[PATCH v4 2/3] Emacs: Add address completion mechanism implemented in elisp

[Michal Sojka]

Currently, notmuch has an address completion mechanism that requires
external command to provide completion candidates. This patch adds a
completion mechanism inspired by https://github.com/tjim/nevermore,
which is implemented in Emacs lisp only.

The preexisting address completion mechanism, activated by pressing TAB
on To/Cc lines, is extended to use the new mechanism when no external
command is configured, i.e. when notmuch-address-command to nil, which
is the new default.

The core of the new mechanism is the function notmuch-address-harvest,
which collects the completion candidates from the notmuch database and
stores them in notmuch-address-completions variable. The address
harvesting can run either synchronously (same as with the previous
mechanism) or asynchronously. When the user presses TAB for the first
time, synchronous harvesting limited to user entered text is performed.
If the entered text is reasonably long, this operation is relatively
fast. Then, asynchronous harvesting over the full database is triggered.
This operation may take long time (minutes on rotating disk). After it
finishes, no harvesting is normally performed again and subsequent
completion requests use the harvested data cached in memory. Completion
cache is updated after 24 hours.

Note that the change of the notmuch-address-command default value
may *BREAK EXISTING SETUPS* when the user used external command named
"notmuch-addresses", i.e. the previous default. The result will be that
the user will use the new mechanism instead of the his command. I
believe that many users may not even recognize this because the new
mechanism works the same as
http://commonmeasure.org/~jkr/git/notmuch_addresses.git and perhaps also
as other commands suggested at
http://notmuchmail.org/emacstips/#address_completion.

---
Changes from v3:
- Implemented both synchronous and asynchronous harvesting. The
  synchronous implementation that uses faster "filtered" query is used
  until the full asynchronous harvesting finishes.
- Added automatic refresh of completion cache every 24 hours.

Changes from v2:
- Updated Makefile.local to not conflict with current master

Changes from v1:
- Use of notmuch-parser.el instead of the custom parser in the
  original code. The notmuch parser is slightly faster.
- Use of functions in notmuch-query.el instead of functions in the
  original code with almost the same functionality.
- Integrated with existing completion mechanism in notmuch.
- notmuch-company.el was moved from emacs/contrib to emacs and
  no-byte-compile directive was added to it.
- Aligned with notmuch naming conventions.
- Documented bugs found in notmuch-company.el
---
 emacs/notmuch-address.el | 123 ++++++++++++++++++++++++++++++++++++++++++++---
 emacs/notmuch-lib.el     |   3 ++
 2 files changed, 118 insertions(+), 8 deletions(-)

diff --git a/emacs/notmuch-address.el b/emacs/notmuch-address.el
index fde3c1b..9f6711b 100644
--- a/emacs/notmuch-address.el
+++ b/emacs/notmuch-address.el
@@ -20,14 +20,18 @@
 ;; Authors: David Edmondson <dme at dme.org>
 
 (require 'message)
+(require 'notmuch-query)
+(require 'notmuch-parser)
 
 ;;
 
-(defcustom notmuch-address-command "notmuch-addresses"
-  "The command which generates possible addresses. It must take a
-single argument and output a list of possible matches, one per
-line."
-  :type 'string
+(defcustom notmuch-address-command nil
+  "The command which generates possible addresses for completion.
+It must take a single argument and output a list of possible
+matches, one per line. If set to nil, addresses are generated by
+a built-in completion mechanism."
+  :type '(radio (const :tag "No command: Use built-in completion" nil)
+		 (string :tag "Custom command" :value "notmuch-addresses"))
   :group 'notmuch-send
   :group 'notmuch-external)
 
@@ -42,6 +46,17 @@ to know how address selection is made by default."
   :group 'notmuch-send
   :group 'notmuch-external)
 
+(defvar notmuch-address-last-harvest 0
+  "Time of last address harvest")
+
+(defvar notmuch-address-completions (make-hash-table :test 'equal)
+  "Hash of email addresses for completion during email composition.
+  This variable is set by calling `notmuch-address-harvest'.")
+
+(defvar notmuch-address-full-harvest-finished nil
+  "t indicates that full completion address harvesting has been
+finished")
+
 (defun notmuch-address-selection-function (prompt collection initial-input)
   "Call (`completing-read'
       PROMPT COLLECTION nil nil INITIAL-INPUT 'notmuch-address-history)"
@@ -59,8 +74,32 @@ to know how address selection is made by default."
     (setq message-completion-alist
 	  (push notmuch-address-message-alist-member message-completion-alist))))
 
+(defun notmuch-address-matching (substring)
+  "Returns a list of completion candidates matching SUBSTRING.
+The candidates are taked form `notmuch-address-completions'."
+  (let ((candidates)
+	(re (regexp-quote substring)))
+    (maphash (lambda (key val)
+	       (when (string-match re key)
+		 (push key candidates)))
+	     notmuch-address-completions)
+    candidates))
+
 (defun notmuch-address-options (original)
-  (process-lines notmuch-address-command original))
+  "Returns a list of completion candidates. Uses either
+elisp-based implementation or older implementation requiring
+external commands."
+  (cond
+   ((null notmuch-address-command)
+    (when (not notmuch-address-full-harvest-finished)
+      ;; First, run quick synchronous harvest based on what the user
+      ;; entered so far
+      (notmuch-address-harvest (format "to:%s*" original) t))
+    (prog1 (notmuch-address-matching original)
+      ;; Then (re)start potentially long-running full asynchronous harvesting
+      (notmuch-address-harvest-trigger)))
+   (t
+    (process-lines notmuch-address-command original))))
 
 (defun notmuch-address-expand-name ()
   (let* ((end (point))
@@ -109,11 +148,79 @@ to know how address selection is made by default."
 			   (not (file-directory-p bin))))
 	      (throw 'found-command bin))))))))
 
+(defun notmuch-address-harvest-msg (msg)
+  (let* ((headers (plist-get msg :headers))
+	 (to (ignore-errors (mail-extract-address-components (plist-get headers :To) t)))
+	 (cc (ignore-errors (mail-extract-address-components (plist-get headers :Cc) t)))
+	 (bcc (ignore-errors (mail-extract-address-components (plist-get headers :Bcc) t))))
+    (mapc (lambda (parts)
+	    (let* ((name (car parts))
+		   (email (cadr parts))
+		   (entry (if name (format "%s <%s>" name email) email)))
+	      (puthash entry t notmuch-address-completions)))
+	  (append to cc bcc))
+    nil))
+
+(defun notmuch-address-harvest-handle-result (obj)
+  (notmuch-query-map-threads 'notmuch-address-harvest-msg (list obj)))
+
+(defun notmuch-address-harvest-filter (proc string)
+  (when (buffer-live-p (process-buffer proc))
+    (with-current-buffer (process-buffer proc)
+      (save-excursion
+	(goto-char (point-max))
+	(insert string))
+      (notmuch-sexp-parse-partial-list
+       'notmuch-address-harvest-handle-result (process-buffer proc)))))
+
+(defvar notmuch-address-harvest-proc nil)   ; the process of a harvest underway
+
+(defun notmuch-address-harvest (&optional filter-query synchronous callback)
+  "Collect addresses completion candidates. It queries the
+notmuch database for all messages sent by the user optionally
+matching FILTER-QUERY (if not nil). It collects the destination
+addresses from those messages and stores them in
+`notmuch-address-completions'. Address harvesting may take some
+time so the address collection runs asynchronously unless
+SYNCHRONOUS is t. In case of asynchronous execution, CALLBACK is
+called when harvesting finishes."
+  (let* ((from-me-query (mapconcat (lambda (x) (concat "from:" x)) (notmuch-user-emails) " or "))
+	 (query (if filter-query
+		    (format "(%s) and (%s)" from-me-query filter-query)
+		  from-me-query))
+	 (args `("show" "--format=sexp" "--format-version=2"
+		 "--body=false" "--entire-thread=false" ,query)))
+    (if synchronous
+	(notmuch-query-map-threads 'notmuch-address-harvest-msg
+				   (apply 'notmuch-call-notmuch-sexp args))
+      ;; Asynchronous
+      (when notmuch-address-harvest-proc
+	(kill-buffer (process-buffer notmuch-address-harvest-proc))) ; this also kills the process
+      (setq notmuch-address-harvest-proc
+	    (apply 'notmuch-start-notmuch
+	     "notmuch-address-harvest"		; process name
+	     " *notmuch-address-harvest*"	; process buffer
+	     callback				; process sentinel
+	     args))
+      (set-process-filter notmuch-address-harvest-proc 'notmuch-address-harvest-filter)
+      (set-process-query-on-exit-flag notmuch-address-harvest-proc nil)))
+  ;; return value
+  nil)
+
 ;; If we can find the program specified by `notmuch-address-command',
-;; insinuate ourselves into `message-mode'.
-(when (notmuch-address-locate-command notmuch-address-command)
+;; or if it is nil, insinuate ourselves into `message-mode'.
+(when (or (null notmuch-address-command)
+	  (notmuch-address-locate-command notmuch-address-command))
   (notmuch-address-message-insinuate))
 
+(defun notmuch-address-harvest-trigger ()
+  (let ((now (float-time)))
+    (when (> (- now notmuch-address-last-harvest) 86400)
+      (setq notmuch-address-last-harvest now)
+      (notmuch-address-harvest nil nil
+			       (lambda (proc event)
+				 (setq notmuch-address-full-harvest-finished t))))))
+
 ;;
 
 (provide 'notmuch-address)
diff --git a/emacs/notmuch-lib.el b/emacs/notmuch-lib.el
index 19269e3..00e8554 100644
--- a/emacs/notmuch-lib.el
+++ b/emacs/notmuch-lib.el
@@ -228,6 +228,9 @@ on the command line, and then retry your notmuch command")))
   "Return the user.other_email value (as a list) from the notmuch configuration."
   (split-string (notmuch-config-get "user.other_email") "\n" t))
 
+(defun notmuch-user-emails ()
+  (cons (notmuch-user-primary-email) (notmuch-user-other-email)))
+
 (defun notmuch-poll ()
   "Run \"notmuch new\" or an external script to import mail.
 
-- 
2.1.0