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DefaultHead.scala
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DefaultHead.scala
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/*
* Copyright 2014 http4s.org
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.http4s
package server
package middleware
import cats.Applicative
import cats.Functor
import cats.Monad
import cats.MonoidK
import cats.data.Kleisli
import cats.syntax.all._
import org.http4s.Method.GET
import org.http4s.Method.HEAD
/** Handles HEAD requests as a GET without a body.
*
* If the service returns the fallthrough response, the request is resubmitted
* as a GET. The resulting response's body is killed, but all headers are
* preserved. This is a naive, but correct, implementation of HEAD. Routes
* requiring more optimization should implement their own HEAD handler.
*/
object DefaultHead {
def apply[F[_]: Functor, G[_]: Applicative](
http: Http[F, G]
)(implicit F: MonoidK[F]): Http[F, G] =
Kleisli { req =>
req.method match {
case HEAD => http(req) <+> http(req.withMethod(GET)).map(drainBody[G])
case _ => http(req)
}
}
def httpRoutes[F[_]: Monad](httpRoutes: HttpRoutes[F]): HttpRoutes[F] =
apply(httpRoutes)
private[this] def drainBody[G[_]](
response: Response[G]
)(implicit G: Applicative[G]): Response[G] =
response.entity match {
case Entity.Empty =>
response
case Entity.Strict(_) =>
response.withEntity(Entity.empty)
case Entity.Streamed(_, _) =>
response.pipeBodyThrough(_.interruptWhen[G](G.pure(Either.unit[Throwable])).drain)
}
}