;;; ol-rmail.el --- Links to Rmail Messages          -*- lexical-binding: t; -*-

;; Copyright (C) 2004-2024 Free Software Foundation, Inc.

;; Author: Carsten Dominik <carsten.dominik@gmail.com>
;; Keywords: outlines, hypermedia, calendar, text
;; URL: https://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 <https://www.gnu.org/licenses/>.
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;
;;; Commentary:

;; This file implements links to Rmail messages from within Org mode.
;; Org mode loads this module by default - if this is not what you
;; want, configure the variable `org-modules'.

;;; Code:

(require 'org-macs)
(org-assert-version)

(require 'ol)

;; Declare external functions and variables
(declare-function rmail-show-message  "rmail" (&optional n no-summary))
(declare-function rmail-what-message  "rmail" (&optional pos))
(declare-function rmail-toggle-header "rmail" (&optional arg))
(declare-function rmail               "rmail" (&optional file-name-arg))
(declare-function rmail-widen         "rmail" ())
(defvar rmail-current-message)  ; From rmail.el
(defvar rmail-header-style)     ; From rmail.el
(defvar rmail-file-name)        ; From rmail.el

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

;; Implementation
(defun org-rmail-store-link (&optional _interactive?)
  "Store a link to an Rmail folder or message."
  (when (or (eq major-mode 'rmail-mode)
	    (eq major-mode 'rmail-summary-mode))
    (save-window-excursion
      (save-restriction
	(when (eq major-mode 'rmail-summary-mode)
	  (rmail-show-message rmail-current-message))
	(when (fboundp 'rmail-narrow-to-non-pruned-header)
	  (rmail-narrow-to-non-pruned-header))
	(when (eq rmail-header-style 'normal)
	  (rmail-toggle-header -1))
	(let* ((folder buffer-file-name)
	       (message-id (mail-fetch-field "message-id"))
	       (from (mail-fetch-field "from"))
	       (to (mail-fetch-field "to"))
	       (subject (mail-fetch-field "subject"))
	       (date (mail-fetch-field "date"))
	       desc link)
	  (org-link-store-props
	   :type "rmail" :from from :to to :date date
	   :subject subject :message-id message-id)
	  (setq message-id (org-unbracket-string "<" ">" message-id))
	  (setq desc (org-link-email-description))
	  (setq link (concat "rmail:" folder "#" message-id))
	  (org-link-add-props :link link :description desc)
	  (rmail-show-message rmail-current-message)
	  link)))))

(defun org-rmail-open (path _)
  "Follow an Rmail message link to the specified PATH."
  (let (folder article)
    (if (not (string-match "\\`\\([^#]+\\)\\(#\\(.*\\)\\)?" path))
	(error "Error in Rmail link"))
    (setq folder (match-string 1 path)
	  article (match-string 3 path))
    (org-rmail-follow-link folder article)))

(defun org-rmail-follow-link (folder article)
  "Follow an Rmail link to FOLDER and ARTICLE."
  (require 'rmail)
  (cond ((null article) (setq article ""))
	((stringp article)
	 (setq article (org-link-add-angle-brackets article)))
	(t (user-error "Wrong RMAIL link format")))
  (let (message-number)
    (save-excursion
      (save-window-excursion
	(rmail (if (string= folder "RMAIL") rmail-file-name folder))
	(setq message-number
	      (save-restriction
		(rmail-widen)
		(goto-char (point-max))
		(if (re-search-backward
		     (concat "^Message-ID:\\s-+" (regexp-quote article))
		     nil t)
		    (rmail-what-message))))))
    (if message-number
	(progn
	  (rmail (if (string= folder "RMAIL") rmail-file-name folder))
	  (rmail-show-message message-number)
	  message-number)
      (error "Message not found"))))

(provide 'ol-rmail)

;;; ol-rmail.el ends here