defmodule GenConsumer do
  @moduledoc """
  Documentation for GenConsumer.

  ## Usage

      defmodule MyApp.EventHandler do
        use GenConsumer, otp_app: :my_app

        @impl true
        def handle(event, state) do
          {:ok, state}
        end

      end
  """

  @doc false
  defmacro __using__(opts) do
    quote bind_quoted: [opts: opts] do
      use GenServer

      config = GenConsumer.Config.compile_config(__MODULE__, opts)
      @config config

      def __adapter__, do: @config

      def child_spec(opts) do
        %{
          id: __MODULE__,
          start: {__MODULE__, :start_link, [opts]},
          type: :worker
        }
      end

      def start_link(opts \\ []) do
        opts = Keyword.merge(@config.opts, opts)
        name = Keyword.get(opts, :name, __MODULE__)
        GenServer.start_link(__MODULE__, opts, name: name)
      end

      def init(opts) do
        callback = __MODULE__.handle_event/1
        opts = Keyword.put(opts, :callback, callback) |> IO.inspect
        @config.module.init(opts)
      end

      def handle_event(_) do
        :ok
      end

      defoverridable handle_event: 1

    end
  end

end