defmodule BridgeEx.Graphql.Formatter.CamelCase do
  @moduledoc """
  Formatter to format map keys to camelCase.
  """

  @behaviour BridgeEx.Graphql.Formatter.Adapter

  @spec format(any()) :: map()
  def format(variable) when is_map(variable) do
    case Enumerable.impl_for(variable) do
      nil ->
        variable

      _ ->
        variable
        |> Enum.map(fn
          {key, value} -> {format_key(key), format(value)}
        end)
        |> Map.new()
    end
  end

  def format(variable) when is_list(variable) do
    Enum.map(variable, &format(&1))
  end

  def format(variable), do: variable

  defp format_key(key) when is_atom(key) do
    key
    |> Atom.to_string()
    |> Absinthe.Utils.camelize(lower: true)
    |> String.to_atom()
  end

  defp format_key(key) when is_binary(key) do
    Absinthe.Utils.camelize(key, lower: true)
  end

  defp format_key(key), do: key
end