Add basic integration for Rmail

Teach piem how to get the associated inbox and message ID for the
current Rmail message.

Message-Id: <20210527232714.8726-1-kyle@kyleam.com>

1 files changed, 72 insertions, 0 deletions

diff --git a/piem-rmail.el b/piem-rmail.el
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+++ b/piem-rmail.el
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+;;; piem-rmail.el --- Rmail integration for piem  -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2021  all contributors <piem@inbox.kyleam.com>
+
+;; Author: Kyle Meyer <kyle@kyleam.com>
+;; Keywords: vc, tools
+;; 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:
+
+;; This library provides a minor mode, `piem-rmail-mode', that
+;; modifies `piem' variables to teach functions like `piem-inbox' how
+;; to extract information from Rmail mode buffers.
+
+;;; Code:
+
+(require 'piem)
+(require 'rmail)
+
+(defgroup piem-rmail nil
+  "Rmail integration for piem."
+  :group 'piem)
+
+(defun piem-rmail--call-with-message (fn)
+  (when (derived-mode-p 'rmail-mode 'rmail-summary-mode)
+    (rmail-apply-in-message
+     rmail-current-message
+     (lambda ()
+       (search-forward "\n\n" nil 'move)
+       (narrow-to-region (point-min) (point))
+       (funcall fn)))))
+
+(defun piem-rmail-get-inbox ()
+  "Return inbox name from an Rmail buffer."
+  (piem-rmail--call-with-message #'piem-inbox-by-header-match))
+
+(defun piem-rmail-get-mid ()
+  "Return the message ID of an Rmail buffer."
+  (when-let ((mid (piem-rmail--call-with-message
+                   (lambda () (mail-fetch-field "message-id")))))
+    (replace-regexp-in-string "\\`<\\(.*\\)>\\'" "\\1" mid)))
+
+;;;###autoload
+(define-minor-mode piem-rmail-mode
+  "Toggle Rmail support for piem.
+With a prefix argument ARG, enable piem-rmail 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-rmail-mode
+      (progn
+        (add-hook 'piem-get-inbox-functions #'piem-rmail-get-inbox)
+        (add-hook 'piem-get-mid-functions #'piem-rmail-get-mid))
+    (remove-hook 'piem-get-inbox-functions #'piem-rmail-get-inbox)
+    (remove-hook 'piem-get-mid-functions #'piem-rmail-get-mid)))
+
+;;; piem-rmail.el ends here
+(provide 'piem-rmail)