HttpRoutesLogger.scala

object HttpRoutesLogger {

  import cats.data.{Kleisli, OptionT}
  import cats.syntax.all.*
  import org.http4s.internal.Logger as Http4sLogger
  import org.http4s.{HttpRoutes, Request, Response}
  import org.typelevel.log4cats.Logger

  def isResponseError[F[_]](res: Response[F]): Boolean =
    !res.status.isSuccess

  private def logError[F[_]: {Concurrent, Logger}](req: Request[F], res: Response[F]): F[Unit] =
    Http4sLogger.logMessage(req)(true, true)(Logger[F].warn) *>
      Http4sLogger.logMessage(res)(true, true)(Logger[F].warn)

  def apply[F[_]: {Concurrent, Logger}]: HttpRoutes[F] => HttpRoutes[F] = http =>
    Kleisli: req =>
      http(req).flatTap: res =>
        OptionT.liftF(logError(req, res)).whenA(isResponseError(res))
}