defmodule ElementTui.Tui do
  @moduledoc """
  This genserver will be started by the application. It will also handle drawing, in order to make sure we write single threaded. In general a user should not need to use this directly, but instead use the main ElementTui module.
  """
  use GenServer

  alias ElementTui.TermBox2Ex

  def start_link(opts \\ []) do
    GenServer.start_link(__MODULE__, %{}, opts)
  end

  def puts(x, y, attr, bg_attr, line) do
    GenServer.cast(ElementTui.Tui, {:puts, x, y, attr, bg_attr, line})
  end

  def clear do
    GenServer.cast(ElementTui.Tui, :clear)
  end

  def clear_region(x, y, width, height) do
    GenServer.cast(ElementTui.Tui, {:clear_region, x, y, width, height})
  end

  def present() do
    GenServer.cast(ElementTui.Tui, {:present})
  end

  def poll(timeout_ms) do
    # TODO: we should pass current time, so we account for potential delay in message handling
    GenServer.call(ElementTui.Tui, {:poll, timeout_ms})
  end

  @impl true
  def init(init) do
    TermBox2Ex.ex_start()
    Process.flag(:trap_exit, true)
    {:ok, init}
  end

  @impl true
  def terminate(_reason, _state) do
    TermBox2Ex.ex_stop()
    # IO.puts "Going Down: #{inspect(state)}"
    :normal
  end

  @impl true
  def handle_call({:poll, timeout_ms}, _from, state) do
    ev = TermBox2Ex.poll(timeout_ms)
    {:reply, ev, state}
  end

  @impl true
  def handle_cast({:puts, x, y, attr, bg_attr, line}, state) do
    TermBox2Ex.puts(x, y, attr, bg_attr, line)
    {:noreply, state}
  end

  def handle_cast(:clear, state) do
    TermBox2Ex.clear()
    {:noreply, state}
  end

  def handle_cast({:clear_region, x, y, width, height}, state) do
    TermBox2Ex.clear_region(x, y, width, height)
    {:noreply, state}
  end

  def handle_cast({:present}, state) do
    TermBox2Ex.present()

    # NOTE: This currently relies on good behaviour by the user, who will need to call present only once every "draw"
    # but I currently do not see a way around that without requiring the user to unset the cursor manually, could have an opt
    # passed to present?
    TermBox2Ex.hide_cursor()
    {:noreply, state}
  end
end