elm-random-gif-translation-to-redux.js

// Elm code from https://github.com/evancz/elm-architecture-tutorial#example-5-random-gif-viewer
// 
// type Action
//     = RequestMore
//     | NewGif (Maybe String)
// 
// 
// update : Action -> Model -> (Model, Effects Action)
// update msg model =
//   case msg of
//     RequestMore ->
//       ( model
//       , getRandomGif model.topic
//       )
// 
//     NewGif maybeUrl ->
//       ( Model model.topic (Maybe.withDefault model.gifUrl maybeUrl)
//       , Effects.none
//       )
// 
// -- getRandomGif : String -> Effects Action

/* 
 * @flow
 * 
 * translation to pseudo-redux:
 */
function reducer(state: Model, action: Action): [Model, Effects] {
  switch(action.type) {
  case RequestMore:
    return [state, getRandomGif(state.topic)];
  case NewGif:
    if (action.gifUrl) {
      return [{...state, gifUrl: action.gifUrl}, null];
    } else {
      return state;
    }
  default:
    return state;
  }
}