[PATCH v2 4/5] emacs: add notmuch hello refresh hook to display message count change

[Jani Nikula <jani@nikula.org>]

Add a notmuch hello refresh hook to display a message about change in
message count in the database since the notmuch-hello buffer was last
refreshed manually (no-display is nil).

Signed-off-by: Jani Nikula <jani@nikula.org>
---
 emacs/notmuch-hello.el |   38 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/emacs/notmuch-hello.el b/emacs/notmuch-hello.el
index fa14443..f7a3c95 100644
--- a/emacs/notmuch-hello.el
+++ b/emacs/notmuch-hello.el
@@ -148,6 +148,7 @@ International Bureau of Weights and Measures."
 (defcustom notmuch-hello-refresh-hook nil
   "Functions called after updating a `notmuch-hello' buffer."
   :type 'hook
+  :options '(notmuch-hello-refresh-status-message)
   :group 'notmuch-hello
   :group 'notmuch-hooks)
 
@@ -749,6 +750,43 @@ following:
     (let ((fill-column (- (window-width) notmuch-hello-indent)))
       (center-region start (point)))))
 
+(defcustom notmuch-hello-refresh-status-query "*"
+  "Query to use for `notmuch-hello-refresh-status-message' hook."
+  :type '(choice (const :tag "All messages" "*")
+		 (string :tag "Custom query"
+			 :value "tag:inbox"))
+  :group 'notmuch-hello)
+
+(defvar notmuch-hello-refresh-count 0
+  "Number of matching messages when `notmuch-hello' was last run.
+
+Used internally by `notmuch-hello-refresh-status-message'.")
+
+(defun notmuch-hello-refresh-status-message (no-display)
+  "Hook to display a status message when refreshing notmuch-hello buffer.
+
+Display a status message about the difference in message count
+matching `notmuch-hello-refresh-status-query' since the last time
+notmuch-hello was refreshed. Only takes into account explicit
+refreshes (NO-DISPLAY is nil)."
+  (unless no-display
+    (let* ((new-count
+	    (string-to-number
+	     (car (process-lines notmuch-command "count"
+				 notmuch-hello-refresh-status-query))))
+	   (diff-count (- new-count notmuch-hello-refresh-count)))
+      (cond
+       ((= notmuch-hello-refresh-count 0)
+	(message "You have %s messages."
+		 (notmuch-hello-nice-number new-count)))
+       ((> diff-count 0)
+	(message "You have %s more messages since last refresh."
+		 (notmuch-hello-nice-number diff-count)))
+       ((< diff-count 0)
+	(message "You have %s fewer messages since last refresh."
+		 (notmuch-hello-nice-number (- diff-count)))))
+      (setq notmuch-hello-refresh-count new-count))))
+
 ;;;###autoload
 (defun notmuch-hello (&optional no-display)
   "Run notmuch and display saved searches, known tags, etc.
-- 
1.7.9.5