Token HTTP Authentication in Elm

Main.elm

import Html.App as Html
import Html exposing (..)
import Html.Events exposing (..)
import Task
import Http
import Json.Decode as Json exposing ((:=))


-- Model


type alias Model =
    { token : Token
    , pendingRequests : List (String -> Task.Task Never Msg)
    , ip : String
    }


type Token
    = Valid String
    | Invalid
    | Refreshing


init : ( Model, Cmd Msg )
init =
    ( Model (Valid "expired") [] "no ip", Cmd.none )



-- Update


type Msg
    = Fetch
    | FetchFailure Http.Error
    | SaveIp String
    | SaveRequest (String -> Task.Task Never Msg)
    | RefreshTokenFailed Never
    | UpdateToken String
    | SendPendingRequests ()


attemptWithToken : Token -> (x -> msg) -> (a -> msg) -> (String -> Task.Task x a) -> Cmd msg
attemptWithToken token failureMsg successMsg requestWithoutToken =
    case token of
        Invalid ->
            Cmd.none

        Refreshing ->
            Cmd.none

        Valid token ->
            Task.perform failureMsg successMsg (requestWithoutToken token)


update : Msg -> Model -> ( Model, Cmd Msg )
update msg model =
    case msg of
        Fetch ->
            ( model, attemptWithToken model.token FetchFailure SaveIp fetchIp )

        FetchFailure error ->
            ( { model | token = Refreshing }, Task.perform RefreshTokenFailed UpdateToken (Task.succeed "valid") )

        SaveIp ip ->
            ( { model | ip = ip }, Cmd.none )

        -- Token Logic
        SaveRequest request ->
            ( { model | pendingRequests = request :: model.pendingRequests }, Cmd.none )

        RefreshTokenFailed error ->
            ( model, Cmd.none )

        UpdateToken newToken ->
            ( { model | token = Valid newToken }, Task.perform SendPendingRequests SendPendingRequests (Task.succeed ()) )

        SendPendingRequests _ ->
            ( model, Cmd.none )



-- View


view : Model -> Html Msg
view model =
    div []
        [ button [ onClick Fetch ] [ text "send request" ]
        , text model.ip
        ]



-- Request


fetchIp : String -> Task.Task Http.Error String
fetchIp token =
    if token == "expired" then
        Http.get ("ip" := Json.string) ("http://thisfails" ++ token)
    else
        Http.get ("ip" := Json.string) ("http://jsonip.com?token=" ++ token)



-- Main


main : Program Never
main =
    Html.program
        { init = init
        , update = update
        , view = view
        , subscriptions = \_ -> Sub.none
        }