CounterNavigation.elm

import Html
import Html.App
import Html.Attributes exposing (..)
import Html.Events exposing (onClick)
import Navigation exposing (Location)
import RouteUrl
import RouteUrl exposing (UrlChange, HistoryEntry(NewEntry))
import String


type alias Model = Int
type Msg = Increment | Decrement | Reset | Set Int


update : Msg -> Model -> (Model, Cmd Msg)
update msg model =
  case msg of
    Increment -> (model + 1, Cmd.none)
    Decrement -> (model - 1, Cmd.none)
    Set value -> (value, Cmd.none)
    Reset -> (0, Cmd.none)


view : Model -> Html.Html Msg
view model =
  Html.div
    []
    [ Html.h1 [] [Html.text <| toString model]
    , Html.br [] []
    , Html.button [onClick Increment] [Html.text "Increment"]
    , Html.button [onClick Decrement] [Html.text "Decrement"]
    , Html.button [onClick Reset] [Html.text "Reset"]
    ]


delta2url : Model -> Model -> Maybe UrlChange
delta2url previous current =
  Just (UrlChange NewEntry ("#" ++ toString current))


location2messages : Location -> List Msg
location2messages location =
  case String.toInt <| String.dropLeft 1 location.hash of
    Ok count ->
      [Set count]

    _ ->
      []


main : Program Never
main =
  RouteUrl.program
    { init = (0, Cmd.none)
    , subscriptions = (\_ -> Sub.none)
    , update = update
    , view = view
    , delta2url = delta2url
    , location2messages = location2messages
    }