{-|
Moves up one level in the directory tree.
-}
let P =
      https://prelude.dhall-lang.org/v20.1.0/package.dhall
        sha256:26b0ef498663d269e4dc6a82b0ee289ec565d683ef4c00d0ebdd25333a5a3c98

let ascend =
      λ(directory : ./Type) →
        if    P.List.null Text directory.directories
        then  directory ⫽ { parents = directory.parents + 1 }
        else    directory
              ⫽ { directories = P.List.drop 1 Text directory.directories }

let movesUpOneLevel =
        assert
      :   ascend { directories = [ "two", "one" ], file = {=}, parents = 0 }
        ≡ { directories = [ "one" ], file = {=}, parents = 0 }

let canArriveAtCurrentDirectory =
        assert
      : ascend { directories = [ "one" ], file = {=}, parents = 0 } ≡ ../current

let canIntroduceReparenting =
        assert
      :   ascend { directories = [] : List Text, file = {=}, parents = 0 }
        ≡ { directories = [] : List Text, file = {=}, parents = 1 }

let canExtendReparenting =
        assert
      :   ascend { directories = [] : List Text, file = {=}, parents = 2 }
        ≡ { directories = [] : List Text, file = {=}, parents = 3 }

in  ascend