defmodule Child do
  def start_link do
    GenServer.start_link(__MODULE__, [])
  end

  def init(_args) do
    {:ok, 0}
  end

  def handle_info({:info, n}, state) do
    IO.puts "info #{n}"
    {:noreply, state + n}
  end

  def handle_cast({:cast, n}, state) do
    IO.puts "cast #{n}"
    {:noreply, state + n}
  end

  def handle_call({:call, n}, _from, state) do
    IO.puts "call #{n}"
    {:reply, state + n, state + n}
  end
end

defmodule ProcessCommunication do
  def run do
    {:ok, child} = Child.start_link()

    send(child, {:info, 7})
    GenServer.cast(child, {:cast, 17})
    result = GenServer.call(child, {:call, 31})

    IO.puts "Rusult: #{result}"
  end
end