Add a very basic, naive auto-move command

Add a very basic, naive auto-move command, which just steps the player
in a direction until they collide with something, regardless of any
surrounding beasties who might want to eat them.

There's a lot of other stuff going on here - in order to get this
working the way I wanted with a slight (I settled on 50ms) delay between
every step in these autocommands while still redrawing in between I had
to do all the extra machinery for custom Brick events with a channel,
and then at the same time adding the bits for actually executing
autocommands in a general fashion (because there will definitely be
more!) hit my threshold for size for App.hs which sent me on a big
journey to break it up into smaller files -- which seems actually like
it was quite successful. Hopefully this will help with compile times
too, though App.hs is still pretty slow (maybe more to do here).

1 files changed, 44 insertions, 0 deletions

diff --git a/src/Xanthous/App/Autocommands.hs b/src/Xanthous/App/Autocommands.hs
new file mode 100644
index 000000000000..e8d94ce741fd
--- /dev/null
+++ b/src/Xanthous/App/Autocommands.hs
@@ -0,0 +1,44 @@
+--------------------------------------------------------------------------------
+module Xanthous.App.Autocommands
+  ( runAutocommand
+  , autoStep
+  ) where
+--------------------------------------------------------------------------------
+import Xanthous.Prelude
+--------------------------------------------------------------------------------
+import Control.Concurrent (threadDelay)
+--------------------------------------------------------------------------------
+import Xanthous.App.Common
+import Xanthous.App.Time
+import Xanthous.Data
+import Xanthous.Data.App
+import Xanthous.Entities.Character (speed)
+import Xanthous.Game.State
+--------------------------------------------------------------------------------
+
+autoStep :: Autocommand -> AppM ()
+autoStep (AutoMove dir) = do
+  newPos <- uses characterPosition $ move dir
+  collisionAt newPos >>= \case
+    Nothing -> do
+      characterPosition .= newPos
+      stepGameBy =<< uses (character . speed) (|*| 1)
+      describeEntitiesAt newPos
+    Just _ -> cancelAutocommand
+
+--------------------------------------------------------------------------------
+
+autocommandIntervalμs :: Int
+autocommandIntervalμs = 1000 * 50 -- 50 ms
+
+runAutocommand :: Autocommand -> AppM ()
+runAutocommand ac = do
+  env <- ask
+  tid <- liftIO . async $ runReaderT go env
+  autocommand .= ActiveAutocommand ac tid
+  where
+    go = everyμs autocommandIntervalμs $ sendEvent AutoContinue
+
+-- | Perform 'act' every μs microseconds forever
+everyμs :: MonadIO m => Int -> m () -> m ()
+everyμs μs act = act >> liftIO (threadDelay μs) >> everyμs μs act