/-  feed=trill-feed, sur=nostrill
/+  sr=sortug, constants
|%
++  latest-page  |=  f=feed:feed  ^-  fc:feed
  =/  nodelist  (tap:orm:feed f)
  =/  subset  (scag feed-page-size:constants nodelist)
  ?~  subset  [f ~ ~]
  =/  start  `id.i.subset
  =/  rev  (flop subset)
  ?~  rev  [f ~ ~]
  =/  end  `id.i.rev
  =/  nf  (gas:orm:feed *feed:feed subset)
  [nf start end]
::
++  latest-page-nostr  |=  f=nostr-feed:sur  ^-  nfc:sur
  =/  nodelist  (tap:norm:sur f)
  =/  subset  (scag feed-page-size:constants nodelist)
  ?~  subset  [f ~ ~]
  =/  start  `id.i.subset
  =/  rev  (flop subset)
  ?~  rev  [f ~ ~]
  =/  end  `id.i.rev
  =/  nf  (gas:norm:sur *nostr-feed:sur subset)
  [nf start end]
:: 
:: NOTE START IS OLD, END IS NEW

++  subset
|=  [=fc:feed replies=? now=@da]  ^-  fc:feed
  ?:  ?&(?=(%~ start.fc) ?=(%~ end.fc))  (latest-page feed.fc)

  =/  count  feed-page-size:constants
  =/  start  ?~  start.fc  0    u.start.fc  
  =/  end    ?~  end.fc    now  u.end.fc
  =/  nodelist  (tap:orm:feed feed.fc)

  =/  threads  %+  skim  nodelist 
  |=  [=id:post =post:post]  ^-  ?
  ?.  replies
  ?&
    ?=  %~  parent.post
    (lte id start)  (gte id end)
  ==
  ?&  (lte id start)  (gte id end)  ==
  =/  thread-count  (lent threads)
  =/  result=(list [id:post post:post])  ?:  newest  (scag count threads)  (flop (scag count (flop threads)))
  =/  cursors=[(unit @da) (unit @da)]  ?~  result  [~ ~]  ?~  threads  [~ ~]  :-
  ?:  .=((head result) (head threads))  ~  `id:(head result)
  ?:  .=((rear result) (rear threads))  ~  `id:(rear result)
  [(gas:orm:feed *feed:feed result) -.cursors +.cursors]
--