EUDC: Add ecomplete and mailabbrev backends

* doc/misc/eudc.texi (Overview): Add ecomplete and mailabbrev
nodes.
(ecomplete, mailabbrev): New nodes.
(Installation): Add ecomplete and mailabbrev nodes.
(LDAP Configuration): Use code formatting instead of quotes.
(macOS Contacts Configuration): Likewise.
(ecomplete Configuration): New node.
(mailabbrev Configuration): Likewise.
* etc/NEWS (EUDC): Mention ecomplete and mailabbrev backends,
mention eudc-server-hotlist default change.
* lisp/net/eudc-vars.el (eudc-known-protocols): Add ecomplete and
mailabbrev.
(eudc-server-hotlist): Add entries for ecomplete and mailabbrev.
* lisp/net/eudcb-ecomplete.el: New EUDC backend file.
* lisp/net/eudcb-mailabbrev.el: Likewise.
* test/lisp/net/eudc-resources/ecompleterc,
test/lisp/net/eudc-resources/mailrc: New eudc-tests resource
files.
* test/lisp/net/eudc-tests.el (eudc-test-rfc5322-quote-phrase)
(eudc-test-make-address, eudcb-ecomplete, eudcb-mailabbrev): New
test cases.

1 files changed, 108 insertions, 0 deletions

diff --git a/lisp/net/eudcb-ecomplete.el b/lisp/net/eudcb-ecomplete.el
new file mode 100644
index 00000000000..55011d29f6c
--- /dev/null
+++ b/lisp/net/eudcb-ecomplete.el
@@ -0,0 +1,108 @@
+;;; eudcb-ecomplete.el --- EUDC - ecomplete backend -*- 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 an interface to the ecomplete package as
+;;    an EUDC data source.
+
+;;; Usage:
+;;    No setup is required, since there is an entry for this backend
+;;    in `eudc-server-hotlist' by default.
+;;
+;;    For example, if your `ecomplete-database-file' (typically
+;;    ~/.emacs.d/ecompleterc) contains:
+;;
+;;    ((mail ("larsi@gnus.org" 38154 1516109510 "Lars <larsi@ecomplete.org>")))
+;;
+;;    Then:
+;;
+;;    C-x m lars C-u M-x eudc-expand-try-all RET
+;;
+;;    should expand the email address into the To: field of the new
+;;    message.
+
+;;; Code:
+
+(require 'eudc)
+(require 'ecomplete)
+(require 'mail-parse)
+
+(defvar eudc-ecomplete-attributes-translation-alist
+  '((email     . mail))
+  "See `eudc-protocol-attributes-translation-alist'.
+The back-end-specific attribute names are used as the \"type\" of
+entry when searching, and they must hence match the types you use
+in your ecompleterc database file.")
+
+;; hook ourselves into the EUDC framework
+(eudc-protocol-set 'eudc-query-function
+		   'eudc-ecomplete-query-internal
+		   'ecomplete)
+(eudc-protocol-set 'eudc-list-attributes-function
+		   nil
+		   'ecomplete)
+(eudc-protocol-set 'eudc-protocol-attributes-translation-alist
+		   'eudc-ecomplete-attributes-translation-alist
+		   'ecomplete)
+(eudc-protocol-set 'eudc-protocol-has-default-query-attributes
+		   nil
+		   'ecomplete)
+
+;;;###autoload
+(defun eudc-ecomplete-query-internal (query &optional _return-attrs)
+  "Query `ecomplete' with QUERY.
+QUERY is a list of cons cells (ATTR . VALUE).  Since `ecomplete'
+does not provide attributes in the usual sense, the
+back-end-specific attribute names in
+`eudc-ecomplete-attributes-translation-alist' are used as the
+KEY (that is, the \"type\" of match) when looking for matches in
+`ecomplete-database'.
+
+RETURN-ATTRS is ignored." ; FIXME: why is this being ignored?
+  (ecomplete-setup)
+  (let ((email-attr (car (eudc-translate-attribute-list '(email))))
+        result)
+    (dolist (term query)
+      (let* ((attr (car term))
+             (value (cdr term))
+             (matches (ecomplete-get-matches attr value)))
+        (when matches
+          (dolist (match (split-string (string-trim (substring-no-properties
+                                                     matches))
+                                       "[\n\r]"))
+            ;; Try to decompose the email address.
+            (let* ((decoded (mail-header-parse-address match t))
+                   (name (cdr decoded))
+                   (email (car decoded)))
+              (if (and decoded (eq attr email-attr))
+                  ;; The email could be decomposed, push individual
+                  ;; fields.
+                  (push `((,attr . ,email)
+                          ,@(when name (list (cons 'name name))))
+                        result)
+                ;; Otherwise just forward the value as-is.
+                (push (list (cons attr match)) result)))))))
+    result))
+
+(eudc-register-protocol 'ecomplete)
+
+(provide 'eudcb-ecomplete)
+;;; eudcb-ecomplete.el ends here