defmodule SpandexTesla.Telemetry do
  @moduledoc """
  Defines the `:telemetry` handlers to attach tracing to Tesla Telemetry.
  """

  @doc """
  Automatic installer. Call it from application.ex to trace all events generated by Tesla.
  """
  def attach do
    if new_telemetry_events_supported?() do
      tesla_events = [
        [:tesla, :request, :start],
        [:tesla, :request, :stop],
        [:tesla, :request, :exception]
      ]

      :telemetry.attach_many(__MODULE__, tesla_events, &SpandexTesla.handle_event/4, nil)
    else
      :telemetry.attach(__MODULE__, [:tesla, :request], &SpandexTesla.handle_event/4, nil)
    end
  end

  defp new_telemetry_events_supported? do
    case :application.get_key(:tesla, :vsn) do
      {:ok, version} ->
        version
        |> List.to_string()
        |> Version.match?(">= 1.3.3")

      _ ->
        false
    end
  end
end