/*
 * @Author: DI JUNKUN
 * @Date: 2025-02-12
 * Copyright (c) 2025 by DI JUNKUN, All Rights Reserved.
 */

#ifndef _NACK_REQUESTER_H_
#define _NACK_REQUESTER_H_

#include <cstddef>
#include <cstdint>
#include <map>
#include <set>
#include <vector>

#include "api/clock/clock.h"
#include "api/units/timestamp.h"
#include "histogram.h"
#include "module_common_types.h"
#include "rtc_base/numerics/sequence_number_util.h"

using namespace webrtc;

class NackRequester {
 private:
  // Which fields to consider when deciding which packet to nack in
  // GetNackBatch.
  enum NackFilterOptions { kSeqNumOnly, kTimeOnly, kSeqNumAndTime };

  struct NackInfo {
    NackInfo();
    NackInfo(uint16_t seq_num, uint16_t send_at_seq_num,
             Timestamp created_at_time);

    uint16_t seq_num;
    uint16_t send_at_seq_num;
    Timestamp created_at_time;
    Timestamp sent_at_time;
    int retries;
  };

 public:
  NackRequester(std::shared_ptr<Clock> clock, NackSender* nack_sender,
                KeyFrameRequestSender* keyframe_request_sender);
  ~NackRequester();

 public:
  int OnReceivedPacket(uint16_t seq_num);
  int OnReceivedPacket(uint16_t seq_num, bool is_recovered);

  void ProcessNacks();

 private:
  void ClearUpTo(uint16_t seq_num);
  void UpdateRtt(int64_t rtt_ms);
  void AddPacketsToNack(uint16_t seq_num_start, uint16_t seq_num_end);
  std::vector<uint16_t> GetNackBatch(NackFilterOptions options);
  void UpdateReorderingStatistics(uint16_t seq_num);
  int WaitNumberOfPackets(float probability) const;

 private:
  std::shared_ptr<Clock> clock_;
  NackSender* const nack_sender_;
  KeyFrameRequestSender* const keyframe_request_sender_;

  std::map<uint16_t, NackInfo, DescendingSeqNumComp<uint16_t>> nack_list_;
  std::set<uint16_t, DescendingSeqNumComp<uint16_t>> recovered_list_;
  Histogram reordering_histogram_;
  bool initialized_;
  TimeDelta rtt_;
  uint16_t newest_seq_num_;
  const TimeDelta send_nack_delay_;
};

#endif