Elm architecture in Haskell: A study case

Elm.hs

data Model = Model
    { name :: String
    , gender :: String
    , loading :: Bool
    , homeworld :: String
    } deriving (Show)


data PersonResponse = PersonResponse
    { personName :: String
    , personGender :: String
    , personLoading :: Bool
    , personHomeworldUrl :: String
    } deriving (Show)


data RealWorldResponse = RealWorldResponse
    { worldName :: String
    } deriving (Show)


data Msg
    = PersonResponseMsg PersonResponse
    | RealWorldResponseMsg RealWorldResponse
    deriving (Show)


update :: Model -> Msg -> (Model, Operation)
update model msg =
    case msg of
        PersonResponseMsg personResponse ->
            (model { name = personName personResponse }, Cmd doRealWorldRequest)
        RealWorldResponseMsg realWorldResponse ->
            ( model { homeworld = worldName realWorldResponse }, CmdNone)


doPersonRequest :: IO Msg
doPersonRequest =
    return $ PersonResponseMsg $ PersonResponse
        { personName = "Carlos"
        , personGender = "male"
        , personLoading = False
        , personHomeworldUrl = "https://github.com/carlosmaniero/"
        }


doRealWorldRequest :: IO Msg
doRealWorldRequest =
    return $ RealWorldResponseMsg $ RealWorldResponse { worldName = "Moon" }


data Operation
    = Cmd (IO Msg)
    | CmdNone


startApplication :: Model -> IO Msg -> IO Model
startApplication model cmd = do
    msg <- cmd
    putStrLn $ show msg
    putStrLn $ show model
    let (model, operation) = update model msg
    case operation of
        Cmd nextCmd ->
            startApplication model nextCmd
        CmdNone ->
            return model


main = do
    let model = Model { name = ""
                      , gender = ""
                      , loading = False
                      , homeworld = ""
                      }
    finalModel <- startApplication model doPersonRequest
    putStrLn $ show finalModel