Decoder.elm

module Decoder exposing (..)

import Json.Decode as Decode exposing ((:=))
import Json.Decode.Extra as Decode exposing ((|:))


type Foo
    = Bar String Int
    | Baz String Int


decode : Decode.Decoder Foo
decode =
    "type" := Decode.string `Decode.andThen` decodeType
    -- ("type" := Decode.string) `Decode.andThen` decodeType


decodeType : String -> Decode.Decoder Foo
decodeType tipe =
    let
        base =
            case tipe of
                "bar" ->
                    Decode.succeed Bar
                        |: ("name" := Decode.string)

                "baz" ->
                    Decode.succeed Baz
                        |: ("name" := Decode.string)

                _ ->
                    Decode.fail ("Type `" ++ tipe ++ "` not supported")
    in
        base
            |: ("count" := Decode.int)


barJson : String
barJson =
    """
      {
        "type": "bar",
        "name": "MyBar",
        "count": 123
      }
      """


decoded : Result String Foo
decoded =
    Decode.decodeString decode barJson


_ =
    Debug.log "decoded?" decoded