[PATCH] Added regress option to threads iterator

[Ruben Pollan <meskio@sindominio.net>]

Added the functions notmuch_threads_regress and notmuch_threads_is_first to
notmuch library. With them is possible to iterate backwards on threads.

* notmuch_threads_regress do the opposite than notmuch_threads_advance,
  getting the threads iterator one position backwards.

* notmuch_threads_is_first return TRUE if the iterator is in the first
  thread.
---
 lib/notmuch.h |    8 ++++++++
 lib/query.cc  |   28 ++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+), 0 deletions(-)

diff --git a/lib/notmuch.h b/lib/notmuch.h
index 69bd98a..e28ce46 100644
--- a/lib/notmuch.h
+++ b/lib/notmuch.h
@@ -429,6 +429,10 @@ notmuch_query_destroy (notmuch_query_t *query);
 notmuch_bool_t
 notmuch_threads_has_more (notmuch_threads_t *threads);
 
+/* Is the given notmuch_threads_t object on the first threads */
+notmuch_bool_t
+notmuch_threads_is_first (notmuch_threads_t *threads);
+
 /* Get the current thread from 'threads' as a notmuch_thread_t.
  *
  * Note: The returned thread belongs to 'threads' and has a lifetime
@@ -451,6 +455,10 @@ notmuch_threads_get (notmuch_threads_t *threads);
 void
 notmuch_threads_advance (notmuch_threads_t *threads);
 
+/* Regress the 'threads' iterator to the previous result. */
+void
+notmuch_threads_regress (notmuch_threads_t *threads);
+
 /* Destroy a notmuch_threads_t object.
  *
  * It's not strictly necessary to call this function. All memory from
diff --git a/lib/query.cc b/lib/query.cc
index 94a6860..cade17b 100644
--- a/lib/query.cc
+++ b/lib/query.cc
@@ -310,6 +310,12 @@ notmuch_threads_has_more (notmuch_threads_t *threads)
     return FALSE;
 }
 
+notmuch_bool_t
+notmuch_threads_is_first (notmuch_threads_t *threads)
+{
+    return (g_hash_table_size (threads->threads) <= 1);
+}
+
 notmuch_thread_t *
 notmuch_threads_get (notmuch_threads_t *threads)
 {
@@ -329,6 +335,28 @@ notmuch_threads_advance (notmuch_threads_t *threads)
 }
 
 void
+notmuch_threads_regress (notmuch_threads_t *threads)
+{
+    notmuch_message_t *message;
+	const char *thread_id;
+
+	thread_id = threads->thread_id;
+
+    while (!notmuch_messages_is_first (threads->messages))
+    {
+	notmuch_messages_regress (threads->messages);
+	message = notmuch_messages_get (threads->messages);
+	threads->thread_id = notmuch_message_get_thread_id (message);
+
+	if (strcmp (threads->thread_id, thread_id))
+	{
+	    g_hash_table_remove (threads->threads, thread_id);
+	    return;
+	}
+    }
+}
+
+void
 notmuch_threads_destroy (notmuch_threads_t *threads)
 {
     talloc_free (threads);
-- 
1.6.5.4