/*
 *  Copyright (c) 2013 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree. An additional intellectual property rights grant can be found
 *  in the file PATENTS.  All contributing project authors may
 *  be found in the AUTHORS file in the root of the source tree.
 */

#include "modules/remote_bitrate_estimator/test/bwe_test_framework.h"

#include <stdio.h>

#include <sstream>

#include "modules/rtp_rtcp/source/rtp_header_extensions.h"
#include "rtc_base/constructormagic.h"
#include "rtc_base/numerics/safe_minmax.h"
#include "rtc_base/system/unused.h"

namespace webrtc {
namespace testing {
namespace bwe {

RateCounter::RateCounter(int64_t window_size_ms)
    : window_size_us_(1000 * window_size_ms),
      recently_received_packets_(0),
      recently_received_bytes_(0),
      last_accumulated_us_(0),
      window_() {}

RateCounter::RateCounter() : RateCounter(1000) {}

RateCounter::~RateCounter() = default;

class DelayCapHelper {
 public:
  // Max delay = 0 stands for +infinite.
  DelayCapHelper() : max_delay_us_(0), delay_stats_() {}

  void set_max_delay_ms(int64_t max_delay_ms) {
    BWE_TEST_LOGGING_ENABLE(false);
    BWE_TEST_LOGGING_LOG1("Max Delay", "%d ms", static_cast<int>(max_delay_ms));
    assert(max_delay_ms >= 0);
    max_delay_us_ = max_delay_ms * 1000;
  }

  bool ShouldSendPacket(int64_t send_time_us, int64_t arrival_time_us) {
    int64_t packet_delay_us = send_time_us - arrival_time_us;
    delay_stats_.Push((std::min(packet_delay_us, max_delay_us_) + 500) / 1000);
    return (max_delay_us_ == 0 || max_delay_us_ >= packet_delay_us);
  }

  const Stats<double>& delay_stats() const { return delay_stats_; }

 private:
  int64_t max_delay_us_;
  Stats<double> delay_stats_;

  RTC_DISALLOW_COPY_AND_ASSIGN(DelayCapHelper);
};

const FlowIds CreateFlowIds(const int* flow_ids_array, size_t num_flow_ids) {
  FlowIds flow_ids(&flow_ids_array[0], flow_ids_array + num_flow_ids);
  return flow_ids;
}

const FlowIds CreateFlowIdRange(int initial_value, int last_value) {
  int size = last_value - initial_value + 1;
  assert(size > 0);
  int* flow_ids_array = new int[size];
  for (int i = initial_value; i <= last_value; ++i) {
    flow_ids_array[i - initial_value] = i;
  }
  return CreateFlowIds(flow_ids_array, size);
}

void RateCounter::UpdateRates(int64_t send_time_us, uint32_t payload_size) {
  ++recently_received_packets_;
  recently_received_bytes_ += payload_size;
  last_accumulated_us_ = send_time_us;
  window_.push_back(std::make_pair(send_time_us, payload_size));
  while (!window_.empty()) {
    const TimeSizePair& packet = window_.front();
    if (packet.first > (last_accumulated_us_ - window_size_us_)) {
      break;
    }
    assert(recently_received_packets_ >= 1);
    assert(recently_received_bytes_ >= packet.second);
    --recently_received_packets_;
    recently_received_bytes_ -= packet.second;
    window_.pop_front();
  }
}

uint32_t RateCounter::bits_per_second() const {
  return (8 * recently_received_bytes_) / BitrateWindowS();
}

uint32_t RateCounter::packets_per_second() const {
  return recently_received_packets_ / BitrateWindowS();
}

double RateCounter::BitrateWindowS() const {
  return static_cast<double>(window_size_us_) / (1000 * 1000);
}

MediaPacket::MediaPacket() {
  memset(&header_, 0, sizeof(header_));
}

MediaPacket::MediaPacket(int flow_id,
                         int64_t send_time_us,
                         size_t payload_size,
                         uint16_t sequence_number)
    : Packet(flow_id, send_time_us, payload_size) {
  header_ = RTPHeader();
  header_.sequenceNumber = sequence_number;
}

MediaPacket::MediaPacket(int flow_id,
                         int64_t send_time_us,
                         size_t payload_size,
                         const RTPHeader& header)
    : Packet(flow_id, send_time_us, payload_size), header_(header) {}

MediaPacket::MediaPacket(int64_t send_time_us, uint16_t sequence_number)
    : Packet(0, send_time_us, 0) {
  header_ = RTPHeader();
  header_.sequenceNumber = sequence_number;
}

void MediaPacket::SetAbsSendTimeMs(int64_t abs_send_time_ms) {
  header_.extension.hasAbsoluteSendTime = true;
  header_.extension.absoluteSendTime =
      ((static_cast<int64_t>(abs_send_time_ms * (1 << 18)) + 500) / 1000) &
      0x00fffffful;
}

// Copies payload size and sequence number.
RtpPacketReceived MediaPacket::GetRtpPacket() const {
  RtpPacketReceived packet;

  packet.SetPayloadSize(payload_size());
  packet.SetSequenceNumber(header_.sequenceNumber);
  return packet;
}

BbrBweFeedback::BbrBweFeedback(
    int flow_id,
    int64_t send_time_us,
    int64_t latest_send_time_ms,
    const std::vector<uint16_t>& packet_feedback_vector)
    : FeedbackPacket(flow_id, send_time_us, latest_send_time_ms),
      packet_feedback_vector_(packet_feedback_vector) {}

RembFeedback::RembFeedback(int flow_id,
                           int64_t send_time_us,
                           int64_t last_send_time_ms,
                           uint32_t estimated_bps,
                           RTCPReportBlock report_block)
    : FeedbackPacket(flow_id, send_time_us, last_send_time_ms),
      estimated_bps_(estimated_bps),
      report_block_(report_block) {}

SendSideBweFeedback::SendSideBweFeedback(
    int flow_id,
    int64_t send_time_us,
    int64_t last_send_time_ms,
    const std::vector<PacketFeedback>& packet_feedback_vector)
    : FeedbackPacket(flow_id, send_time_us, last_send_time_ms),
      packet_feedback_vector_(packet_feedback_vector) {}

bool IsTimeSorted(const Packets& packets) {
  PacketsConstIt last_it = packets.begin();
  for (PacketsConstIt it = last_it; it != packets.end(); ++it) {
    if (it != last_it && **it < **last_it) {
      return false;
    }
    last_it = it;
  }
  return true;
}

PacketProcessor::PacketProcessor(PacketProcessorListener* listener,
                                 int flow_id,
                                 ProcessorType type)
    : listener_(listener), flow_ids_(&flow_id, &flow_id + 1) {
  if (listener_) {
    listener_->AddPacketProcessor(this, type);
  }
}

PacketProcessor::PacketProcessor(PacketProcessorListener* listener,
                                 const FlowIds& flow_ids,
                                 ProcessorType type)
    : listener_(listener), flow_ids_(flow_ids) {
  if (listener_) {
    listener_->AddPacketProcessor(this, type);
  }
}

PacketProcessor::~PacketProcessor() {
  if (listener_) {
    listener_->RemovePacketProcessor(this);
  }
}

uint32_t PacketProcessor::packets_per_second() const {
  return rate_counter_.packets_per_second();
}

uint32_t PacketProcessor::bits_per_second() const {
  return rate_counter_.bits_per_second();
}

RateCounterFilter::RateCounterFilter(PacketProcessorListener* listener,
                                     int flow_id,
                                     const char* name,
                                     const std::string& algorithm_name)
    : PacketProcessor(listener, flow_id, kRegular),
      packets_per_second_stats_(),
      kbps_stats_(),
      start_plotting_time_ms_(0),
      flow_id_(flow_id),
      name_(name),
      algorithm_name_(algorithm_name) {
  // Only used when compiling with BWE test logging enabled.
  RTC_UNUSED(flow_id_);
}

RateCounterFilter::RateCounterFilter(PacketProcessorListener* listener,
                                     const FlowIds& flow_ids,
                                     const char* name,
                                     const std::string& algorithm_name)
    : PacketProcessor(listener, flow_ids, kRegular),
      packets_per_second_stats_(),
      kbps_stats_(),
      start_plotting_time_ms_(0),
      name_(name),
      algorithm_name_(algorithm_name) {
  // TODO(terelius): Appending the flow IDs to the algorithm name is a hack to
  // keep the current plot functionality without having to print the full
  // context for each PLOT line. It is unclear whether multiple flow IDs are
  // needed at all in the long term.
  std::stringstream ss;
  ss << algorithm_name_;
  for (int flow_id : flow_ids) {
    ss << ',' << flow_id;
  }
  algorithm_name_ = ss.str();
}

RateCounterFilter::RateCounterFilter(PacketProcessorListener* listener,
                                     const FlowIds& flow_ids,
                                     const char* name,
                                     int64_t start_plotting_time_ms,
                                     const std::string& algorithm_name)
    : RateCounterFilter(listener, flow_ids, name, algorithm_name) {
  start_plotting_time_ms_ = start_plotting_time_ms;
}

RateCounterFilter::~RateCounterFilter() {
  LogStats();
}

void RateCounterFilter::LogStats() {
  BWE_TEST_LOGGING_CONTEXT("RateCounterFilter");
  packets_per_second_stats_.Log("pps");
  kbps_stats_.Log("kbps");
}

Stats<double> RateCounterFilter::GetBitrateStats() const {
  return kbps_stats_;
}

void RateCounterFilter::Plot(int64_t timestamp_ms) {
  // TODO(stefan): Reorganize logging configuration to reduce amount
  // of preprocessor conditionals in the code.
  uint32_t plot_kbps = 0;
  if (timestamp_ms >= start_plotting_time_ms_) {
    plot_kbps = rate_counter_.bits_per_second() / 1000.0;
  }
  BWE_TEST_LOGGING_CONTEXT(name_.c_str());
  if (algorithm_name_.empty()) {
    BWE_TEST_LOGGING_PLOT_WITH_SSRC(0, "Throughput_kbps#1", timestamp_ms,
                                    plot_kbps, flow_id_);
  } else {
    BWE_TEST_LOGGING_PLOT_WITH_NAME_AND_SSRC(0, "Throughput_kbps#1",
                                             timestamp_ms, plot_kbps, flow_id_,
                                             algorithm_name_);
  }
  RTC_UNUSED(plot_kbps);
}

void RateCounterFilter::RunFor(int64_t /*time_ms*/, Packets* in_out) {
  assert(in_out);
  for (const Packet* packet : *in_out) {
    rate_counter_.UpdateRates(packet->send_time_us(),
                              static_cast<int>(packet->payload_size()));
  }
  packets_per_second_stats_.Push(rate_counter_.packets_per_second());
  kbps_stats_.Push(rate_counter_.bits_per_second() / 1000.0);
}

LossFilter::LossFilter(PacketProcessorListener* listener, int flow_id)
    : PacketProcessor(listener, flow_id, kRegular),
      random_(0x12345678),
      loss_fraction_(0.0f) {}

LossFilter::LossFilter(PacketProcessorListener* listener,
                       const FlowIds& flow_ids)
    : PacketProcessor(listener, flow_ids, kRegular),
      random_(0x12345678),
      loss_fraction_(0.0f) {}

void LossFilter::SetLoss(float loss_percent) {
  BWE_TEST_LOGGING_ENABLE(false);
  BWE_TEST_LOGGING_LOG1("Loss", "%f%%", loss_percent);
  assert(loss_percent >= 0.0f);
  assert(loss_percent <= 100.0f);
  loss_fraction_ = loss_percent * 0.01f;
}

void LossFilter::RunFor(int64_t /*time_ms*/, Packets* in_out) {
  assert(in_out);
  for (PacketsIt it = in_out->begin(); it != in_out->end();) {
    if (random_.Rand<float>() < loss_fraction_) {
      delete *it;
      it = in_out->erase(it);
    } else {
      ++it;
    }
  }
}

const int64_t kDefaultOneWayDelayUs = 0;

DelayFilter::DelayFilter(PacketProcessorListener* listener, int flow_id)
    : PacketProcessor(listener, flow_id, kRegular),
      one_way_delay_us_(kDefaultOneWayDelayUs),
      last_send_time_us_(0) {}

DelayFilter::DelayFilter(PacketProcessorListener* listener,
                         const FlowIds& flow_ids)
    : PacketProcessor(listener, flow_ids, kRegular),
      one_way_delay_us_(kDefaultOneWayDelayUs),
      last_send_time_us_(0) {}

void DelayFilter::SetOneWayDelayMs(int64_t one_way_delay_ms) {
  BWE_TEST_LOGGING_ENABLE(false);
  BWE_TEST_LOGGING_LOG1("Delay", "%d ms", static_cast<int>(one_way_delay_ms));
  assert(one_way_delay_ms >= 0);
  one_way_delay_us_ = one_way_delay_ms * 1000;
}

void DelayFilter::RunFor(int64_t /*time_ms*/, Packets* in_out) {
  assert(in_out);
  for (Packet* packet : *in_out) {
    int64_t new_send_time_us = packet->send_time_us() + one_way_delay_us_;
    last_send_time_us_ = std::max(last_send_time_us_, new_send_time_us);
    packet->set_send_time_us(last_send_time_us_);
  }
}

JitterFilter::JitterFilter(PacketProcessorListener* listener, int flow_id)
    : PacketProcessor(listener, flow_id, kRegular),
      random_(0x89674523),
      stddev_jitter_us_(0),
      last_send_time_us_(0),
      reordering_(false) {}

JitterFilter::JitterFilter(PacketProcessorListener* listener,
                           const FlowIds& flow_ids)
    : PacketProcessor(listener, flow_ids, kRegular),
      random_(0x89674523),
      stddev_jitter_us_(0),
      last_send_time_us_(0),
      reordering_(false) {}

const int kN = 3;  // Truncated N sigma gaussian.

void JitterFilter::SetMaxJitter(int64_t max_jitter_ms) {
  BWE_TEST_LOGGING_ENABLE(false);
  BWE_TEST_LOGGING_LOG1("Max Jitter", "%d ms", static_cast<int>(max_jitter_ms));
  assert(max_jitter_ms >= 0);
  // Truncated gaussian, Max jitter = kN*sigma.
  stddev_jitter_us_ = (max_jitter_ms * 1000 + kN / 2) / kN;
}

namespace {
inline int64_t TruncatedNSigmaGaussian(Random* const random,
                                       int64_t mean,
                                       int64_t std_dev) {
  const int64_t gaussian_random = random->Gaussian(mean, std_dev);
  return rtc::SafeClamp(gaussian_random, -kN * std_dev, kN * std_dev);
}
}  // namespace

void JitterFilter::RunFor(int64_t /*time_ms*/, Packets* in_out) {
  assert(in_out);
  for (Packet* packet : *in_out) {
    int64_t jitter_us =
        std::abs(TruncatedNSigmaGaussian(&random_, 0, stddev_jitter_us_));
    int64_t new_send_time_us = packet->send_time_us() + jitter_us;

    if (!reordering_) {
      new_send_time_us = std::max(last_send_time_us_, new_send_time_us);
    }

    // Receiver timestamp cannot be lower than sender timestamp.
    assert(new_send_time_us >= packet->sender_timestamp_us());

    packet->set_send_time_us(new_send_time_us);
    last_send_time_us_ = new_send_time_us;
  }
}

// Computes the expected value for a right sided (abs) truncated gaussian.
// Does not take into account  possible reoerdering updates.
int64_t JitterFilter::MeanUs() {
  const double kPi = 3.1415926535897932;
  double max_jitter_us = static_cast<double>(kN * stddev_jitter_us_);
  double right_sided_mean_us =
      static_cast<double>(stddev_jitter_us_) / sqrt(kPi / 2.0);
  double truncated_mean_us =
      right_sided_mean_us *
          (1.0 - exp(-pow(static_cast<double>(kN), 2.0) / 2.0)) +
      max_jitter_us * erfc(static_cast<double>(kN));
  return static_cast<int64_t>(truncated_mean_us + 0.5);
}

ReorderFilter::ReorderFilter(PacketProcessorListener* listener, int flow_id)
    : PacketProcessor(listener, flow_id, kRegular),
      random_(0x27452389),
      reorder_fraction_(0.0f) {}

ReorderFilter::ReorderFilter(PacketProcessorListener* listener,
                             const FlowIds& flow_ids)
    : PacketProcessor(listener, flow_ids, kRegular),
      random_(0x27452389),
      reorder_fraction_(0.0f) {}

void ReorderFilter::SetReorder(float reorder_percent) {
  BWE_TEST_LOGGING_ENABLE(false);
  BWE_TEST_LOGGING_LOG1("Reordering", "%f%%", reorder_percent);
  assert(reorder_percent >= 0.0f);
  assert(reorder_percent <= 100.0f);
  reorder_fraction_ = reorder_percent * 0.01f;
}

void ReorderFilter::RunFor(int64_t /*time_ms*/, Packets* in_out) {
  assert(in_out);
  if (in_out->size() >= 2) {
    PacketsIt last_it = in_out->begin();
    PacketsIt it = last_it;
    while (++it != in_out->end()) {
      if (random_.Rand<float>() < reorder_fraction_) {
        int64_t t1 = (*last_it)->send_time_us();
        int64_t t2 = (*it)->send_time_us();
        std::swap(*last_it, *it);
        (*last_it)->set_send_time_us(t1);
        (*it)->set_send_time_us(t2);
      }
      last_it = it;
    }
  }
}

const uint32_t kDefaultKbps = 1200;

ChokeFilter::ChokeFilter(PacketProcessorListener* listener, int flow_id)
    : PacketProcessor(listener, flow_id, kRegular),
      capacity_kbps_(kDefaultKbps),
      last_send_time_us_(0),
      delay_cap_helper_(new DelayCapHelper()) {}

ChokeFilter::ChokeFilter(PacketProcessorListener* listener,
                         const FlowIds& flow_ids)
    : PacketProcessor(listener, flow_ids, kRegular),
      capacity_kbps_(kDefaultKbps),
      last_send_time_us_(0),
      delay_cap_helper_(new DelayCapHelper()) {}

ChokeFilter::~ChokeFilter() {}

void ChokeFilter::set_capacity_kbps(uint32_t kbps) {
  BWE_TEST_LOGGING_ENABLE(false);
  BWE_TEST_LOGGING_LOG1("BitrateChoke", "%d kbps", kbps);
  capacity_kbps_ = kbps;
}

uint32_t ChokeFilter::capacity_kbps() {
  return capacity_kbps_;
}

void ChokeFilter::RunFor(int64_t /*time_ms*/, Packets* in_out) {
  assert(in_out);
  for (PacketsIt it = in_out->begin(); it != in_out->end();) {
    int64_t earliest_send_time_us =
        std::max(last_send_time_us_, (*it)->send_time_us());
    int64_t new_send_time_us =
        earliest_send_time_us +
        ((*it)->payload_size() * 8 * 1000 + capacity_kbps_ / 2) /
            capacity_kbps_;
    BWE_TEST_LOGGING_PLOT(0, "MaxThroughput_", new_send_time_us / 1000,
                          capacity_kbps_);
    if (delay_cap_helper_->ShouldSendPacket(new_send_time_us,
                                            (*it)->send_time_us())) {
      (*it)->set_send_time_us(new_send_time_us);
      last_send_time_us_ = new_send_time_us;
      ++it;
    } else {
      delete *it;
      it = in_out->erase(it);
    }
  }
}

void ChokeFilter::set_max_delay_ms(int64_t max_delay_ms) {
  delay_cap_helper_->set_max_delay_ms(max_delay_ms);
}

Stats<double> ChokeFilter::GetDelayStats() const {
  return delay_cap_helper_->delay_stats();
}

TraceBasedDeliveryFilter::TraceBasedDeliveryFilter(
    PacketProcessorListener* listener,
    int flow_id)
    : PacketProcessor(listener, flow_id, kRegular),
      current_offset_us_(0),
      delivery_times_us_(),
      next_delivery_it_(),
      local_time_us_(-1),
      rate_counter_(new RateCounter),
      name_(""),
      delay_cap_helper_(new DelayCapHelper()),
      packets_per_second_stats_(),
      kbps_stats_() {}

TraceBasedDeliveryFilter::TraceBasedDeliveryFilter(
    PacketProcessorListener* listener,
    const FlowIds& flow_ids)
    : PacketProcessor(listener, flow_ids, kRegular),
      current_offset_us_(0),
      delivery_times_us_(),
      next_delivery_it_(),
      local_time_us_(-1),
      rate_counter_(new RateCounter),
      name_(""),
      delay_cap_helper_(new DelayCapHelper()),
      packets_per_second_stats_(),
      kbps_stats_() {}

TraceBasedDeliveryFilter::TraceBasedDeliveryFilter(
    PacketProcessorListener* listener,
    int flow_id,
    const char* name)
    : PacketProcessor(listener, flow_id, kRegular),
      current_offset_us_(0),
      delivery_times_us_(),
      next_delivery_it_(),
      local_time_us_(-1),
      rate_counter_(new RateCounter),
      name_(name),
      delay_cap_helper_(new DelayCapHelper()),
      packets_per_second_stats_(),
      kbps_stats_() {}

TraceBasedDeliveryFilter::~TraceBasedDeliveryFilter() {}

bool TraceBasedDeliveryFilter::Init(const std::string& filename) {
  FILE* trace_file = fopen(filename.c_str(), "r");
  if (!trace_file) {
    return false;
  }
  int64_t first_timestamp = -1;
  while (!feof(trace_file)) {
    const size_t kMaxLineLength = 100;
    char line[kMaxLineLength];
    if (fgets(line, kMaxLineLength, trace_file)) {
      std::string line_string(line);
      std::istringstream buffer(line_string);
      int64_t timestamp;
      buffer >> timestamp;
      timestamp /= 1000;  // Convert to microseconds.
      if (first_timestamp == -1)
        first_timestamp = timestamp;
      assert(delivery_times_us_.empty() ||
             timestamp - first_timestamp - delivery_times_us_.back() >= 0);
      delivery_times_us_.push_back(timestamp - first_timestamp);
    }
  }
  assert(!delivery_times_us_.empty());
  next_delivery_it_ = delivery_times_us_.begin();
  fclose(trace_file);
  return true;
}

void TraceBasedDeliveryFilter::Plot(int64_t timestamp_ms) {
  BWE_TEST_LOGGING_CONTEXT(name_.c_str());
  // This plots the max possible throughput of the trace-based delivery filter,
  // which will be reached if a packet sent on every packet slot of the trace.
  BWE_TEST_LOGGING_PLOT(0, "MaxThroughput_#1", timestamp_ms,
                        rate_counter_->bits_per_second() / 1000.0);
}

void TraceBasedDeliveryFilter::RunFor(int64_t time_ms, Packets* in_out) {
  assert(in_out);
  for (PacketsIt it = in_out->begin(); it != in_out->end();) {
    while (local_time_us_ < (*it)->send_time_us()) {
      ProceedToNextSlot();
    }
    // Drop any packets that have been queued for too long.
    while (!delay_cap_helper_->ShouldSendPacket(local_time_us_,
                                                (*it)->send_time_us())) {
      delete *it;
      it = in_out->erase(it);
      if (it == in_out->end()) {
        return;
      }
    }
    if (local_time_us_ >= (*it)->send_time_us()) {
      (*it)->set_send_time_us(local_time_us_);
      ProceedToNextSlot();
    }
    ++it;
  }
  packets_per_second_stats_.Push(rate_counter_->packets_per_second());
  kbps_stats_.Push(rate_counter_->bits_per_second() / 1000.0);
}

void TraceBasedDeliveryFilter::set_max_delay_ms(int64_t max_delay_ms) {
  delay_cap_helper_->set_max_delay_ms(max_delay_ms);
}

Stats<double> TraceBasedDeliveryFilter::GetDelayStats() const {
  return delay_cap_helper_->delay_stats();
}

Stats<double> TraceBasedDeliveryFilter::GetBitrateStats() const {
  return kbps_stats_;
}

void TraceBasedDeliveryFilter::ProceedToNextSlot() {
  if (*next_delivery_it_ <= local_time_us_) {
    ++next_delivery_it_;
    if (next_delivery_it_ == delivery_times_us_.end()) {
      // When the trace wraps we allow two packets to be sent back-to-back.
      for (int64_t& delivery_time_us : delivery_times_us_) {
        delivery_time_us += local_time_us_ - current_offset_us_;
      }
      current_offset_us_ += local_time_us_ - current_offset_us_;
      next_delivery_it_ = delivery_times_us_.begin();
    }
  }
  local_time_us_ = *next_delivery_it_;
  const int kPayloadSize = 1200;
  rate_counter_->UpdateRates(local_time_us_, kPayloadSize);
}

VideoSource::VideoSource(int flow_id,
                         float fps,
                         uint32_t kbps,
                         uint32_t ssrc,
                         int64_t first_frame_offset_ms)
    : kMaxPayloadSizeBytes(1200),
      kTimestampBase(0xff80ff00ul),
      frame_period_ms_(1000.0 / fps),
      bits_per_second_(1000 * kbps),
      frame_size_bytes_(bits_per_second_ / 8 / fps),
      random_(0x12345678),
      flow_id_(flow_id),
      next_frame_ms_(first_frame_offset_ms),
      next_frame_rand_ms_(0),
      now_ms_(0),
      prototype_header_() {
  memset(&prototype_header_, 0, sizeof(prototype_header_));
  prototype_header_.ssrc = ssrc;
  prototype_header_.sequenceNumber = 0xf000u;
}

int VideoSource::flow_id() const {
  return flow_id_;
}

uint32_t VideoSource::NextFrameSize() {
  return frame_size_bytes_;
}

int64_t VideoSource::GetTimeUntilNextFrameMs() const {
  return next_frame_ms_ + next_frame_rand_ms_ - now_ms_;
}

uint32_t VideoSource::NextPacketSize(uint32_t frame_size,
                                     uint32_t remaining_payload) {
  return std::min(kMaxPayloadSizeBytes, remaining_payload);
}

void VideoSource::RunFor(int64_t time_ms, Packets* in_out) {
  assert(in_out);

  now_ms_ += time_ms;
  Packets new_packets;

  while (now_ms_ >= next_frame_ms_) {
    const int64_t kRandAmplitude = 2;
    // A variance picked uniformly from {-1, 0, 1} ms is added to the frame
    // timestamp.
    next_frame_rand_ms_ = kRandAmplitude * (random_.Rand<float>() - 0.5);

    // Ensure frame will not have a negative timestamp.
    int64_t next_frame_ms =
        std::max<int64_t>(next_frame_ms_ + next_frame_rand_ms_, 0);

    prototype_header_.timestamp =
        kTimestampBase + static_cast<uint32_t>(next_frame_ms * 90.0);
    prototype_header_.extension.transmissionTimeOffset = 0;

    // Generate new packets for this frame, all with the same timestamp,
    // but the payload size is capped, so if the whole frame doesn't fit in
    // one packet, we will see a number of equally sized packets followed by
    // one smaller at the tail.

    int64_t send_time_us = next_frame_ms * 1000.0;

    uint32_t frame_size = NextFrameSize();
    uint32_t payload_size = frame_size;

    while (payload_size > 0) {
      ++prototype_header_.sequenceNumber;
      uint32_t size = NextPacketSize(frame_size, payload_size);
      MediaPacket* new_packet =
          new MediaPacket(flow_id_, send_time_us, size, prototype_header_);
      new_packets.push_back(new_packet);
      new_packet->SetAbsSendTimeMs(next_frame_ms);
      new_packet->set_sender_timestamp_us(send_time_us);
      payload_size -= size;
    }

    next_frame_ms_ += frame_period_ms_;
  }

  in_out->merge(new_packets, DereferencingComparator<Packet>);
}

AdaptiveVideoSource::AdaptiveVideoSource(int flow_id,
                                         float fps,
                                         uint32_t kbps,
                                         uint32_t ssrc,
                                         int64_t first_frame_offset_ms)
    : VideoSource(flow_id, fps, kbps, ssrc, first_frame_offset_ms) {}

void AdaptiveVideoSource::SetBitrateBps(int bitrate_bps) {
  bits_per_second_ = bitrate_bps;
  frame_size_bytes_ = (bits_per_second_ / 8 * frame_period_ms_ + 500) / 1000;
}

PeriodicKeyFrameSource::PeriodicKeyFrameSource(int flow_id,
                                               float fps,
                                               uint32_t kbps,
                                               uint32_t ssrc,
                                               int64_t first_frame_offset_ms,
                                               int key_frame_interval)
    : AdaptiveVideoSource(flow_id, fps, kbps, ssrc, first_frame_offset_ms),
      key_frame_interval_(key_frame_interval),
      frame_counter_(0),
      compensation_bytes_(0),
      compensation_per_frame_(0) {}

uint32_t PeriodicKeyFrameSource::NextFrameSize() {
  uint32_t payload_size = frame_size_bytes_;
  if (frame_counter_ == 0) {
    payload_size = kMaxPayloadSizeBytes * 12;
    compensation_bytes_ = 4 * frame_size_bytes_;
    compensation_per_frame_ = compensation_bytes_ / 30;
  } else if (key_frame_interval_ > 0 &&
             (frame_counter_ % key_frame_interval_ == 0)) {
    payload_size *= 5;
    compensation_bytes_ = payload_size - frame_size_bytes_;
    compensation_per_frame_ = compensation_bytes_ / 30;
  } else if (compensation_bytes_ > 0) {
    if (compensation_per_frame_ > static_cast<int>(payload_size)) {
      // Skip this frame.
      compensation_bytes_ -= payload_size;
      payload_size = 0;
    } else {
      payload_size -= compensation_per_frame_;
      compensation_bytes_ -= compensation_per_frame_;
    }
  }
  if (compensation_bytes_ < 0)
    compensation_bytes_ = 0;
  ++frame_counter_;
  return payload_size;
}

uint32_t PeriodicKeyFrameSource::NextPacketSize(uint32_t frame_size,
                                                uint32_t remaining_payload) {
  uint32_t fragments =
      (frame_size + (kMaxPayloadSizeBytes - 1)) / kMaxPayloadSizeBytes;
  uint32_t avg_size = (frame_size + fragments - 1) / fragments;
  return std::min(avg_size, remaining_payload);
}
}  // namespace bwe
}  // namespace testing
}  // namespace webrtc