defmodule Driver do
  @moduledoc """
  Communicates with the elevator hardware. Delivered as a part of the course
  TTK4145: Real-time programming.
  """

  use GenServer

  @call_timeout 1_000
  @button_map %{:hall_up => 0, :hall_down => 1, :cab => 2}
  @state_map %{:on => 1, :off => 0}
  @direction_map %{:up => 1, :down => 255, :stop => 0}

  def start_link([]) do
    start_link([{127, 0, 0, 1}, 15657])
  end

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

  def stop() do
    GenServer.stop(__MODULE__)
  end

  def init([address, port]) do
    {:ok, socket} = :gen_tcp.connect(address, port, [{:active, false}])
    {:ok, socket}
  end

  # User API --------------------------------------------
  # direction can be :up/:down/:stop
  def set_motor_direction(direction) do
    GenServer.cast(__MODULE__, {:set_motor_direction, direction})
  end

  # button_type can be :hall_up/:hall_down/:cab
  # state can be :on/:off
  def set_order_button_light(button_type, floor, state) do
    GenServer.cast(__MODULE__, {:set_order_button_light, button_type, floor, state})
  end

  def set_floor_indicator(floor) do
    GenServer.cast(__MODULE__, {:set_floor_indicator, floor})
  end

  # state can be :on/:off
  def set_stop_button_light(state) do
    GenServer.cast(__MODULE__, {:set_stop_button_light, state})
  end

  # state can be :on/:off
  def set_door_open_light(state) do
    GenServer.cast(__MODULE__, {:set_door_open_light, state})
  end

  def get_order_button_state(floor, button_type) do
    GenServer.call(__MODULE__, {:get_order_button_state, floor, button_type})
  end

  def get_floor_sensor_state do
    GenServer.call(__MODULE__, :get_floor_sensor_state)
  end

  def get_stop_button_state do
    GenServer.call(__MODULE__, :get_stop_button_state)
  end

  def get_obstruction_switch_state do
    GenServer.call(__MODULE__, :get_obstruction_switch_state)
  end

  # Casts  ----------------------------------------------
  def handle_cast({:set_motor_direction, direction}, socket) do
    :gen_tcp.send(socket, [1, @direction_map[direction], 0, 0])
    {:noreply, socket}
  end

  def handle_cast({:set_order_button_light, button_type, floor, state}, socket) do
    :gen_tcp.send(socket, [2, @button_map[button_type], floor, @state_map[state]])
    {:noreply, socket}
  end

  def handle_cast({:set_floor_indicator, floor}, socket) do
    :gen_tcp.send(socket, [3, floor, 0, 0])
    {:noreply, socket}
  end

  def handle_cast({:set_door_open_light, state}, socket) do
    :gen_tcp.send(socket, [4, @state_map[state], 0, 0])
    {:noreply, socket}
  end

  def handle_cast({:set_stop_button_light, state}, socket) do
    :gen_tcp.send(socket, [5, @state_map[state], 0, 0])
    {:noreply, socket}
  end

  # Calls  ----------------------------------------------
  def handle_call({:get_order_button_state, floor, order_type}, _from, socket) do
    :gen_tcp.send(socket, [6, @button_map[order_type], floor, 0])
    {:ok, [6, state, 0, 0]} = :gen_tcp.recv(socket, 4, @call_timeout)
    {:reply, state, socket}
  end

  def handle_call(:get_floor_sensor_state, _from, socket) do
    :gen_tcp.send(socket, [7, 0, 0, 0])

    button_state =
      case :gen_tcp.recv(socket, 4, @call_timeout) do
        {:ok, [7, 0, _, 0]} -> :between_floors
        {:ok, [7, 1, floor, 0]} -> floor
      end

    {:reply, button_state, socket}
  end

  def handle_call(:get_stop_button_state, _from, socket) do
    :gen_tcp.send(socket, [8, 0, 0, 0])

    button_state =
      case :gen_tcp.recv(socket, 4, @call_timeout) do
        {:ok, [8, 0, 0, 0]} -> :inactive
        {:ok, [8, 1, 0, 0]} -> :active
      end

    {:reply, button_state, socket}
  end

  def handle_call(:get_obstruction_switch_state, _from, socket) do
    :gen_tcp.send(socket, [9, 0, 0, 0])

    button_state =
      case :gen_tcp.recv(socket, 4, @call_timeout) do
        {:ok, [9, 0, 0, 0]} -> :inactive
        {:ok, [9, 1, 0, 0]} -> :active
      end

    {:reply, button_state, socket}
  end
end