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#include "base/clock.h"

#include <ctime>

#include "absl/time/clock.h"
#include "absl/time/time.h"
#include "base/singleton.h"

#if defined(OS_CHROMEOS) || defined(_WIN32)
constexpr bool kUseAbslLocalTimeZone = false;

#else  // defined(OS_CHROMEOS) || defined(_WIN32)
constexpr bool kUseAbslLocalTimeZone = true;

#endif  // defined(OS_CHROMEOS) || defined(_WIN32)

namespace mozc {
namespace {

absl::TimeZone GetLocalTimeZone() {
  if constexpr (kUseAbslLocalTimeZone) {
    return absl::LocalTimeZone();
  } else {
    // Do not use absl::LocalTimeZone() here because
    // - on Chrome OS, it returns UTC: b/196271425
    // - on Windows, it crashes: https://github.com/google/mozc/issues/856
    const time_t epoch(24 * 60 * 60);  // 1970-01-02 00:00:00 UTC
    const std::tm* offset = std::localtime(&epoch);
    if (offset == nullptr) {
      return absl::FixedTimeZone(9 * 60 * 60);  // JST as fallback
    }
    return absl::FixedTimeZone(
        (offset->tm_mday - 2) * 24 * 60 * 60  // date offset from Jan 2.
        + offset->tm_hour * 60 * 60           // hour offset from 00 am.
        + offset->tm_min * 60);               // minute offset.
  }
}

class ClockImpl : public ClockInterface {
 public:
  ClockImpl() = default;
  ~ClockImpl() override = default;

  absl::Time GetAbslTime() override { return absl::Now(); }

  absl::TimeZone GetTimeZone() override { return GetLocalTimeZone(); }
};
}  // namespace

using ClockSingleton = SingletonMockable<ClockInterface, ClockImpl>;

absl::Time Clock::GetAbslTime() { return ClockSingleton::Get()->GetAbslTime(); }

absl::TimeZone Clock::GetTimeZone() {
  return ClockSingleton::Get()->GetTimeZone();
}

void Clock::SetClockForUnitTest(ClockInterface* clock) {
  ClockSingleton::SetMock(clock);
}

}  // namespace mozc
