Simple typing interface with FRP

Typer.hs

module ReactionTest
    ( main
    ) where

import Control.Event.Handler
import Reactive.Banana
import Reactive.Banana.Frameworks

import System.IO
import System.Console.ANSI
import Control.Monad

main :: IO ()
main = do
    -- Setup the fancy UI
    hSetEcho stdin False
    hSetBuffering stdin NoBuffering
    showCursor
    resetScreen

    (addHandler, pushEvent) <- newAddHandler

    network <- compile $ sentenceNetwork addHandler
    actuate network

    forever $ getChar >>= pushEvent

resetScreen :: IO ()
resetScreen = setCursorPosition 0 0 >> clearScreen

data CharAction = DEL | ADD Char

sentenceNetwork :: AddHandler Char -> MomentIO ()
sentenceNetwork addHandler = do
    eChar <- fromAddHandler addHandler
    let eCharAction = toCharAction <$> eChar

    bString <- accumB "" $ handleCharAction <$> eCharAction
    eStringChange <- changes bString
    reactimate' $ fmap logString <$> eStringChange
  where
    toCharAction '\DEL' = DEL
    toCharAction c      = ADD c
    handleCharAction DEL     = init
    handleCharAction (ADD c) = \s -> s ++ pure c
    logString s = resetScreen >> putStrLn s