nndiscourse.el

@@ -221,7 +221,7 @@ Starting in emacs-src commit c1b63af, Gnus moved from obarrays to normal hashtab
 (defvar-local nndiscourse--refs-hashtb (gnus-make-hashtable)
   "Id -> parent.  Buffer-local to individual servers' proc buffer.")
 
-(defun nndiscourse-get-ref (server id)
+(defun nndiscourse-get-refs (server id)
   "Amongst SERVER refs, return list of descending ancestors for ID."
   (declare (indent defun))
   (with-current-buffer (nndiscourse--server-buffer server)
@@ -649,6 +649,13 @@ Originally written by Paul Issartel."
                                 (= post-number* (plist-get plst :post_number))))))))
     (elt headers found)))
 
+(defun nndiscourse--earliest-header (server group topic-id)
+  "O(n) search for first header satisfying SERVER GROUP TOPIC-ID."
+  (declare (indent defun))
+  (-when-let* ((headers (nndiscourse-get-headers server group)))
+    (seq-find (lambda (plst) (= topic-id (plist-get plst :topic_id)))
+              headers)))
+
 (defsubst nndiscourse-hash-count (table-or-obarray)
   "Return number items in TABLE-OR-OBARRAY."
   (let ((result 0))
@@ -688,13 +695,18 @@ Originally written by Paul Issartel."
                     (full-group (gnus-group-full-name
                                  group
                                  (cons 'nndiscourse (list server)))))
-         (when-let ((parent-number (plist-get plst :reply_to_post_number)))
+         (aif (plist-get plst :reply_to_post_number)
              (nndiscourse-set-ref server
                                   (plist-get plst :id)
                                   (plist-get (nndiscourse--number-to-header
-                                             server group (plist-get plst :topic_id)
-                                             parent-number)
-                                           :id)))
+                                               server group
+                                               (plist-get plst :topic_id) it)
+                                             :id))
+           (awhen (plist-get (nndiscourse--earliest-header
+                               server group
+                               (plist-get plst :topic_id))
+                             :id)
+             (nndiscourse-set-ref server (plist-get plst :id) it)))
          (nndiscourse--replace-hash type (lambda (x) (1+ (or x 0))) counts)
          (if-let ((info (gnus-get-info full-group)))
              (progn
@@ -742,7 +754,7 @@ Originally written by Paul Issartel."
 (defsubst nndiscourse--make-references (server id)
   "For SERVER, construct a space delimited string of message ancestors of ID."
   (mapconcat (lambda (ref) (nndiscourse--make-message-id ref))
-             (nndiscourse-get-ref server id) " "))
+             (nndiscourse-get-refs server id) " "))
 
 (defsubst nndiscourse--make-header (server group article-number)
   "Construct mail headers from article header.
@@ -797,7 +809,7 @@ article header.  Gnus manual does say the term `header` is oft conflated."
            "Score: " score "\n"
            "\n")
           (-when-let*
-              ((parent (plist-get header :parent))
+              ((parent (car (last (nndiscourse-get-refs server (plist-get header :id)))))
                (parent-author
                 (or (plist-get (nndiscourse--get-header server group parent)
                                :username)