cache REPL history

I think this is the proper way to do things: we give the entire REPL
history to brick so that it can render the entire thing and thus draw
the scroll bar correctly, scroll through the history with PgUp/PgDown
etc., but we cache it so that it is only re-rendered when the history
changes (i.e. when a new input is entered, or a new output becomes
available).

src/Swarm/TUI/Controller.hs

@@ -815,6 +815,7 @@ updateUI = do
       let itName = fromString $ "it" ++ show itIx
       let out = T.intercalate " " [itName, ":", prettyText finalType, "=", into (prettyValue v)]
       uiState . uiREPL . replHistory %= addREPLItem (REPLOutput out)
+      invalidateCacheEntry REPLHistoryCache
       vScrollToEnd replScroll
       gameState . replStatus .= REPLDone (Just val)
       gameState . baseRobot . robotContext . at itName .= Just val
@@ -1129,7 +1130,9 @@ handleREPLEventTyping = \case
 
         if not $ s ^. gameState . replWorking
           then case repl ^. replPromptType of
-            CmdPrompt _ -> runBaseCode topCtx uinput
+            CmdPrompt _ -> do
+              runBaseCode topCtx uinput
+              invalidateCacheEntry REPLHistoryCache
             SearchPrompt hist ->
               case lastEntry uinput hist of
                 Nothing -> uiState %= resetREPL "" (CmdPrompt [])

src/Swarm/TUI/Model/Name.hs

@@ -64,6 +64,8 @@ data Name
     WorldEditorPanelControl WorldEditorFocusable
   | -- | The REPL input form.
     REPLInput
+  | -- | The REPL history cache.
+    REPLHistoryCache
   | -- | The render cache for the world view.
     WorldCache
   | -- | The cached extent for the world view.

src/Swarm/TUI/Model/Repl.hs

@@ -188,8 +188,8 @@ getLatestREPLHistoryItems n h = toList latestN
 
 -- | Get only the items from the REPL history that were entered during
 --   the current session.
-getSessionREPLHistoryItems :: REPLHistory -> [REPLHistItem]
-getSessionREPLHistoryItems h = toList $ Seq.drop (h ^. replStart) (h ^. replSeq)
+getSessionREPLHistoryItems :: REPLHistory -> Seq REPLHistItem
+getSessionREPLHistoryItems h = Seq.drop (h ^. replStart) (h ^. replSeq)
 
 data TimeDir = Newer | Older deriving (Eq, Ord, Show)
 

src/Swarm/TUI/View.hs

@@ -51,6 +51,7 @@ import Control.Lens as Lens hiding (Const, from)
 import Control.Monad (guard)
 import Data.Array (range)
 import Data.Bits (shiftL, shiftR, (.&.))
+import Data.Foldable (toList)
 import Data.Foldable qualified as F
 import Data.Functor (($>))
 import Data.IntMap qualified as IM
@@ -1330,13 +1331,16 @@ renderREPLPrompt focus repl = ps1 <+> replE
 drawREPL :: AppState -> Widget Name
 drawREPL s =
   vBox
-    [ withLeftPaddedVScrollBars . viewport REPLViewport Vertical . vBox $ history <> [currentPrompt]
+    [ withLeftPaddedVScrollBars
+        . viewport REPLViewport Vertical
+        . vBox
+        $ [cached REPLHistoryCache (vBox history), currentPrompt]
     , vBox mayDebug
     ]
  where
   -- rendered history lines fitting above REPL prompt
   history :: [Widget n]
-  history = map fmt . getSessionREPLHistoryItems $ repl ^. replHistory
+  history = map fmt . toList . getSessionREPLHistoryItems $ repl ^. replHistory
   currentPrompt :: Widget Name
   currentPrompt = case (isActive <$> base, repl ^. replControlMode) of
     (_, Handling) -> padRight Max $ txt "[key handler running, M-k to toggle]"