defmodule LineMessage.Event do
  use GenServer

  def start_link do
    GenServer.start_link(__MODULE__, [], name: __MODULE__)
  end

  def on(event_type, module, func) do
    apply_func = fn -> apply(module, func, []) end
    GenServer.cast(__MODULE__, {:on, event_type, module, apply_func})
  end
  def on(event_type, func) do
    GenServer.cast(__MODULE__, {:on, event_type, func})
  end

  def notify(event) do
    GenServer.cast(__MODULE__, {:notify, event})
  end

  def listeners_list do
    GenServer.call(__MODULE__, :listeners)
  end

  def handle_cast({:on, event_type, func}, listeners) do
    {:noreply, [ {event_type, func} | listeners ]}
  end

  def handle_cast({:notify, event}, listeners) do
    Enum.each(listeners, fn {event_type, func} ->
      if event_type == event.type, do: func.(event)
    end)
    {:noreply, listeners}
  end

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