;;; planner-db.el --- multiple task views for planner.el
;; sacha@free.net.ph, GPL

;; Copyright (C) 2004 Sandra Jean Chua (Sacha) <sacha@free.net.ph>

;; This file is not part of GNU Emacs.

;; This 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 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:
;; 
;; Usage:
;;
;; Add (require 'planner-db) to your ~/.emacs . Then you can use
;;
;; <taskdb s="someregexp">
;; </taskdb>
;;
;; in your planner pages to get a list of all the tasks from a
;; particular page. To regenerate the contents, call
;; `planner-db-update-page'.
;;
;; What works: 
;; - updating the list of tasks
;; - marking a task as closed, whatever (changes reflected in main
;;   database)
;;
;; Note that this module redefines the behavior of
;; planner-jump-to-linked-task! I currently wouldn't advise it for
;; people who use plan pages, as planner-db.el can't tell the
;; difference between tasks it manages and tasks you manually put on
;; plan pages.
;;
;; Be very, very careful about mismatched tags! This will _DELETE_ any
;; text between the opening and closing tags.
;; 
;; Also, I haven't figured out how to neatly do the following:
;; - publishing
;; - updating lots of pages
;; - working nicely with the rest of the code
;; - getting the planner task-related functions to all do the 
;;   Right Thing.

;; Not bad, though, for a proof-of-concept one-hour hack.

;;; Code:
(defvar planner-db-page "TaskPool"
  "Page containing all the current tasks.")
(defvar planner-db-task-tag "taskdb"
  "Tag name for tasks from database.")
(defvar planner-db-task-condition-attribute "s"
  "Attribute name for `planner-db-task-tag' conditions.")

(defun planner-db-get-tasks (condition)
  "Return a list of tasks matching CONDITION.
Tasks are looked up in `planner-db-page'.  CONDITION is a
regexp."
  (save-window-excursion
    (save-excursion
      (save-restriction
	(planner-find-file planner-db-page)
	(widen)
	(goto-char (point-min))
	(let (results info description condition line)
	  (while (re-search-forward planner-task-regexp nil t)
	    (when
		(or (not condition)
		    (string-match
		     condition
		     (buffer-substring (line-beginning-position)
				       (line-end-position))))
	      (setq results (cons (planner-current-task-info) results))))
	  results)))))

(defun planner-db-insert-tasks (condition)
  "Insert tasks matching CONDITION.
Lines should match CONDITION is a regexp."
  (let (tasks)
    (setq tasks (planner-db-get-tasks condition))
    (while tasks
      (insert (planner-format-task (car tasks)) "\n")
      (setq tasks (cdr tasks)))))

;; A general function should be moved into emacs-wiki for edit-time
;; markup.
(defun planner-db-update-page ()
  "Search forward for all tasks tag and replace the text."
  (interactive)
  (save-excursion
    (save-restriction
      (widen)
      (goto-char (point-min))
      (while (re-search-forward emacs-wiki-tag-regexp nil t)
	(let ((tag-name (match-string-no-properties 1))
	      beg
	      attrs)
	  (when (string= tag-name planner-db-task-tag)
	    (setq beg (match-end 0))
	    (let ((attrstr (match-string 2)))
	      (while (and attrstr
			  (string-match
			   "\\([^ \t\n=]+\\)\\(=\"\\([^\"]+\\)\"\\)?"
			   attrstr))
		(let ((attr (cons (downcase
				   (match-string-no-properties 1 attrstr))
				  (match-string-no-properties 3 attrstr))))
		  (setq attrstr (replace-match "" t t attrstr))
		  (if attrs
		      (nconc attrs (list attr))
		    (setq attrs (list attr))))))
	    (when (search-forward (concat "</" tag-name ">") nil t)
	      (save-restriction
		(goto-char beg)
		(unless (= (point) (line-beginning-position))
		  (insert "\n"))
		(narrow-to-region (point) (match-beginning 0))
		(delete-region (point-min) (point-max))
		(planner-db-insert-tasks
		 (cdr (assoc planner-db-task-condition-attribute attrs)))
		(add-text-properties (point-min) (point-max)
				     '(planner-db t))))))))))
	  
(defun planner-db-jump-to-linked-task (&optional task-info)
  "Display the task page linked to by the current task or TASK-INFO."
  (interactive)
  (let* ((task-info (or task-info (planner-current-task-info))))
    (planner-find-file planner-db-page)
    (widen)
    (goto-char (point-min))
    (when (search-forward (planner-task-description task-info) nil t)
      (beginning-of-line)
      t)))

(defalias 'planner-jump-to-linked-task 'planner-db-jump-to-linked-task)

(provide 'planner-db)

;;; planner-db.el ends here