;;;_ org-choose.el --- decision management for org-mode

;;;_. Headers
;;;_ , License
;; Copyright (C) 2009  Tom Breton (Tehom)

;; Author: Tom Breton (Tehom)
;; Keywords: outlines, convenience

;; This file 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.

;; This file 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., 59 Temple Place - Suite 330,
;; Boston, MA 02111-1307, USA.

;;;_ , Commentary:

; This is code to support decision management.  It lets you treat a
; group of sibling items in org-mode as alternatives in a decision.

; There are no user commands in this file.  You use it by:
;   * Loading it (manually or by M-x customize-apropos org-modules)

;;   * Setting up at least one set of TODO keywords with the
;;     interpretation "choose" by either:

;;     * Using the file directive #+CHOOSE_TODO:

;;       * For instance, "#+CHOOSE_TODO: NO(,-) MAYBE(,0) YES"

;;     * Or by M-x customize-apropos org-todo-keywords

;;   * Operating on single items with the TODO commands.

;;     * Use C-S-right to change the keyword set.  Use this to change to
;;       the "choose" keyword set that you just defined.

;;     * Use S-right to advance the TODO mark to the next setting.  

;;       For "choose", that means you like this alternative more than
;;       before.  Other alternatives will be automatically demoted to
;;       keep your settings consistent.

;;     * Use S-left to demote TODO to the previous setting.  

;;       For "choose", that means you don't like this alternative as much
;;       as before.  Other alternatives will be automatically promoted,
;;       if this item was all that was keeping them down.

;;     * All the other TODO commands are available and behave essentially
;;       the normal way.


;;;_ , Requires

(require 'org)
(eval-when-compile
   (require 'cl))

;;;_. Body
;;;_ , The variables

(defstruct (org-choose-mark-data. (:type list))
   "The format of an entry in org-choose-mark-data.
Indexes are 0-based or `nil'.
"
   keyword
   bot-lower-range
   top-upper-range
   range-length
   static-default
   all-keywords)

(defvar org-choose-mark-data 
   ()
   "Alist of information for choose marks.

Each entry is an `org-choose-mark-data.'" )
(make-variable-buffer-local 'org-choose-mark-data)
;;;_ , For setup
;;;_  . org-choose-filter-one

(defun org-choose-filter-one (i)
   "Return a list of
 * a canonized version of the string
 * optionally one symbol"

   (if
      (not
	 (string-match "(.*)" i))
      (list i i)
      (let* 
	 (
	    (end-text (match-beginning 0))
	    (vanilla-text (substring i 0 end-text))
	    ;;Get the parenthesized part.
	    (match (match-string 0 i))
	    ;;Remove the parentheses.
	    (args (substring match 1 -1))
	    ;;Split it
	    (arglist
	       (let
		  ((arglist-x (split-string args ",")))
		  ;;When string starts with "," `split-string' doesn't
		  ;;make a first arg, so in that case make one
		  ;;manually.
		  (if 
		     (string-match "^," args)
		     (cons nil arglist-x)
		     arglist-x)))
	    (decision-arg (second arglist))
	    (type
	       (cond
		  ((string= decision-arg "0")
		     'default-mark)
		  ((string= decision-arg "+")
		     'top-upper-range)
		  ((string= decision-arg "-")
		     'bot-lower-range)
		  (t nil)))
	    (vanilla-arg (first arglist))
	    (vanilla-mark
	       (if vanilla-arg
		  (concat vanilla-text "("vanilla-arg")")
		  vanilla-text)))
	 (if type
	    (list vanilla-text vanilla-mark type)
	    (list vanilla-text vanilla-mark)))))

;;;_  . org-choose-setup-vars
(defun org-choose-setup-vars (bot-lower-range top-upper-range
				   static-default num-items all-mark-texts)
   "Add to org-choose-mark-data according to arguments"

   (let*
      (
	 (tail
	    ;;If there's no bot-lower-range or no default, we don't
	    ;;have ranges.
	    (cdr
	       (if (and static-default bot-lower-range)
		  (let*
		     (
			;;If there's no top-upper-range, use the last
			;;item.
			(top-upper-range
			   (or top-upper-range (1- num-items)))
			(lower-range-length 
			   (1+ (- static-default bot-lower-range)))
			(upper-range-length 
			   (- top-upper-range static-default))
			(range-length 
			   (min upper-range-length lower-range-length)))


		     (make-org-choose-mark-data.
			:keyword nil
			:bot-lower-range bot-lower-range
			:top-upper-range top-upper-range
			:range-length    range-length
			:static-default static-default
			:all-keywords all-mark-texts))

		  (make-org-choose-mark-data.
		     :keyword nil
		     :bot-lower-range nil
		     :top-upper-range nil
		     :range-length    nil
		     :static-default (or static-default 0)
		     :all-keywords all-mark-texts)))))

      (dolist (text all-mark-texts)
	 (pushnew (cons text tail)
	    org-choose-mark-data
	    :test
	    #'(lambda (a b)
		 (equal (car a) (car b)))))))




;;;_  . org-choose-filter-tail
(defun org-choose-filter-tail (raw)
   "Return a translation of RAW to vanilla and set appropriate
buffer-local variables. 

RAW is a list of strings representing the input text of a choose
interpretation."
   (let
      ((vanilla-list nil)
	 (all-mark-texts nil)
	 (index 0)
	 bot-lower-range top-upper-range range-length static-default)
      (dolist (i raw)
	 (destructuring-bind
	    (vanilla-text vanilla-mark &optional type)
	    (org-choose-filter-one i)
	    (cond
	       ((eq type 'bot-lower-range)
		  (setq bot-lower-range index))
	       ((eq type 'top-upper-range)
		  (setq top-upper-range index))
	       ((eq type 'default-mark)
		  (setq static-default index)))
	    (incf index)
	    (push vanilla-text all-mark-texts)
	    (push vanilla-mark vanilla-list)))

      (org-choose-setup-vars bot-lower-range top-upper-range
	 static-default index (reverse all-mark-texts)) 
      (nreverse vanilla-list)))

;;;_  . org-choose-setup-filter

(defun org-choose-setup-filter (raw)
   "A setup filter for choose interpretations."
   (when (eq (car raw) 'choose)
      (cons
	 'choose
	 (org-choose-filter-tail (cdr raw)))))

;;;_  . org-choose-conform-after-promotion
(defun org-choose-conform-after-promotion (entry-pos keywords highest-ok-ix)
  "Conform the current item after another item was promoted"
   
   (unless
      ;;Skip the entry that triggered this by skipping any entry with
      ;;the same starting position.  Both map and plist use the start
      ;;of the header line as the position, so we can just compare
      ;;them with `='
      (= (point) entry-pos)
      (let
	 ((ix
	     (org-choose-get-entry-index keywords)))
	 ;;If the index of the entry exceeds the highest allowable
	 ;;index, change it to that.
	 (when (and ix 
		  (> ix highest-ok-ix))
	    (org-todo 
	       (nth highest-ok-ix keywords))))))
;;;_  . org-choose-conform-after-demotion
(defun org-choose-conform-after-demotion (entry-pos keywords
					       raise-to-ix
					       old-highest-ok-ix) 
  "Conform the current item after another item was demoted."

   (unless
      ;;Skip the entry that triggered this.
      (= (point) entry-pos)
      (let
	 ((ix
	     (org-choose-get-entry-index keywords)))
	 ;;If the index of the entry was at or above the old allowable
	 ;;position, change it to the new mirror position if there is
	 ;;one.
	 (when (and 
		  ix 
		  raise-to-ix
		  (>= ix old-highest-ok-ix))
	    (org-todo 
	       (nth raise-to-ix keywords))))))

;;;_ , org-choose-keep-sensible (the org-trigger-hook function)
(defun org-choose-keep-sensible (change-plist)
  "Bring the other items back into a sensible state after an item's
setting was changed."

   (let*
      (  (from (plist-get change-plist :from))
	 (to (plist-get change-plist :to))
	 (entry-pos 
	    (set-marker
	       (make-marker)
	       (plist-get change-plist :position)))
	 (kwd-data
	    (assoc to org-todo-kwd-alist)))
      (when
	 (eq (nth 1 kwd-data) 'choose)
	 (let*
	    (
	       (data
		  (assoc to org-choose-mark-data))
	       (keywords
		  (org-choose-mark-data.-all-keywords data))
	       (old-index
		  (org-choose-get-index-in-keywords
		     from 
		     keywords))
	       (new-index
		  (org-choose-get-index-in-keywords
		     to 
		     keywords))
	       (highest-ok-ix
		  (org-choose-highest-other-ok
		     new-index
		     data))
	       (funcdata
		  (cond
		     ;;The entry doesn't participate in conformance,
		     ;;so give `nil' which does nothing.
		     ((not highest-ok-ix) nil)
		     ;;The entry was created or promoted
		     ((or
			 (not old-index)
			 (> new-index old-index))
			(list
			   #'org-choose-conform-after-promotion
			   entry-pos keywords 
			   highest-ok-ix))
		     (t	;;Otherwise the entry was demoted.
			(let
			   (
			      (raise-to-ix
				 (min
				    highest-ok-ix
				    (org-choose-mark-data.-static-default
				       data)))
			      (old-highest-ok-ix
				 (org-choose-highest-other-ok
				    old-index
				    data)))
			   
			   (list
			      #'org-choose-conform-after-demotion 
			      entry-pos 
			      keywords
			      raise-to-ix
			      old-highest-ok-ix))))))
	    
	    (if funcdata
	       ;;The funny-looking names are to make variable capture
	       ;;unlikely.  (Poor-man's lexical bindings).
	       (destructuring-bind (func-d473 . args-46k) funcdata
		  (let
		     ((map-over-entries
			 (org-choose-get-fn-map-group))
			;;We may call `org-todo', so let various hooks
			;;`nil' so we don't cause loops.
			org-after-todo-state-change-hook
			org-trigger-hook 
			org-blocker-hook 
			org-todo-get-default-hook
			;;Also let this alist `nil' so we don't log
			;;secondary transitions.
			org-todo-log-states)
		     ;;Map over group
		     (funcall map-over-entries
			#'(lambda ()
			     (apply func-d473 args-46k))))))))
      
      ;;Remove the marker
      (set-marker entry-pos nil)))



;;;_ , Getting the default mark
;;;_  . org-choose-get-index-in-keywords
(defun org-choose-get-index-in-keywords (ix all-keywords)
  "Return the index of the current entry."

   (if ix
      (position ix all-keywords
	 :test #'equal)))

;;;_  . org-choose-get-entry-index
(defun org-choose-get-entry-index (all-keywords)
   "Return index of current entry."

   (let*
      ((state (org-entry-get (point) "TODO")))
      (org-choose-get-index-in-keywords state all-keywords)))

;;;_  . org-choose-get-fn-map-group

(defun org-choose-get-fn-map-group ()
   "Return a function to map over the group"
   
   #'(lambda (fn)
	(save-excursion
	  (unless (org-up-heading-safe)
	    (error "Chosing is only supported between siblings in a tree, not on top level"))
	  (save-restriction
	    (org-map-entries fn nil 'tree)))))

;;;_  . org-choose-get-highest-mark-index

(defun org-choose-get-highest-mark-index (keywords)
   "Get the index of the highest current mark in the group.
If there is none, return 0"

   (let*
      (
	 ;;Func maps over applicable entries.
	 (map-over-entries
	    (org-choose-get-fn-map-group))
	 
	 (indexes-list
	    (remove nil
	       (funcall map-over-entries 
		  #'(lambda ()
		       (org-choose-get-entry-index keywords))))))
      (if
	 indexes-list
	 (apply #'max indexes-list)
	 0)))


;;;_  . org-choose-highest-ok

(defun org-choose-highest-other-ok (ix data)
  "Return the highest index that any choose mark can sensibly have,
given that another mark has index IX.
DATA must be a `org-choose-mark-data.'."


   (let
      (		
	 (bot-lower-range
	    (org-choose-mark-data.-bot-lower-range data))
	 (top-upper-range
	    (org-choose-mark-data.-top-upper-range data))
	 (range-length
	    (org-choose-mark-data.-range-length data)))
      (when (and ix bot-lower-range)
	 (let*
	    ((delta
		(- top-upper-range ix)))
	    (unless
	       (< range-length delta)
	       (+ bot-lower-range delta))))))

;;;_  . org-choose-get-default-mark-index

(defun org-choose-get-default-mark-index (data) 
  "Return the index of the default mark in a choose interpretation.

DATA must be a `org-choose-mark-data.'."


   (or
      (let
	 ((highest-mark-index
	     (org-choose-get-highest-mark-index
		(org-choose-mark-data.-all-keywords data))))
	 (org-choose-highest-other-ok
	    highest-mark-index data))
      (org-choose-mark-data.-static-default data)))



;;;_  . org-choose-get-mark-N
(defun org-choose-get-mark-N (n data)
   "Get the text of the nth mark in a choose interpretation."
   
   (let*
      ((l (org-choose-mark-data.-all-keywords data)))
      (nth n l)))

;;;_  . org-choose-get-default-mark

(defun org-choose-get-default-mark (new-mark old-mark)
   "Get the default mark IFF in a choose interpretation.
NEW-MARK and OLD-MARK are the text of the new and old marks."

   (let*
      (
	 (old-kwd-data
	    (assoc old-mark org-todo-kwd-alist))
	 (new-kwd-data
	    (assoc new-mark org-todo-kwd-alist))
	 (becomes-choose
	    (and
	       (or
		  (not old-kwd-data)
		  (not
		     (eq (nth 1 old-kwd-data) 'choose)))
	       (eq (nth 1 new-kwd-data) 'choose))))
      (when
	 becomes-choose
	 (let
	    ((new-mark-data
		(assoc new-mark org-choose-mark-data)))
	    (if
	       new-mark
	       (org-choose-get-mark-N
		  (org-choose-get-default-mark-index
		     new-mark-data)
		  new-mark-data)
	       (error "Somehow got an unrecognizable mark"))))))

;;;_ , Setting it all up

(eval-after-load "org"
  '(progn
     (add-to-list 'org-todo-setup-filter-hook
		  #'org-choose-setup-filter)
     (add-to-list 'org-todo-get-default-hook
		  #'org-choose-get-default-mark)
     (add-to-list 'org-trigger-hook
		  #'org-choose-keep-sensible)
     (add-to-list 'org-todo-interpretation-widgets
		  '(:tag "Choose   (to record decisions)" choose)
		  'append)
     ))


;;;_. Footers
;;;_ , Provides

(provide 'org-choose)

;;;_ * Local emacs vars.
;;;_  + Local variables:
;;;_  + End:

;;;_ , End
;;; org-choose.el ends here