//  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).

//

#pragma once

#include <cassert>

#include <cstdint>

#include <cstdlib>

#include <mutex>

#include <unordered_map>

#include <vector>

#include "rocksdb/rocksdb_namespace.h"

namespace ROCKSDB_NAMESPACE {

// This class is used to track the log files with outstanding prepare entries.

class LogsWithPrepTracker {

 public:

  // Called when a transaction prepared in `log` has been committed or aborted.

  void MarkLogAsHavingPrepSectionFlushed(uint64_t log);

  // Called when a transaction is prepared in `log`.

  void MarkLogAsContainingPrepSection(uint64_t log);

  // Return the earliest log file with outstanding prepare entries.

  uint64_t FindMinLogContainingOutstandingPrep();

  size_t TEST_PreparedSectionCompletedSize() {

    return prepared_section_completed_.size();

  }

  size_t TEST_LogsWithPrepSize() { return logs_with_prep_.size(); }

 private:

  // REQUIRES: logs_with_prep_mutex_ held

  //

  // sorted list of log numbers still containing prepared data.

  // this is used by FindObsoleteFiles to determine which

  // flushed logs we must keep around because they still

  // contain prepared data which has not been committed or rolled back

  struct LogCnt {

    uint64_t log;  // the log number

    uint64_t cnt;  // number of prepared sections in the log

  };

  std::vector<LogCnt> logs_with_prep_;

  std::mutex logs_with_prep_mutex_;

  // REQUIRES: prepared_section_completed_mutex_ held

  //

  // to be used in conjunction with logs_with_prep_.

  // once a transaction with data in log L is committed or rolled back

  // rather than updating logs_with_prep_ directly we keep track of that

  // in prepared_section_completed_ which maps LOG -> instance_count. This helps

  // avoiding contention between a commit thread and the prepare threads.

  //

  // when trying to determine the minimum log still active we first

  // consult logs_with_prep_. while that root value maps to

  // an equal value in prepared_section_completed_ we erase the log from

  // both logs_with_prep_ and prepared_section_completed_.

  std::unordered_map<uint64_t, uint64_t> prepared_section_completed_;

  std::mutex prepared_section_completed_mutex_;

};

}  // namespace ROCKSDB_NAMESPACE