Http4sServlet.scala

/*
 * Copyright 2013 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.servlet

import cats.effect.kernel.Async
import cats.effect.std.Dispatcher
import cats.syntax.all._
import com.comcast.ip4s.{IpAddress, Port, SocketAddress}
import java.security.cert.X509Certificate
import javax.servlet.ServletConfig
import javax.servlet.http.{HttpServlet, HttpServletRequest, HttpServletResponse, HttpSession}
import org.http4s._
import org.http4s.internal.CollectionCompat.CollectionConverters._
import org.http4s.server.SecureSession
import org.http4s.server.ServerRequestKeys
import org.log4s.getLogger
import org.typelevel.ci._
import org.typelevel.vault._

abstract class Http4sServlet[F[_]](
    service: HttpApp[F],
    servletIo: ServletIo[F],
    dispatcher: Dispatcher[F])(implicit F: Async[F])
    extends HttpServlet {
  protected val logger = getLogger

  // micro-optimization: unwrap the service and call its .run directly
  protected val serviceFn: Request[F] => F[Response[F]] = service.run

  protected var servletApiVersion: ServletApiVersion = _
  private[this] var serverSoftware: ServerSoftware = _

  object ServletRequestKeys {
    val HttpSession: Key[Option[HttpSession]] = {
      val result = Key.newKey[F, Option[HttpSession]]
      dispatcher.unsafeRunSync(result)
    }
  }

  override def init(config: ServletConfig): Unit = {
    super.init(config)
    val servletContext = config.getServletContext
    servletApiVersion = ServletApiVersion(servletContext)
    logger.info(s"Detected Servlet API version $servletApiVersion")
    serverSoftware = ServerSoftware(servletContext.getServerInfo)
  }

  protected def onParseFailure(
      parseFailure: ParseFailure,
      servletResponse: HttpServletResponse,
      bodyWriter: BodyWriter[F]
  ): F[Unit] = {
    val response = Response[F](Status.BadRequest).withEntity(parseFailure.sanitized)
    renderResponse(response, servletResponse, bodyWriter)
  }

  protected def renderResponse(
      response: Response[F],
      servletResponse: HttpServletResponse,
      bodyWriter: BodyWriter[F]
  ): F[Unit] =
    F.delay {
      servletResponse.setStatus(response.status.code)
      for (header <- response.headers.headers if header.name != ci"Transfer-Encoding")
        servletResponse.addHeader(header.name.toString, header.value)
    }.attempt
      .flatMap {
        case Right(()) => bodyWriter(response)
        case Left(t) =>
          response.body.drain.compile.drain.handleError { t2 =>
            logger.error(t2)("Error draining body")
          } *> F.raiseError(t)
      }

  protected def toRequest(req: HttpServletRequest): ParseResult[Request[F]] =
    for {
      method <- Method.fromString(req.getMethod)
      uri <- Uri.requestTarget(
        Option(req.getQueryString)
          .map { q =>
            s"${req.getRequestURI}?$q"
          }
          .getOrElse(req.getRequestURI))
      version <- HttpVersion.fromString(req.getProtocol)
    } yield Request(
      method = method,
      uri = uri,
      httpVersion = version,
      headers = toHeaders(req),
      body = servletIo.reader(req),
      attributes = Vault.empty
        .insert(Request.Keys.PathInfoCaret, getPathInfoIndex(req, uri))
        .insert(
          Request.Keys.ConnectionInfo,
          Request.Connection(
            local = SocketAddress(
              IpAddress.fromString(stripBracketsFromAddr(req.getLocalAddr)).get,
              Port.fromInt(req.getLocalPort).get),
            remote = SocketAddress(
              IpAddress.fromString(stripBracketsFromAddr(req.getRemoteAddr)).get,
              Port.fromInt(req.getRemotePort).get),
            secure = req.isSecure
          )
        )
        .insert(Request.Keys.ServerSoftware, serverSoftware)
        .insert(ServletRequestKeys.HttpSession, Option(req.getSession(false)))
        .insert(
          ServerRequestKeys.SecureSession,
          (
            Option(req.getAttribute("javax.servlet.request.ssl_session_id").asInstanceOf[String]),
            Option(req.getAttribute("javax.servlet.request.cipher_suite").asInstanceOf[String]),
            Option(req.getAttribute("javax.servlet.request.key_size").asInstanceOf[Int]),
            Option(
              req
                .getAttribute("javax.servlet.request.X509Certificate")
                .asInstanceOf[Array[X509Certificate]]))
            .mapN(SecureSession.apply)
        )
    )

  private def getPathInfoIndex(req: HttpServletRequest, uri: Uri) = {
    val pathInfo =
      Uri.Path
        .unsafeFromString(req.getContextPath)
        .concat(Uri.Path.unsafeFromString(req.getServletPath))
    uri.path
      .findSplit(pathInfo)
      .getOrElse(-1)
  }

  protected def toHeaders(req: HttpServletRequest): Headers = {
    val headers = for {
      name <- req.getHeaderNames.asScala
      value <- req.getHeaders(name).asScala
    } yield name -> value
    Headers(headers.toList)
  }
  private final def stripBracketsFromAddr(addr: String): String =
    addr.stripPrefix("[").stripSuffix("]")
}