mercury_client

defmodule Mercury.CaseConverter do
  @moduledoc """
  Converts the (snake_case, idiomatic-Elixir) keys of maps and keyword lists
  you pass to `create`/`update` functions into the camelCase keys the
  Mercury API expects, recursively.

  Values are left untouched — enum-like values (e.g. payment methods, wire
  types) should be given as atoms or strings that already match Mercury's
  wire format exactly, e.g. `:domesticWire`, `"businessChecking"`.
  """

  @doc "Recursively camelizes the keys of a map, keyword list, or list of either."
  @spec camelize_keys(value :: term()) :: term()
  def camelize_keys(value) when is_map(value) and not is_struct(value) do
    Map.new(value, fn {k, v} -> {camelize(k), camelize_keys(v)} end)
  end

  def camelize_keys(value) when is_struct(value), do: value

  def camelize_keys(value) when is_list(value) do
    if Keyword.keyword?(value) do
      Map.new(value, fn {k, v} -> {camelize(k), camelize_keys(v)} end)
    else
      Enum.map(value, &camelize_keys/1)
    end
  end

  def camelize_keys(value), do: value

  defp camelize(key) when is_atom(key), do: key |> Atom.to_string() |> camelize()

  defp camelize(key) when is_binary(key) do
    case String.split(key, "_") do
      [single] ->
        single

      [first | rest] ->
        Enum.join([first | Enum.map(rest, &String.capitalize/1)])
    end
  end
end