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// A utility function that convert string array into existence filter data file.

#include "rewriter/gen_existence_data.h"

#include <cstdint>
#include <iostream>
#include <ostream>
#include <string>

#include "absl/log/log.h"
#include "absl/strings/string_view.h"
#include "absl/types/span.h"
#include "base/codegen_bytearray_stream.h"
#include "storage/existence_filter.h"

namespace mozc {
namespace {

using ::mozc::storage::ExistenceFilterBuilder;

std::string GenExistenceData(const absl::Span<const std::string> entries,
                             double error_rate) {
  const int n = entries.size();
  const int m =
      ExistenceFilterBuilder::MinFilterSizeInBytesForErrorRate(error_rate, n);
  LOG(INFO) << "entry: " << n << " err: " << error_rate << " bytes: " << m;

  ExistenceFilterBuilder builder(ExistenceFilterBuilder::CreateOptimal(m, n));

  for (absl::string_view entry : entries) {
    builder.Insert(entry);
  }
  return builder.SerializeAsString();
}

}  // namespace

void OutputExistenceHeader(const absl::Span<const std::string> entries,
                           const absl::string_view data_namespace,
                           std::ostream* ofs, double error_rate) {
  const std::string existence_data = GenExistenceData(entries, error_rate);

  *ofs << "// This header file is generated by " << "gen_existence_data."
       << std::endl;

  *ofs << "namespace " << data_namespace << "{" << std::endl;

  CodeGenByteArrayOutputStream codegen_stream(*ofs);
  codegen_stream.OpenVarDef("ExistenceFilter");
  codegen_stream.write(existence_data.data(), existence_data.size());
  codegen_stream.CloseVarDef();
  *ofs << "}  // namespace " << data_namespace << std::endl;
}

void OutputExistenceBinary(const absl::Span<const std::string> entries,
                           std::ostream* ofs, double error_rate) {
  const std::string existence_data = GenExistenceData(entries, error_rate);
  ofs->write(existence_data.data(), existence_data.size());
}
}  // namespace mozc
