ErrorHandling.scala

import cats.implicits._
import cats.MonadError
import cats.data.{Kleisli, OptionT}
import org.http4s._

object ErrorHandling {
  def apply[F[_], G[_]](
      k: Kleisli[F, Request[G], Response[G]],
      pf: Request[G] => PartialFunction[Throwable, F[Response[G]]] = inDefaultServiceErrorHandler[F, G]
  )(implicit F: MonadError[F, Throwable]): Kleisli[F, Request[G], Response[G]] =
    Kleisli { req =>
      k.run(req).handleErrorWith { e =>
        pf(req).lift(e) match {
          case Some(resp) => resp
          case None       => F.raiseError(e)
        }
      }
    }

  def httpRoutes[F[_]: MonadError[*[_], Throwable]](
      httpRoutes: HttpRoutes[F],
      pf: Request[F] => PartialFunction[Throwable, OptionT[F, Response[F]]] = inDefaultServiceErrorHandler[F, OptionT[F, *]]
  ): HttpRoutes[F] =
    apply(httpRoutes, pf)

  def httpApp[F[_]: MonadError[*[_], Throwable]](
      httpApp: HttpApp[F],
      pf: Request[F] => PartialFunction[Throwable, F[Response[F]]] = inDefaultServiceErrorHandler[F, F]
  ): HttpApp[F] =
    apply(httpApp, pf)
}