//  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 <limits>

#include <string>

#include <vector>

#include "db/column_family.h"

#include "db/log_writer.h"

#include "db/version_set.h"

#include "util/autovector.h"

#include "util/hash_containers.h"

namespace ROCKSDB_NAMESPACE {

class MemTable;

struct SuperVersion;

// The purpose of this struct is to simplify pushing work such as

// allocation/construction, de-allocation/destruction, and notifications to

// outside of holding the DB mutex.

struct SuperVersionContext {

  struct WriteStallNotification {

    WriteStallInfo write_stall_info;

    const ImmutableOptions* immutable_options;

  };

  autovector<SuperVersion*> superversions_to_free;

#ifndef ROCKSDB_DISABLE_STALL_NOTIFICATION

  autovector<WriteStallNotification> write_stall_notifications;

#endif

  std::unique_ptr<SuperVersion>

      new_superversion;  // if nullptr no new superversion

  explicit SuperVersionContext(bool create_superversion = false)

      : new_superversion(create_superversion ? new SuperVersion() : nullptr) {}

  explicit SuperVersionContext(SuperVersionContext&& other) noexcept

      : superversions_to_free(std::move(other.superversions_to_free)),

#ifndef ROCKSDB_DISABLE_STALL_NOTIFICATION

        write_stall_notifications(std::move(other.write_stall_notifications)),

#endif

        new_superversion(std::move(other.new_superversion)) {

  }

  // No copies

  SuperVersionContext(const SuperVersionContext& other) = delete;

  void operator=(const SuperVersionContext& other) = delete;

  void NewSuperVersion() {

    new_superversion = std::unique_ptr<SuperVersion>(new SuperVersion());

  }

  inline bool HaveSomethingToDelete() const {

#ifndef ROCKSDB_DISABLE_STALL_NOTIFICATION

    return !superversions_to_free.empty() || !write_stall_notifications.empty();

#else

    return !superversions_to_free.empty();

#endif

  }

  void PushWriteStallNotification(WriteStallCondition old_cond,

                                  WriteStallCondition new_cond,

                                  const std::string& name,

                                  const ImmutableOptions* ioptions) {

#if !defined(ROCKSDB_DISABLE_STALL_NOTIFICATION)

    WriteStallNotification notif;

    notif.write_stall_info.cf_name = name;

    notif.write_stall_info.condition.prev = old_cond;

    notif.write_stall_info.condition.cur = new_cond;

    notif.immutable_options = ioptions;

    write_stall_notifications.push_back(notif);

#else

    (void)old_cond;

    (void)new_cond;

    (void)name;

    (void)ioptions;

#endif  // !defined(ROCKSDB_DISABLE_STALL_NOTIFICATION)

  }

  void Clean() {

#if !defined(ROCKSDB_DISABLE_STALL_NOTIFICATION)

    // notify listeners on changed write stall conditions

    for (auto& notif : write_stall_notifications) {

      for (auto& listener : notif.immutable_options->listeners) {

        listener->OnStallConditionsChanged(notif.write_stall_info);

      }

    }

    write_stall_notifications.clear();

#endif

    // free superversions

    for (auto s : superversions_to_free) {

      delete s;

    }

    superversions_to_free.clear();

  }

  ~SuperVersionContext() {

#ifndef ROCKSDB_DISABLE_STALL_NOTIFICATION

    assert(write_stall_notifications.empty());

#endif

    assert(superversions_to_free.empty());

  }

};

struct JobContext {

  inline bool HaveSomethingToDelete() const {

    return !(full_scan_candidate_files.empty() && sst_delete_files.empty() &&

             blob_delete_files.empty() && log_delete_files.empty() &&

             manifest_delete_files.empty());

  }

  inline bool HaveSomethingToClean() const {

    bool sv_have_sth = false;

    for (const auto& sv_ctx : superversion_contexts) {

      if (sv_ctx.HaveSomethingToDelete()) {

        sv_have_sth = true;

        break;

      }

    }

    return memtables_to_free.size() > 0 || wals_to_free.size() > 0 ||

           job_snapshot != nullptr || sv_have_sth;

  }

  SequenceNumber GetJobSnapshotSequence() const {

    if (job_snapshot) {

      assert(job_snapshot->snapshot());

      return job_snapshot->snapshot()->GetSequenceNumber();

    }

    return kMaxSequenceNumber;

  }

  SequenceNumber GetLatestSnapshotSequence() const {

    assert(snapshot_context_initialized);

    if (snapshot_seqs.empty()) {

      return 0;

    }

    return snapshot_seqs.back();

  }

  SequenceNumber GetEarliestSnapshotSequence() const {

    assert(snapshot_context_initialized);

    if (snapshot_seqs.empty()) {

      return kMaxSequenceNumber;

    }

    return snapshot_seqs.front();

  }

  void InitSnapshotContext(SnapshotChecker* checker,

                           std::unique_ptr<ManagedSnapshot> managed_snapshot,

                           SequenceNumber earliest_write_conflict,

                           std::vector<SequenceNumber>&& snapshots) {

    if (snapshot_context_initialized) {

      return;

    }

    snapshot_context_initialized = true;

    snapshot_checker = checker;

    assert(!job_snapshot);

    job_snapshot = std::move(managed_snapshot);

    earliest_write_conflict_snapshot = earliest_write_conflict;

    snapshot_seqs = std::move(snapshots);

  }

  // Structure to store information for candidate files to delete.

  struct CandidateFileInfo {

    std::string file_name;

    std::string file_path;

    CandidateFileInfo(std::string name, std::string path)

        : file_name(std::move(name)), file_path(std::move(path)) {}

    bool operator==(const CandidateFileInfo& other) const {

      return file_name == other.file_name && file_path == other.file_path;

    }

  };

  // a list of all files that we'll consider deleting

  // (every once in a while this is filled up with all files

  // in the DB directory)

  // (filled only if we're doing full scan)

  std::vector<CandidateFileInfo> full_scan_candidate_files;

  // the list of all live sst files that cannot be deleted

  std::vector<uint64_t> sst_live;

  // the list of sst files that we need to delete

  std::vector<ObsoleteFileInfo> sst_delete_files;

  // the list of all live blob files that cannot be deleted

  std::vector<uint64_t> blob_live;

  // the list of blob files that we need to delete

  std::vector<ObsoleteBlobFileInfo> blob_delete_files;

  // a list of log files that we need to delete

  std::vector<uint64_t> log_delete_files;

  // a list of log files that we need to preserve during full purge since they

  // will be reused later

  std::vector<uint64_t> log_recycle_files;

  // Files quarantined from deletion. This list contains file numbers for files

  // that are in an ambiguous states. This includes newly generated SST files

  // and blob files from flush and compaction job whose VersionEdits' persist

  // state in Manifest are unclear. An old manifest file whose immediately

  // following new manifest file's CURRENT file creation is in an unclear state.

  // WAL logs don't have this premature deletion risk since

  // min_log_number_to_keep is only updated after successful manifest commits.

  // So this data structure doesn't track log files.

  autovector<uint64_t> files_to_quarantine;

  // Blob file numbers that PurgeObsoleteFiles must keep. This includes both

  // actively written direct-write files and sealed direct-write files that are

  // still reachable through live memtables / old SuperVersions.

  // Collected under db_mutex_ in FindObsoleteFiles so PurgeObsoleteFiles can

  // safely use the snapshot without taking DB mutex.

  UnorderedSet<uint64_t> active_blob_direct_write_files;

  // Snapshot of VersionSet's next file number taken before collecting active

  // direct-write blob files. This keeps the current purge pass from racing a

  // concurrently created blob file that was not yet part of the active set.

  uint64_t min_blob_file_number_to_keep = std::numeric_limits<uint64_t>::max();

  // a list of manifest files that we need to delete

  std::vector<std::string> manifest_delete_files;

  // a list of memtables to be free

  autovector<ReadOnlyMemTable*> memtables_to_free;

  // contexts for installing superversions for multiple column families

  std::vector<SuperVersionContext> superversion_contexts;

  autovector<log::Writer*> wals_to_free;

  // the current manifest_file_number, log_number and prev_log_number

  // that corresponds to the set of files in 'live'.

  uint64_t manifest_file_number = 0;

  uint64_t pending_manifest_file_number = 0;

  // Used for remote compaction. To prevent OPTIONS files from getting

  // purged by PurgeObsoleteFiles() of the primary host

  uint64_t min_options_file_number;

  uint64_t log_number = 0;

  uint64_t prev_log_number = 0;

  uint64_t min_pending_output = 0;

  uint64_t prev_wals_total_size = 0;

  size_t num_alive_wal_files = 0;

  uint64_t size_log_to_delete = 0;

  // Snapshot taken before flush/compaction job.

  std::unique_ptr<ManagedSnapshot> job_snapshot;

  SnapshotChecker* snapshot_checker = nullptr;

  std::vector<SequenceNumber> snapshot_seqs;

  // This is the earliest snapshot that could be used for write-conflict

  // checking by a transaction.  For any user-key newer than this snapshot, we

  // should make sure not to remove evidence that a write occurred.

  SequenceNumber earliest_write_conflict_snapshot = kMaxSequenceNumber;

  // Unique job id

  int job_id;

  bool snapshot_context_initialized = false;

  explicit JobContext(int _job_id, bool create_superversion = false) {

    job_id = _job_id;

    superversion_contexts.emplace_back(

        SuperVersionContext(create_superversion));

  }

  // Delete the default constructor

  JobContext() = delete;

  // For non-empty JobContext Clean() has to be called at least once before

  // before destruction (see asserts in ~JobContext()). Should be called with

  // unlocked DB mutex. Destructor doesn't call Clean() to avoid accidentally

  // doing potentially slow Clean() with locked DB mutex.

  void Clean() {

    // free superversions

    for (auto& sv_context : superversion_contexts) {

      sv_context.Clean();

    }

    // free pending memtables

    for (auto m : memtables_to_free) {

      delete m;

    }

    for (auto l : wals_to_free) {

      delete l;

    }

    memtables_to_free.clear();

    wals_to_free.clear();

    job_snapshot.reset();

  }

  ~JobContext() {

    assert(memtables_to_free.size() == 0);

    assert(wals_to_free.size() == 0);

  }

};

}  // namespace ROCKSDB_NAMESPACE