opentelemetry_tesla

defmodule Tesla.Middleware.OpenTelemetry do
  require OpenTelemetry.Tracer
  @behaviour Tesla.Middleware

  def call(env, next, _options) do
    %URI{path: path} = URI.parse(env.url)

    OpenTelemetry.Tracer.with_span path, %{kind: :client} do
      env
      |> Tesla.put_headers(:otel_propagator_text_map.inject([]))
      |> Tesla.run(next)
      |> case do
        {:ok, env} ->
          OpenTelemetry.Tracer.set_attributes(build_attrs(env))

          {:ok, env}

        {:error, _} = e ->
          e |> IO.inspect(label: "------>")
          IO.puts("---------> HAAAAAAAAAAA")
          # TODO: update span's status to with appropriate error code and message
          e
      end
    end
  end

  defp build_attrs(%Tesla.Env{
         method: method,
         url: url,
         status: status_code,
         headers: headers,
         query: query
       }) do
    url = Tesla.build_url(url, query)
    uri = URI.parse(url)

    attrs = %{
      "http.method": http_method(method),
      "http.url": url,
      "http.target": uri.path,
      "http.host": uri.host,
      "http.scheme": uri.scheme,
      "http.status_code": status_code
    }

    maybe_append_content_length(attrs, headers)
  end

  defp maybe_append_content_length(attrs, headers) do
    case Enum.find(headers, fn {k, _v} -> k == "content-length" end) do
      nil ->
        attrs

      {_key, content_length} ->
        Map.put(attrs, :"http.response_content_length", content_length)
    end
  end

  defp http_method(method) do
    method
    |> Atom.to_string()
    |> String.upcase()
  end
end