defmodule JwtDecoder do

  @moduledoc """
    Module that references jwt helper
  """

  def get_data(jwt, padding \\ false) do
    with {:ok, payload_base64} <- get_payload_encode(jwt),
         {:ok, payload} <- decode_base64(payload_base64, padding),
         {:ok, payload_map} <- decode_string_to_map(payload),
         payload_struct <- map_to_atom(payload_map) do

      {:ok, payload_struct}
    else
      :error_decode_base64 -> :error_decode_base64
      :error_get_payload_encode -> :error_get_payload_encode
      :error_decode_string_to_map -> :error_decode_string_to_map
    end
  end

  defp get_payload_encode(jwt) do
    with splitted_jwt <- String.split(jwt, "."),
         3 <- Enum.count(splitted_jwt),
         payload_base64 <- Enum.at(splitted_jwt, 1) do

      {:ok, payload_base64}
      else
      _ -> :error_get_payload_encode
    end
  end

  defp decode_string_to_map(value) do
    case Poison.decode(value) do
      {:ok, map} -> {:ok, map}
      _ -> :error_decode_string_to_map
    end
  end

  defp decode_base64(value, padding) do
    case Base.decode64(value, padding: padding) do
      {:ok, payload} -> {:ok, payload}
      _ -> :error_decode_base64
    end
  end

  defp map_to_atom(map), do: Map.to_list(map) |> Enum.map(fn {k, v} -> {String.to_atom(k), v} end) |> Map.new()
end