;;; nndraft.el --- draft article access for Gnus

;; Copyright (C) 1995-2020 Free Software Foundation, Inc.

;; Author: Lars Magne Ingebrigtsen <larsi@gnus.org>
;; Keywords: news

;; 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:

;;; Code:

(require 'nnheader)
(require 'nnmail)
(require 'gnus-start)
(require 'gnus-group)
(require 'nnmh)
(require 'nnoo)
(require 'mm-util)

;; The nnoo-import at the end, I think.
(declare-function nndraft-request-list "nndraft" (&rest args) t)

(nnoo-declare nndraft
  nnmh)

(defvoo nndraft-directory (nnheader-concat gnus-directory "drafts/")
  "Where nndraft will store its files."
  nnmh-directory)

(defcustom nndraft-required-headers '(Date)
  "Headers to be generated when saving a draft message.
The headers in this variable and the ones in `message-required-headers'
are generated if and only if they are also in `message-draft-headers'."
  :type '(repeat sexp)
  :group 'message-headers)		; FIXME wrong group

\f

(defvoo nndraft-current-group "" nil nnmh-current-group)
(defvoo nndraft-get-new-mail nil nil nnmh-get-new-mail)
(defvoo nndraft-current-directory nil nil nnmh-current-directory)

(defconst nndraft-version "nndraft 1.0")
(defvoo nndraft-status-string "" nil nnmh-status-string)

\f

;;; Interface functions.

(nnoo-define-basics nndraft)

(deffoo nndraft-open-server (server &optional defs)
  (nnoo-change-server 'nndraft server defs)
  (cond
   ((not (file-exists-p nndraft-directory))
    (nndraft-close-server)
    (nnheader-report 'nndraft "No such file or directory: %s"
		     nndraft-directory))
   ((not (file-directory-p (file-truename nndraft-directory)))
    (nndraft-close-server)
    (nnheader-report 'nndraft "Not a directory: %s" nndraft-directory))
   (t
    (nnheader-report 'nndraft "Opened server %s using directory %s"
		     server nndraft-directory)
    t)))

(deffoo nndraft-retrieve-headers (articles &optional group server fetch-old)
  (nndraft-possibly-change-group group)
  (with-current-buffer nntp-server-buffer
    (erase-buffer)
    (let (article lines chars)
      ;; We don't support fetching by Message-ID.
      (if (stringp (car articles))
	  'headers
	(while articles
	  (narrow-to-region (point) (point))
	  (when (nndraft-request-article
		 (setq article (pop articles)) group server (current-buffer))
	    (goto-char (point-min))
	    (if (search-forward "\n\n" nil t)
		(forward-line -1)
	      (goto-char (point-max)))
	    (setq lines (count-lines (point) (point-max))
		  chars (- (point-max) (point)))
	    (delete-region (point) (point-max))
	    (goto-char (point-min))
	    (insert (format "221 %d Article retrieved.\n" article))
	    (insert (format "Lines: %d\nChars: %d\n" lines chars))
	    (widen)
	    (goto-char (point-max))
	    (insert ".\n")))

	(nnheader-fold-continuation-lines)
	'headers))))

(deffoo nndraft-request-article (id &optional group server buffer)
  (nndraft-possibly-change-group group)
  (when (numberp id)
    ;; We get the newest file of the auto-saved file and the
    ;; "real" file.
    (let* ((file (nndraft-article-filename id))
	   (auto (nndraft-auto-save-file-name file))
	   (newest (if (file-newer-than-file-p file auto) file auto))
	   (nntp-server-buffer (or buffer nntp-server-buffer)))
      (when (and (file-exists-p newest)
		 (let ((nnmail-file-coding-system
			(if (file-newer-than-file-p file auto)
			    (if (member group '("drafts" "delayed"))
				message-draft-coding-system
			      mm-text-coding-system)
			  mm-auto-save-coding-system)))
		   (nnmail-find-file newest)))
	(with-current-buffer nntp-server-buffer
	  (goto-char (point-min))
	  ;; If there's a mail header separator in this file,
	  ;; we remove it.
	  (when (re-search-forward
		 (concat "^" (regexp-quote mail-header-separator) "$") nil t)
	    (replace-match "" t t)))
	t))))

(deffoo nndraft-request-restore-buffer (article &optional group server)
  "Request a new buffer that is restored to the state of ARTICLE."
  (nndraft-possibly-change-group group)
  (when (nndraft-request-article article group server (current-buffer))
    (message-remove-header "xref")
    (message-remove-header "lines")
    ;; Articles in nndraft:queue are considered as sent messages.  The
    ;; Date field should be the time when they are sent.
    ;;(message-remove-header "date")
    t))

(deffoo nndraft-request-update-info (group info &optional server)
  (nndraft-possibly-change-group group)
  (setf (gnus-info-read info)
	(gnus-update-read-articles
	 (gnus-group-prefixed-name group '(nndraft ""))
	 (nndraft-articles) t))
  (let ((marks (nth 3 info)))
    (when marks
      ;; Nix out all marks except the `unsend'-able article marks.
      (setcar (nthcdr 3 info)
	      (if (assq 'unsend marks)
		  (list (assq 'unsend marks))
		nil))))
  t)

(defun nndraft-generate-headers ()
  (save-excursion
    (message-generate-headers
     (message-headers-to-generate
      nndraft-required-headers message-draft-headers nil))))

(defun nndraft-update-unread-articles ()
  "Update groups' unread articles in the group buffer."
  (nndraft-request-list)
  (with-current-buffer gnus-group-buffer
    (let* ((groups (mapcar (lambda (elem)
			     (gnus-group-prefixed-name (car elem)
						       (list 'nndraft "")))
			   (nnmail-get-active)))
	   (gnus-group-marked (copy-sequence groups))
	   ;; Don't send delayed articles.
	   (gnus-get-new-news-hook nil)
	   (inhibit-read-only t))
      (gnus-group-get-new-news-this-group nil t)
      (save-excursion
	(dolist (group groups)
	  (unless (and gnus-permanently-visible-groups
		       (string-match gnus-permanently-visible-groups
				     group))
	    (gnus-group-goto-group group)
	    (when (zerop (gnus-group-group-unread))
	      (gnus-delete-line))))))))

(deffoo nndraft-request-associate-buffer (group)
  "Associate the current buffer with some article in the draft group."
  (nndraft-open-server "")
  (nndraft-request-group group)
  (nndraft-possibly-change-group group)
  (let ((gnus-verbose-backends nil)
	(buf (current-buffer))
	article file)
    (with-temp-buffer
      (insert-buffer-substring buf)
      (setq article (nndraft-request-accept-article
		     group (nnoo-current-server 'nndraft) t 'noinsert)
	    file (nndraft-article-filename article)))
    (setq buffer-file-name (expand-file-name file)
	  buffer-auto-save-file-name (make-auto-save-file-name))
    (clear-visited-file-modtime)
    (add-hook 'write-contents-functions 'nndraft-generate-headers nil t)
    (add-hook 'after-save-hook 'nndraft-update-unread-articles nil t)
    (message-add-action '(nndraft-update-unread-articles)
			'exit 'postpone 'kill)
    article))

(deffoo nndraft-request-group (group &optional server dont-check info)
  (nndraft-possibly-change-group group)
  (unless dont-check
    (let* ((pathname (nnmail-group-pathname group nndraft-directory))
	   (file-name-coding-system nnmail-pathname-coding-system)
	   dir file)
      (nnheader-re-read-dir pathname)
      (setq dir (mapcar (lambda (name) (string-to-number (substring name 1)))
			(ignore-errors (directory-files
					pathname nil "^#[0-9]+#$" t))))
      (dolist (n dir)
	(unless (file-exists-p
		 (setq file (expand-file-name (int-to-string n) pathname)))
	  (rename-file (nndraft-auto-save-file-name file) file)))))
  (nnoo-parent-function 'nndraft
			'nnmh-request-group
			(list group server dont-check)))

(deffoo nndraft-request-move-article (article group server accept-form
				      &optional last move-is-internal)
  (nndraft-possibly-change-group group)
  (let ((buf (get-buffer-create " *nndraft move*"))
	result)
    (and
     (nndraft-request-article article group server)
     (with-current-buffer buf
       (erase-buffer)
       (insert-buffer-substring nntp-server-buffer)
       (setq result (eval accept-form))
       (kill-buffer (current-buffer))
       result)
     (null (nndraft-request-expire-articles (list article) group server 'force))
     result)))

(deffoo nndraft-request-expire-articles (articles group &optional server force)
  (nndraft-possibly-change-group group)
  (let* ((nnmh-allow-delete-final t)
	 (nnmail-expiry-target 'delete)
	 ;; FIXME: If we want to move a draft message to an expiry group,
	 ;; there are things to have to improve:
	 ;; - Remove a header separator.
	 ;; - Encode it, including attachments, into a MIME message.
	 ;;(nnmail-expiry-target
	 ;; (or (gnus-group-find-parameter
	 ;;      (gnus-group-prefixed-name group (list 'nndraft server))
	 ;;      'expiry-target t)
	 ;;     nnmail-expiry-target))
	 (res (nnoo-parent-function 'nndraft
				    'nnmh-request-expire-articles
				    (list articles group server force)))
	 article)
    ;; Delete all the "state" files of articles that have been expired.
    (while articles
      (unless (memq (setq article (pop articles)) res)
	(let ((auto (nndraft-auto-save-file-name
		     (nndraft-article-filename article))))
	  (when (file-exists-p auto)
	    (funcall nnmail-delete-file-function auto)))
	(dolist (backup
		 (let ((kept-new-versions 1)
		       (kept-old-versions 0))
		   (find-backup-file-name
		    (nndraft-article-filename article))))
	  (when (file-exists-p backup)
	    (funcall nnmail-delete-file-function backup)))))
    res))

(deffoo nndraft-request-accept-article (group &optional server last noinsert)
  (nndraft-possibly-change-group group)
  (let ((gnus-verbose-backends nil))
    (nnoo-parent-function 'nndraft 'nnmh-request-accept-article
			  (list group server last noinsert))))

(deffoo nndraft-request-replace-article (article group buffer)
  (nndraft-possibly-change-group group)
  (let ((nnmail-file-coding-system
	 (if (member group '("drafts" "delayed"))
	     message-draft-coding-system
	   mm-text-coding-system)))
    (nnoo-parent-function 'nndraft 'nnmh-request-replace-article
			  (list article group buffer))))

(deffoo nndraft-request-create-group (group &optional server args)
  (nndraft-possibly-change-group group)
  (if (file-exists-p nndraft-current-directory)
      (if (file-directory-p nndraft-current-directory)
	  t
	nil)
    (condition-case ()
	(progn
	  (gnus-make-directory nndraft-current-directory)
	  t)
      (file-error nil))))

\f
;;; Low-Level Interface

(defun nndraft-possibly-change-group (group)
  (when (and group
	     (not (equal group nndraft-current-group)))
    (nndraft-open-server "")
    (setq nndraft-current-group group)
    (setq nndraft-current-directory
	  (nnheader-concat nndraft-directory group))))

(defun nndraft-article-filename (article &rest args)
  (apply 'concat
	 (file-name-as-directory nndraft-current-directory)
	 (int-to-string article)
	 args))

(defun nndraft-auto-save-file-name (file)
  (save-excursion
    (prog1
	(progn
	  (set-buffer (get-buffer-create " *draft tmp*"))
	  (setq buffer-file-name file)
	  (make-auto-save-file-name))
      (kill-buffer (current-buffer)))))

(defun nndraft-articles ()
  "Return the list of messages in the group."
  (gnus-make-directory nndraft-current-directory)
  (sort
   (mapcar 'string-to-number
	   (directory-files nndraft-current-directory nil "\\`[0-9]+\\'" t))
   '<))

(nnoo-import nndraft
  (nnmh
   nnmh-retrieve-headers
   nnmh-request-group
   nnmh-close-group
   nnmh-request-list))

(provide 'nndraft)

;;; nndraft.el ends here