defmodule Todo do
  use GenServer

  def init(tasks // "") do
    {:ok, tasks}
  end

  def handle_cast({:add, task}, tasks) do
    {:noreply, tasks <> " | " <>  task}
  end

  def handle_cast({:remove, task}, tasks) do
    {:noreply, tasks |> String.replace("| #{task}", "")}
  end

  def handle_call(:all, _from,  tasks) do
    {:reply, tasks, tasks}
  end
end

# {:ok, pid} = GenServer.start(Todo, "foo")
# tasks = GenServer.call(pid, :all)
# GenServer.cast(pid, {:add, "bar"})
# GenServer.cast(pid, {:remove, "bar"})

## TODO
  # Encapsolate the GenServer logic in the module