-file-layout))
  nil)


;;;; Mouse commands

(defun gametree-mouse-break-line-here (event)
  (interactive "e")
  (mouse-set-point event)
  (gametree-break-line-here))

(defun gametree-mouse-show-children-and-entry (event)
  (interactive "e")
  (mouse-set-point event)
  (gametree-show-children-and-entry))

(defun gametree-mouse-show-subtree (event)
  (interactive "e")
  (mouse-set-point event)
  (outline-show-subtree))

(defun gametree-mouse-hide-subtree (event)
  (interactive "e")
  (mouse-set-point event)
  (outline-hide-subtree))


;;;; Key bindings

(defvar-keymap gametree-mode-map
  "C-c C-j"     #'gametree-break-line-here
  "C-c C-v"     #'gametree-insert-new-leaf
  "C-c C-m"     #'gametree-merge-line
  "C-c C-r SPC" #'gametree-layout-to-register
  "C-c C-r /"   #'gametree-layout-to-register
  "C-c C-r j"   #'gametree-apply-register-layout
  "C-c C-y"     #'gametree-save-and-hack-layout
  "C-c ;"       #'gametree-insert-score
  "C-c ^"       #'gametree-compute-and-insert-score
  "M-<down-mouse-2> M-<mouse-2>" #'gametree-mouse-break-line-here
  "S-<down-mouse-1> S-<mouse-1>" #'gametree-mouse-show-children-and-entry
  "S-<down-mouse-2> S-<mouse-2>" #'gametree-mouse-show-subtree
  "S-<down-mouse-3> S-<mouse-3>" #'gametree-mouse-hide-subtree)

(define-derived-mode gametree-mode outline-mode "GameTree"
  "Major mode for managing game analysis trees.
Useful to postal and email chess (and, it is hoped, also checkers, go,
shogi, etc.) players, it is a slightly modified version of Outline mode.

\\{gametree-mode-map}"
  (auto-fill-mode 0)
  (add-hook 'write-contents-functions 'gametree-save-and-hack-layout nil t))

(provide 'gametree)

;;; gametree.el ends here