defmodule Odinsea.Channel.Server do
  @moduledoc """
  A single game channel server.
  """

  use GenServer

  require Logger

  defstruct [:channel_id, :socket, :port, :clients]

  def start_link(channel_id) do
    GenServer.start_link(__MODULE__, channel_id, name: via_tuple(channel_id))
  end

  def via_tuple(channel_id) do
    {:via, Registry, {Odinsea.Channel.Registry, channel_id}}
  end

  @impl true
  def init(channel_id) do
    ports = Application.get_env(:odinsea, :game, [])[:channel_ports] || %{}
    port = Map.get(ports, channel_id, 8584 + channel_id)

    case :gen_tcp.listen(port, tcp_options()) do
      {:ok, socket} ->
        Logger.info("Channel #{channel_id} listening on port #{port}")
        send(self(), :accept)

        {:ok,
         %__MODULE__{
           channel_id: channel_id,
           socket: socket,
           port: port,
           clients: %{}
         }}

      {:error, reason} ->
        Logger.error("Failed to start channel #{channel_id} on port #{port}: #{inspect(reason)}")
        {:stop, reason}
    end
  end

  @impl true
  def handle_info(:accept, %{socket: socket, channel_id: channel_id} = state) do
    case :gen_tcp.accept(socket) do
      {:ok, client_socket} ->
        {:ok, _pid} =
          DynamicSupervisor.start_child(
            Odinsea.ClientSupervisor,
            {Odinsea.Channel.Client, {client_socket, channel_id}}
          )

        send(self(), :accept)
        {:noreply, state}

      {:error, reason} ->
        Logger.warning("Channel #{channel_id} accept error: #{inspect(reason)}")
        send(self(), :accept)
        {:noreply, state}
    end
  end

  defp tcp_options do
    [
      :binary,
      packet: :raw,
      active: false,
      reuseaddr: true,
      backlog: 100
    ]
  end
end