notmuch-query.el: new file to support access to the notmuch database.

Initially this file provides one main function
notmuch-query-get-threads, which takes a set of search terms, and
returns a parsed set of matching threads as a lisp data structure.

A set of notmuch-query-map-* functions are provided to help map
functions over the data structure.

The function notmuch-query-get-message-ids uses this machinery to get
the set of message-ids matching a query.

Edited-by: Carl Worth <cworth@cworth.org>: Change comment syntax,
(";;" rather than ";" to make emacs-lisp mode happy), and eliminate
some excess whitespace, as suggested by David Edmonson.

emacs/Makefile.local

@@ -4,6 +4,7 @@ dir := emacs
 emacs_sources := \
 	$(dir)/notmuch-lib.el \
 	$(dir)/notmuch.el \
+	$(dir)/notmuch-query.el \
 	$(dir)/notmuch-show.el
 
 emacs_bytecode := $(subst .el,.elc,$(emacs_sources))

emacs/notmuch-query.el

@@ -0,0 +1,81 @@
+;; notmuch-query.el --- provide an emacs api to query notmuch
+;;
+;; Copyright © David Bremner
+;;
+;; This file is part of Notmuch.
+;;
+;; Notmuch 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.
+;;
+;; Notmuch 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 Notmuch.  If not, see <http://www.gnu.org/licenses/>.
+;;
+;; Authors: David Bremner <david@tethera.net>
+
+(require 'notmuch-lib)
+(require 'json)
+
+(defun notmuch-query-get-threads (search-terms &rest options)
+  "Return a list of threads of messages matching SEARCH-TERMS.
+
+A thread is a forest or list of trees. A tree is a two element
+list where the first element is a message, and the second element
+is a possibly empty forest of replies.
+"
+  (let  ((args (append '("show" "--format=json") search-terms))
+	 (json-object-type 'plist)
+	 (json-array-type 'list)
+	 (json-false 'nil))
+    (with-temp-buffer
+      (progn
+	(apply 'call-process (append (list notmuch-command nil t nil) args))
+	(goto-char (point-min))
+	(json-read)))))
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; Mapping functions across collections of messages.
+
+(defun notmuch-query-map-aux  (mapper function seq)
+  "private function to do the actual mapping and flattening"
+  (apply 'append
+	 (mapcar
+	   (lambda (tree)
+	     (funcall mapper fn tree))
+	   seq)))
+
+(defun notmuch-query-map-threads (fn threads)
+  "apply FN to every thread in  THREADS. Flatten results to a list.
+
+See the function notmuch-query-get-threads for more information."
+  (notmuch-query-map-aux 'notmuch-query-map-forest fn threads))
+
+(defun notmuch-query-map-forest (fn forest)
+  "apply function to every message in a forest. Flatten results to a list.
+
+See the function notmuch-query-get-threads for more information.
+"
+  (notmuch-query-map-aux 'notmuch-query-map-tree fn forest))
+
+(defun notmuch-query-map-tree (fn tree)
+  "Apply function FN to every message in TREE. Flatten results to a list
+
+See the function notmuch-query-get-threads for more information."
+  (cons (funcall fn (car tree)) (notmuch-query-map-forest fn (cadr tree))))
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; Predefined queries
+
+(defun notmuch-query-get-message-ids (&rest search-terms)
+  "Return a list of message-ids of messages that match SEARCH-TERMS"
+  (notmuch-query-map-threads
+   (lambda (msg) (plist-get msg :id))
+   (notmuch-query-get-threads search-terms)))
+
+(provide 'notmuch-query)