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| | ;;; eudc-capf.el --- EUDC - completion-at-point bindings -*- lexical-binding:t -*-
;; Copyright (C) 2022 Free Software Foundation, Inc.
;;
;; Author: Alexander Adolf
;;
;; 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 library provides functions to deliver email addresses from
;; EUDC search results to `completion-at-point'.
;;
;; Email address completion will likely be desirable only in
;; situations where designating email recipients plays a role, such
;; as when composing or replying to email messages, or when posting
;; to newsgroups, possibly with copies of the post being emailed.
;; Hence, modes relevant in such contexts, such as for example
;; `message-mode' and `mail-mode', often at least to some extent
;; provide infrastructure for different functions to be called when
;; completing in certain message header fields, or in the body of
;; the message. In other modes for editing email messages or
;; newsgroup posts, which do not provide such infrastructure, any
;; completion function providing email addresses will need to check
;; whether the completion attempt occurs in an appropriate context
;; (that is, in a relevant message header field) before providing
;; completion candidates. Two mechanisms are thus provided by this
;; library.
;;
;; The first mechanism is intended for use by the modes listed in
;; `eudc-capf-modes', and relies on these modes adding
;; `eudc-capf-complete' to `completion-at-point-functions', as
;; would be usually done for any general-purpose completion
;; function. In this mode of operation, and in order to offer
;; email addresses only in contexts where the user would expect
;; them, a check is performed whether point is on a line that is a
;; message header field suitable for email addresses, such as for
;; example "To:", "Cc:", etc.
;;
;; The second mechanism is intended for when the user modifies
;; `message-completion-alist' to replace `message-expand-name' with
;; the function `eudc-capf-message-expand-name'. As a result,
;; minibuffer completion (`completing-read') for email addresses
;; would no longer enabled in `message-mode', but
;; `completion-at-point' (in-buffer completion) only.
;;; Usage:
;; In a major mode, or context where you want email address
;; completion, you would do something along the lines of:
;;
;; (require 'eudc-capf)
;; (add-hook 'completion-at-point-functions #'eudc-capf-complete -1 t)
;;
;; The minus one argument puts it at the front of the list so it is
;; called first, and the t value for the LOCAL parameter causes the
;; setting to be buffer local, so as to avoid modifying any global
;; setting.
;;
;; The value of the variable `eudc-capf-modes' indicates which
;; major modes do such a setup as part of their initialization
;; code.
;;; Code:
(require 'eudc)
(defvar message-email-recipient-header-regexp)
(defvar mail-abbrev-mode-regexp)
(declare-function mail-abbrev-in-expansion-header-p "mailabbrev" ())
(defconst eudc-capf-modes '(message-mode)
"List of modes in which email address completion is to be attempted.")
;; completion functions
;;;###autoload
(defun eudc-capf-complete ()
"Email address completion function for `completion-at-point-functions'.
This function checks whether the current major mode is one of the
modes listed in `eudc-capf-modes', and whether point is on a line
with a message header listing email recipients, that is, a line
whose beginning matches `message-email-recipient-header-regexp',
and, if the check succeeds, searches for records matching the
words before point.
The return value is either nil when no match is found, or a
completion table as required for functions listed in
`completion-at-point-functions'."
(if (and (seq-some #'derived-mode-p eudc-capf-modes)
(let ((mail-abbrev-mode-regexp message-email-recipient-header-regexp))
(mail-abbrev-in-expansion-header-p)))
(eudc-capf-message-expand-name)))
;;;###autoload
(defun eudc-capf-message-expand-name ()
"Email address completion function for `message-completion-alist'.
When this function is added to `message-completion-alist',
replacing any existing entry for `message-expand-name' there,
with an appropriate regular expression such as for example
`message-email-recipient-header-regexp', then EUDC will be
queried for email addresses, and the results delivered to
`completion-at-point'."
(if (or eudc-server eudc-server-hotlist)
(progn
(let* ((beg (save-excursion
(re-search-backward "\\([:,]\\|^\\)[ \t]*")
(match-end 0)))
(end (point))
(prefix (save-excursion (buffer-substring-no-properties beg end))))
(let ((result
(eudc-query-with-words (split-string prefix "[ \t]+") t)))
(when result
(list beg end
(completion-table-with-cache
(lambda (_) result) t))))))))
(provide 'eudc-capf)
;;; eudc-capf.el ends here
|