// Copyright (c) 2018 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "net/third_party/quiche/src/quic/core/quic_stream_id_manager.h"

#include <cstdint>
#include <string>

#include "net/third_party/quiche/src/quic/core/quic_connection.h"
#include "net/third_party/quiche/src/quic/core/quic_constants.h"
#include "net/third_party/quiche/src/quic/core/quic_session.h"
#include "net/third_party/quiche/src/quic/core/quic_utils.h"
#include "net/third_party/quiche/src/quic/platform/api/quic_flag_utils.h"
#include "net/third_party/quiche/src/quic/platform/api/quic_flags.h"
#include "net/third_party/quiche/src/quic/platform/api/quic_logging.h"
#include "net/third_party/quiche/src/common/platform/api/quiche_str_cat.h"

namespace quic {

#define ENDPOINT \
  (perspective_ == Perspective::IS_SERVER ? " Server: " : " Client: ")

QuicStreamIdManager::QuicStreamIdManager(
    DelegateInterface* delegate,
    bool unidirectional,
    Perspective perspective,
    QuicTransportVersion transport_version,
    QuicStreamCount max_allowed_outgoing_streams,
    QuicStreamCount max_allowed_incoming_streams)
    : delegate_(delegate),
      unidirectional_(unidirectional),
      perspective_(perspective),
      transport_version_(transport_version),
      outgoing_max_streams_(max_allowed_outgoing_streams),
      next_outgoing_stream_id_(GetFirstOutgoingStreamId()),
      outgoing_stream_count_(0),
      incoming_actual_max_streams_(max_allowed_incoming_streams),
      // Advertised max starts at actual because it's communicated in the
      // handshake.
      incoming_advertised_max_streams_(max_allowed_incoming_streams),
      incoming_initial_max_open_streams_(max_allowed_incoming_streams),
      incoming_stream_count_(0),
      largest_peer_created_stream_id_(
          QuicUtils::GetInvalidStreamId(transport_version)),
      max_streams_window_(0) {
  CalculateIncomingMaxStreamsWindow();
}

QuicStreamIdManager::~QuicStreamIdManager() {}

bool QuicStreamIdManager::OnMaxStreamsFrame(const QuicMaxStreamsFrame& frame) {
  // Ensure that the frame has the correct directionality.
  DCHECK_EQ(frame.unidirectional, unidirectional_);
  QUIC_CODE_COUNT_N(quic_max_streams_received, 2, 2);

  // Set the limit to be exactly the stream count in the frame.
  // Also informs the higher layers that they can create more
  // streams if the limit is increased.
  return SetMaxOpenOutgoingStreams(frame.stream_count);
}

// The peer sends a streams blocked frame when it can not open any more
// streams because it has runs into the limit.
bool QuicStreamIdManager::OnStreamsBlockedFrame(
    const QuicStreamsBlockedFrame& frame) {
  // Ensure that the frame has the correct directionality.
  DCHECK_EQ(frame.unidirectional, unidirectional_);
  if (frame.stream_count > incoming_advertised_max_streams_) {
    // Peer thinks it can send more streams that we've told it.
    // This is a protocol error.
    QUIC_CODE_COUNT(quic_streams_blocked_too_big);
    delegate_->OnStreamIdManagerError(QUIC_STREAMS_BLOCKED_ERROR,
                                      "Invalid stream count specified");
    return false;
  }
  if (frame.stream_count < incoming_actual_max_streams_) {
    // Peer thinks it's blocked on a stream count that is less than our current
    // max. Inform the peer of the correct stream count. Sending a MAX_STREAMS
    // frame in this case is not controlled by the window.
    SendMaxStreamsFrame();
  }
  QUIC_CODE_COUNT(quic_streams_blocked_id_correct);
  return true;
}

// Used when configuration has been done and we have an initial
// maximum stream count from the peer.
bool QuicStreamIdManager::SetMaxOpenOutgoingStreams(
    QuicStreamCount max_open_streams) {
  if (max_open_streams <= outgoing_max_streams_) {
    // Only update the stream count if it would increase the limit.
    // If it decreases the limit, or doesn't change it, then do not update.
    // Note that this handles the case of receiving a count of 0 in the frame
    return true;
  }

  // This implementation only supports 32 bit Stream IDs, so limit max streams
  // if it would exceed the max 32 bits can express.
  outgoing_max_streams_ =
      std::min(max_open_streams, QuicUtils::GetMaxStreamCount());

  // Inform the higher layers that the stream limit has increased and that
  // new streams may be created.
  delegate_->OnCanCreateNewOutgoingStream(unidirectional_);

  return true;
}

void QuicStreamIdManager::SetMaxOpenIncomingStreams(
    QuicStreamCount max_open_streams) {
  if (max_open_streams < incoming_stream_count_) {
    delegate_->OnStreamIdManagerError(
        QUIC_MAX_STREAMS_ERROR, "Stream limit less than existing stream count");
    return;
  }
  incoming_actual_max_streams_ = max_open_streams;
  incoming_advertised_max_streams_ = max_open_streams;
  incoming_initial_max_open_streams_ = max_open_streams;
  CalculateIncomingMaxStreamsWindow();
}

void QuicStreamIdManager::MaybeSendMaxStreamsFrame() {
  if ((incoming_advertised_max_streams_ - incoming_stream_count_) >
      max_streams_window_) {
    // window too large, no advertisement
    return;
  }
  SendMaxStreamsFrame();
}

void QuicStreamIdManager::SendMaxStreamsFrame() {
  incoming_advertised_max_streams_ = incoming_actual_max_streams_;
  delegate_->SendMaxStreams(incoming_advertised_max_streams_, unidirectional_);
}

void QuicStreamIdManager::OnStreamClosed(QuicStreamId stream_id) {
  DCHECK_NE(QuicUtils::IsBidirectionalStreamId(stream_id), unidirectional_);
  if (!IsIncomingStream(stream_id)) {
    // Nothing to do for outgoing streams.
    return;
  }
  // If the stream is inbound, we can increase the actual stream limit and maybe
  // advertise the new limit to the peer.  Have to check to make sure that we do
  // not exceed the maximum.
  if (incoming_actual_max_streams_ == QuicUtils::GetMaxStreamCount()) {
    // Reached the maximum stream id value that the implementation
    // supports. Nothing can be done here.
    return;
  }
  // One stream closed ... another can be opened.
  incoming_actual_max_streams_++;
  MaybeSendMaxStreamsFrame();
}

QuicStreamId QuicStreamIdManager::GetNextOutgoingStreamId() {
  // Applications should always consult CanOpenNextOutgoingStream() first.
  // If they ask for stream ids that violate the limit, it's an implementation
  // bug.
  QUIC_BUG_IF(outgoing_stream_count_ >= outgoing_max_streams_)
      << "Attempt to allocate a new outgoing stream that would exceed the "
         "limit ("
      << outgoing_max_streams_ << ")";
  QuicStreamId id = next_outgoing_stream_id_;
  next_outgoing_stream_id_ += QuicUtils::StreamIdDelta(transport_version_);
  outgoing_stream_count_++;
  return id;
}

bool QuicStreamIdManager::CanOpenNextOutgoingStream() const {
  DCHECK(VersionHasIetfQuicFrames(transport_version_));
  return outgoing_stream_count_ < outgoing_max_streams_;
}

bool QuicStreamIdManager::MaybeIncreaseLargestPeerStreamId(
    const QuicStreamId stream_id) {
  // |stream_id| must be an incoming stream of the right directionality.
  DCHECK_NE(QuicUtils::IsBidirectionalStreamId(stream_id), unidirectional_);
  DCHECK_NE(QuicUtils::IsServerInitiatedStreamId(transport_version_, stream_id),
            perspective() == Perspective::IS_SERVER);
  if (available_streams_.erase(stream_id) == 1) {
    // stream_id is available.
    return true;
  }

  if (largest_peer_created_stream_id_ !=
      QuicUtils::GetInvalidStreamId(transport_version_)) {
    DCHECK_GT(stream_id, largest_peer_created_stream_id_);
  }

  // Calculate increment of incoming_stream_count_ by creating stream_id.
  const QuicStreamCount delta = QuicUtils::StreamIdDelta(transport_version_);
  const QuicStreamId least_new_stream_id =
      largest_peer_created_stream_id_ ==
              QuicUtils::GetInvalidStreamId(transport_version_)
          ? GetFirstIncomingStreamId()
          : largest_peer_created_stream_id_ + delta;
  const QuicStreamCount stream_count_increment =
      (stream_id - least_new_stream_id) / delta + 1;

  if (incoming_stream_count_ + stream_count_increment >
      incoming_advertised_max_streams_) {
    QUIC_DLOG(INFO) << ENDPOINT
                    << "Failed to create a new incoming stream with id:"
                    << stream_id << ", reaching MAX_STREAMS limit: "
                    << incoming_advertised_max_streams_ << ".";
    delegate_->OnStreamIdManagerError(
        QUIC_INVALID_STREAM_ID,
        quiche::QuicheStrCat("Stream id ", stream_id,
                             " would exceed stream count limit ",
                             incoming_advertised_max_streams_));
    return false;
  }

  for (QuicStreamId id = least_new_stream_id; id < stream_id; id += delta) {
    available_streams_.insert(id);
  }
  incoming_stream_count_ += stream_count_increment;
  largest_peer_created_stream_id_ = stream_id;
  return true;
}

bool QuicStreamIdManager::IsAvailableStream(QuicStreamId id) const {
  DCHECK_NE(QuicUtils::IsBidirectionalStreamId(id), unidirectional_);
  if (!IsIncomingStream(id)) {
    // Stream IDs under next_ougoing_stream_id_ are either open or previously
    // open but now closed.
    return id >= next_outgoing_stream_id_;
  }
  // For peer created streams, we also need to consider available streams.
  return largest_peer_created_stream_id_ ==
             QuicUtils::GetInvalidStreamId(transport_version_) ||
         id > largest_peer_created_stream_id_ ||
         QuicContainsKey(available_streams_, id);
}

bool QuicStreamIdManager::IsIncomingStream(QuicStreamId id) const {
  DCHECK_NE(QuicUtils::IsBidirectionalStreamId(id), unidirectional_);
  // The 0x1 bit in the stream id indicates whether the stream id is
  // server- or client- initiated. Next_OUTGOING_stream_id_ has that bit
  // set based on whether this node is a server or client. Thus, if the stream
  // id in question has the 0x1 bit set opposite of next_OUTGOING_stream_id_,
  // then that stream id is incoming -- it is for streams initiated by the peer.
  return (id & 0x1) != (next_outgoing_stream_id_ & 0x1);
}

QuicStreamId QuicStreamIdManager::GetFirstOutgoingStreamId() const {
  return (unidirectional_) ? QuicUtils::GetFirstUnidirectionalStreamId(
                                 transport_version_, perspective())
                           : QuicUtils::GetFirstBidirectionalStreamId(
                                 transport_version_, perspective());
}

QuicStreamId QuicStreamIdManager::GetFirstIncomingStreamId() const {
  return (unidirectional_) ? QuicUtils::GetFirstUnidirectionalStreamId(
                                 transport_version_, peer_perspective())
                           : QuicUtils::GetFirstBidirectionalStreamId(
                                 transport_version_, peer_perspective());
}

Perspective QuicStreamIdManager::perspective() const {
  return perspective_;
}

Perspective QuicStreamIdManager::peer_perspective() const {
  return QuicUtils::InvertPerspective(perspective());
}

QuicStreamCount QuicStreamIdManager::available_incoming_streams() {
  return incoming_advertised_max_streams_ - incoming_stream_count_;
}

void QuicStreamIdManager::CalculateIncomingMaxStreamsWindow() {
  max_streams_window_ = incoming_actual_max_streams_ / kMaxStreamsWindowDivisor;
  if (max_streams_window_ == 0) {
    max_streams_window_ = 1;
  }
}

}  // namespace quic