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#include <algorithm>
#include <cstdint>
#include <memory>
#include <string>

#include "base/codegen_bytearray_stream.h"
#include "base/file_stream.h"
#include "base/hash.h"
#include "base/init_mozc.h"
#include "base/logging.h"
#include "base/util.h"
#include "storage/existence_filter.h"
#include "absl/flags/flag.h"

ABSL_FLAG(std::string, input, "", "per-line suggestion filter list");
ABSL_FLAG(std::string, output, "", "output bloom filter");
ABSL_FLAG(bool, header, true, "make header file instead of raw bloom filter");
ABSL_FLAG(std::string, name, "SuggestionFilterData",
          "name for variable name in the header file");

namespace {
void ReadWords(const std::string &name, std::vector<uint64_t> *words) {
  std::string line;
  mozc::InputFileStream input(name.c_str());
  while (std::getline(input, line)) {
    if (line.empty() || line[0] == '#') {
      continue;
    }
    std::string lower_value = line;
    mozc::Util::LowerString(&lower_value);
    words->push_back(mozc::Hash::Fingerprint(lower_value));
  }
}

const size_t kMinimumFilterBytes = 100 * 1000;
}  // namespace

using mozc::storage::ExistenceFilter;

// read per-line word list and generate
// bloom filter in raw byte array or header file format
int main(int argc, char **argv) {
  mozc::InitMozc(argv[0], &argc, &argv);

  if ((absl::GetFlag(FLAGS_input).empty() ||
       absl::GetFlag(FLAGS_output).empty()) && argc > 2) {
    absl::SetFlag(&FLAGS_input, argv[1]);
    absl::SetFlag(&FLAGS_output, argv[2]);
  }

  std::vector<uint64_t> words;

  ReadWords(absl::GetFlag(FLAGS_input), &words);

  LOG(INFO) << words.size() << " words found";

  static const float kErrorRate = 0.00001;
  const size_t num_bytes =
      std::max(ExistenceFilter::MinFilterSizeInBytesForErrorRate(kErrorRate,
                                                                 words.size()),
               kMinimumFilterBytes);

  LOG(INFO) << "num_bytes: " << num_bytes;

  std::unique_ptr<ExistenceFilter> filter(
      ExistenceFilter::CreateOptimal(num_bytes, words.size()));
  for (size_t i = 0; i < words.size(); ++i) {
    filter->Insert(words[i]);
  }

  char *buf = nullptr;
  size_t size = 0;

  LOG(INFO) << "writing bloomfilter: " << absl::GetFlag(FLAGS_output);
  filter->Write(&buf, &size);

  if (absl::GetFlag(FLAGS_header)) {
    mozc::OutputFileStream ofs(absl::GetFlag(FLAGS_output).c_str());
    mozc::CodeGenByteArrayOutputStream codegen_stream(
        &ofs, mozc::codegenstream::NOT_OWN_STREAM);
    codegen_stream.OpenVarDef(absl::GetFlag(FLAGS_name));
    codegen_stream.write(buf, size);
    codegen_stream.CloseVarDef();
  } else {
    mozc::OutputFileStream ofs(
        absl::GetFlag(FLAGS_output).c_str(),
        std::ios::out | std::ios::trunc | std::ios::binary);
    ofs.write(buf, size);
  }

  delete[] buf;

  return 0;
}
