/*
 * Copyright (c) 2017-2019 Cisco and/or its affiliates.
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at:
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <hicn/transport/interfaces/callbacks.h>
#include <hicn/transport/interfaces/rtc_socket_producer.h>
#include <stdlib.h>
#include <time.h>

#define NACK_HEADER_SIZE 8  // bytes
#define TIMESTAMP_LEN 8     // bytes
#define TCP_HEADER_SIZE 20
#define IP6_HEADER_SIZE 40
#define INIT_PACKET_PRODUCTION_RATE 100  // pps random value (almost 1Mbps)
#define STATS_INTERVAL_DURATION 500      // ms
#define INTEREST_LIFETIME_REDUCTION_FACTOR 0.8
#define INACTIVE_TIME \
  500                        // ms without producing before the socket
                             // is considered inactive
#define MILLI_IN_A_SEC 1000  // ms in a second

#define HICN_MAX_DATA_SEQ 0xefffffff

// slow production rate param
#define MIN_PRODUCTION_RATE \
  10  // in pacekts per sec. this value is computed
      // through experiments
#define LIFETIME_FRACTION 0.5

// NACK HEADER
//   +-----------------------------------------+
//   | 4 bytes: current segment in production  |
//   +-----------------------------------------+
//   | 4 bytes: production rate (bytes x sec)  |
//   +-----------------------------------------+
//

// PACKET HEADER
//   +-----------------------------------------+
//   | 8 bytes: TIMESTAMP                      |
//   +-----------------------------------------+
//   | packet                                  |
//   +-----------------------------------------+

namespace transport {

namespace interface {

RTCProducerSocket::RTCProducerSocket(asio::io_service &io_service)
    : ProducerSocket(io_service),
      currentSeg_(1),
      producedBytes_(0),
      producedPackets_(0),
      bytesProductionRate_(INIT_PACKET_PRODUCTION_RATE * 1400),
      packetsProductionRate_(INIT_PACKET_PRODUCTION_RATE),
      perSecondFactor_(MILLI_IN_A_SEC / STATS_INTERVAL_DURATION),
      timer_on_(false) {
  srand((unsigned int)time(NULL));
  prodLabel_ = ((rand() % 255) << 24UL);
  interests_cache_timer_ =
      std::make_unique<asio::steady_timer>(this->getIoService());
  round_timer_ = std::make_unique<asio::steady_timer>(this->getIoService());
  setSocketOption(GeneralTransportOptions::OUTPUT_BUFFER_SIZE, 10000U);
  scheduleRoundTimer();
}

RTCProducerSocket::RTCProducerSocket()
    : ProducerSocket(),
      currentSeg_(1),
      producedBytes_(0),
      producedPackets_(0),
      bytesProductionRate_(INIT_PACKET_PRODUCTION_RATE * 1400),
      packetsProductionRate_(INIT_PACKET_PRODUCTION_RATE),
      perSecondFactor_(MILLI_IN_A_SEC / STATS_INTERVAL_DURATION),
      timer_on_(false) {
  srand((unsigned int)time(NULL));
  prodLabel_ = ((rand() % 255) << 24UL);
  interests_cache_timer_ =
      std::make_unique<asio::steady_timer>(this->getIoService());
  round_timer_ = std::make_unique<asio::steady_timer>(this->getIoService());
  setSocketOption(GeneralTransportOptions::OUTPUT_BUFFER_SIZE, 10000U);
  scheduleRoundTimer();
}

RTCProducerSocket::~RTCProducerSocket() {}

void RTCProducerSocket::registerPrefix(const Prefix &producer_namespace) {
  ProducerSocket::registerPrefix(producer_namespace);

  flowName_ = producer_namespace.getName();
  auto family = flowName_.getAddressFamily();

  switch (family) {
    case AF_INET6:
      headerSize_ = (uint32_t)Packet::getHeaderSizeFromFormat(HF_INET6_TCP);
      break;
    case AF_INET:
      headerSize_ = (uint32_t)Packet::getHeaderSizeFromFormat(HF_INET_TCP);
      break;
    default:
      throw errors::RuntimeException("Unknown name format.");
  }
}

void RTCProducerSocket::scheduleRoundTimer() {
  round_timer_->expires_from_now(
      std::chrono::milliseconds(STATS_INTERVAL_DURATION));
  round_timer_->async_wait([this](std::error_code ec) {
    if (ec) return;
    updateStats();
  });
}

void RTCProducerSocket::updateStats() {
  bytesProductionRate_ = producedBytes_.load() * perSecondFactor_;
  packetsProductionRate_ = producedPackets_.load() * perSecondFactor_;
  if (packetsProductionRate_.load() == 0) packetsProductionRate_ = 1;
  producedBytes_ = 0;
  producedPackets_ = 0;
  scheduleRoundTimer();
}

void RTCProducerSocket::produce(std::unique_ptr<utils::MemBuf> &&buffer) {
  auto buffer_size = buffer->length();

  if (TRANSPORT_EXPECT_FALSE(buffer_size == 0)) {
    return;
  }

  if (TRANSPORT_EXPECT_FALSE((buffer_size + headerSize_ + TIMESTAMP_LEN) >
                             data_packet_size_)) {
    return;
  }

  uint64_t now = std::chrono::duration_cast<std::chrono::milliseconds>(
                     std::chrono::steady_clock::now().time_since_epoch())
                     .count();

  producedBytes_ += (uint32_t)(buffer_size + headerSize_ + TIMESTAMP_LEN);
  producedPackets_++;

  Name n(flowName_);
  auto content_object =
      std::make_shared<ContentObject>(n.setSuffix(currentSeg_.load()));
  auto payload = utils::MemBuf::create(TIMESTAMP_LEN);

  memcpy(payload->writableData(), &now, TIMESTAMP_LEN);
  payload->append(TIMESTAMP_LEN);
  payload->prependChain(std::move(buffer));
  content_object->appendPayload(std::move(payload));

  content_object->setLifetime(500);  // XXX this should be set by the APP

  content_object->setPathLabel(prodLabel_);

  output_buffer_.insert(std::static_pointer_cast<ContentObject>(
      content_object->shared_from_this()));

  if (on_content_object_in_output_buffer_) {
    on_content_object_in_output_buffer_(*this, *content_object);
  }

  TRANSPORT_LOGD("Send content %u (produce)", content_object->getName().getSuffix());
  portal_->sendContentObject(*content_object);

  if (on_content_object_output_) {
    on_content_object_output_(*this, *content_object);
  }

  uint32_t old_curr = currentSeg_.load();
  currentSeg_ = (currentSeg_.load() + 1) % HICN_MAX_DATA_SEQ;

  // remove interests from the interest cache if it exists
  // this generates nacks that will tell to the consumer
  // that a new data packet was produced
  utils::SpinLock::Acquire locked(interests_cache_lock_);
  if (!seqs_map_.empty()) {
    for (auto it = seqs_map_.begin(); it != seqs_map_.end(); it++) {
      if (it->first != old_curr) sendNack(it->first);
    }
    seqs_map_.clear();
    timers_map_.clear();
  }
}

void RTCProducerSocket::onInterest(Interest::Ptr &&interest) {
  uint32_t interestSeg = interest->getName().getSuffix();
  uint32_t lifetime = interest->getLifetime();

  if (on_interest_input_) {
    on_interest_input_(*this, *interest);
  }

  uint64_t now = std::chrono::duration_cast<std::chrono::milliseconds>(
                     std::chrono::steady_clock::now().time_since_epoch())
                     .count();

  if (interestSeg > HICN_MAX_DATA_SEQ) {
    sendNack(interestSeg);
    return;
  }

  const std::shared_ptr<ContentObject> content_object =
      output_buffer_.find(*interest);

  if (content_object) {
    if (on_interest_satisfied_output_buffer_) {
      on_interest_satisfied_output_buffer_(*this, *interest);
    }

    if (on_content_object_output_) {
      on_content_object_output_(*this, *content_object);
    }

    TRANSPORT_LOGD("Send content %u (onInterest)", content_object->getName().getSuffix());
    portal_->sendContentObject(*content_object);
    return;
  } else {
    if (on_interest_process_) {
      on_interest_process_(*this, *interest);
    }
  }

  // if the production rate is less than MIN_PRODUCTION_RATE we put the
  // interest in a queue, otherwise we handle it in the usual way
  if (packetsProductionRate_.load() < MIN_PRODUCTION_RATE &&
      interestSeg >= currentSeg_.load()) {
    utils::SpinLock::Acquire locked(interests_cache_lock_);

    uint64_t next_timer = ~0;
    if (!timers_map_.empty()) {
      next_timer = timers_map_.begin()->first;
    }

    uint64_t expiration = now + (lifetime * LIFETIME_FRACTION);
    // check if the seq number exists already
    auto it_seqs = seqs_map_.find(interestSeg);
    if (it_seqs != seqs_map_.end()) {
      // the seq already exists
      if (expiration < it_seqs->second) {
        // we need to update the timer becasue we got a smaller one
        // 1) remove the entry from the multimap
        // 2) update this entry
        auto range = timers_map_.equal_range(it_seqs->second);
        for (auto it_timers = range.first; it_timers != range.second;
             it_timers++) {
          if (it_timers->second == it_seqs->first) {
            timers_map_.erase(it_timers);
            break;
          }
        }
        timers_map_.insert(
            std::pair<uint64_t, uint32_t>(expiration, interestSeg));
        it_seqs->second = expiration;
      } else {
        // nothing to do here
        return;
      }
    } else {
      // add the new seq
      timers_map_.insert(
          std::pair<uint64_t, uint32_t>(expiration, interestSeg));
      seqs_map_.insert(std::pair<uint32_t, uint64_t>(interestSeg, expiration));
    }

    // here we have at least one interest in the queue, we need to start or
    // update the timer
    if (!timer_on_) {
      // set timeout
      timer_on_ = true;
      scheduleCacheTimer(timers_map_.begin()->first - now);
    } else {
      // re-schedule the timer because a new interest will expires sooner
      if (next_timer > timers_map_.begin()->first) {
        interests_cache_timer_->cancel();
        scheduleCacheTimer(timers_map_.begin()->first - now);
      }
    }
    return;
  }

  uint32_t max_gap = (uint32_t)floor(
      (double)((double)((double)lifetime * INTEREST_LIFETIME_REDUCTION_FACTOR /
                        1000.0) *
               (double)packetsProductionRate_.load()));

  if (interestSeg < currentSeg_.load() ||
      interestSeg > (max_gap + currentSeg_.load())) {
    sendNack(interestSeg);
  }
  // else drop packet
}

void RTCProducerSocket::scheduleCacheTimer(uint64_t wait) {
  interests_cache_timer_->expires_from_now(std::chrono::milliseconds(wait));
  interests_cache_timer_->async_wait([this](std::error_code ec) {
    if (ec) return;
    interestCacheTimer();
  });
}

void RTCProducerSocket::interestCacheTimer() {
  uint64_t now = std::chrono::duration_cast<std::chrono::milliseconds>(
                     std::chrono::steady_clock::now().time_since_epoch())
                     .count();

  utils::SpinLock::Acquire locked(interests_cache_lock_);

  for (auto it_timers = timers_map_.begin(); it_timers != timers_map_.end();) {
    uint64_t expire = it_timers->first;
    if (expire <= now) {
      uint32_t seq = it_timers->second;
      sendNack(seq);
      // remove the interest from the other map
      seqs_map_.erase(seq);
      it_timers = timers_map_.erase(it_timers);
    } else {
      // stop, we are done!
      break;
    }
  }
  if (timers_map_.empty()) {
    timer_on_ = false;
  } else {
    timer_on_ = true;
    scheduleCacheTimer(timers_map_.begin()->first - now);
  }
}

void RTCProducerSocket::sendNack(uint32_t sequence) {
  auto nack_payload = utils::MemBuf::create(NACK_HEADER_SIZE);
  nack_payload->append(NACK_HEADER_SIZE);
  ContentObject nack;

  Name n(flowName_);
  nack.appendPayload(std::move(nack_payload));
  nack.setName(n.setSuffix(sequence));

  uint32_t *payload_ptr = (uint32_t *)nack.getPayload()->data();
  *payload_ptr = currentSeg_.load();

  *(++payload_ptr) = bytesProductionRate_.load();

  nack.setLifetime(0);
  nack.setPathLabel(prodLabel_);

  if (on_content_object_output_) {
    on_content_object_output_(*this, nack);
  }

  TRANSPORT_LOGD("Send nack %u", sequence);
  portal_->sendContentObject(nack);
}

}  // namespace interface

}  // end namespace transport