fix backlog truncation bug

That I was stuck on for hours yesterday, oops!

This commit was sponsored by Bruno BEAUFILS on Patreon.

1 files changed, 11 insertions, 4 deletions

diff --git a/debug-me.hs b/debug-me.hs
index 9332270..7a9f527 100644
--- a/debug-me.hs
+++ b/debug-me.hs
@@ -278,19 +278,26 @@ sendPtyInput ichan ochan p backlog logger = go
 				go
 
 -- | Truncate the Backlog to remove entries older than the one
--- that the Activity refers to.
+-- that the Activity Entered refers to, but only if the referred
+-- to Activity is an Activity Seen. 
 --
--- If the activity refers to an item not in the backlog, no truncation is
+-- Once the developer has referred to a given Activity Seen in
+-- their Activity Entered, they cannot refer backwards to anything
+-- that came before it.
+--
+-- If the Activity refers to an item not in the backlog, no truncation is
 -- done.
 truncateBacklog :: Backlog -> Activity Entered -> Backlog
 truncateBacklog (Backlog (b :| l)) (Activity _ hp _)
-	| Just (activityLogHash b) == hp = Backlog (b :| [])
+	| truncationpoint b = Backlog (b :| [])
 	| otherwise = Backlog (b :| go [] l)
   where
 	go c [] = reverse c
 	go c (x:xs)
-		| Just (activityLogHash x) == hp = reverse (x:c)
+		| truncationpoint x = reverse (x:c)
 		| otherwise = go (x:c) xs
+	truncationpoint x@(ActivitySeen {}) = Just (activityLogHash x) == hp
+	truncationpoint _ = False
 
 -- | Entered activity is legal when it points to the last Seen activvity,
 -- because this guarantees that the person who entered it saw