module Main exposing (..)

import Html exposing (..)
import Html.Attributes exposing (..)
import Html.Events exposing (..)
import Html.App as App
import String


-- model


type alias Model =
    String


initModel : Model
initModel =
    ""



-- update


type Msg
    = ChangeInput String


nextInput : String -> String -> String
nextInput current new =
    case String.toInt new of
        Ok _ ->
            new

        Err _ ->
            if new == "" then
                new
            else
                current


update : Msg -> Model -> Model
update msg model =
    case msg of
        ChangeInput newInput ->
            nextInput model newInput



-- view


view : Model -> Html Msg
view model =
    div []
        [ input
            [ type' "text"
            , value model
            , onInput ChangeInput
            ]
            []
        ]


main : Program Never
main =
    App.beginnerProgram
        { model = initModel
        , update = update
        , view = view
        }