// 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_stream_sequencer.h"

#include <algorithm>
#include <limits>
#include <utility>

#include "base/logging.h"
#include "net/quic/quic_clock.h"
#include "net/quic/quic_flags.h"
#include "net/quic/quic_frame_list.h"
#include "net/quic/quic_protocol.h"
#include "net/quic/reliable_quic_stream.h"
#include "net/quic/stream_sequencer_buffer.h"

using std::min;
using std::numeric_limits;
using std::string;

namespace net {

QuicStreamSequencer::QuicStreamSequencer(ReliableQuicStream* quic_stream,
                                         const QuicClock* clock)
    : stream_(quic_stream),
      close_offset_(numeric_limits<QuicStreamOffset>::max()),
      blocked_(false),
      num_frames_received_(0),
      num_duplicate_frames_received_(0),
      num_early_frames_received_(0),
      clock_(clock),
      ignore_read_data_(false) {
  if (FLAGS_quic_use_stream_sequencer_buffer) {
    DVLOG(1) << "Use StreamSequencerBuffer for stream: " << stream_->id();
    buffered_frames_.reset(
        new StreamSequencerBuffer(kStreamReceiveWindowLimit));
  } else {
    buffered_frames_.reset(new QuicFrameList());
  }
}

QuicStreamSequencer::~QuicStreamSequencer() {}

void QuicStreamSequencer::OnStreamFrame(const QuicStreamFrame& frame) {
  ++num_frames_received_;
  const QuicStreamOffset byte_offset = frame.offset;
  const size_t data_len = frame.data.length();
  if (data_len == 0 && !frame.fin) {
    // Stream frames must have data or a fin flag.
    stream_->CloseConnectionWithDetails(QUIC_INVALID_STREAM_FRAME,
                                        "Empty stream frame without FIN set.");
    return;
  }

  if (frame.fin) {
    CloseStreamAtOffset(frame.offset + data_len);
    if (data_len == 0) {
      return;
    }
  }
  size_t bytes_written;
  QuicErrorCode result = buffered_frames_->OnStreamData(
      byte_offset, frame.data, clock_->ApproximateNow(), &bytes_written);

  if (result == QUIC_INVALID_STREAM_DATA) {
    stream_->CloseConnectionWithDetails(
        QUIC_INVALID_STREAM_FRAME, "Stream frame overlaps with buffered data.");
    return;
  }
  if (result == QUIC_NO_ERROR && bytes_written == 0) {
    ++num_duplicate_frames_received_;
    // Silently ignore duplicates.
    return;
  }

  if (byte_offset > buffered_frames_->BytesConsumed()) {
    ++num_early_frames_received_;
  }

  if (blocked_) {
    return;
  }

  if (byte_offset == buffered_frames_->BytesConsumed()) {
    if (FLAGS_quic_implement_stop_reading && ignore_read_data_) {
      FlushBufferedFrames();
    } else {
      stream_->OnDataAvailable();
    }
  }
}

void QuicStreamSequencer::CloseStreamAtOffset(QuicStreamOffset offset) {
  const QuicStreamOffset kMaxOffset = numeric_limits<QuicStreamOffset>::max();

  // If there is a scheduled close, the new offset should match it.
  if (close_offset_ != kMaxOffset && offset != close_offset_) {
    stream_->Reset(QUIC_MULTIPLE_TERMINATION_OFFSETS);
    return;
  }

  close_offset_ = offset;

  MaybeCloseStream();
}

bool QuicStreamSequencer::MaybeCloseStream() {
  if (blocked_ || !IsClosed()) {
    return false;
  }

  DVLOG(1) << "Passing up termination, as we've processed "
           << buffered_frames_->BytesConsumed() << " of " << close_offset_
           << " bytes.";
  // This will cause the stream to consume the FIN.
  // Technically it's an error if |num_bytes_consumed| isn't exactly
  // equal to |close_offset|, but error handling seems silly at this point.
  if (FLAGS_quic_implement_stop_reading && ignore_read_data_) {
    // The sequencer is discarding stream data and must notify the stream on
    // receipt of a FIN because the consumer won't.
    stream_->OnFinRead();
  } else {
    stream_->OnDataAvailable();
  }
  buffered_frames_->Clear();
  return true;
}

int QuicStreamSequencer::GetReadableRegions(iovec* iov, size_t iov_len) const {
  DCHECK(!blocked_);
  return buffered_frames_->GetReadableRegions(iov, iov_len);
}

bool QuicStreamSequencer::GetReadableRegion(iovec* iov,
                                            QuicTime* timestamp) const {
  DCHECK(!blocked_);
  return buffered_frames_->GetReadableRegion(iov, timestamp);
}

int QuicStreamSequencer::Readv(const struct iovec* iov, size_t iov_len) {
  DCHECK(!blocked_);
  size_t bytes_read = buffered_frames_->Readv(iov, iov_len);
  stream_->AddBytesConsumed(bytes_read);
  return static_cast<int>(bytes_read);
}

bool QuicStreamSequencer::HasBytesToRead() const {
  return buffered_frames_->HasBytesToRead();
}

bool QuicStreamSequencer::IsClosed() const {
  return buffered_frames_->BytesConsumed() >= close_offset_;
}

void QuicStreamSequencer::MarkConsumed(size_t num_bytes_consumed) {
  DCHECK(!blocked_);
  bool result = buffered_frames_->MarkConsumed(num_bytes_consumed);
  if (!result) {
    LOG(DFATAL) << "Invalid argument to MarkConsumed."
                << " expect to consume: " << num_bytes_consumed
                << ", but not enough bytes available.";
    stream_->Reset(QUIC_ERROR_PROCESSING_STREAM);
    return;
  }
  stream_->AddBytesConsumed(num_bytes_consumed);
}

void QuicStreamSequencer::SetBlockedUntilFlush() {
  blocked_ = true;
}

void QuicStreamSequencer::SetUnblocked() {
  blocked_ = false;
  if (IsClosed() || HasBytesToRead()) {
    stream_->OnDataAvailable();
  }
}

void QuicStreamSequencer::StopReading() {
  if (ignore_read_data_) {
    return;
  }
  ignore_read_data_ = true;
  FlushBufferedFrames();
}

void QuicStreamSequencer::FlushBufferedFrames() {
  DCHECK(ignore_read_data_);
  size_t bytes_flushed = buffered_frames_->FlushBufferedFrames();
  DVLOG(1) << "Flushing buffered data at offset "
           << buffered_frames_->BytesConsumed() << " length " << bytes_flushed
           << " for stream " << stream_->id();
  stream_->AddBytesConsumed(bytes_flushed);
  MaybeCloseStream();
}

size_t QuicStreamSequencer::NumBytesBuffered() const {
  return buffered_frames_->BytesBuffered();
}

QuicStreamOffset QuicStreamSequencer::NumBytesConsumed() const {
  return buffered_frames_->BytesConsumed();
}

}  // namespace net