//  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).
//
#include "file/file_util.h"

#include <string>
#include <algorithm>

#include "file/random_access_file_reader.h"
#include "file/sequence_file_reader.h"
#include "file/sst_file_manager_impl.h"
#include "file/writable_file_writer.h"
#include "rocksdb/env.h"

namespace ROCKSDB_NAMESPACE {

// Utility function to copy a file up to a specified length
IOStatus CopyFile(FileSystem* fs, const std::string& source,
                  const std::string& destination, uint64_t size,
                  bool use_fsync) {
  const FileOptions soptions;
  IOStatus io_s;
  std::unique_ptr<SequentialFileReader> src_reader;
  std::unique_ptr<WritableFileWriter> dest_writer;

  {
    std::unique_ptr<FSSequentialFile> srcfile;
    io_s = fs->NewSequentialFile(source, soptions, &srcfile, nullptr);
    if (!io_s.ok()) {
      return io_s;
    }
    std::unique_ptr<FSWritableFile> destfile;
    io_s = fs->NewWritableFile(destination, soptions, &destfile, nullptr);
    if (!io_s.ok()) {
      return io_s;
    }

    if (size == 0) {
      // default argument means copy everything
      io_s = fs->GetFileSize(source, IOOptions(), &size, nullptr);
      if (!io_s.ok()) {
        return io_s;
      }
    }
    src_reader.reset(new SequentialFileReader(std::move(srcfile), source));
    dest_writer.reset(
        new WritableFileWriter(std::move(destfile), destination, soptions));
  }

  char buffer[4096];
  Slice slice;
  while (size > 0) {
    size_t bytes_to_read = std::min(sizeof(buffer), static_cast<size_t>(size));
    io_s = status_to_io_status(src_reader->Read(bytes_to_read, &slice, buffer));
    if (!io_s.ok()) {
      return io_s;
    }
    if (slice.size() == 0) {
      return IOStatus::Corruption("file too small");
    }
    io_s = dest_writer->Append(slice);
    if (!io_s.ok()) {
      return io_s;
    }
    size -= slice.size();
  }
  return dest_writer->Sync(use_fsync);
}

// Utility function to create a file with the provided contents
IOStatus CreateFile(FileSystem* fs, const std::string& destination,
                    const std::string& contents, bool use_fsync) {
  const EnvOptions soptions;
  IOStatus io_s;
  std::unique_ptr<WritableFileWriter> dest_writer;

  std::unique_ptr<FSWritableFile> destfile;
  io_s = fs->NewWritableFile(destination, soptions, &destfile, nullptr);
  if (!io_s.ok()) {
    return io_s;
  }
  dest_writer.reset(
      new WritableFileWriter(std::move(destfile), destination, soptions));
  io_s = dest_writer->Append(Slice(contents));
  if (!io_s.ok()) {
    return io_s;
  }
  return dest_writer->Sync(use_fsync);
}

Status DeleteDBFile(const ImmutableDBOptions* db_options,
                    const std::string& fname, const std::string& dir_to_sync,
                    const bool force_bg, const bool force_fg) {
#ifndef ROCKSDB_LITE
  SstFileManagerImpl* sfm =
      static_cast<SstFileManagerImpl*>(db_options->sst_file_manager.get());
  if (sfm && !force_fg) {
    return sfm->ScheduleFileDeletion(fname, dir_to_sync, force_bg);
  } else {
    return db_options->env->DeleteFile(fname);
  }
#else
  (void)dir_to_sync;
  (void)force_bg;
  (void)force_fg;
  // SstFileManager is not supported in ROCKSDB_LITE
  // Delete file immediately
  return db_options->env->DeleteFile(fname);
#endif
}

bool IsWalDirSameAsDBPath(const ImmutableDBOptions* db_options) {
  bool same = false;
  assert(!db_options->db_paths.empty());
  Status s = db_options->env->AreFilesSame(db_options->wal_dir,
                                           db_options->db_paths[0].path, &same);
  if (s.IsNotSupported()) {
    same = db_options->wal_dir == db_options->db_paths[0].path;
  }
  return same;
}

IOStatus GenerateOneFileChecksum(FileSystem* fs, const std::string& file_path,
                                 FileChecksumGenFactory* checksum_factory,
                                 std::string* file_checksum,
                                 std::string* file_checksum_func_name,
                                 size_t verify_checksums_readahead_size,
                                 bool allow_mmap_reads) {
  if (checksum_factory == nullptr) {
    return IOStatus::InvalidArgument("Checksum factory is invalid");
  }
  assert(file_checksum != nullptr);
  assert(file_checksum_func_name != nullptr);

  FileChecksumGenContext gen_context;
  std::unique_ptr<FileChecksumGenerator> checksum_generator =
      checksum_factory->CreateFileChecksumGenerator(gen_context);
  uint64_t size;
  IOStatus io_s;
  std::unique_ptr<RandomAccessFileReader> reader;
  {
    std::unique_ptr<FSRandomAccessFile> r_file;
    io_s = fs->NewRandomAccessFile(file_path, FileOptions(), &r_file, nullptr);
    if (!io_s.ok()) {
      return io_s;
    }
    io_s = fs->GetFileSize(file_path, IOOptions(), &size, nullptr);
    if (!io_s.ok()) {
      return io_s;
    }
    reader.reset(new RandomAccessFileReader(std::move(r_file), file_path));
  }

  // Found that 256 KB readahead size provides the best performance, based on
  // experiments, for auto readahead. Experiment data is in PR #3282.
  size_t default_max_read_ahead_size = 256 * 1024;
  size_t readahead_size = (verify_checksums_readahead_size != 0)
                              ? verify_checksums_readahead_size
                              : default_max_read_ahead_size;

  FilePrefetchBuffer prefetch_buffer(
      reader.get(), readahead_size /* readadhead_size */,
      readahead_size /* max_readahead_size */, !allow_mmap_reads /* enable */);

  Slice slice;
  uint64_t offset = 0;
  while (size > 0) {
    size_t bytes_to_read =
        static_cast<size_t>(std::min(uint64_t{readahead_size}, size));
    if (!prefetch_buffer.TryReadFromCache(offset, bytes_to_read, &slice,
                                          false)) {
      return IOStatus::Corruption("file read failed");
    }
    if (slice.size() == 0) {
      return IOStatus::Corruption("file too small");
    }
    checksum_generator->Update(slice.data(), slice.size());
    size -= slice.size();
    offset += slice.size();
  }
  checksum_generator->Finalize();
  *file_checksum = checksum_generator->GetChecksum();
  *file_checksum_func_name = checksum_generator->Name();
  return IOStatus::OK();
}

}  // namespace ROCKSDB_NAMESPACE
