todo_server.exs

defmodule Todo.Server do
  use GenServer
  def init(_) do
    {:ok, Todo.List.new}
  end

  def start do
    GenServer.start(Todo.Server, nil)
  end

  def add_entry(todo_server, new_entry) do
    GenServer.cast(todo_server, {:add_entry, new_entry})
  end

  def entries(todo_server, date) do
    GenServer.call(todo_server, {:entries, date})
  end

  def update_entry(todo_server, id, updater) do
    GenServer.cast(todo_server, {:update_entry, id, updater})
  end

  def delete(todo_server, id) do
    GenServer.cast(todo_server, {:delete, id})
  end

  def handle_call({:entries, date}, _,state) do
    {:reply, Todo.List.entries(state, date), state}
  end

  def handle_cast({:add_entry, new_entry}, state) do
    {:noreply, Todo.List.add_entry(state, new_entry)}
  end

  def handle_cast({:update_entry, id, updater}, state) do
    {:noreply, Todo.List.update_entry(state, id, updater)}
  end

  def handle_cast({:delete, id}, state) do
    {:noreply, Todo.List.delete(state, id)}
  end
end