;;; gnus-delay.el --- Delayed posting of articles  -*- lexical-binding: t; -*-

;; Copyright (C) 2001-2022 Free Software Foundation, Inc.

;; Author: Kai Großjohann <Kai.Grossjohann@CS.Uni-Dortmund.DE>
;; Keywords: mail, news, extensions

;; 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:

;; Provide delayed posting of articles.

;;; Todo:

;; * `gnus-delay-send-queue' barfs when group does not exist.
;; * Integrate gnus-delay.el into the rest of Gnus automatically.  How
;;   should this be done?  Basically, we need to do what
;;   `gnus-delay-initialize' does.  But in which files?

;;; Code:

(require 'nndraft)
(require 'gnus-draft)
(autoload 'parse-time-string "parse-time" nil nil)

(defgroup gnus-delay nil
  "Arrange for sending postings later."
  :version "22.1"
  :group 'gnus)

(defcustom gnus-delay-group "delayed"
  "Group name for storing delayed articles."
  :type 'string)

(defcustom gnus-delay-header "X-Gnus-Delayed"
  "Header name for storing info about delayed articles."
  :type 'string)

(defcustom gnus-delay-default-delay "3d"
  "Default length of delay."
  :type 'string)

(defcustom gnus-delay-default-hour 8
  "If deadline is given as date, then assume this time of day."
  :version "22.1"
  :type 'integer)

;;;###autoload
(defun gnus-delay-article (delay)
  "Delay this article by some time.
DELAY is a string, giving the length of the time.  Possible values are:

* <digits><units> for <units> in minutes (`m'), hours (`h'), days (`d'),
  weeks (`w'), months (`M'), or years (`Y');

* YYYY-MM-DD for a specific date.  The time of day is given by the
  variable `gnus-delay-default-hour', minute and second are zero.

* hh:mm for a specific time.  Use 24h format.  If it is later than this
  time, then the deadline is tomorrow, else today.

The value of `message-draft-headers' determines which headers are
generated when the article is delayed.  Remaining headers are
generated when the article is sent."
  (interactive (list (read-string
		      "Target date (YYYY-MM-DD), time (hh:mm), or length of delay (units in [mhdwMY]): "
		      gnus-delay-default-delay))
	       message-mode)
  ;; Allow spell checking etc.
  (run-hooks 'message-send-hook)
  (let (num unit year month day hour minute deadline) ;; days
    (cond ((string-match
	    "\\([0-9][0-9][0-9]?[0-9]?\\)-\\([0-9]+\\)-\\([0-9]+\\)"
	    delay)
	   (setq year  (string-to-number (match-string 1 delay))
		 month (string-to-number (match-string 2 delay))
		 day   (string-to-number (match-string 3 delay)))
	   (setq deadline
		 (message-make-date
		  (encode-time 0 0      ; second and minute
			       gnus-delay-default-hour
			       day month year))))
	  ((string-match "\\([0-9]+\\):\\([0-9]+\\)" delay)
	   (setq hour   (string-to-number (match-string 1 delay))
		 minute (string-to-number (match-string 2 delay)))
	   ;; Use current time, except...
	   (setq deadline (decode-time nil nil t))
	   ;; ... for minute and hour.
	   (setq deadline (apply #'encode-time (car deadline) minute hour
				 (nthcdr 3 deadline)))
	   ;; If this time has passed already, add a day.
	   (when (time-less-p deadline nil)
	     (setq deadline (time-add 86400 deadline))) ; 86400 secs/day
	   ;; Convert seconds to date header.
	   (setq deadline (message-make-date deadline)))
	  ((string-match "\\([0-9]+\\)\\s-*\\([mhdwMY]\\)" delay)
	   (setq num (match-string 1 delay))
	   (setq unit (match-string 2 delay))
	   ;; Start from seconds, then multiply into needed units.
	   (setq num (string-to-number num))
	   (cond ((string= unit "Y")
		  (setq delay (* num 60 60 24 365)))
		 ((string= unit "M")
		  (setq delay (* num 60 60 24 30)))
		 ((string= unit "w")
		  (setq delay (* num 60 60 24 7)))
		 ((string= unit "d")
		  (setq delay (* num 60 60 24)))
		 ((string= unit "h")
		  (setq delay (* num 60 60)))
		 (t
		  (setq delay (* num 60))))
	   (setq deadline (message-make-date (time-add nil delay))))
	  (t (error "Malformed delay `%s'" delay)))
    (message-add-header (format "%s: %s" gnus-delay-header deadline)))
  (set-buffer-modified-p t)
  ;; If group does not exist, create it.
  (gnus-agent-queue-setup gnus-delay-group)
  (message-disassociate-draft)
  (nndraft-request-associate-buffer gnus-delay-group)
  (save-buffer 0)
  (kill-buffer (current-buffer))
  (message-do-actions message-postpone-actions))

;;;###autoload
(defun gnus-delay-send-queue ()
  "Send all the delayed messages that are due now."
  (interactive)
  (save-excursion
    (let* ((group (format "nndraft:%s" gnus-delay-group))
	   (message-send-hook (copy-sequence message-send-hook))
	   articles
	   article deadline)
      (when (gnus-group-entry group)
	(gnus-activate-group group)
	(add-hook 'message-send-hook
		  (lambda () (message-remove-header gnus-delay-header)) t)
	(setq articles (nndraft-articles))
	(while (setq article (pop articles))
	  (gnus-request-head article group)
	  (set-buffer nntp-server-buffer)
	  (goto-char (point-min))
	  (if (re-search-forward
	       (concat "^" (regexp-quote gnus-delay-header) ":\\s-+")
	       nil t)
	      (progn
		(setq deadline (nnheader-header-value))
		(setq deadline (encode-time (parse-time-string deadline)))
		(unless (time-less-p nil deadline)
		  (message "Sending delayed article %d" article)
		  (gnus-draft-send article group)
		  (message "Sending delayed article %d...done" article)))
	    (message "Delay header missing for article %d" article)))))))

;;;###autoload
(defun gnus-delay-initialize (&optional _no-keymap no-check)
  "Initialize the gnus-delay package.
This sets up a key binding in `message-mode' to delay a message.
This tells Gnus to look for delayed messages after getting new news.

The optional arg NO-KEYMAP is ignored.
Checking delayed messages is skipped if optional arg NO-CHECK is non-nil."
  (unless no-check
    (add-hook 'gnus-get-new-news-hook #'gnus-delay-send-queue)))

(provide 'gnus-delay)

;; Local Variables:
;; coding: utf-8
;; End:

;;; gnus-delay.el ends here
