Restartable timer

SuperTimer.elm

module SuperTimer where

import Html exposing (..)
import Html.Events exposing (onClick)
import Time exposing (Time)
import Signal exposing (Address)

type Action = Tick Time | Toggle Bool

type alias Model = { running: Bool, count: Float}

model : Model
model = {running = False, count = 0}

view : Model -> Html.Html
view {running, count} =
  div []
    [ div [] [ text (toString (count / 1000)) ]
    , button
      [ onClick mailbox.address (not running) ]
      [ text (if running then "Stop Timer" else "Start Timer") ]
    ]

mailbox = Signal.mailbox model.running

clicks : Signal Bool
clicks = mailbox.signal

ticks : Signal Action
ticks = Signal.map Tick (Time.fpsWhen 60 clicks)

actions : Signal Action
actions = Signal.merge (Signal.map Toggle clicks) ticks

update : Action -> Model -> Model
update action model =
  case action of
    Tick dt ->
      if model.running then
        { model | count = model.count + dt }
      else
        model
     
    Toggle b ->
      { model | running = b }
      
model_signal : Signal Model
model_signal =
  Signal.foldp update model actions

main : Signal Html.Html
main =
  Signal.map view model_signal