Decoders in Elm

Decoder.elm

[deprecated]. See : https://gist.github.com/TwistingTwists/1bf880bea1300a26966ddccd9a2c7c8e

-- using Json.Decoder.Pipeline -- elm install noredink/elm-decode-pipeline

{- 

Please take note that in 

type Map = Map {version: String, node : Node}

is not  `List` of `Node` type. It is RootNode. Does the following make more sense? 

type Map = Map {version: String, root_node : Node}

instead of line 6 ?

-}
module Main exposing (Map(..))

-- import Json.Encode

import Element exposing (Color)
import Html
import Json.Decode as Decode exposing (Decoder, decodeString, float, int, lazy, list, nullable, string)
import Json.Decode.Pipeline exposing (hardcoded, optional, required)
import Time


type Map
    = Map
        { version : String
        -- root node
        , node : Node
        }


type Node
    = Node String NodeAttributes (List Node)


type alias NodeAttributes =
    { style : Maybe String
    , folded : Bool
    , id : Maybe String
    , created : Maybe Time.Posix
    , modified : Maybe Time.Posix

    -- , position : Maybe Position
    }



-- Decoders

timestamp : Decoder Time.Posix
timestamp =
  Decode.map Time.millisToPosix Decode.int


decodeMindMap : Decoder Map
decodeMindMap =
    Decode.succeed Map
        |> required "@version" string
        -- should there be a separate `decodeRootNode`
        |> required "node" decodeNode


decodeNode : Decoder Node
decodeNode =
    let
        decodeNodeAttributes =
            Decode.succeed NodeAttributes
                |> required "@LOCALIZEDSTYLEREF" (nullable string)
                |> required "@FOLDED" bool
                |> required "@ID" (nullable string)
                |> required "@CREATED" (nullable timestamp)
                |> required "@MODIFIED" (nullable timestamp)
    in
    Decode.succeed Node
        |> required "@TEXT" string
        |> ???? decodeNodeAttributes
        |> required "node" (list (lazy (\_ -> decodeNode)))

main =
    Html.text (Debug.toString Node)

sample.json

{
  "map": {
    "@version": "freeplane 1.7.0",
    "node": 
    {
      "@TEXT": "UPSC",
      "@LOCALIZED_STYLE_REF": "default",
      "@FOLDED": "false",
      "@ID": "ID_523629448",
      "@CREATED": "1487759666321",
      "@MODIFIED": "1489498611522",
      "node": [
        {
          "@TEXT": "TIME",
          "@ID": "ID_414266408",
          "@CREATED": "1490340755453",
          "@MODIFIED": "1490340755929"
        },
        {
          "@TEXT": "CLASSES",
          "@ID": "ID_1943867701",
          "@CREATED": "1490340779136",
          "@MODIFIED": "1490340918221"
        },
        {
          "@TEXT": "Magnify",
          "@ID": "ID_1818534457",
          "@CREATED": "1490340772926",
          "@MODIFIED": "1490341014628"
        }
      ]
    }
  }
}