defmodule Tamnoon.SocketHandler do
  @moduledoc """
  A default `:cowboy_websocket` implementation. Usually there should not be a reason to do anything
  directly with this module, as it gets its options from `Tamnoon.start_link/1` and
  adapts to them automatically. However, it is still documented for the sake of allowing
  extensiblity.
  You can replace the module with a custom one via setting it as the _(drumroll..)_ `:socket_handler`
  key's value in `Tamnoon.start_link/1`'s options.
  """
  @behaviour :cowboy_websocket

  @doc """
  Initiates the websocket connection
  """
  @impl true
  @spec init(:cowboy_req.req(), map()) :: {:cowboy_websocket, req :: :cowboy_req.req(), initial_state :: map()}
  def init(req, _state) do
    {:cowboy_websocket, req, initial_state()}
  end

  @doc """
  Initiates the websocket and adds the client to the registry under the `"clients"` channel.
  """
  @impl true
  @spec websocket_init(map()) :: {:ok, state :: map()}
  def websocket_init(state) do
    Tamnoon.Registry
    |> Registry.register("clients", {})
    {:ok, state}
  end

  @doc """
  Receives a websocket request and decodes it, sending it to the `Tamnoon.MethodManager.route_request/3`
  function.
  """
  @impl true
  @spec websocket_handle({:text, tuple()}, map()) :: {:reply, {:text, return_val :: String.t()}, new_state :: map()}
  def websocket_handle({:text, json}, state) do
    payload = Jason.decode!(json)
    Tamnoon.MethodManager.route_request(methods_module(), payload, state)
  end

  @doc """
  Handles messages from other BEAM processes. By default it is only used for handling
  `"pub"` requests, and as such it simply forwards the message to `websocket_handle/2`.
  """
  @impl true
  @spec websocket_info(info :: map(), map()) :: {:reply, {:text, return_val :: String.t()}, new_state :: map()}
  def websocket_info(info, state) do
    websocket_handle({:text, info}, state)
  end

  defp initial_state(), do: Tamnoon.Registry |> Registry.meta(:initial_state) |> elem(1)
  defp methods_module(), do: Tamnoon.Registry |> Registry.meta(:methods_module) |> elem(1)
end