// Copyright (c) 2012 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/quic/quic_packet_generator.h"

#include "base/basictypes.h"
#include "base/logging.h"
#include "net/quic/quic_fec_group.h"
#include "net/quic/quic_utils.h"

using base::StringPiece;

namespace net {

namespace {

// We want to put some space between a protected packet and the FEC packet to
// avoid losing them both within the same loss episode. On the other hand,
// we expect to be able to recover from any loss in about an RTT.
// We resolve this tradeoff by sending an FEC packet atmost half an RTT,
// or equivalently, half a cwnd, after the first protected packet. Since we
// don't want to delay an FEC packet past half an RTT, we set the max FEC
// group size to be half the current congestion window.
const float kCongestionWindowMultiplierForFecGroupSize = 0.5;

}  // namespace

class QuicAckNotifier;

QuicPacketGenerator::QuicPacketGenerator(QuicConnectionId connection_id,
                                         QuicFramer* framer,
                                         QuicRandom* random_generator,
                                         DelegateInterface* delegate)
    : delegate_(delegate),
      debug_delegate_(nullptr),
      packet_creator_(connection_id, framer, random_generator),
      batch_mode_(false),
      should_fec_protect_(false),
      should_send_ack_(false),
      should_send_feedback_(false),
      should_send_stop_waiting_(false) {}

QuicPacketGenerator::~QuicPacketGenerator() {
  for (QuicFrames::iterator it = queued_control_frames_.begin();
       it != queued_control_frames_.end(); ++it) {
    switch (it->type) {
      case PADDING_FRAME:
        delete it->padding_frame;
        break;
      case STREAM_FRAME:
        delete it->stream_frame;
        break;
      case ACK_FRAME:
        delete it->ack_frame;
        break;
      case CONGESTION_FEEDBACK_FRAME:
        delete it->congestion_feedback_frame;
        break;
      case RST_STREAM_FRAME:
        delete it->rst_stream_frame;
        break;
      case CONNECTION_CLOSE_FRAME:
        delete it->connection_close_frame;
        break;
      case GOAWAY_FRAME:
        delete it->goaway_frame;
        break;
      case WINDOW_UPDATE_FRAME:
        delete it->window_update_frame;
        break;
      case BLOCKED_FRAME:
        delete it->blocked_frame;
        break;
      case STOP_WAITING_FRAME:
        delete it->stop_waiting_frame;
        break;
      case PING_FRAME:
        delete it->ping_frame;
        break;
      case NUM_FRAME_TYPES:
        DCHECK(false) << "Cannot delete type: " << it->type;
    }
  }
}

// NetworkChangeVisitor method.
void QuicPacketGenerator::OnCongestionWindowChange(
    QuicByteCount congestion_window) {
  packet_creator_.set_max_packets_per_fec_group(
      static_cast<size_t>(kCongestionWindowMultiplierForFecGroupSize *
                          congestion_window / kDefaultTCPMSS));
}

void QuicPacketGenerator::SetShouldSendAck(bool also_send_feedback,
                                           bool also_send_stop_waiting) {
  should_send_ack_ = true;
  should_send_feedback_ = also_send_feedback;
  should_send_stop_waiting_ = also_send_stop_waiting;
  SendQueuedFrames(false);
}

void QuicPacketGenerator::SetShouldSendStopWaiting() {
  should_send_stop_waiting_ = true;
  SendQueuedFrames(false);
}

void QuicPacketGenerator::AddControlFrame(const QuicFrame& frame) {
  queued_control_frames_.push_back(frame);
  SendQueuedFrames(false);
}

QuicConsumedData QuicPacketGenerator::ConsumeData(QuicStreamId id,
                                                  const IOVector& data_to_write,
                                                  QuicStreamOffset offset,
                                                  bool fin,
                                                  FecProtection fec_protection,
                                                  QuicAckNotifier* notifier) {
  IsHandshake handshake = id == kCryptoStreamId ? IS_HANDSHAKE : NOT_HANDSHAKE;
  // To make reasoning about crypto frames easier, we don't combine them with
  // other retransmittable frames in a single packet.
  const bool flush = handshake == IS_HANDSHAKE &&
      packet_creator_.HasPendingRetransmittableFrames();
  SendQueuedFrames(flush);

  size_t total_bytes_consumed = 0;
  bool fin_consumed = false;

  if (!packet_creator_.HasRoomForStreamFrame(id, offset)) {
    SerializeAndSendPacket();
  }

  if (fec_protection == MUST_FEC_PROTECT) {
    MaybeStartFecProtection();
  }

  IOVector data = data_to_write;
  size_t data_size = data.TotalBufferSize();
  while (delegate_->ShouldGeneratePacket(NOT_RETRANSMISSION,
                                         HAS_RETRANSMITTABLE_DATA, handshake)) {
    QuicFrame frame;
    size_t bytes_consumed;
    if (notifier != nullptr) {
      // We want to track which packet this stream frame ends up in.
      bytes_consumed = packet_creator_.CreateStreamFrameWithNotifier(
          id, data, offset + total_bytes_consumed, fin, notifier, &frame);
    } else {
      bytes_consumed = packet_creator_.CreateStreamFrame(
          id, data, offset + total_bytes_consumed, fin, &frame);
    }
    if (!AddFrame(frame)) {
      LOG(DFATAL) << "Failed to add stream frame.";
      // Inability to add a STREAM frame creates an unrecoverable hole in a
      // the stream, so it's best to close the connection.
      delegate_->CloseConnection(QUIC_INTERNAL_ERROR, false);
      return QuicConsumedData(0, false);
    }

    total_bytes_consumed += bytes_consumed;
    fin_consumed = fin && total_bytes_consumed == data_size;
    data.Consume(bytes_consumed);
    DCHECK(data.Empty() || packet_creator_.BytesFree() == 0u);

    // TODO(ianswett): Restore packet reordering.
    if (!InBatchMode() || !packet_creator_.HasRoomForStreamFrame(id, offset)) {
      SerializeAndSendPacket();
    }

    if (data.Empty()) {
      // We're done writing the data. Exit the loop.
      // We don't make this a precondition because we could have 0 bytes of data
      // if we're simply writing a fin.
      if (fec_protection == MUST_FEC_PROTECT) {
        // Turn off FEC protection when we're done writing protected data.
        DVLOG(1) << "Turning FEC protection OFF";
        should_fec_protect_ = false;
      }
      break;
    }
  }

  // Don't allow the handshake to be bundled with other retransmittable frames.
  if (handshake == IS_HANDSHAKE) {
    SendQueuedFrames(true);
  }

  // Try to close FEC group since we've either run out of data to send or we're
  // blocked. If not in batch mode, force close the group.
  // TODO(jri): This method should be called with flush=false here
  // once the timer-based FEC sending is done, to separate FEC sending from
  // the end of batch operations.
  MaybeSendFecPacketAndCloseGroup(!InBatchMode());

  DCHECK(InBatchMode() || !packet_creator_.HasPendingFrames());
  return QuicConsumedData(total_bytes_consumed, fin_consumed);
}

bool QuicPacketGenerator::CanSendWithNextPendingFrameAddition() const {
  DCHECK(HasPendingFrames());
  HasRetransmittableData retransmittable =
      (should_send_ack_ || should_send_feedback_ || should_send_stop_waiting_)
      ? NO_RETRANSMITTABLE_DATA : HAS_RETRANSMITTABLE_DATA;
  if (retransmittable == HAS_RETRANSMITTABLE_DATA) {
      DCHECK(!queued_control_frames_.empty());  // These are retransmittable.
  }
  return delegate_->ShouldGeneratePacket(NOT_RETRANSMISSION, retransmittable,
                                         NOT_HANDSHAKE);
}

void QuicPacketGenerator::SendQueuedFrames(bool flush) {
  // Only add pending frames if we are SURE we can then send the whole packet.
  while (HasPendingFrames() &&
         (flush || CanSendWithNextPendingFrameAddition())) {
    if (!AddNextPendingFrame()) {
      // Packet was full, so serialize and send it.
      SerializeAndSendPacket();
    }
  }

  if (!InBatchMode() || flush) {
    if (packet_creator_.HasPendingFrames()) {
      SerializeAndSendPacket();
    }
    // Ensure the FEC group is closed at the end of this method unless other
    // writes are pending.
    MaybeSendFecPacketAndCloseGroup(true);
  }
}

void QuicPacketGenerator::MaybeStartFecProtection() {
  if (!packet_creator_.IsFecEnabled()) {
    return;
  }
  DVLOG(1) << "Turning FEC protection ON";
  should_fec_protect_ = true;
  if (packet_creator_.IsFecProtected()) {
    // Only start creator's FEC protection if not already on.
    return;
  }
  if (HasQueuedFrames()) {
    // TODO(jri): This currently requires that the generator flush out any
    // pending frames when FEC protection is turned on. If current packet can be
    // converted to an FEC protected packet, do it. This will require the
    // generator to check if the resulting expansion still allows the incoming
    // frame to be added to the packet.
    SendQueuedFrames(true);
  }
  packet_creator_.StartFecProtectingPackets();
  DCHECK(packet_creator_.IsFecProtected());
}

void QuicPacketGenerator::MaybeSendFecPacketAndCloseGroup(bool force) {
  if (!packet_creator_.IsFecProtected() ||
      packet_creator_.HasPendingFrames() ||
      !packet_creator_.ShouldSendFec(force)) {
    return;
  }
  // TODO(jri): SerializeFec can return a NULL packet, and this should
  // cause an early return, with a call to delegate_->OnPacketGenerationError.
  SerializedPacket serialized_fec = packet_creator_.SerializeFec();
  DCHECK(serialized_fec.packet);
  delegate_->OnSerializedPacket(serialized_fec);
  // Turn FEC protection off if creator's protection is on and the creator
  // does not have an open FEC group.
  // Note: We only wait until the frames queued in the creator are flushed;
  // pending frames in the generator will not keep us from turning FEC off.
  if (!should_fec_protect_ && !packet_creator_.IsFecGroupOpen()) {
    packet_creator_.StopFecProtectingPackets();
    DCHECK(!packet_creator_.IsFecProtected());
  }
}

bool QuicPacketGenerator::InBatchMode() {
  return batch_mode_;
}

void QuicPacketGenerator::StartBatchOperations() {
  batch_mode_ = true;
}

void QuicPacketGenerator::FinishBatchOperations() {
  batch_mode_ = false;
  SendQueuedFrames(false);
}

void QuicPacketGenerator::FlushAllQueuedFrames() {
  SendQueuedFrames(true);
}

bool QuicPacketGenerator::HasQueuedFrames() const {
  return packet_creator_.HasPendingFrames() || HasPendingFrames();
}

bool QuicPacketGenerator::HasPendingFrames() const {
  return should_send_ack_ || should_send_feedback_ ||
      should_send_stop_waiting_ || !queued_control_frames_.empty();
}

bool QuicPacketGenerator::AddNextPendingFrame() {
  if (should_send_ack_) {
    pending_ack_frame_.reset(delegate_->CreateAckFrame());
    // If we can't this add the frame now, then we still need to do so later.
    should_send_ack_ = !AddFrame(QuicFrame(pending_ack_frame_.get()));
    // Return success if we have cleared out this flag (i.e., added the frame).
    // If we still need to send, then the frame is full, and we have failed.
    return !should_send_ack_;
  }

  if (should_send_feedback_) {
    pending_feedback_frame_.reset(delegate_->CreateFeedbackFrame());
    // If we can't this add the frame now, then we still need to do so later.
    should_send_feedback_ = !AddFrame(QuicFrame(pending_feedback_frame_.get()));
    // Return success if we have cleared out this flag (i.e., added the frame).
    // If we still need to send, then the frame is full, and we have failed.
    return !should_send_feedback_;
  }

  if (should_send_stop_waiting_) {
    pending_stop_waiting_frame_.reset(delegate_->CreateStopWaitingFrame());
    // If we can't this add the frame now, then we still need to do so later.
    should_send_stop_waiting_ =
        !AddFrame(QuicFrame(pending_stop_waiting_frame_.get()));
    // Return success if we have cleared out this flag (i.e., added the frame).
    // If we still need to send, then the frame is full, and we have failed.
    return !should_send_stop_waiting_;
  }

  LOG_IF(DFATAL, queued_control_frames_.empty())
      << "AddNextPendingFrame called with no queued control frames.";
  if (!AddFrame(queued_control_frames_.back())) {
    // Packet was full.
    return false;
  }
  queued_control_frames_.pop_back();
  return true;
}

bool QuicPacketGenerator::AddFrame(const QuicFrame& frame) {
  bool success = packet_creator_.AddSavedFrame(frame);
  if (success && debug_delegate_) {
    debug_delegate_->OnFrameAddedToPacket(frame);
  }
  return success;
}

void QuicPacketGenerator::SerializeAndSendPacket() {
  SerializedPacket serialized_packet = packet_creator_.SerializePacket();
  DCHECK(serialized_packet.packet);
  delegate_->OnSerializedPacket(serialized_packet);
  MaybeSendFecPacketAndCloseGroup(false);
}

void QuicPacketGenerator::StopSendingVersion() {
  packet_creator_.StopSendingVersion();
}

QuicPacketSequenceNumber QuicPacketGenerator::sequence_number() const {
  return packet_creator_.sequence_number();
}

size_t QuicPacketGenerator::max_packet_length() const {
  return packet_creator_.max_packet_length();
}

void QuicPacketGenerator::set_max_packet_length(size_t length) {
  packet_creator_.set_max_packet_length(length);
}

QuicEncryptedPacket* QuicPacketGenerator::SerializeVersionNegotiationPacket(
    const QuicVersionVector& supported_versions) {
  return packet_creator_.SerializeVersionNegotiationPacket(supported_versions);
}

SerializedPacket QuicPacketGenerator::ReserializeAllFrames(
    const QuicFrames& frames,
    QuicSequenceNumberLength original_length) {
  return packet_creator_.ReserializeAllFrames(frames, original_length);
}

void QuicPacketGenerator::UpdateSequenceNumberLength(
      QuicPacketSequenceNumber least_packet_awaited_by_peer,
      QuicByteCount congestion_window) {
  return packet_creator_.UpdateSequenceNumberLength(
      least_packet_awaited_by_peer, congestion_window);
}

void QuicPacketGenerator::set_encryption_level(EncryptionLevel level) {
  packet_creator_.set_encryption_level(level);
}

}  // namespace net