;;; piem-gnus.el --- Gnus integration for piem  -*- lexical-binding: t; -*-

;; Copyright (C) 2020  Kyle Meyer

;; Author: Kyle Meyer <kyle@kyleam.com>
;; Keywords: vc, tools
;; Version: 0.0.0
;; Package-Requires: ((emacs "26.3"))

;; This program 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.

;; This program 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 this program.  If not, see <https://www.gnu.org/licenses/>.

;;; Commentary:

;;

;;; Code:

(require 'gnus)
(require 'message)
(require 'piem)

(defgroup piem-gnus nil
  "Gnus integration for piem."
  :link '(info-link "(piem)Gnus integration")
  :group 'piem)

(defun piem-gnus-get-inbox ()
  "Return inbox name from a Gnus article"
  (when (derived-mode-p 'gnus-article-mode)
    (with-current-buffer gnus-original-article-buffer
      (piem-inbox-by-header-match))))

(defun piem-gnus-get-mid ()
  "Return the message ID of a Gnus article."
  (when (derived-mode-p 'gnus-article-mode)
    (with-current-buffer gnus-original-article-buffer
      (when-let ((mid (message-field-value "Message-ID")))
        (if (string-match (rx string-start (zero-or-more space) "<"
                              (group (one-or-more (not (any ">"))))
                              ">" (zero-or-more space) string-end)
                          mid)
            (match-string 1 mid)
          mid)))))

;; If there is an easy way to generate an mbox for a thread in Gnus, a
;; function for `piem-mid-to-thread-functions' should be defined.

(define-minor-mode piem-gnus-mode
  "Toggle Gnus support for piem.
With a prefix argument ARG, enable piem-gnus mode if ARG is
positive, and disable it otherwise.  If called from Lisp, enable
the mode if ARG is omitted or nil."
  :global t
  :init-value nil
  (if piem-gnus-mode
      (progn
        (add-hook 'piem-get-inbox-functions #'piem-gnus-get-inbox)
        (add-hook 'piem-get-mid-functions #'piem-gnus-get-mid))
    (remove-hook 'piem-get-inbox-functions #'piem-gnus-get-inbox)
    (remove-hook 'piem-get-mid-functions #'piem-gnus-get-mid)))

;;; piem-gnus.el ends here
(provide 'piem-gnus)