defmodule ExWeb.Assets do
  defmacro __using__(opts) do
    quote do
      @before_compile unquote(__MODULE__)

      def init(options) do
        options
      end

      def asset_map do
        %{}
      end

      defoverridable [asset_map: 0]
    end
  end

  defmacro __before_compile__(_env) do

    module_name = __CALLER__.module

    root_folder = "assets"
    [_lang_root_mod, _app_name|folder_modules] = "#{module_name}" |> String.split(".")

    inner_folder_name = Enum.map(folder_modules, &String.downcase(&1)) |> Path.join

    folder = Path.join(root_folder, inner_folder_name)

    quote do
      require Logger
      def call(%{path_info: path_info} = conn, _opts) do
        {:ok, start_folder} = File.cwd
        folder = Path.join(start_folder, unquote(folder))
        Logger.debug "[ExWeb] Assets served from #{folder}"
        location_of_file = Path.join(path_info)
        location_of_file = Map.get(asset_map(), location_of_file) || location_of_file
        file = Path.join(unquote(folder), location_of_file)
        case File.stat(file) do
          {:ok, %{type: :regular}}  -> Plug.Conn.send_file(conn, 200, file)
          _                         -> ExWeb.Errors.render(conn, 404)
        end
      end
    end
  end
end