Dummy front

default.nix

@@ -1,11 +1,18 @@
 { nixpkgs, haskellPackages }:
 
-let jsaddle = nixpkgs.fetchFromGitHub {
+let
+  jsaddle = nixpkgs.fetchFromGitHub {
     owner = "ghcjs";
     repo = "jsaddle";
     rev = "68208be806c49a2a0c9f037dfac85feae10a8c80";
     sha256 = "0acj0x716ikfb08ndib36jmwxkwq399lvkip46sfkh1ynn0pvc1c";
   };
+  miso = nixpkgs.fetchFromGitHub {
+    owner = "dmjio";
+    repo = "miso";
+    rev = "a9c4f0a3a6e7d87f9432dc6cf4b1d0c052bf7ef1";
+    sha256 = "1yq5y4vffslm6abnfnggp5m3k6vla6mzcwmhmm23l8yizsvdkwv2";
+  };
 
 in
 
@@ -19,6 +26,7 @@ in
     generic-lens = nixpkgs.haskell.lib.dontCheck super.generic-lens;
     jsaddle-warp = nixpkgs.haskell.lib.dontCheck (super.callPackage (jsaddle + "/jsaddle-warp") {});
     jsaddle = super.callPackage (jsaddle + "/jsaddle") {};
+    miso = super.callPackage (miso + "/miso-ghc-jsaddle.nix") {};
   };
   tools = with haskellPackages; [
     ghcid

frontend/frontend.cabal

@@ -23,5 +23,6 @@ executable frontend
                      , common
                      , miso
                      , jsaddle-warp
+                     , mtl
   hs-source-dirs:      src
   default-language:    Haskell2010

frontend/src/Main.hs

@@ -1,4 +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 = putStrLn "Hello, Haskell!"
+main = run 8081 $ startApp App{..}
+  where
+    model = Model 0
+    initialAction = SayHello
+    update = updateModel
+    view = viewModel
+    subs = []
+    events = defaultEvents
+    mountPoint = Nothing