defmodule DeribitApi.API.WebSockets do
  @moduledoc """
    Deribit WebSockets API.
  """
  use Agent

  require Logger
  @api_v2 "/ws/api/v2"

  def child_spec(opts) do
    %{
      id: __MODULE__,
      start: {__MODULE__, :start_link, [opts]},
      type: :worker,
      restart: :permanent,
      shutdown: 500
    }
  end

  def start_link do
    Agent.start_link(
      fn ->
        %{
          "websocket" =>
            Socket.Web.connect!(base_endpoint(),
              path: @api_v2,
              secure: true
            )
        }
      end,
      name: __MODULE__
    )
  end

  def socket do
    Agent.get(__MODULE__, fn x -> Map.get(x, "websocket") end)
  end

  def obtain_result(text) do
    json = M.dec!(text)

    # I'm looking for a map with a result entry
    case Map.has_key?(json, "result") do
      true ->
        result = Map.get(json, "result")
        access = Map.has_key?(result, "access_token")
        refresh = Map.has_key?(result, "refresh_token")

        case access && refresh do
          true -> result
        end
    end
    nil
  end

  ####### Authentication section

  ########## private
  defp params_for_auth(params \\ %{}) do
    %{}
    |> Map.put("grant_type", "client_credentials")
    |> Map.put("client_id", Map.get(params, "client_id"))
    |> Map.put("client_secret", Map.get(params, "client_secret"))
  end

  ########## private
  defp payload_for_auth(cid, csk) do
    %{}
    |> Map.put("method", "public/auth")
    |> Map.put("params", params_for_auth(%{"client_id" => cid, "client_secret" => csk}))
  end

  def authenticate(client_id, client_secret) do
    # The response contains 'result' if all is well, and you can use the
    # access_token and refresh_token to authenticate subsequent requests.
    # we store the entire deserialized 'result' in this module's Agent.
    #
    # So far, the Agent is keeping track of just 2 things:
    #     1) the underlying tcp socket used to maintain the websocket connection
    #
    #     2) the 'result' payload from the initial response from '/public/auth'
    #        this includes the following:
    #          access_token
    #          refresh_token
    #          token_type          "bearer"
    #          scope               account permissions
    #          expires_in          basically a TTL until access_token expires
    #
    # Now for every request until we need to re-authenticate (we know how long
    # we can use our access_token, from the expires_in TTL.

    new_m =
      Agent.get(__MODULE__, fn data ->
        websocket = Map.get(data, "websocket")

        case Socket.Web.send!(
               websocket,
               {:text, M.enc!(payload_for_auth(client_id, client_secret))}
             ) do
          :ok ->
            case Socket.Web.recv!(websocket) do
              {:text, text} ->
                dec_text = M.dec!(text)
                IO.inspect(dec_text)
                {:ok, Map.put(data, "result", obtain_result(text))}
              {:ping, _} ->
                {Socket.Web.send!(websocket, {:pong, ""}), data}
              abc ->
                IO.puts "This is abc..."
                IO.inspect(abc)
            end

          :error ->
            raise "Error!"

          x ->
            IO.puts "This is x..."
            IO.inspect(x)
        end
      end)

    {status, x} = new_m

    case status do
      :ok -> Agent.update(__MODULE__, fn m -> x end)
      _y -> raise "no new map: #{_y}"
    end
  end

  def base_method(mode, url, params \\ %{}) do
    case mode do
      :public ->
        pub = %{
          "method" => "public/" <> url,
          "params" => params
        }

        pub

      :private ->
        prv = %{
          "method" => "private/" <> url,
          "params" => params
        }

        prv
    end
  end

  # def ws, do: Agent.get(__MODULE__, fn data -> Map.get(data, "websocket") end)

  @spec get_public(any, any, any) :: any
  def get_public(url, params \\ %{}, f) do
    Agent.get(__MODULE__, fn data ->
      IO.inspect(data)
      websocket = Map.get(data, "websocket")
      IO.inspect(params)

      case Socket.Web.send!(websocket, {:text, M.enc!(base_method(:public, url, params))}) do
        :ok ->
          case Socket.Web.recv!(websocket) do
            {:text, text} ->
              parsed_text = M.dec!(text)
              f.(parsed_text)
              {:ok, spawn(DeribitApi.Listener, :listen, [websocket, data, f])}
            {:ping, _} ->
              Socket.Web.send!(websocket, {:pong, ""})
            other ->
              IO.inspect(other)
          end
      end
    end)
  end

  def get_private(url, client_id, client_secret, params \\ %{}, f) do
    Agent.get(__MODULE__, fn data ->
      access_token =
        data
        |> Map.get("result")
        |> Map.get("access_token")

      websocket = Map.get(data, "websocket")
      params = Map.put(params, "access_token", access_token)

      case Socket.Web.send!(websocket, {:text, M.enc!(base_method(:private, url, params))}) do
        :ok ->
          case Socket.Web.recv!(websocket) do
            {:text, text} ->
              parsed_text = M.dec!(text)
              f.(parsed_text)
              {:ok, parsed_text}
            {:ping, _} -> Socket.Web.send!(websocket, {:pong, ""})
          end
      end
    end)
  end

  defp get_timestamp do
    DateTime.utc_now()
    |> DateTime.to_unix()
    |> Kernel.*(1000)
  end

  def base_endpoint do
    case Application.get_env(:deribit_api, :test) do
      false -> Application.get_env(:deribit_api, :base_url)
      true -> Application.get_env(:deribit_api, :test_url)
    end
  end
end