simple_dns.ex

defmodule SimpleDNS do
  def start do
    pid = spawn __MODULE__, :loop, [%{}]
    {:ok, pid}
  end

  def get_entry(pid, hostname) do
    send pid, {self(), {:get_entry, hostname}}
    get_response pid
  end

  def add_entry(pid, hostname, ip) do
    send pid, {self(), {:add_entry, hostname, ip}}
    get_response pid
  end

  def loop(dns_entries) do
    receive do
      {from, {:get_entry, hostname}} ->
        ip = Map.get dns_entries, hostname
        send from, {self(), ip}
        loop dns_entries
      {from, {:add_entry, hostname, new_ip}} ->
        updated_dns_entries = Map.put dns_entries, hostname, new_ip
        send from, {self(), :ok}
        loop updated_dns_entries
    end
  end

  defp get_response(pid) do
    receive do
      {^pid, msg} ->
        msg
      _ -> :error
    end
  end
end