[PATCH v4 3/3] Emacs: Add address completion based on company-mode

[Michal Sojka]

With this patch, address completion candidates are shown automatically
after short typing delay in a nice popup box. This requires company-mode
to be installed and it works only on Emacs >= 24. The completion is
based entirely on the asynchronous address harvesting from
notmuch-address.el so the GUI is theoretically not blocked for long
time.

The completion works similarly as the TAB-initiated completion from
notmuch-address.el, i.e. quick harvest based on user input is executed
first and only after full harvesting is finished, in-memory cached data
is used.

The notmuch-company.el is excluded from byte-compilation, because it
would require every person who want to compile notmuch to have
company-mode installed.
---
 emacs/Makefile.local     |  6 +++-
 emacs/notmuch-company.el | 81 ++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 86 insertions(+), 1 deletion(-)
 create mode 100644 emacs/notmuch-company.el

diff --git a/emacs/Makefile.local b/emacs/Makefile.local
index 1109cfa..6c93e73 100644
--- a/emacs/Makefile.local
+++ b/emacs/Makefile.local
@@ -20,6 +20,7 @@ emacs_sources := \
 	$(dir)/notmuch-print.el \
 	$(dir)/notmuch-version.el \
 	$(dir)/notmuch-jump.el \
+	$(dir)/notmuch-company.el
 
 $(dir)/notmuch-version.el: $(dir)/Makefile.local version.stamp
 $(dir)/notmuch-version.el: $(srcdir)/$(dir)/notmuch-version.el.tmpl
@@ -30,7 +31,10 @@ $(dir)/notmuch-version.el: $(srcdir)/$(dir)/notmuch-version.el.tmpl
 emacs_images := \
 	$(srcdir)/$(dir)/notmuch-logo.png
 
-emacs_bytecode = $(emacs_sources:.el=.elc)
+# Do not try to install files that are not byte-compiled.
+emacs_no_byte_compile := $(dir)/notmuch-company.el
+
+emacs_bytecode = $(patsubst %.el,%.elc,$(filter-out $(emacs_no_byte_compile),$(emacs_sources)))
 
 # Because of defmacro's and defsubst's, we have to account for load
 # dependencies between Elisp files when byte compiling.  Otherwise,
diff --git a/emacs/notmuch-company.el b/emacs/notmuch-company.el
new file mode 100644
index 0000000..0d4fe49
--- /dev/null
+++ b/emacs/notmuch-company.el
@@ -0,0 +1,81 @@
+;; notmuch-company.el --- Mail address completion for notmuch via company-mode  -*- no-byte-compile: t; lexical-binding: t -*-
+
+
+;; Authors: Trevor Jim <tjim at mac.com>
+;; 	    Michal Sojka <sojkam1 at fel.cvut.cz>
+;;
+;; Keywords: mail, completion
+
+;; 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 <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; To enable this, install company mode (https://company-mode.github.io/)
+;; and add
+;;
+;;     (require 'notmuch-company)
+;;
+;; to your .emacs.
+;;
+;; NB company-minimum-prefix-length defaults to 3 so you don't get
+;; completion unless you type 3 characters
+
+;;; Code:
+
+(require 'company)
+(require 'message)
+(require 'notmuch-address)
+(require 'cl-lib)
+
+(defvar-local notmuch-company-last-prefix nil)
+
+;;;###autoload
+(defun notmuch-company (command &optional arg &rest ignore)
+  "`company-mode' completion back-end for `notmuch'."
+  (interactive (list 'interactive))
+  (let ((case-fold-search t)
+	(completion-ignore-case t))
+    (cl-case command
+      (interactive (company-begin-backend 'notmuch-company))
+      (prefix (and (eq major-mode 'message-mode)
+		   (looking-back "^\\(To\\|Cc\\|Bcc\\):.*"
+				 (line-beginning-position))
+		   (setq notmuch-company-last-prefix (company-grab "[:,][ \t]*\\(.*\\)" 1 (point-at-bol)))))
+      (candidates (cond
+		   (notmuch-address-full-harvest-finished
+		    ;; Update harvested addressed from time to time
+		    (notmuch-address-harvest-trigger)
+		    (notmuch-address-matching arg))
+		   (t
+		    (cons :async
+			  (lambda (callback)
+			    ;; First run quick asynchronous harvest based on what the user entered so far
+			    (notmuch-address-harvest
+			     (format "to:%s*" arg) nil
+			     (lambda (proc event)
+			       (funcall callback (notmuch-address-matching arg))
+			       ;; Then (re)start potentially long-running full asynchronous harvesting
+			       (notmuch-address-harvest-trigger))))))))
+      (match (if (string-match notmuch-company-last-prefix arg)
+		 (match-end 0)
+	       0))
+      (no-cache t))))
+
+;;;###autoload
+(add-hook 'message-mode-hook '(lambda ()
+                                (company-mode)
+                                (make-local-variable 'company-backends)
+                                (setq company-backends '(notmuch-company))))
+
+(provide 'notmuch-company)
-- 
2.1.0