defmodule Membrane.RTC.Engine.Endpoint.ExWebRTC.Metrics do
  @moduledoc """
  Defines metrics and events for stats received from the ExWebRTC Endpoint
  """

  require Logger

  alias Membrane.RTC.Engine.Endpoint

  @webrtc_event [Endpoint.ExWebRTC, :transport]

  @spec metrics() :: [Telemetry.Metrics.t()]
  def metrics() do
    [
      Telemetry.Metrics.sum(
        "ex-webrtc.trasnport.bytes_received_total",
        event_name: @webrtc_event,
        measurement: :bytes_received
      ),
      Telemetry.Metrics.sum(
        "ex-webrtc.transport.bytes_sent_total",
        event_name: @webrtc_event,
        measurement: :bytes_sent
      )
    ]
  end

  @spec emit_transport_event(map(), Keyword.t(), map() | nil) :: :ok
  def emit_transport_event(rtc_stats, telemetry_label, nil) do
    emit_transport_event(rtc_stats, telemetry_label, %{bytes_received: 0, bytes_sent: 0})
  end

  def emit_transport_event(%{transport: transport}, telemetry_label, %{
        bytes_received: prev_bytes_received,
        bytes_sent: prev_bytes_sent
      }) do
    :telemetry.execute(
      [Endpoint.ExWebRTC, :transport],
      %{
        bytes_received: transport.bytes_received - prev_bytes_received,
        bytes_sent: transport.bytes_sent - prev_bytes_sent
      },
      Map.new(telemetry_label)
    )

    transport
  end
end