defmodule NeonVertigoService.MessageProcessor do
  alias NeonVertigoService.Repo

  def process_message(mqtt_pid, {"auctions", "create"}, payload, properties) do
    changeset = Auction.changeset(%Auction{}, payload)
    reply = case Repo.insert(changeset) do
      {:ok, auction} ->
        %{ok: true, gid: auction.gid}
      {:error, changeset} ->
        %{ok: false, gid: changeset |> Ecto.Changeset.get_field(:gid)}
    end

    reply(reply, mqtt_pid, properties)
  end

  def process_message(_, _, _, _) do
    {:ok, :unknown_message}
  end

  defp reply(data, mqtt_pid, orig_properties, message_properties \\ []) do
    response_topic = orig_properties[:"Response-Topic"]
    if is_nil(response_topic) do
      {:ok, :no_response_topic}
    else
      send_mqtt(data, mqtt_pid, response_topic, message_properties)
    end
  end

  defp send_mqtt(data, mqtt_pid, response_topic, message_properties \\ [])

  defp send_mqtt(data, mqtt_pid, response_topic, message_properties) when is_binary(response_topic) and byte_size(response_topic) > 0 do
    if String.valid?(response_topic) && String.length(response_topic) > 0 do
      :emqtt.publish(mqtt_pid, response_topic, JSON.encode!(data), message_properties)
    else
      {:error, :invalid_topic}
    end
  end

  defp send_mqtt(_, _, _, _), do: {:error, :invalid_topic}
end