//  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 <memory>

#include <set>

#include <string>

#include <unordered_set>

#include <vector>

#include "db/compaction/compaction.h"

#include "db/snapshot_checker.h"

#include "db/version_set.h"

#include "options/cf_options.h"

#include "rocksdb/env.h"

#include "rocksdb/options.h"

#include "rocksdb/status.h"

namespace ROCKSDB_NAMESPACE {

// The file contains an abstract class CompactionPicker, and its two

// sub-classes LevelCompactionPicker and NullCompactionPicker, as

// well as some helper functions used by them.

class LogBuffer;

class Compaction;

class VersionStorageInfo;

struct CompactionInputFiles;

// An abstract class to pick compactions from an existing LSM-tree.

//

// Each compaction style inherits the class and implement the

// interface to form automatic compactions. If NeedCompaction() is true,

// then call PickCompaction() to find what files need to be compacted

// and where to put the output files.

//

// Non-virtual functions CompactRange() and CompactFiles() are used to

// pick files to compact based on users' DB::CompactRange() and

// DB::CompactFiles() requests, respectively. There is little

// compaction style specific logic for them.

class CompactionPicker {

 public:

  CompactionPicker(const ImmutableOptions& ioptions,

                   const InternalKeyComparator* icmp);

  virtual ~CompactionPicker();

  // Pick level and inputs for a new compaction.

  //

  // Returns nullptr if there is no compaction to be done.

  // Otherwise returns a pointer to a heap-allocated object that

  // describes the compaction.  Caller should delete the result.

  // Currently, only universal compaction will query existing snapshots and

  // pass it to aid compaction picking. And it's only passed when user-defined

  // timestamps is not enabled. The other compaction styles do not pass or use

  // `existing_snapshots` or `snapshot_checker`.

  virtual Compaction* PickCompaction(

      const std::string& cf_name, const MutableCFOptions& mutable_cf_options,

      const MutableDBOptions& mutable_db_options,

      const std::vector<SequenceNumber>& existing_snapshots,

      const SnapshotChecker* snapshot_checker, VersionStorageInfo* vstorage,

      LogBuffer* log_buffer, const std::string& full_history_ts_low,

      bool require_max_output_level = false) = 0;

  // The returned Compaction might not include the whole requested range.

  // In that case, compaction_end will be set to the next key that needs

  // compacting. In case the compaction will compact the whole range,

  // compaction_end will be set to nullptr.

  // Client is responsible for compaction_end storage -- when called,

  // *compaction_end should point to valid InternalKey!

  // REQUIRES: If not compacting all levels (input_level == kCompactAllLevels),

  // then levels between input_level and output_level should be empty.

  virtual Compaction* PickCompactionForCompactRange(

      const std::string& cf_name, const MutableCFOptions& mutable_cf_options,

      const MutableDBOptions& mutable_db_options, VersionStorageInfo* vstorage,

      int input_level, int output_level,

      const CompactRangeOptions& compact_range_options,

      const InternalKey* begin, const InternalKey* end,

      InternalKey** compaction_end, bool* manual_conflict,

      uint64_t max_file_num_to_ignore, const std::string& trim_ts,

      const std::string& full_history_ts_low);

  // The maximum allowed output level.  Default value is NumberLevels() - 1.

  virtual int MaxOutputLevel() const { return NumberLevels() - 1; }

  virtual bool NeedsCompaction(const VersionStorageInfo* vstorage) const = 0;

  // Sanitize the input set of compaction input files and convert it to

  // `std::vector<CompactionInputFiles>` in the output parameter

  // `converted_input_files`.

  // When the input parameters do not describe a valid

  // compaction, the function will try to fix the input_files by adding

  // necessary files.  If it's not possible to convert an invalid input_files

  // into a valid one by adding more files, the function will return a

  // non-ok status with specific reason.

  //

  Status SanitizeAndConvertCompactionInputFiles(

      std::unordered_set<uint64_t>* input_files, const int output_level,

      Version* version,

      std::vector<CompactionInputFiles>* converted_input_files) const;

  // Free up the files that participated in a compaction

  //

  // Requirement: DB mutex held

  void ReleaseCompactionFiles(Compaction* c, const Status& status);

  // Returns true if any one of the specified files are being compacted

  bool AreFilesInCompaction(const std::vector<FileMetaData*>& files);

  // Takes a list of CompactionInputFiles and returns a (manual) Compaction

  // object.

  //

  // Caller must provide a set of input files that has been passed through

  // `SanitizeAndConvertCompactionInputFiles` earlier. The lock should not be

  // released between that call and this one.

  //

  //  TODO - Remove default values for earliest_snapshot and snapshot_checker

  //  and require all callers to pass them in so that DB::CompactFiles() can

  //  also benefit from Standalone Range Tombstone Optimization

  Compaction* PickCompactionForCompactFiles(

      const CompactionOptions& compact_options,

      const std::vector<CompactionInputFiles>& input_files, int output_level,

      VersionStorageInfo* vstorage, const MutableCFOptions& mutable_cf_options,

      const MutableDBOptions& mutable_db_options, uint32_t output_path_id,

      std::optional<SequenceNumber> earliest_snapshot = std::nullopt,

      const SnapshotChecker* snapshot_checker = nullptr);

  // Converts a set of compaction input file numbers into

  // a list of CompactionInputFiles.

  // TODO(hx235): remove the unused paramter `compact_options`

  Status GetCompactionInputsFromFileNumbers(

      std::vector<CompactionInputFiles>* input_files,

      std::unordered_set<uint64_t>* input_set,

      const VersionStorageInfo* vstorage,

      const CompactionOptions& compact_options) const;

  // Is there currently a compaction involving level 0 taking place

  bool IsLevel0CompactionInProgress() const {

    return !level0_compactions_in_progress_.empty();

  }

  // Is any compaction in progress

  bool IsCompactionInProgress() const {

    return !(level0_compactions_in_progress_.empty() &&

             compactions_in_progress_.empty());

  }

  // Return true if the passed key range overlap with a compaction output

  // that is currently running.

  bool RangeOverlapWithCompaction(const Slice& smallest_user_key,

                                  const Slice& largest_user_key,

                                  int level) const;

  // Stores the minimal range that covers all entries in inputs in

  // *smallest, *largest.

  // REQUIRES: inputs is not empty

  void GetRange(const CompactionInputFiles& inputs, InternalKey* smallest,

                InternalKey* largest) const;

  // Stores the minimal range that covers all entries in inputs1 and inputs2

  // in *smallest, *largest.

  // REQUIRES: inputs is not empty

  void GetRange(const CompactionInputFiles& inputs1,

                const CompactionInputFiles& inputs2, InternalKey* smallest,

                InternalKey* largest) const;

  // Stores the minimal range that covers all entries in inputs

  // in *smallest, *largest.

  // REQUIRES: inputs is not empty (at least on entry have one file)

  void GetRange(const std::vector<CompactionInputFiles>& inputs,

                InternalKey* smallest, InternalKey* largest,

                int exclude_level) const;

  int NumberLevels() const { return ioptions_.num_levels; }

  // Add more files to the inputs on "level" to make sure that

  // no newer version of a key is compacted to "level+1" while leaving an older

  // version in a "level". Otherwise, any Get() will search "level" first,

  // and will likely return an old/stale value for the key, since it always

  // searches in increasing order of level to find the value. This could

  // also scramble the order of merge operands. This function should be

  // called any time a new Compaction is created, and its inputs_[0] are

  // populated.

  //

  // Will return false if it is impossible to apply this compaction.

  bool ExpandInputsToCleanCut(const std::string& cf_name,

                              VersionStorageInfo* vstorage,

                              CompactionInputFiles* inputs,

                              InternalKey** next_smallest = nullptr);

  // Returns true if any one of the parent files are being compacted

  bool IsRangeInCompaction(VersionStorageInfo* vstorage,

                           const InternalKey* smallest,

                           const InternalKey* largest, int level, int* index);

  // Returns true if the key range that `inputs` files cover overlap with the

  // key range of a currently running compaction.

  bool FilesRangeOverlapWithCompaction(

      const std::vector<CompactionInputFiles>& inputs, int level,

      int proximal_level) const;

  // @param starting_l0_file If not null, restricts L0 file selection to only

  //                         include files at or older than starting_l0_file.

  bool SetupOtherInputs(const std::string& cf_name,

                        const MutableCFOptions& mutable_cf_options,

                        VersionStorageInfo* vstorage,

                        CompactionInputFiles* inputs,

                        CompactionInputFiles* output_level_inputs,

                        int* parent_index, int base_index,

                        bool only_expand_towards_right = false,

                        const FileMetaData* starting_l0_file = nullptr);

  void GetGrandparents(VersionStorageInfo* vstorage,

                       const CompactionInputFiles& inputs,

                       const CompactionInputFiles& output_level_inputs,

                       std::vector<FileMetaData*>* grandparents);

  void PickFilesMarkedForCompaction(

      const std::string& cf_name, VersionStorageInfo* vstorage,

      int* start_level, int* output_level,

      CompactionInputFiles* start_level_inputs,

      std::function<bool(const FileMetaData*)> skip_marked_file);

  // @param starting_l0_file If not null, restricts L0 file selection to only

  //                         include files at or older than starting_l0_file.

  bool GetOverlappingL0Files(VersionStorageInfo* vstorage,

                             CompactionInputFiles* start_level_inputs,

                             int output_level, int* parent_index,

                             const FileMetaData* starting_l0_file = nullptr);

  // Register this compaction in the set of running compactions

  void RegisterCompaction(Compaction* c);

  // Remove this compaction from the set of running compactions

  void UnregisterCompaction(Compaction* c);

  std::set<Compaction*>* level0_compactions_in_progress() {

    return &level0_compactions_in_progress_;

  }

  std::unordered_set<Compaction*>* compactions_in_progress() {

    return &compactions_in_progress_;

  }

  const InternalKeyComparator* icmp() const { return icmp_; }

 protected:

  const ImmutableOptions& ioptions_;

  // A helper function to SanitizeAndConvertCompactionInputFiles() that

  // sanitizes "input_files" by adding necessary files.

  virtual Status SanitizeCompactionInputFilesForAllLevels(

      std::unordered_set<uint64_t>* input_files,

      const ColumnFamilyMetaData& cf_meta, const int output_level) const;

  // Keeps track of all compactions that are running on Level0.

  // Protected by DB mutex

  std::set<Compaction*> level0_compactions_in_progress_;

  // Keeps track of all compactions that are running.

  // Protected by DB mutex

  std::unordered_set<Compaction*> compactions_in_progress_;

  const InternalKeyComparator* const icmp_;

};

// A dummy compaction that never triggers any automatic

// compaction.

class NullCompactionPicker : public CompactionPicker {

 public:

  NullCompactionPicker(const ImmutableOptions& ioptions,

                       const InternalKeyComparator* icmp)

      : CompactionPicker(ioptions, icmp) {}

  virtual ~NullCompactionPicker() {}

  // Always return "nullptr"

  Compaction* PickCompaction(

      const std::string& /*cf_name*/,

      const MutableCFOptions& /*mutable_cf_options*/,

      const MutableDBOptions& /*mutable_db_options*/,

      const std::vector<SequenceNumber>& /*existing_snapshots*/,

      const SnapshotChecker* /*snapshot_checker*/,

      VersionStorageInfo* /*vstorage*/, LogBuffer* /* log_buffer */,

      const std::string& /*full_history_ts_low*/,

      bool /*require_max_output_level*/) override {

    return nullptr;

  }

  // Always return "nullptr"

  Compaction* PickCompactionForCompactRange(

      const std::string& /*cf_name*/,

      const MutableCFOptions& /*mutable_cf_options*/,

      const MutableDBOptions& /*mutable_db_options*/,

      VersionStorageInfo* /*vstorage*/, int /*input_level*/,

      int /*output_level*/,

      const CompactRangeOptions& /*compact_range_options*/,

      const InternalKey* /*begin*/, const InternalKey* /*end*/,

      InternalKey** /*compaction_end*/, bool* /*manual_conflict*/,

      uint64_t /*max_file_num_to_ignore*/, const std::string& /*trim_ts*/,

      const std::string& /*full_history_ts_low*/) override {

    return nullptr;

  }

  // Always returns false.

  bool NeedsCompaction(const VersionStorageInfo* /*vstorage*/) const override {

    return false;

  }

};

// Attempts to find an intra L0 compaction conforming to the given parameters.

//

// @param level_files                     Metadata for L0 files.

// @param min_files_to_compact            Minimum number of files required to

//                                        do the compaction.

// @param max_compact_bytes_per_del_file  Maximum average size in bytes per

//                                        file that is going to get deleted by

//                                        the compaction.

// @param max_compaction_bytes            Maximum total size in bytes (in terms

//                                        of compensated file size) for files

//                                        to be compacted.

// @param [out] comp_inputs               If a compaction was found, will be

//                                        initialized with corresponding input

//                                        files. Cannot be nullptr.

//

// @return                                true iff compaction was found.

bool FindIntraL0Compaction(const std::vector<FileMetaData*>& level_files,

                           size_t min_files_to_compact,

                           uint64_t max_compact_bytes_per_del_file,

                           uint64_t max_compaction_bytes,

                           CompactionInputFiles* comp_inputs);

CompressionType GetCompressionType(const VersionStorageInfo* vstorage,

                                   const MutableCFOptions& mutable_cf_options,

                                   int level, int base_level,

                                   const bool enable_compression = true);

CompressionOptions GetCompressionOptions(

    const MutableCFOptions& mutable_cf_options,

    const VersionStorageInfo* vstorage, int level,

    const bool enable_compression = true);

}  // namespace ROCKSDB_NAMESPACE