// Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.

//  This source code is licensed under both the GPLv2 (found in the

//  COPYING file in the root directory) and Apache 2.0 License

//  (found in the LICENSE.Apache file in the root directory).

// Copyright (c) 2011 The LevelDB Authors. All rights reserved.

// Use of this source code is governed by a BSD-style license that can be

// found in the LICENSE file. See the AUTHORS file for names of contributors.

#pragma once

#include "db/db_impl/db_impl.h"

#include "rocksdb/stats_history.h"

namespace ROCKSDB_NAMESPACE {

extern const std::string kFormatVersionKeyString;

extern const std::string kCompatibleVersionKeyString;

extern const uint64_t kStatsCFCurrentFormatVersion;

extern const uint64_t kStatsCFCompatibleFormatVersion;

enum StatsVersionKeyType : uint32_t {

  kFormatVersion = 1,

  kCompatibleVersion = 2,

  kKeyTypeMax = 3

};

// Read the version number from persitent stats cf depending on type provided

// stores the version number in `*version_number`

// returns Status::OK() on success, or other status code on failure

Status DecodePersistentStatsVersionNumber(DBImpl* db, StatsVersionKeyType type,

                                          uint64_t* version_number);

// Encode timestamp and stats key into buf

// Format: timestamp(10 digit) + '#' + key

// Total length of encoded key will be capped at 100 bytes

int EncodePersistentStatsKey(uint64_t timestamp, const std::string& key,

                             int size, char* buf);

void OptimizeForPersistentStats(ColumnFamilyOptions* cfo);

class PersistentStatsHistoryIterator final : public StatsHistoryIterator {

 public:

  PersistentStatsHistoryIterator(uint64_t start_time, uint64_t end_time,

                                 DBImpl* db_impl)

      : time_(0),

        start_time_(start_time),

        end_time_(end_time),

        valid_(true),

        db_impl_(db_impl) {

    AdvanceIteratorByTime(start_time_, end_time_);

  }

  ~PersistentStatsHistoryIterator() override;

  bool Valid() const override;

  Status status() const override;

  void Next() override;

  uint64_t GetStatsTime() const override;

  const std::map<std::string, uint64_t>& GetStatsMap() const override;

 private:

  // advance the iterator to the next stats history record with timestamp

  // between [start_time, end_time)

  void AdvanceIteratorByTime(uint64_t start_time, uint64_t end_time);

  // No copying allowed

  PersistentStatsHistoryIterator(const PersistentStatsHistoryIterator&) =

      delete;

  void operator=(const PersistentStatsHistoryIterator&) = delete;

  PersistentStatsHistoryIterator(PersistentStatsHistoryIterator&&) = delete;

  PersistentStatsHistoryIterator& operator=(PersistentStatsHistoryIterator&&) =

      delete;

  uint64_t time_;

  uint64_t start_time_;

  uint64_t end_time_;

  std::map<std::string, uint64_t> stats_map_;

  Status status_;

  bool valid_;

  DBImpl* db_impl_;

};

}  // namespace ROCKSDB_NAMESPACE