add lisp/gnus/gnus-sync.el

[bpt/emacs.git] / lisp / gnus / gnus-sync.el

;;; gnus-sync.el --- synchronization facility for Gnus

;;; Copyright (C) 2010
;;; Free Software Foundation, Inc.

;; Author: Ted Zlatanov <tzz@lifelogs.com>
;; Keywords: news synchronization nntp nnrss

;; 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 <http://www.gnu.org/licenses/>.

;;; Commentary:

;; This is the gnus-sync.el package.

;; Put this in your startup file (~/.gnus.el for instance)

;; (setq gnus-sync-backend `("/remote:/path.gpg") ; will use Tramp+EPA if loaded
;;       gnus-sync-global-vars `(gnus-newsrc-last-checked-date)
;;       gnus-sync-newsrc-groups `("nntp" "nnrss")
;;       gnus-sync-newsrc-vars `(read marks))

;; TODO:

;; - after gnus-sync-read, the message counts are wrong

;;; Code:

(eval-when-compile (require 'cl))
(require 'gnus-util)

(defgroup gnus-sync nil
  "The Gnus synchronization facility."
  :version "23.1"
  :group 'gnus)

(defcustom gnus-sync-newsrc-groups `("nntp" "nnrss")
  "List of groups to be synchronized in the gnus-newsrc-alist.
The group names are matched, they don't have to be fully
qualified.  Typically you would choose all of these.  That's the
default because there is no active sync backend by default, so
this setting is harmless until the user chooses a sync backend."
  :group 'gnus-sync
  :type '(repeat regexp))

(defcustom gnus-sync-newsrc-offsets '(2 3)
  "List of per-group data to be synchronized."
  :group 'gnus-sync
  :type '(set (const :tag "Read ranges" 2)
              (const :tag "Marks" 3)))

(defcustom gnus-sync-global-vars nil
  "List of global variables to be synchronized.
You may want to sync `gnus-newsrc-last-checked-date' but pretty
much any symbol is fair game.  You could additionally sync
`gnus-newsrc-alist', `gnus-server-alist', `gnus-topic-topology',
and `gnus-topic-alist' to cover all the variables in
newsrc.eld (except for `gnus-format-specs' which should not be
synchronized, I believe).  Also see `gnus-variable-list'."
  :group 'gnus-sync
  :type '(repeat (choice (variable :tag "A known variable")
                         (symbol :tag "Any symbol"))))

(defcustom gnus-sync-backend nil
  "The synchronization backend."
  :group 'gnus-sync
  :type '(radio (const :format "None" nil)
                (string :tag "Sync to a file")))

(defvar gnus-sync-newsrc-loader nil
  "Carrier for newsrc data")

(defun gnus-sync-save ()
"Save the Gnus sync data to the backend."
  (interactive)
  (gnus-message 6 "Saving the Gnus sync data")
  (cond
   ((stringp gnus-sync-backend)
    (gnus-message 7 "gnus-sync: saving to backend %s" gnus-sync-backend)
    ;; populate gnus-sync-newsrc-loader from all but the first dummy
    ;; entry in gnus-newsrc-alist whose group matches any of the
    ;; gnus-sync-newsrc-groups
    (let ((gnus-sync-newsrc-loader
           (loop for entry in (cdr gnus-newsrc-alist)
                 when (gnus-grep-in-list
                       (car entry)     ;the group name
                       gnus-sync-newsrc-groups)
                 collect (cons (car entry)
                               (mapcar (lambda (offset)
                                         (cons offset (nth offset entry)))
                                       gnus-sync-newsrc-offsets)))))

      (with-temp-file gnus-sync-backend
        (progn
          (let ((coding-system-for-write gnus-ding-file-coding-system)
                (standard-output (current-buffer)))
            (princ (format ";; -*- mode:emacs-lisp; coding: %s; -*-\n"
                           gnus-ding-file-coding-system))
            (princ ";; Gnus sync data v. 0.0.1\n")
            (let* ((print-quoted t)
                   (print-readably t)
                   (print-escape-multibyte nil)
                   (print-escape-nonascii t)
                   (print-length nil)
                   (print-level nil)
                   (print-circle nil)
                   (print-escape-newlines t)
                   (variables (cons 'gnus-sync-newsrc-loader
                                    gnus-sync-global-vars)))
              (while variables
                (when (and (boundp (setq variable (pop variables)))
                           (symbol-value variable))
                  (princ "\n(setq ")
                  (princ (symbol-name variable))
                  (princ " '")
                  (prin1 (symbol-value variable))
                  (princ ")\n"))))
            (gnus-message
             7
             "gnus-sync: stored variables %s and %d groups in %s"
             gnus-sync-global-vars
             (length gnus-sync-newsrc-loader)
             gnus-sync-backend)

            ;; Idea from Dan Christensen <jdc@chow.mat.jhu.edu>
            ;; Save the .eld file with extra line breaks.
            (gnus-message 8 "gnus-sync: adding whitespace to %s"
                          gnus-sync-backend)
            (save-excursion
              (goto-char (point-min))
              (while (re-search-forward "^(\\|(\\\"" nil t)
                (replace-match "\n\\&" t))
              (goto-char (point-min))
              (while (re-search-forward " $" nil t)
                (replace-match "" t t))))))))
    ;; the pass-through case: gnus-sync-backend is not a known choice
    (nil)))

(defun gnus-sync-read ()
"Load the Gnus sync data from the backend."
  (interactive)
  (when gnus-sync-backend
    (gnus-message 7 "gnus-sync: loading from backend %s" gnus-sync-backend)
    (cond ((stringp gnus-sync-backend)
           ;; read data here...
           (if (or debug-on-error debug-on-quit)
               (load gnus-sync-backend nil t)
             (condition-case var
                 (load gnus-sync-backend nil t)
               (error
                (error "Error in %s: %s" gnus-sync-backend (cadr var)))))
           (let ((valid-nodes
                  (loop for node in gnus-sync-newsrc-loader
                        if (gnus-gethash (car node) gnus-newsrc-hashtb)
                        collect node)))
             (dolist (node valid-nodes)
               (loop for store in (cdr node)
                     do (setf (nth (car store)
                                   (assoc (car node) gnus-newsrc-alist))
                              (cdr store))))
            (gnus-message
             7
             "gnus-sync: loaded %d groups (out of %d) from %s"
             (length valid-nodes)
             (length gnus-sync-newsrc-loader)
             gnus-sync-backend)
           (setq gnus-sync-newsrc-loader nil)))
          (nil))
    ;; make the hashtable again because the newsrc-alist may have been modified
    (when gnus-sync-newsrc-vars
      (gnus-message 9 "gnus-sync: remaking the newsrc hashtable")
      (gnus-make-hashtable-from-newsrc-alist))))

;;;###autoload
(defun gnus-sync-initialize ()
"Initialize the Gnus sync facility."
  (interactive)
  (gnus-message 5 "Initializing the sync facility")
  (gnus-sync-install-hooks))

;;;###autoload
(defun gnus-sync-install-hooks ()
  "Install the sync hooks."
  (interactive)
  (add-hook 'gnus-get-new-news-hook 'gnus-sync-read)
  (add-hook 'gnus-save-newsrc-hook 'gnus-sync-save)
  (add-hook 'gnus-read-newsrc-el-hook 'gnus-sync-read))

(defun gnus-sync-unload-hook ()
  "Uninstall the sync hooks."
  (interactive)
  (remove-hook 'gnus-get-new-news-hook 'gnus-sync-read)
  (remove-hook 'gnus-save-newsrc-hook 'gnus-sync-save)
  (remove-hook 'gnus-read-newsrc-el-hook 'gnus-sync-read))

(add-hook 'gnus-sync-unload-hook 'gnus-sync-unload-hook)

;; this is harmless by default, until the gnus-sync-backend is set
(gnus-sync-initialize)

(provide 'gnus-sync)

;;; gnus-sync.el ends here