Separate backend and frontend

frontend/src/Main.hs

@@ -0,0 +1,41 @@
+{-# LANGUAGE GeneralizedNewtypeDeriving #-}
+{-# LANGUAGE LambdaCase                 #-}
+{-# LANGUAGE OverloadedStrings          #-}
+{-# LANGUAGE RecordWildCards            #-}
+module Main where
+
+import           Control.Monad.Trans              (liftIO)
+import           Language.Javascript.JSaddle.Warp
+import           Miso
+import           Miso.String
+
+data Action = Add
+            | Subtract
+            | SayHello
+            | NoOp
+
+newtype Model = Model Int deriving (Eq, Num, ToMisoString)
+
+updateModel :: Action -> Model -> Effect Action Model
+updateModel Add m      = noEff (m + 1)
+updateModel Subtract m = noEff (m - 1)
+updateModel SayHello m = m <# (liftIO (putStrLn "Hello world") >> pure NoOp)
+updateModel NoOp m     = noEff m
+
+viewModel :: Model -> View Action
+viewModel x =
+  div_ [] [ button_  [ onClick Add ] [ text "+" ]
+          , text (ms x)
+          , button_ [ onClick Subtract ] [ text "-" ]
+  ]
+
+main :: IO ()
+main = run 8081 $ startApp App{..}
+  where
+    model = Model 0
+    initialAction = SayHello
+    update = updateModel
+    view = viewModel
+    subs = []
+    events = defaultEvents
+    mountPoint = Nothing