[PATCH 9/9] lib/thread: change _resolve_thread_relationships to use depths

[David Bremner <david@tethera.net>]

We (finally) implement the XXX comment. It requires a bit of care not
to reparent all of the possible toplevel messages. There is some
slightly naughty low level access to the list structures here that can
be cleaned up in a later commit.
---
 lib/thread.cc             | 53 +++++++++++++++++++--------------------
 test/T260-thread-order.sh |  1 -
 2 files changed, 26 insertions(+), 28 deletions(-)

diff --git a/lib/thread.cc b/lib/thread.cc
index 2eed724b..6a567caa 100644
--- a/lib/thread.cc
+++ b/lib/thread.cc
@@ -466,12 +466,6 @@ _resolve_thread_relationships (notmuch_thread_t *thread)
 	    _notmuch_message_list_add_message (maybe_toplevel_list, message);
     }
 
-    for (notmuch_messages_t *roots = _notmuch_messages_create (maybe_toplevel_list);
-	 notmuch_messages_valid (roots);
-	 notmuch_messages_move_to_next (roots)) {
-	notmuch_message_t *message = notmuch_messages_get (roots);
-	_parent_or_toplevel (thread, message);
-    }
     /*
      * if we reach the end of the list without finding a top-level
      * message, that means the thread is a cycle (or set of cycles)
@@ -480,31 +474,36 @@ _resolve_thread_relationships (notmuch_thread_t *thread)
      */
     if (first_node) {
 	message = first_node->message;
-	if (! thread->toplevel_list->head ||
+	DEBUG_PRINTF("checking first message  %s\n",
+		     notmuch_message_get_message_id (message));
+
+	if (! maybe_toplevel_list->head ||
 	    ! _parent_via_in_reply_to (thread, message)) {
-	    /*
-	     * If the oldest message happens to be in-reply-to a
-	     * missing message, we only check for references if there
-	     * is some other candidate for root message.
-	     */
-	    if (thread->toplevel_list->head)
-		_parent_or_toplevel (thread, message);
-	    else
-		_notmuch_message_list_add_message (thread->toplevel_list, message);
+	    DEBUG_PRINTF("adding first message as toplevel = %s\n",
+		     notmuch_message_get_message_id (message));
+	    _notmuch_message_list_add_message (maybe_toplevel_list, message);
 	}
     }
 
-    /* XXX: After scanning through the entire list looking for parents
-     * via "In-Reply-To", we should do a second pass that looks at the
-     * list of messages IDs in the "References" header instead.
-     * Unlike the current quick fix, the parent should be the
-     * "deepest" message of all the messages found in the "References"
-     * list.
-     *
-     * Doing this will allow messages and sub-threads to be positioned
-     * correctly in the thread even when an intermediate message is
-     * missing from the thread.
-     */
+    for (notmuch_messages_t *messages = _notmuch_messages_create (maybe_toplevel_list);
+	 notmuch_messages_valid (messages);
+	 notmuch_messages_move_to_next (messages))
+    {
+	notmuch_message_t *message = notmuch_messages_get (messages);
+	_notmuch_message_label_depths (message, 0);
+    }
+
+    for (notmuch_messages_t *roots = _notmuch_messages_create (maybe_toplevel_list);
+	 notmuch_messages_valid (roots);
+	 notmuch_messages_move_to_next (roots)) {
+	notmuch_message_t *message = notmuch_messages_get (roots);
+	/* XXX add _notmuch_messages_count */
+	if (roots->iterator->next || thread->toplevel_list->head)
+	    _parent_or_toplevel (thread, message);
+	else
+	    _notmuch_message_list_add_message (thread->toplevel_list, message);
+    }
+
     talloc_free (local);
 }
 
diff --git a/test/T260-thread-order.sh b/test/T260-thread-order.sh
index 9565f296..0dd985c2 100755
--- a/test/T260-thread-order.sh
+++ b/test/T260-thread-order.sh
@@ -85,7 +85,6 @@ EOF
 test_expect_equal_file EXPECTED OUTPUT
 
 test_begin_subtest "reply to ghost (tree view)"
-test_subtest_known_broken
 test_emacs '(notmuch-tree "tag:inbox")
 	    (notmuch-test-wait)
 	    (test-output)
-- 
2.18.0