import Html exposing (Html, text)
import Svg exposing (Svg, svg, circle)
import Svg.Attributes exposing (width, height, viewBox, cx, cy, r)
import Time exposing (Time, every, second, inSeconds)

type alias Model =
  { x : Float
  , y : Float
  , r : Float
  }

model : Model
model = Model 400 300 25

init : (Model, Cmd Msg)
init = (model, Cmd.none)

type Msg = Tick Time

subscriptions : Model -> Sub Msg
subscriptions model =
  every (second / 60) Tick

updateBall : Model -> Time -> Model
updateBall model t =
  let speed = t / 2 in
  let angle = turns <| inSeconds speed in
  { x = (cos angle) * 200 + 400
  , y = (sin angle) *  50 + 300
  , r = (sin angle) *   8 +  25
  }

update : Msg -> Model -> (Model, Cmd Msg)
update msg model =
  case msg of
    Tick t -> (updateBall model t, Cmd.none)

view : Model -> Html Msg
view model =
  svg
    [ width "800"
    , height "600"
    , viewBox "0 0 800 600"
    ]
    [ circle
        [ cx <| toString model.x
        , cy <| toString model.y
        ,  r <| toString model.r
        ] []
    ]

main : Platform.Program Never Model Msg
main =
  Html.program
    { init = init
    , subscriptions = subscriptions
    , update = update
    , view = view
    }