http1.elm

import Html exposing (..)
import Html.Attributes exposing (..)
import Html.Events exposing (..)
import Http
import Json.Decode as Decode


main =
    Html.program
    { init = init "cats"
    , view = view
    , update = update
    , subscriptions = subscriptions
    }


--MODEL

type alias Model = 
    { topic : String
    , gifUrl : String
    , error : String
    }


init : String -> (Model, Cmd Msg)
init topic =
  ( Model topic "waiting.gif" ""
  , getRandomGif topic
  )


--UPDATE

type Msg = MorePlease | NewGif (Result Http.Error String)

update : Msg -> Model -> (Model, Cmd Msg)
update msg model =
    case msg of 
        MorePlease -> 
            (model, getRandomGif model.topic)
        NewGif (Ok newUrl) ->
            ({model | gifUrl = newUrl, error = "OK" }, Cmd.none)
        NewGif (Err err) ->
            ({model | gifUrl = "", error = toString err }, Cmd.none)


--VIEW

view : Model -> Html Msg
view model =
    div []
    [ select [] [ option [] [ text model.topic ], option [] [ text "pig" ] ] 
    , img [ src model.gifUrl ] []
    , button [ onClick MorePlease ] [ text "More Pleased" ]
    , span [] [ text  model.error ]
    ]


--SUBSCRIPTIONS

subscriptions : Model -> Sub Msg
subscriptions model =
    Sub.none


--HTTP  

getRandomGif : String -> Cmd Msg
getRandomGif topic =
    let 
        url = "https://api.giphy.com/v1/gifs/random?api_key=dc6zaTOxFJmzC&tag=" ++ topic
        request = Http.get url decodeGifUrl
    in 
        Http.send NewGif request


decodeGifUrl : Decode.Decoder String
decodeGifUrl =
    Decode.at ["data", "image_url"] Decode.string