problem

1 files changed, 24 insertions, 0 deletions

diff --git a/TODO b/TODO
index 4ea0ce4..c8a2398 100644
--- a/TODO
+++ b/TODO
@@ -1,3 +1,27 @@
+* The current rules for when an Activity Entered is accepted allow it to
+  refer to an older activity than the last one. If echoing is disabled,
+  two Activity Entered could be sent, each pointing at the most recent
+  Activity Seen, and there would be no proof of the order of the two.
+  Reordering the two might cause different results though.
+
+  This is not only a problem when 2 developers are connected; it also
+  lets a single developer produce a proof chain that is ambiguous about
+  what order they entered 2 things.
+
+  Fix: Make a Activity Entered have a pointer to the previous Activity
+  Entered that was accepted, in addition to the existing pointer. Then
+  when one developer sends two Activity Entered that don't echo, there's
+  still proof of ordering. When two developers are typing at the same
+  time, only one of their inputs will be accepted. The client should only
+  consider an Activity Entered legal if it points to the last Activity
+  Entered that the client saw.
+
+  May as well make Activity Seen have a pointer to the last accepted
+  Activity Entered as well. This will make it easier when supported
+  multiple developers, as each time a developer gets an Activity Seen,
+  they can update their state to use the Activity Entered that it points
+  to.
+ 
 * --watch and --download only get Seen messages, not Entered messages,
   because the server does not send Developer messages to them.
   To fix, need a way to avoid looping Entered messages sent by a developer