NodeId.elm

NodeId.elm

module Utils.NodeId exposing (NodeId, child, root, toZipper)

import Tree exposing (Tree)
import Tree.Zipper as Zipper exposing (Zipper)



--- NODE ID


type NodeId
    = Child Int NodeId
    | Root


root : NodeId
root =
    Root


child : Int -> NodeId -> NodeId
child =
    Child


toZipper :
    Tree a
    -> NodeId
    -> Maybe (Zipper a)
toZipper treeRoot nodeId =
    case nodeId of
        Root ->
            Zipper.fromTree treeRoot
                |> Just

        Child index nextNodeId ->
            toZipper treeRoot nextNodeId
                |> Maybe.andThen Zipper.firstChild
                |> Maybe.andThen (repeat index Zipper.nextSibling)


repeat : Int -> (x -> Maybe x) -> x -> Maybe x
repeat times fn x =
    if times == 0 then
        Just x

    else
        repeat (abs times - 1) fn x
            |> Maybe.andThen fn