defmodule EchoServer.Echo do

  def accept(port) do
    {:ok, socket} = :gen_tcp.listen(
      port,
      [:binary, packet: :line, active: false, reuseaddr: true])
    loop_acceptor(socket)
  end

  defp loop_acceptor(socket) do
    {:ok, client} = :gen_tcp.accept(socket)
    {:ok, pid} = Task.Supervisor.start_child(
      EchoServer.TaskSupervisor, fn -> serve(client) end)
    :ok = :gen_tcp.controlling_process(client, pid)
    loop_acceptor(socket)
  end

  defp serve(socket) do
    socket
      |> read_line
      |> (fn(x) -> "> " <> x end).()
      |> write_line(socket)

    serve(socket)
  end

  defp read_line(socket) do
    {:ok, data} = :gen_tcp.recv(socket, 0)
    data
  end

  defp write_line(line, socket) do
    :gen_tcp.send(socket, line)
  end

end