Deprecate HTTP/2 implementation

blaze-core/src/main/scala/org/http4s/blazecore/util/Http2Writer.scala

@@ -29,6 +29,7 @@ import org.http4s.blaze.pipeline.TailStage
 
 import scala.concurrent._
 
+@deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
 private[http4s] class Http2Writer[F[_]](
     tail: TailStage[StreamFrame],
     private var headers: Headers,

blaze-server/src/main/scala/org/http4s/blaze/server/BlazeServerBuilder.scala

@@ -243,6 +243,7 @@ class BlazeServerBuilder[F[_]] private (
   def withWebSockets(enableWebsockets: Boolean): Self =
     this
 
+  @deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
   def enableHttp2(enabled: Boolean): Self = copy(http2Support = enabled)
 
   def withHttpApp(httpApp: HttpApp[F]): Self =

blaze-server/src/main/scala/org/http4s/blaze/server/Http2NodeStage.scala

@@ -46,6 +46,7 @@ import scala.concurrent.duration.Duration
 import scala.concurrent.duration.FiniteDuration
 import scala.util._
 
+@deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
 private class Http2NodeStage[F[_]](
     streamId: Int,
     timeout: Duration,

blaze-server/src/main/scala/org/http4s/blaze/server/ProtocolSelector.scala

@@ -33,11 +33,13 @@ import org.typelevel.vault._
 
 import java.nio.ByteBuffer
 import javax.net.ssl.SSLEngine
+import scala.annotation.nowarn
 import scala.concurrent.ExecutionContext
 import scala.concurrent.duration.Duration
 
 /** Facilitates the use of ALPN when using blaze http2 support */
 private[http4s] object ProtocolSelector {
+  @nowarn("cat=deprecation")
   def apply[F[_]](
       engine: SSLEngine,
       httpApp: HttpApp[F],

http/src/main/scala/org/http4s/blaze/http/http2/ByteBufferInputStream.scala

@@ -22,6 +22,7 @@ import java.nio.ByteBuffer
 /** Wrap a `ByteBuffer` in an `InputStream` interface. This is just an adapter to work with the
   * twitter hpack implementation. I would really like to get rid of it.
   */
+@deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
 private final class ByteBufferInputStream(buffer: ByteBuffer) extends InputStream {
   private[this] var markSize = -1
 

http/src/main/scala/org/http4s/blaze/http/http2/Connection.scala

@@ -23,6 +23,7 @@ import scala.concurrent.Future
 import scala.concurrent.duration.Duration
 
 /** Representation of the HTTP connection or session */
+@deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
 private trait Connection {
 
   /** An estimate for the current quality of the connection
@@ -78,6 +79,7 @@ private trait Connection {
   def onClose: Future[Unit]
 }
 
+@deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
 private[blaze] object Connection {
   sealed abstract class State extends Product with Serializable {
     final def closing: Boolean = !running

http/src/main/scala/org/http4s/blaze/http/http2/ConnectionImpl.scala

@@ -35,6 +35,7 @@ import scala.util.{Failure, Success}
   *   the TailStage needs to be ready to go as this session will start reading from the channel
   *   immediately.
   */
+@deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
 private final class ConnectionImpl(
     tailStage: TailStage[ByteBuffer],
     val localSettings: Http2Settings,

http/src/main/scala/org/http4s/blaze/http/http2/DefaultFlowStrategy.scala

@@ -18,6 +18,7 @@ package org.http4s.blaze.http.http2
 
 import org.http4s.blaze.http.http2.FlowStrategy.Increment
 
+@deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
 final class DefaultFlowStrategy(localSettings: Http2Settings) extends FlowStrategy {
   override def checkSession(session: SessionFlowControl): Int =
     check(

http/src/main/scala/org/http4s/blaze/http/http2/FlowStrategy.scala

@@ -22,6 +22,7 @@ import org.http4s.blaze.http.http2.FlowStrategy.Increment
   *
   * A `FlowStrategy` will be shared among many sessions.
   */
+@deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
 trait FlowStrategy {
 
   /** Decide if the session window needs to send a WINDOW_UPDATE frame
@@ -52,6 +53,7 @@ trait FlowStrategy {
   def checkStream(stream: StreamFlowWindow): Increment
 }
 
+@deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
 object FlowStrategy {
   // Make the object private to restrict construction of
   // `Increment`s to the `makeIncrement` method

http/src/main/scala/org/http4s/blaze/http/http2/FrameDecoder.scala

@@ -24,6 +24,7 @@ import org.http4s.blaze.http.http2.bits.{Flags, Masks}
 
 /* The job of the Http2FrameDecoder is to slice the ByteBuffers. It does
    not attempt to decode headers or perform any size limiting operations */
+@deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
 private class FrameDecoder(localSettings: Http2Settings, listener: FrameListener) {
   import bits._
   import FrameDecoder._
@@ -310,6 +311,7 @@ private class FrameDecoder(localSettings: Http2Settings, listener: FrameListener
       listener.onContinuationFrame(streamId, Flags.END_HEADERS(flags), buffer.slice())
 }
 
+@deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
 private object FrameDecoder {
 
   /** Get the length field of the frame, consuming the bytes from the buffer.

http/src/main/scala/org/http4s/blaze/http/http2/FrameEncoder.scala

@@ -23,6 +23,7 @@ import org.http4s.blaze.util.BufferTools
 import scala.collection.mutable.ArrayBuffer
 
 /** A more humane interface for writing HTTP messages. */
+@deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
 private final class FrameEncoder(remoteSettings: Http2Settings, headerEncoder: HeaderEncoder) {
   // Just a shortcut
   private[this] def maxFrameSize: Int = remoteSettings.maxFrameSize

http/src/main/scala/org/http4s/blaze/http/http2/FrameListener.scala

@@ -30,6 +30,7 @@ import Http2Settings.Setting
   * is 4 bytes long and the [[FrameListener]] would be expected to signal an error if the window
   * increment was 0 or the update was for an idle stream.
   */
+@deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
 private trait FrameListener {
 
   /** Determine whether we are in the midst of a sequence of header and header continuation frames

http/src/main/scala/org/http4s/blaze/http/http2/FrameSerializer.scala

@@ -22,6 +22,7 @@ import java.nio.charset.StandardCharsets
 import org.http4s.blaze.http.http2.Http2Settings.Setting
 import org.http4s.blaze.util.BufferTools
 
+@deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
 private[http2] object FrameSerializer {
   import bits._
 

http/src/main/scala/org/http4s/blaze/http/http2/HeaderAggregatingFrameListener.scala

@@ -33,6 +33,7 @@ import Http2Exception.PROTOCOL_ERROR
   * @note
   *   This class is not 'thread safe' and should be treated accordingly.
   */
+@deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
 private abstract class HeaderAggregatingFrameListener(
     localSettings: Http2Settings,
     headerDecoder: HeaderDecoder

http/src/main/scala/org/http4s/blaze/http/http2/HeaderDecoder.scala

@@ -38,6 +38,7 @@ import scala.util.control.NonFatal
   * @param maxTableSize
   *   maximum compression table to maintain
   */
+@deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
 private final class HeaderDecoder(
     maxHeaderListSize: Int,
     discardOverflowHeaders: Boolean,

http/src/main/scala/org/http4s/blaze/http/http2/HeaderEncoder.scala

@@ -29,6 +29,7 @@ import com.twitter.hpack.Encoder
   * @param initialMaxTableSize
   *   maximum HPACK table size the peer will allow.
   */
+@deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
 class HeaderEncoder(initialMaxTableSize: Int) {
   private[this] val encoder = new Encoder(initialMaxTableSize)
   private[this] val os = new ByteArrayOutputStream(1024)

http/src/main/scala/org/http4s/blaze/http/http2/Http2Exception.scala

@@ -21,6 +21,7 @@ import java.nio.charset.StandardCharsets.UTF_8
 import scala.collection.mutable
 import scala.util.control.NoStackTrace
 
+@deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
 sealed abstract class Http2Exception(msg: String)
     extends Exception(msg)
     with NoStackTrace
@@ -61,12 +62,15 @@ sealed abstract class Http2Exception(msg: String)
   final def msgBuffer(): ByteBuffer = ByteBuffer.wrap(msg.getBytes(UTF_8))
 }
 
+@deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
 final case class Http2StreamException(stream: Int, code: Long, msg: String)
     extends Http2Exception(msg)
 
+@deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
 final case class Http2SessionException(code: Long, msg: String) extends Http2Exception(msg)
 
 ///////////////////// HTTP/2.0 Errors //////////////////////////////
+@deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
 object Http2Exception {
   final class ErrorGenerator private[http2] (val code: Long, val name: String) {
 

http/src/main/scala/org/http4s/blaze/http/http2/Http2Settings.scala

@@ -27,6 +27,7 @@ import scala.collection.mutable
   * @see
   *   https://tools.ietf.org/html/rfc7540#section-6.5.2, where the doc strings were obtained.
   */
+@deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
 sealed abstract class Http2Settings {
 
   /** Allows the sender to inform the remote endpoint of the maximum size of the header compression
@@ -82,6 +83,7 @@ sealed abstract class Http2Settings {
 }
 
 /** Immutable representation of [[Http2Settings]] for configuring clients and servers */
+@deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
 case class ImmutableHttp2Settings(
     headerTableSize: Int,
     initialWindowSize: Int,
@@ -91,6 +93,7 @@ case class ImmutableHttp2Settings(
     maxHeaderListSize: Int
 ) extends Http2Settings
 
+@deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
 object Http2Settings {
   type SettingValue = Int
 
@@ -192,6 +195,7 @@ object Http2Settings {
 }
 
 /** Internal mutable representation of the [[Http2Settings]] */
+@deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
 private[blaze] final class MutableHttp2Settings private (
     var headerTableSize: Int,
     var initialWindowSize: Int,
@@ -229,6 +233,7 @@ private[blaze] final class MutableHttp2Settings private (
     s"MutableHttp2Settings(${toSeq.mkString(", ")})"
 }
 
+@deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
 private object MutableHttp2Settings {
   private val logger = getLogger
 

http/src/main/scala/org/http4s/blaze/http/http2/InboundStreamState.scala

@@ -21,4 +21,5 @@ package org.http4s.blaze.http.http2
   * @note
   *   this is only a marker trait
   */
+@deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
 private trait InboundStreamState extends StreamState

http/src/main/scala/org/http4s/blaze/http/http2/InboundStreamStateImpl.scala

@@ -16,6 +16,7 @@
 
 package org.http4s.blaze.http.http2
 
+@deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
 private final class InboundStreamStateImpl(
     session: SessionCore,
     val streamId: Int,

http/src/main/scala/org/http4s/blaze/http/http2/OutboundStreamState.scala

@@ -25,4 +25,5 @@ package org.http4s.blaze.http.http2
   * @note
   *   this is a marker trait
   */
+@deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
 private trait OutboundStreamState extends StreamState

http/src/main/scala/org/http4s/blaze/http/http2/OutboundStreamStateImpl.scala

@@ -19,6 +19,7 @@ package org.http4s.blaze.http.http2
 import scala.concurrent.Promise
 import scala.concurrent.duration.Duration
 
+@deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
 private abstract class OutboundStreamStateImpl(session: SessionCore)
     extends StreamStateImpl(session)
     with OutboundStreamState {

http/src/main/scala/org/http4s/blaze/http/http2/PingManager.scala

@@ -24,6 +24,7 @@ import org.log4s.getLogger
 import scala.concurrent.{Future, Promise}
 import scala.concurrent.duration.Duration
 
+@deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
 private class PingManager(session: SessionCore) {
   import PingManager._
 
@@ -99,6 +100,7 @@ private class PingManager(session: SessionCore) {
     }
 }
 
+@deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
 private object PingManager {
   private sealed trait State
 

http/src/main/scala/org/http4s/blaze/http/http2/PriorKnowledgeHandshaker.scala

@@ -24,6 +24,7 @@ import org.http4s.blaze.util.{BufferTools, Execution}
 import scala.concurrent.{ExecutionContext, Future}
 
 /** Base type for performing the HTTP/2 prior knowledge handshake */
+@deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
 abstract class PriorKnowledgeHandshaker[T](localSettings: ImmutableHttp2Settings)
     extends TailStage[ByteBuffer] {
   implicit protected final def ec: ExecutionContext = Execution.trampoline

http/src/main/scala/org/http4s/blaze/http/http2/Priority.scala

@@ -16,10 +16,12 @@
 
 package org.http4s.blaze.http.http2
 
+@deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
 sealed trait Priority {
   def isDefined: Boolean
 }
 
+@deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
 object Priority {
 
   /** object representing the contents of a PRIORITY frame

http/src/main/scala/org/http4s/blaze/http/http2/PseudoHeaders.scala

@@ -17,6 +17,7 @@
 package org.http4s.blaze.http.http2
 
 /** HTTP/2 pseudo headers */
+@deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
 object PseudoHeaders {
   // Request pseudo headers
   val Method = ":method"

http/src/main/scala/org/http4s/blaze/http/http2/Result.scala

@@ -17,16 +17,20 @@
 package org.http4s.blaze.http.http2
 
 /** Result type of many of the codec methods */
+@deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
 private sealed trait Result extends Product with Serializable
 
 /** Didn't get enough data to decode a full HTTP/2 frame */
+@deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
 private case object BufferUnderflow extends Result
 
 /** Represents the possibility of failure */
+@deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
 private sealed abstract class MaybeError extends Result {
   final def success: Boolean = this == Continue
 }
 
+@deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
 private object MaybeError {
   def apply(option: Option[Http2Exception]): MaybeError =
     option match {
@@ -35,5 +39,8 @@ private object MaybeError {
     }
 }
 
+@deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
 private case object Continue extends MaybeError
+
+@deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
 private final case class Error(err: Http2Exception) extends MaybeError

http/src/main/scala/org/http4s/blaze/http/http2/SessionCore.scala

@@ -23,6 +23,7 @@ import scala.concurrent.duration.Duration
   * 'bag-o-references' so that each component can reference each other. This helps to avoid
   * construction order conflicts.
   */
+@deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
 private abstract class SessionCore {
   // Fields
   def serialExecutor: ExecutionContext

http/src/main/scala/org/http4s/blaze/http/http2/SessionFlowControl.scala

@@ -17,6 +17,7 @@
 package org.http4s.blaze.http.http2
 
 /** Flow control representation of a Http2 Session */
+@deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
 abstract class SessionFlowControl {
 
   /** Create a new [[StreamFlowWindow]] for a stream which will update and check the bounds of the

http/src/main/scala/org/http4s/blaze/http/http2/SessionFlowControlImpl.scala

@@ -21,6 +21,7 @@ import org.http4s.blaze.http.http2.Http2Exception.{FLOW_CONTROL_ERROR, PROTOCOL_
 import org.log4s.getLogger
 
 /** Flow control representation of a Http2 Session */
+@deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
 private class SessionFlowControlImpl(
     session: SessionCore,
     flowStrategy: FlowStrategy

http/src/main/scala/org/http4s/blaze/http/http2/SessionFrameListener.scala

@@ -28,6 +28,7 @@ import org.http4s.blaze.http.http2.Http2Settings.Setting
   * Concurrency is not controlled by this type; it is expected that thread safety will be managed by
   * the [[ConnectionImpl]].
   */
+@deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
 private class SessionFrameListener(
     session: SessionCore,
     isClient: Boolean,

http/src/main/scala/org/http4s/blaze/http/http2/SettingsDecoder.scala

@@ -25,6 +25,7 @@ import org.http4s.blaze.http.http2.bits.{Flags, FrameTypes}
   * @see
   *   https://tools.ietf.org/html/rfc7540#section-6.5
   */
+@deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
 private[blaze] object SettingsDecoder {
 
   /** Representation of a settings frame

http/src/main/scala/org/http4s/blaze/http/http2/StageTools.scala

@@ -19,6 +19,7 @@ package org.http4s.blaze.http.http2
 import java.util.Locale
 import scala.collection.mutable.{ArrayBuffer, Builder}
 
+@deprecated("HTTP/2 support is unmaintained and will be removed in a future version.", "0.23.18")
 private[http2] object StageTools {
   // There are two copies of this because `Growable` moved in Scala
   // 2.13 and we're stuck with the deprecation warning.  It's private