;;; org-gnus.el --- Support for Links to Gnus Groups and Messages -*- lexical-binding: t; -*-

;; Copyright (C) 2004-2017 Free Software Foundation, Inc.

;; Author: Carsten Dominik <carsten at orgmode dot org>
;;         Tassilo Horn <tassilo at member dot fsf dot org>
;; Keywords: outlines, hypermedia, calendar, wp
;; Homepage: http://orgmode.org
;;
;; 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 file implements links to Gnus groups and messages from within Org.
;; Org mode loads this module by default - if this is not what you want,
;; configure the variable `org-modules'.

;;; Code:

(require 'org)
(require 'gnus-util)
(eval-when-compile (require 'gnus-sum))

;; Declare external functions and variables

(declare-function message-fetch-field "message" (header &optional not-all))
(declare-function message-narrow-to-head-1 "message" nil)
(declare-function gnus-summary-last-subject "gnus-sum" nil)
(declare-function nnvirtual-map-article "nnvirtual" (article))

;; Customization variables

(defvaralias 'org-usenet-links-prefer-google 'org-gnus-prefer-web-links)

(defcustom org-gnus-prefer-web-links nil
  "If non-nil, `org-store-link' creates web links to Google groups or Gmane.
\\<org-mode-map>When nil, Gnus will be used for such links.
Using a prefix argument to the command `\\[org-store-link]' (`org-store-link')
negates this setting for the duration of the command."
  :group 'org-link-store
  :type 'boolean)

(defcustom org-gnus-no-server nil
  "Should Gnus be started using `gnus-no-server'?"
  :group 'org-gnus
  :version "24.4"
  :package-version '(Org . "8.0")
  :type 'boolean)

;; Install the link type
(org-link-set-parameters "gnus" :follow #'org-gnus-open :store #'org-gnus-store-link)

;; Implementation

(defun org-gnus-group-link (group)
  "Create a link to the Gnus group GROUP.
If GROUP is a newsgroup and `org-gnus-prefer-web-links' is
non-nil, create a link to groups.google.com or gmane.org.
Otherwise create a link to the group inside Gnus.

If `org-store-link' was called with a prefix arg the meaning of
`org-gnus-prefer-web-links' is reversed."
  (let ((unprefixed-group (replace-regexp-in-string "^[^:]+:" "" group)))
    (if (and (string-prefix-p "nntp" group) ;; Only for nntp groups
	     (org-xor current-prefix-arg
		      org-gnus-prefer-web-links))
	(concat (if (string-match "gmane" unprefixed-group)
		    "http://news.gmane.org/"
		  "http://groups.google.com/group/")
		unprefixed-group)
      (concat "gnus:" group))))

(defun org-gnus-article-link (group newsgroups message-id x-no-archive)
  "Create a link to a Gnus article.
The article is specified by its MESSAGE-ID.  Additional
parameters are the Gnus GROUP, the NEWSGROUPS the article was
posted to and the X-NO-ARCHIVE header value of that article.

If GROUP is a newsgroup and `org-gnus-prefer-web-links' is
non-nil, create a link to groups.google.com or gmane.org.
Otherwise create a link to the article inside Gnus.

If `org-store-link' was called with a prefix arg the meaning of
`org-gnus-prefer-web-links' is reversed."
  (if (and (org-xor current-prefix-arg org-gnus-prefer-web-links)
	   newsgroups	  ;; Make web links only for nntp groups
	   (not x-no-archive)) ;; and if X-No-Archive isn't set.
      (format (if (string-match "gmane\\." newsgroups)
		  "http://mid.gmane.org/%s"
		"http://groups.google.com/groups/search?as_umsgid=%s")
	      (org-fixup-message-id-for-http message-id))
    (concat "gnus:" group "#" message-id)))

(defun org-gnus-store-link ()
  "Store a link to a Gnus folder or message."
  (cond
   ((eq major-mode 'gnus-group-mode)
    (let* ((group (cond ((fboundp 'gnus-group-group-name) ; depending on Gnus
			 (gnus-group-group-name))         ; version
			((fboundp 'gnus-group-name)
			 (gnus-group-name))
			(t "???")))
	   desc link)
      (when group
	(org-store-link-props :type "gnus" :group group)
	(setq desc (org-gnus-group-link group)
	      link desc)
	(org-add-link-props :link link :description desc)
	link)))

   ((memq major-mode '(gnus-summary-mode gnus-article-mode))
    (let* ((group gnus-newsgroup-name)
	   (header (with-current-buffer gnus-summary-buffer
		     (gnus-summary-article-header)))
	   (from (mail-header-from header))
	   (message-id (org-unbracket-string "<" ">" (mail-header-id header)))
	   (date (org-trim (mail-header-date header)))
	   (subject (copy-sequence (mail-header-subject header)))
	   (to (cdr (assq 'To (mail-header-extra header))))
	   newsgroups x-no-archive desc link)
      (cl-case  (car (gnus-find-method-for-group gnus-newsgroup-name))
	(nnvirtual
	 (setq group (car (nnvirtual-map-article
			   (gnus-summary-article-number)))))
	(nnir
	 (setq group (nnir-article-group (gnus-summary-article-number)))))
      ;; Remove text properties of subject string to avoid Emacs bug
      ;; #3506
      (set-text-properties 0 (length subject) nil subject)

      ;; Fetching an article is an expensive operation; newsgroup and
      ;; x-no-archive are only needed for web links.
      (when (org-xor current-prefix-arg org-gnus-prefer-web-links)
	;; Make sure the original article buffer is up-to-date
	(save-window-excursion (gnus-summary-select-article))
	(setq to (or to (gnus-fetch-original-field "To"))
	      newsgroups (gnus-fetch-original-field "Newsgroups")
	      x-no-archive (gnus-fetch-original-field "x-no-archive")))
      (org-store-link-props :type "gnus" :from from :date date :subject subject
			    :message-id message-id :group group :to to)
      (setq desc (org-email-link-description)
	    link (org-gnus-article-link
		  group	newsgroups message-id x-no-archive))
      (org-add-link-props :link link :description desc)
      link))
   ((eq major-mode 'message-mode)
    (setq org-store-link-plist nil)  ; reset
    (save-excursion
      (save-restriction
        (message-narrow-to-headers)
        (and (not (message-fetch-field "Message-ID"))
             (message-generate-headers '(Message-ID)))
        (goto-char (point-min))
        (re-search-forward "^Message-ID: *.*$" nil t)
        (put-text-property (match-beginning 0) (match-end 0) 'message-deletable nil)
        (let ((gcc (car (last
                         (message-unquote-tokens
                          (message-tokenize-header (mail-fetch-field "gcc" nil t) " ,")))))
              (id (org-unbracket-string "<" ">" (mail-fetch-field "Message-ID")))
              (to (mail-fetch-field "To"))
              (from (mail-fetch-field "From"))
              (subject (mail-fetch-field "Subject"))
              desc link
              newsgroup xarchive)       ; those are always nil for gcc
          (and (not gcc)
               (error "Can not create link: No Gcc header found"))
          (org-store-link-props :type "gnus" :from from :subject subject
                                :message-id id :group gcc :to to)
          (setq desc (org-email-link-description)
                link (org-gnus-article-link
                      gcc newsgroup id xarchive))
          (org-add-link-props :link link :description desc)
          link))))))

(defun org-gnus-open-nntp (path)
  "Follow the nntp: link specified by PATH."
  (let* ((spec (split-string path "/"))
	 (server (split-string (nth 2 spec) "@"))
	 (group (nth 3 spec))
	 (article (nth 4 spec)))
    (org-gnus-follow-link
     (format "nntp+%s:%s" (or (cdr server) (car server)) group)
     article)))

(defun org-gnus-open (path)
  "Follow the Gnus message or folder link specified by PATH."
  (let (group article)
    (if (not (string-match "\\`\\([^#]+\\)\\(#\\(.*\\)\\)?" path))
	(error "Error in Gnus link"))
    (setq group (match-string 1 path)
	  article (match-string 3 path))
    (when group
      (setq group (org-no-properties group)))
    (when article
      (setq article (org-no-properties article)))
    (org-gnus-follow-link group article)))

(defun org-gnus-follow-link (&optional group article)
  "Follow a Gnus link to GROUP and ARTICLE."
  (require 'gnus)
  (funcall (cdr (assq 'gnus org-link-frame-setup)))
  (when gnus-other-frame-object (select-frame gnus-other-frame-object))
  (let ((group (org-no-properties group))
	(article (org-no-properties article)))
    (cond
     ((and group article)
      (gnus-activate-group group)
      (condition-case nil
	  (let ((msg "Couldn't follow Gnus link.  Summary couldn't be opened."))
	    (pcase (gnus-find-method-for-group group)
	      (`(nndoc . ,_)
	       (if (gnus-group-read-group t nil group)
		   (gnus-summary-goto-article article nil t)
		 (message msg)))
	      (_
	       (let ((articles 1)
		     group-opened)
		 (while (and (not group-opened)
			     ;; Stop on integer overflows.
			     (> articles 0))
		   (setq group-opened (gnus-group-read-group articles t group))
		   (setq articles (if (< articles 16)
				      (1+ articles)
				    (* articles 2))))
		 (if group-opened
		     (gnus-summary-goto-article article nil t)
		   (message msg))))))
	(quit
	 (message "Couldn't follow Gnus link.  The linked group is empty."))))
     (group (gnus-group-jump-to-group group)))))

(defun org-gnus-no-new-news ()
  "Like `\\[gnus]' but doesn't check for new news."
  (if (not (gnus-alive-p)) (if org-gnus-no-server (gnus-no-server) (gnus))))

(provide 'org-gnus)


;;; org-gnus.el ends here