//  Copyright (c) 2013, Facebook, Inc.  All rights reserved.
//  This source code is licensed under the BSD-style license found in the
//  LICENSE file in the root directory of this source tree. An additional grant
//  of patent rights can be found in the PATENTS file in the same 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.
//
// We recover the contents of the descriptor from the other files we find.
// (1) Any log files are first converted to tables
// (2) We scan every table to compute
//     (a) smallest/largest for the table
//     (b) largest sequence number in the table
// (3) We generate descriptor contents:
//      - log number is set to zero
//      - next-file-number is set to 1 + largest file number we found
//      - last-sequence-number is set to largest sequence# found across
//        all tables (see 2c)
//      - compaction pointers are cleared
//      - every table file is added at level 0
//
// Possible optimization 1:
//   (a) Compute total size and use to pick appropriate max-level M
//   (b) Sort tables by largest sequence# in the table
//   (c) For each table: if it overlaps earlier table, place in level-0,
//       else place in level-M.
// Possible optimization 2:
//   Store per-table metadata (smallest, largest, largest-seq#, ...)
//   in the table's meta section to speed up ScanTable.

#ifndef ROCKSDB_LITE

#define __STDC_FORMAT_MACROS
#include <inttypes.h>
#include "db/builder.h"
#include "db/db_impl.h"
#include "db/dbformat.h"
#include "db/filename.h"
#include "db/log_reader.h"
#include "db/log_writer.h"
#include "db/memtable.h"
#include "db/table_cache.h"
#include "db/version_edit.h"
#include "db/write_batch_internal.h"
#include "rocksdb/comparator.h"
#include "rocksdb/db.h"
#include "rocksdb/env.h"

namespace rocksdb {

namespace {

class Repairer {
 public:
  Repairer(const std::string& dbname, const Options& options)
      : dbname_(dbname),
        env_(options.env),
        icmp_(options.comparator),
        ipolicy_(options.filter_policy),
        options_(SanitizeOptions(dbname, &icmp_, &ipolicy_, options)),
        raw_table_cache_(
            // TableCache can be small since we expect each table to be opened
            // once.
            NewLRUCache(10, options_.table_cache_numshardbits,
                        options_.table_cache_remove_scan_count_limit)),
        next_file_number_(1) {
    table_cache_ =
        new TableCache(&options_, storage_options_, raw_table_cache_.get());
    edit_ = new VersionEdit();
  }

  ~Repairer() {
    delete table_cache_;
    raw_table_cache_.reset();
    delete edit_;
  }

  Status Run() {
    Status status = FindFiles();
    if (status.ok()) {
      ConvertLogFilesToTables();
      ExtractMetaData();
      status = WriteDescriptor();
    }
    if (status.ok()) {
      uint64_t bytes = 0;
      for (size_t i = 0; i < tables_.size(); i++) {
        bytes += tables_[i].meta.fd.GetFileSize();
      }
      Log(options_.info_log,
          "**** Repaired rocksdb %s; "
          "recovered %zu files; %" PRIu64
          "bytes. "
          "Some data may have been lost. "
          "****",
          dbname_.c_str(), tables_.size(), bytes);
    }
    return status;
  }

 private:
  struct TableInfo {
    FileMetaData meta;
    SequenceNumber min_sequence;
    SequenceNumber max_sequence;
  };

  std::string const dbname_;
  Env* const env_;
  InternalKeyComparator const icmp_;
  InternalFilterPolicy const ipolicy_;
  Options const options_;
  std::shared_ptr<Cache> raw_table_cache_;
  TableCache* table_cache_;
  VersionEdit* edit_;

  std::vector<std::string> manifests_;
  std::vector<FileDescriptor> table_fds_;
  std::vector<uint64_t> logs_;
  std::vector<TableInfo> tables_;
  uint64_t next_file_number_;
  const EnvOptions storage_options_;

  Status FindFiles() {
    std::vector<std::string> filenames;
    bool found_file = false;
    for (uint32_t path_id = 0; path_id < options_.db_paths.size(); path_id++) {
      Status status =
          env_->GetChildren(options_.db_paths[path_id].path, &filenames);
      if (!status.ok()) {
        return status;
      }
      if (!filenames.empty()) {
        found_file = true;
      }

      uint64_t number;
      FileType type;
      for (size_t i = 0; i < filenames.size(); i++) {
        if (ParseFileName(filenames[i], &number, &type)) {
          if (type == kDescriptorFile) {
            assert(path_id == 0);
            manifests_.push_back(filenames[i]);
          } else {
            if (number + 1 > next_file_number_) {
              next_file_number_ = number + 1;
            }
            if (type == kLogFile) {
              assert(path_id == 0);
              logs_.push_back(number);
            } else if (type == kTableFile) {
              table_fds_.emplace_back(number, path_id, 0);
            } else {
              // Ignore other files
            }
          }
        }
      }
    }
    if (!found_file) {
      return Status::Corruption(dbname_, "repair found no files");
    }
    return Status::OK();
  }

  void ConvertLogFilesToTables() {
    for (size_t i = 0; i < logs_.size(); i++) {
      std::string logname = LogFileName(dbname_, logs_[i]);
      Status status = ConvertLogToTable(logs_[i]);
      if (!status.ok()) {
        Log(options_.info_log,
            "Log #%" PRIu64 ": ignoring conversion error: %s", logs_[i],
            status.ToString().c_str());
      }
      ArchiveFile(logname);
    }
  }

  Status ConvertLogToTable(uint64_t log) {
    struct LogReporter : public log::Reader::Reporter {
      Env* env;
      std::shared_ptr<Logger> info_log;
      uint64_t lognum;
      virtual void Corruption(size_t bytes, const Status& s) {
        // We print error messages for corruption, but continue repairing.
        Log(info_log, "Log #%" PRIu64 ": dropping %d bytes; %s", lognum,
            static_cast<int>(bytes), s.ToString().c_str());
      }
    };

    // Open the log file
    std::string logname = LogFileName(dbname_, log);
    unique_ptr<SequentialFile> lfile;
    Status status = env_->NewSequentialFile(logname, &lfile, storage_options_);
    if (!status.ok()) {
      return status;
    }

    // Create the log reader.
    LogReporter reporter;
    reporter.env = env_;
    reporter.info_log = options_.info_log;
    reporter.lognum = log;
    // We intentially make log::Reader do checksumming so that
    // corruptions cause entire commits to be skipped instead of
    // propagating bad information (like overly large sequence
    // numbers).
    log::Reader reader(std::move(lfile), &reporter, false/*do not checksum*/,
                       0/*initial_offset*/);

    // Read all the records and add to a memtable
    std::string scratch;
    Slice record;
    WriteBatch batch;
    MemTable* mem = new MemTable(icmp_, options_);
    auto cf_mems_default = new ColumnFamilyMemTablesDefault(mem, &options_);
    mem->Ref();
    int counter = 0;
    while (reader.ReadRecord(&record, &scratch)) {
      if (record.size() < 12) {
        reporter.Corruption(
            record.size(), Status::Corruption("log record too small"));
        continue;
      }
      WriteBatchInternal::SetContents(&batch, record);
      status = WriteBatchInternal::InsertInto(&batch, cf_mems_default);
      if (status.ok()) {
        counter += WriteBatchInternal::Count(&batch);
      } else {
        Log(options_.info_log, "Log #%" PRIu64 ": ignoring %s", log,
            status.ToString().c_str());
        status = Status::OK();  // Keep going with rest of file
      }
    }

    // Do not record a version edit for this conversion to a Table
    // since ExtractMetaData() will also generate edits.
    FileMetaData meta;
    meta.fd = FileDescriptor(next_file_number_++, 0, 0);
    ReadOptions ro;
    Iterator* iter = mem->NewIterator(ro, true /* enforce_total_order */);
    status = BuildTable(dbname_, env_, options_, storage_options_, table_cache_,
                        iter, &meta, icmp_, 0, 0, kNoCompression);
    delete iter;
    delete mem->Unref();
    delete cf_mems_default;
    mem = nullptr;
    if (status.ok()) {
      if (meta.fd.GetFileSize() > 0) {
        table_fds_.push_back(meta.fd);
      }
    }
    Log(options_.info_log,
        "Log #%" PRIu64 ": %d ops saved to Table #%" PRIu64 " %s", log, counter,
        meta.fd.GetNumber(), status.ToString().c_str());
    return status;
  }

  void ExtractMetaData() {
    for (size_t i = 0; i < table_fds_.size(); i++) {
      TableInfo t;
      t.meta.fd = table_fds_[i];
      Status status = ScanTable(&t);
      if (!status.ok()) {
        std::string fname = TableFileName(
            options_.db_paths, t.meta.fd.GetNumber(), t.meta.fd.GetPathId());
        Log(options_.info_log, "Table #%s: ignoring %s",
            FormatFileNumber(t.meta.fd.GetNumber(), t.meta.fd.GetPathId())
                .c_str(),
            status.ToString().c_str());
        ArchiveFile(fname);
      } else {
        tables_.push_back(t);
      }
    }
  }

  Status ScanTable(TableInfo* t) {
    std::string fname = TableFileName(options_.db_paths, t->meta.fd.GetNumber(),
                                      t->meta.fd.GetPathId());
    int counter = 0;
    uint64_t file_size;
    Status status = env_->GetFileSize(fname, &file_size);
    t->meta.fd = FileDescriptor(t->meta.fd.GetNumber(), t->meta.fd.GetPathId(),
                                file_size);
    if (status.ok()) {
      Iterator* iter = table_cache_->NewIterator(
          ReadOptions(), storage_options_, icmp_, t->meta.fd);
      bool empty = true;
      ParsedInternalKey parsed;
      t->min_sequence = 0;
      t->max_sequence = 0;
      for (iter->SeekToFirst(); iter->Valid(); iter->Next()) {
        Slice key = iter->key();
        if (!ParseInternalKey(key, &parsed)) {
          Log(options_.info_log, "Table #%" PRIu64 ": unparsable key %s",
              t->meta.fd.GetNumber(), EscapeString(key).c_str());
          continue;
        }

        counter++;
        if (empty) {
          empty = false;
          t->meta.smallest.DecodeFrom(key);
        }
        t->meta.largest.DecodeFrom(key);
        if (parsed.sequence < t->min_sequence) {
          t->min_sequence = parsed.sequence;
        }
        if (parsed.sequence > t->max_sequence) {
          t->max_sequence = parsed.sequence;
        }
      }
      if (!iter->status().ok()) {
        status = iter->status();
      }
      delete iter;
    }
    Log(options_.info_log, "Table #%" PRIu64 ": %d entries %s",
        t->meta.fd.GetNumber(), counter, status.ToString().c_str());
    return status;
  }

  Status WriteDescriptor() {
    std::string tmp = TempFileName(dbname_, 1);
    unique_ptr<WritableFile> file;
    Status status = env_->NewWritableFile(
        tmp, &file, env_->OptimizeForManifestWrite(storage_options_));
    if (!status.ok()) {
      return status;
    }

    SequenceNumber max_sequence = 0;
    for (size_t i = 0; i < tables_.size(); i++) {
      if (max_sequence < tables_[i].max_sequence) {
        max_sequence = tables_[i].max_sequence;
      }
    }

    edit_->SetComparatorName(icmp_.user_comparator()->Name());
    edit_->SetLogNumber(0);
    edit_->SetNextFile(next_file_number_);
    edit_->SetLastSequence(max_sequence);

    for (size_t i = 0; i < tables_.size(); i++) {
      // TODO(opt): separate out into multiple levels
      const TableInfo& t = tables_[i];
      edit_->AddFile(0, t.meta.fd.GetNumber(), t.meta.fd.GetPathId(),
                     t.meta.fd.GetFileSize(), t.meta.smallest, t.meta.largest,
                     t.min_sequence, t.max_sequence);
    }

    //fprintf(stderr, "NewDescriptor:\n%s\n", edit_.DebugString().c_str());
    {
      log::Writer log(std::move(file));
      std::string record;
      edit_->EncodeTo(&record);
      status = log.AddRecord(record);
    }

    if (!status.ok()) {
      env_->DeleteFile(tmp);
    } else {
      // Discard older manifests
      for (size_t i = 0; i < manifests_.size(); i++) {
        ArchiveFile(dbname_ + "/" + manifests_[i]);
      }

      // Install new manifest
      status = env_->RenameFile(tmp, DescriptorFileName(dbname_, 1));
      if (status.ok()) {
        status = SetCurrentFile(env_, dbname_, 1, nullptr);
      } else {
        env_->DeleteFile(tmp);
      }
    }
    return status;
  }

  void ArchiveFile(const std::string& fname) {
    // Move into another directory.  E.g., for
    //    dir/foo
    // rename to
    //    dir/lost/foo
    const char* slash = strrchr(fname.c_str(), '/');
    std::string new_dir;
    if (slash != nullptr) {
      new_dir.assign(fname.data(), slash - fname.data());
    }
    new_dir.append("/lost");
    env_->CreateDir(new_dir);  // Ignore error
    std::string new_file = new_dir;
    new_file.append("/");
    new_file.append((slash == nullptr) ? fname.c_str() : slash + 1);
    Status s = env_->RenameFile(fname, new_file);
    Log(options_.info_log, "Archiving %s: %s\n",
        fname.c_str(), s.ToString().c_str());
  }
};
}  // namespace

Status RepairDB(const std::string& dbname, const Options& options) {
  Repairer repairer(dbname, options);
  return repairer.Run();
}

}  // namespace rocksdb

#endif  // ROCKSDB_LITE
