Union type lists, and data structure help from elm slack for diffing purposes (Thanks @gilbert, and jordan.wilcken)

UnionTypePlayground.elm

module Main exposing (..)

import Html exposing (Html, text, div, img)


---- MODEL ----


type alias Transition =
    { transitionType : String, toStoryNode : Int, text : Maybe String }


type alias NewsItem =
    { id : Int
    , content : List (Html Msg)
    }


type alias ChatMessage =
    { id : Int
    , chatId : Int
    , userId : Int
    , content : List (Html Msg)
    }


type alias StoryNode =
    { id : Int
    , nodeType : NodeType
    , nodeContent : StoryNodeContent
    , state : Maybe String
    , transitions : List Transition
    }


type NodeType
    = NewsNode
    | ChatNode


type StoryNodeContent
    = NewsItemContent NewsItem
    | ChatMessageContent ChatMessage


type alias Player =
    { visitedStoryNodes : List StoryNode
    , currentStoryNode : Maybe StoryNode
    }


type alias Model =
    {}


init : ( Model, Cmd Msg )
init =
    ( {}, Cmd.none )



---- UPDATE ----


type Msg
    = NoOp


update : Msg -> Model -> ( Model, Cmd Msg )
update msg model =
    ( model, Cmd.none )



---- VIEW ----


findById : Int -> List StoryNode
findById id =
    rawStoryNodes
        |> List.filter
            (\node -> node.id == id)


nodeTypeToString : NodeType -> String
nodeTypeToString nodeType =
    case nodeType of
        ChatNode ->
            "ChatNode"

        NewsNode ->
            "NewsNode"


mapListFn : List String
mapListFn =
    List.map
        (nodeTypeToString << .nodeType)
        rawStoryNodes


view : Model -> Html Msg
view model =
    -- div []
    --     [ text (unionFn (ARecord { id = 1, nestedRecord = { string = "String" } })) ]
    div []
        [ text (toString mapListFn)
        , text (toString (findById 5))
        ]



---- PROGRAM ----


main : Program Never Model Msg
main =
    Html.program
        { view = view
        , init = init
        , update = update
        , subscriptions = always Sub.none
        }


rawStoryNodes : List StoryNode
rawStoryNodes =
    [ { id = 1
      , nodeType = ChatNode
      , state = Nothing
      , nodeContent =
            ChatMessageContent
                { id = 1
                , chatId = 1
                , userId = 1
                , content = [ text "1: [1]" ]
                }
      , transitions =
            [ { transitionType = "AUTOMATIC"
              , toStoryNode = 2
              , text = Nothing
              }
            ]
      }
    , { id = 5
      , nodeType = NewsNode
      , state = Nothing
      , nodeContent =
            NewsItemContent
                { id = 4
                , content = [ text "2: [1]" ]
                }
      , transitions =
            [ { transitionType = "OptionInList"
              , toStoryNode = 6
              , text = Just "6"
              }
            , { transitionType = "OptionInList"
              , toStoryNode = 6
              , text = Just "6"
              }
            ]
      }
    ]