defmodule UrbitEx.Server do
  alias UrbitEx.{API}
  use GenServer
  require Logger

  @moduledoc """
  Main GenServer, called by the UrbitEx module. Starts a GenServer which keeps an Urbit login session as its state,
  keeping track of the Eyre channel, the actions sent and events received.
  """

  def start_link(options, name) when is_list(options) do
    GenServer.start_link(__MODULE__, options, name: name)
  end

  def start(options, name) when is_list(options) do
    GenServer.start(__MODULE__, options, name: name)
  end

  def die(name \\ :urbit_server) when is_atom(name) do
    pid = Process.whereis(name)
    Process.exit(pid, :kill)
  end

  def die(pid), do: Process.exit(pid, :kill)

  # callbacks

  @impl true
  def init(args) do
    [{:url, url}, {:code, code}] = args

    session =
      API.init(url, code)
      |> API.login()
      |> API.open_channel()
      |> API.start_sse()

    {:ok, session}
  end

  @impl true
  def handle_info(%HTTPoison.AsyncStatus{}, session) do
    {:noreply, session}
  end

  @impl true
  # ignore keep-alive messages
  def handle_info(%{chunk: "\n"}, session) do
    {:noreply, session}
  end

  def handle_info(%{chunk: ""}, session) do
    {:noreply, session}
  end

  @impl true
  def handle_info(%{chunk: data}, session) do
    parsed_events = data |> parse_stream

    parsed_events
    |> Enum.each(fn {_event_id, message} ->
      broadcast(session, message)
    end)

    {last_event_id, last_message} = parsed_events |> Enum.at(-1)
    new_session = %{session | last_sse: last_event_id, events: [last_message | session.events]}
    {:noreply, new_session}
  end

  @impl true
  def handle_info(_message, session) do
    {:noreply, session}
  end

  defp parse_stream(event) do
    event |> String.split("\n") |> Enum.filter(fn x -> String.length(x) > 0 end)

    # received events can be either single or multiple, which is rather annoying.
    received_event = event |> String.split("\n") |> Enum.filter(fn x -> String.length(x) > 0 end)

    received_event
    |> Enum.chunk_every(2)
    |> Enum.map(fn [id_string, data_string] ->
      [id] = Regex.run(~r(\d), id_string)
      [_, data] = data_string |> String.split("data: ")
      {String.to_integer(id), Jason.decode!(data)}
    end)
  end

  @impl true
  def handle_call(:get, _from, session) do
    {:reply, session, session}
  end

  @impl true
  def handle_cast({:subscribe, subscriptions}, session) do
    session = API.subscribe(session, subscriptions)

    session = %{session | subscriptions: [subscriptions | session.subscriptions]}
    {:noreply, session}
  end

  @impl true
  def handle_cast({:consume, pid}, session) do
    IO.inspect(pid, label: :consooming)
    {:noreply, %{session | consumers: [pid | session.consumers]}}
  end

  defp broadcast(session, message) do
    session.consumers |> Enum.each(&send(&1, message))
  end
end