server.ex

defmodule QuotesBot.Polling.Server do
  use GenServer
  alias QuotesBot.{Polling.Logic, Config}

  def start_link do
    GenServer.start_link(__MODULE__, 0, name: __MODULE__)
  end

  def init(offset) do
    schedule_polling()

    {:ok, offset}
  end

  def handle_info(:poll, offset) do
    new_offset = poll(offset)
    schedule_polling()

    {:noreply, new_offset + 1}
  end

  @spec poll(integer()) :: integer()
  defp poll(offset) do
    Logic.poll(offset)
  end

  defp schedule_polling do
    Process.send_after(self(), :poll, Config.polling_period)
  end
end