starkcore

defmodule StarkCore.Utils.Case do
  @moduledoc false

  def camel_to_kebab(string) do
    string
    |> camel_to_snake()
    |> String.replace("_", "-")
  end

  def camel_to_snake(string) do
    string
    |> String.graphemes()
    |> camel_to_snake_graphemes()
    |> strip_underscore()
    |> Enum.join()
  end

  defp camel_to_snake_graphemes([letter | rest]) do
    cond do
      letter == letter |> String.upcase() ->
        ["_" | [String.downcase(letter) | camel_to_snake_graphemes(rest)]]

      :error != Integer.parse(letter) ->
        ["_" | [letter | camel_to_snake_graphemes(rest)]]

      true ->
        [letter | camel_to_snake_graphemes(rest)]
    end
  end

  defp camel_to_snake_graphemes([]) do
    []
  end

  defp strip_underscore([letter | rest]) when letter == "_" do
    rest
  end

  defp strip_underscore(string) do
    string
  end

  def snake_to_camel(string) do
    string
    |> String.graphemes()
    |> snake_to_camel_graphemes()
    |> Enum.join()
  end

  defp snake_to_camel_graphemes([letter | rest]) when letter == "_" do
    snake_to_camel_graphemes([String.upcase(hd(rest)) | tl(rest)])
  end

  defp snake_to_camel_graphemes([letter | rest]) do
    [letter | snake_to_camel_graphemes(rest)]
  end

  defp snake_to_camel_graphemes([]) do
    []
  end
end