// Copyright 2016 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "src/lib/util/datetime_util.h"

#include <ctime>

#include <gtest/gtest.h>

#include "src/lib/util/clock.h"
#include "src/public/lib/statusor/status_macros.h"

namespace cobalt::util {

namespace {

MetricDefinition MetricWithTimeZonePolicy(MetricDefinition::TimeZonePolicy policy) {
  MetricDefinition metric;
  metric.set_time_zone_policy(policy);
  return metric;
}

}  // namespace

// This is an alternate definition of CalendarDateToDayIndex from the one
// in datetime_util.cc. It appears to be simpler than the one we chose. The
// reasons we did not choose this implementation are:
// (a) It uses the function timegm which is nonstandard and may not be supported
// on all platforms we want to support. See:
// http://man7.org/linux/man-pages/man3/timegm.3.html#CONFORMING_TO
// (b) In order to implement timegm ourselves using standard library functions
// it is necessary to invoke functions that make use of the local timezone
// and that are not thread-safe because they use global state. Both of these
// things are unnecessary. It seemed like a better idea to use a pure
// algorithm that would work anywhere.
uint32_t CalendarDateToDayIndexAltImpl(const CalendarDate& calendar_date) {
  struct tm time_info;
  time_info.tm_sec = 0;
  time_info.tm_min = 0;
  time_info.tm_hour = 0;
  time_info.tm_mday = static_cast<int>(calendar_date.day_of_month);
  time_info.tm_mon = static_cast<int>(calendar_date.month) - 1;
  time_info.tm_year = static_cast<int>(calendar_date.year) - 1900;
  time_t unix_time = timegm(&time_info);
  return static_cast<uint32_t>(unix_time / kNumUnixSecondsPerDay);
}

TEST(DatetimeUtilTest, CalendarDateToDayIndex) {
  CalendarDate calendar_date;

  // January 1, 1970
  calendar_date.day_of_month = 1;
  calendar_date.month = 1;
  calendar_date.year = 1970;
  EXPECT_EQ(0u, CalendarDateToDayIndex(calendar_date));
  EXPECT_EQ(0u, CalendarDateToDayIndexAltImpl(calendar_date));

  // January 2, 1970
  calendar_date.day_of_month = 2;
  EXPECT_EQ(1u, CalendarDateToDayIndex(calendar_date));
  EXPECT_EQ(1u, CalendarDateToDayIndexAltImpl(calendar_date));

  // January 31, 1970
  calendar_date.day_of_month = 31;
  EXPECT_EQ(30u, CalendarDateToDayIndex(calendar_date));
  EXPECT_EQ(30u, CalendarDateToDayIndexAltImpl(calendar_date));

  // Febrary 1, 1970
  calendar_date.month = 2;
  calendar_date.day_of_month = 1;
  EXPECT_EQ(31u, CalendarDateToDayIndex(calendar_date));
  EXPECT_EQ(31u, CalendarDateToDayIndexAltImpl(calendar_date));

  // 1972 Was a leap year...

  // January 1, 1972
  calendar_date.day_of_month = 1;
  calendar_date.month = 1;
  calendar_date.year = 1972;
  EXPECT_EQ(365 * 2u, CalendarDateToDayIndex(calendar_date));
  EXPECT_EQ(365 * 2u, CalendarDateToDayIndexAltImpl(calendar_date));

  // February 1, 1972
  calendar_date.day_of_month = 1;
  calendar_date.month = 2;
  calendar_date.year = 1972;
  EXPECT_EQ(365 * 2u + 31, CalendarDateToDayIndex(calendar_date));
  EXPECT_EQ(365 * 2u + 31, CalendarDateToDayIndexAltImpl(calendar_date));

  // February 28, 1972
  calendar_date.day_of_month = 28;
  calendar_date.month = 2;
  calendar_date.year = 1972;
  EXPECT_EQ(365 * 2u + 31 + 27, CalendarDateToDayIndex(calendar_date));
  EXPECT_EQ(365 * 2u + 31 + 27, CalendarDateToDayIndexAltImpl(calendar_date));

  // February 29, 1972
  calendar_date.day_of_month = 29;
  calendar_date.month = 2;
  calendar_date.year = 1972;
  EXPECT_EQ(365 * 2u + 31 + 28, CalendarDateToDayIndex(calendar_date));
  EXPECT_EQ(365 * 2u + 31 + 28, CalendarDateToDayIndexAltImpl(calendar_date));

  // March 1, 1972
  calendar_date.day_of_month = 1;
  calendar_date.month = 3;
  calendar_date.year = 1972;
  EXPECT_EQ(365 * 2u + 31 + 29, CalendarDateToDayIndex(calendar_date));
  EXPECT_EQ(365 * 2u + 31 + 29, CalendarDateToDayIndexAltImpl(calendar_date));

  // January 1, 1973
  calendar_date.day_of_month = 1;
  calendar_date.month = 1;
  calendar_date.year = 1973;
  EXPECT_EQ(365 * 2u + 366, CalendarDateToDayIndex(calendar_date));
  EXPECT_EQ(365 * 2u + 366, CalendarDateToDayIndexAltImpl(calendar_date));

  // March 1, 2000 (2000 years after March 1, year 0)
  calendar_date.day_of_month = 1;
  calendar_date.month = 3;
  calendar_date.year = 2000;
  // See comments at KEpochOffset.
  EXPECT_EQ(11017u, CalendarDateToDayIndex(calendar_date));
  EXPECT_EQ(11017u, CalendarDateToDayIndexAltImpl(calendar_date));

  // October 18, 2016
  calendar_date.day_of_month = 18;
  calendar_date.month = 10;
  calendar_date.year = 2016;
  EXPECT_EQ(17092u, CalendarDateToDayIndex(calendar_date));
  EXPECT_EQ(17092u, CalendarDateToDayIndexAltImpl(calendar_date));
}

void doDayIndexToCalendarDateTest(uint32_t day_index, uint32_t expected_month,
                                  uint32_t expected_day_of_month, uint32_t expected_year) {
  auto calendar_date = DayIndexToCalendarDate(day_index);
  EXPECT_EQ(expected_day_of_month, calendar_date.day_of_month) << "day_index=" << day_index;
  EXPECT_EQ(expected_month, calendar_date.month) << "day_index=" << day_index;
  EXPECT_EQ(expected_year, calendar_date.year) << "day_index=" << day_index;
}

TEST(DatetimeUtilTest, DayIndexToCalendarDate) {
  // January 1, 1970
  doDayIndexToCalendarDateTest(0, 1, 1, 1970);

  // January 2, 1970
  doDayIndexToCalendarDateTest(1, 1, 2, 1970);

  // January 31, 1970
  doDayIndexToCalendarDateTest(30, 1, 31, 1970);

  // Febrary 1, 1970
  doDayIndexToCalendarDateTest(31, 2, 1, 1970);

  // 1972 Was a leap year...

  // January 1, 1972
  doDayIndexToCalendarDateTest(365 * 2, 1, 1, 1972);

  // February 1, 1972
  doDayIndexToCalendarDateTest(365 * 2 + 31, 2, 1, 1972);

  // February 28, 1972
  doDayIndexToCalendarDateTest(365 * 2 + 31 + 27, 2, 28, 1972);

  // February 29, 1972
  doDayIndexToCalendarDateTest(365 * 2 + 31 + 28, 2, 29, 1972);

  // March 1, 1972
  doDayIndexToCalendarDateTest(365 * 2 + 31 + 29, 3, 1, 1972);

  // January 1, 1973
  doDayIndexToCalendarDateTest(365 * 2 + 366, 1, 1, 1973);

  // March 1, 2000
  doDayIndexToCalendarDateTest(11017, 3, 1, 2000);

  // October 18, 2016
  doDayIndexToCalendarDateTest(17092, 10, 18, 2016);
}

TEST(DatetimeUtilTest, DayIndexCalendarDateInversesTest) {
  for (uint32_t day_index = 16000; day_index < 19000; day_index++) {
    CalendarDate calendar_date = DayIndexToCalendarDate(day_index);
    EXPECT_EQ(day_index, CalendarDateToDayIndex(calendar_date));
    EXPECT_EQ(day_index, CalendarDateToDayIndexAltImpl(calendar_date));
  }
}

TEST(DatetimeUtilTest, DayIndexToWeekIndex) {
  // This is the day index for Friday Dec 2, 2016
  static const uint32_t kSomeDayIndex = 17137;
  // The week index for the week containing that day.
  static const uint32_t kSomeWeekIndex = 2448;
  EXPECT_EQ(kSomeWeekIndex, DayIndexToWeekIndex(kSomeDayIndex));
}

TEST(DatetimeUtilTest, CalendarDateToWeekIndex) {
  CalendarDate calendar_date;

  // Thurs, January 1, 1970
  calendar_date.day_of_month = 1;
  calendar_date.month = 1;
  calendar_date.year = 1970;
  EXPECT_EQ(0u, CalendarDateToWeekIndex(calendar_date));

  // Fri, January 2, 1970
  calendar_date.day_of_month = 2;
  EXPECT_EQ(0u, CalendarDateToWeekIndex(calendar_date));

  // Sat, January 3, 1970
  calendar_date.day_of_month = 3;
  EXPECT_EQ(0u, CalendarDateToWeekIndex(calendar_date));

  // Sun, January 4, 1970
  calendar_date.day_of_month = 4;
  EXPECT_EQ(1u, CalendarDateToWeekIndex(calendar_date));

  // Mon January 5, 1970
  calendar_date.day_of_month = 5;
  EXPECT_EQ(1u, CalendarDateToWeekIndex(calendar_date));

  // Sat January 10, 1970
  calendar_date.day_of_month = 10;
  EXPECT_EQ(1u, CalendarDateToWeekIndex(calendar_date));

  // Sun January 11, 1970
  calendar_date.day_of_month = 11;
  EXPECT_EQ(2u, CalendarDateToWeekIndex(calendar_date));

  // Mon January 12, 1970
  calendar_date.day_of_month = 12;
  EXPECT_EQ(2u, CalendarDateToWeekIndex(calendar_date));

  // Wed March 4, 1970
  calendar_date.day_of_month = 4;
  calendar_date.month = 3;
  EXPECT_EQ(9u, CalendarDateToWeekIndex(calendar_date));

  // Sat March 7, 1970
  calendar_date.day_of_month = 7;
  EXPECT_EQ(9u, CalendarDateToWeekIndex(calendar_date));

  // Sun March 8, 1970
  calendar_date.day_of_month = 8;
  EXPECT_EQ(10u, CalendarDateToWeekIndex(calendar_date));
}

void doWeekIndexToCalendarDateTest(uint32_t week_index, uint32_t expected_month,
                                   uint32_t expected_day_of_month, uint32_t expected_year) {
  auto calendar_date = WeekIndexToCalendarDate(week_index);
  EXPECT_EQ(expected_day_of_month, calendar_date.day_of_month) << "week_index=" << week_index;
  EXPECT_EQ(expected_month, calendar_date.month) << "week_index=" << week_index;
  EXPECT_EQ(expected_year, calendar_date.year) << "week_index=" << week_index;
}

TEST(DatetimeUtilTest, WeekIndexToCalendarDate) {
  // January 1, 1970
  doWeekIndexToCalendarDateTest(0, 1, 1, 1970);

  // January 4, 1970
  doWeekIndexToCalendarDateTest(1, 1, 4, 1970);

  // January 11, 1970
  doWeekIndexToCalendarDateTest(2, 1, 11, 1970);

  // Marcy 8, 1970
  doWeekIndexToCalendarDateTest(10, 3, 8, 1970);

  // Marcy 15, 1970
  doWeekIndexToCalendarDateTest(11, 3, 15, 1970);
}

TEST(DatetimeUtilTest, WeekIndexCalendarDateInversesTest) {
  for (uint32_t week_index = 2000; week_index < 3000; week_index++) {
    CalendarDate calendar_date = WeekIndexToCalendarDate(week_index);
    EXPECT_EQ(week_index, CalendarDateToWeekIndex(calendar_date));
  }
}

TEST(DatetimeUtilTest, CalendarDateToMonthIndex) {
  CalendarDate calendar_date;

  // January 1, 1970
  calendar_date.day_of_month = 1;
  calendar_date.month = 1;
  calendar_date.year = 1970;
  EXPECT_EQ(0u, CalendarDateToMonthIndex(calendar_date));

  // January 31, 1970
  calendar_date.day_of_month = 31;
  EXPECT_EQ(0u, CalendarDateToMonthIndex(calendar_date));

  // February 1, 1970
  calendar_date.month = 2;
  calendar_date.day_of_month = 1;
  EXPECT_EQ(1u, CalendarDateToMonthIndex(calendar_date));

  // December 31, 1970
  calendar_date.month = 12;
  calendar_date.day_of_month = 31;
  EXPECT_EQ(11u, CalendarDateToMonthIndex(calendar_date));

  // January 1, 1971
  calendar_date.month = 1;
  calendar_date.day_of_month = 1;
  calendar_date.year = 1971;
  EXPECT_EQ(12u, CalendarDateToMonthIndex(calendar_date));

  // March 4, 1971
  calendar_date.month = 3;
  calendar_date.day_of_month = 4;
  calendar_date.year = 1971;
  EXPECT_EQ(14u, CalendarDateToMonthIndex(calendar_date));

  // March 4, 1976
  calendar_date.month = 3;
  calendar_date.day_of_month = 4;
  calendar_date.year = 1976;
  EXPECT_EQ(74u, CalendarDateToMonthIndex(calendar_date));
}

TEST(DatetimeUtilTest, DayIndexToMonthIndex) {
  // This is the day index for Friday Dec 2, 2016
  static const uint32_t kSomeDayIndex = 17137;
  // The month index for December, 2016.
  static const uint32_t kSomeMonthIndex = 563;
  EXPECT_EQ(kSomeMonthIndex, DayIndexToMonthIndex(kSomeDayIndex));
}

void doMonthIndexToCalendarDateTest(uint32_t month_index, uint32_t expected_month,
                                    uint32_t expected_year) {
  auto calendar_date = MonthIndexToCalendarDate(month_index);
  EXPECT_EQ(1u, calendar_date.day_of_month) << "month_index=" << month_index;
  EXPECT_EQ(expected_month, calendar_date.month) << "month_index=" << month_index;
  EXPECT_EQ(expected_year, calendar_date.year) << "month_index=" << month_index;
}

TEST(DatetimeUtilTest, MonthIndexToCalendarDate) {
  // January, 1970
  doMonthIndexToCalendarDateTest(0, 1, 1970);

  // February, 1970
  doMonthIndexToCalendarDateTest(1, 2, 1970);

  // March, 1970
  doMonthIndexToCalendarDateTest(2, 3, 1970);

  // April, 1978
  doMonthIndexToCalendarDateTest(123, 4, 1980);
}

TEST(DatetimeUtilTest, MonthIndexCalendarDateInversesTest) {
  for (uint32_t month_index = 500; month_index < 1000; month_index++) {
    CalendarDate calendar_date = MonthIndexToCalendarDate(month_index);
    EXPECT_EQ(month_index, CalendarDateToMonthIndex(calendar_date));
  }
}

TEST(DatetimeUtilTest, TimeToHourIdTest) {
  // This unix timestamp corresponds to:
  // UTC:  00:00:00 on August 6, 2019
  // PDT:  17:00:00 on August 5, 2019
  static const time_t kSummerExactHourTimestamp = 1565049600;
  static const uint32_t kUtcSummerExactHourId =
      (18114 /* Days */ * kHourIdsPerDay) + 1 /* Not DST */;
  static const uint32_t kPacificSummerExactHourId =
      (18113 /* Days */ * kHourIdsPerDay) + (17 * 2) /* DST */;
  // This unix timestamp corresponds to:
  // UTC:  13:42:07 on August 6, 2019
  // PDT:  06:42:07 on August 6, 2019
  static const time_t kSummerOffHourTimestamp = 1565098927;
  static const uint32_t kUtcSummerOffHourId =
      (18114 /* Days */ * kHourIdsPerDay) + (13 * 2) + 1 /* Not DST */;
  static const uint32_t kPacificSummerOffHourId =
      (18114 /* Days */ * kHourIdsPerDay) + (6 * 2) /* DST */;
  // This unix timestamp corresponds to:
  // UTC:  00:00:00 on January 6, 2019
  // PST:  16:00:00 on January 5, 2019
  static const time_t kWinterTimestamp = 1546732800;
  static const uint32_t kUtcWinterHourId = (17902 /* Days */ * kHourIdsPerDay) + 1 /* Not DST */;
  static const uint32_t kPacificWinterHourId =
      (17901 /* Days */ * kHourIdsPerDay) + (16 * 2) + 1 /* Not DST*/;

  EXPECT_EQ(kUtcSummerExactHourId, TimeToHourId(kSummerExactHourTimestamp, MetricDefinition::UTC));
  EXPECT_EQ(kUtcSummerOffHourId, TimeToHourId(kSummerOffHourTimestamp, MetricDefinition::UTC));
  EXPECT_EQ(kUtcWinterHourId, TimeToHourId(kWinterTimestamp, MetricDefinition::UTC));
  // Only perform the following check when running this test in the Pacific
  // timezone. Note that |timezone| is a global variable defined in <ctime>
  // that stores difference between UTC and the latest local standard time, in
  // seconds west of UTC. This value is not adjusted for daylight saving.
  // See https://www.gnu.org/software/libc/manual/html_node/ \
  //                              Time-Zone-Functions.html#Time-Zone-Functions
  if (timezone / 3600 == 8) {
    EXPECT_EQ(kPacificSummerExactHourId,
              TimeToHourId(kSummerExactHourTimestamp, MetricDefinition::LOCAL));
    EXPECT_EQ(kPacificSummerOffHourId,
              TimeToHourId(kSummerOffHourTimestamp, MetricDefinition::LOCAL));
    EXPECT_EQ(kPacificWinterHourId, TimeToHourId(kWinterTimestamp, MetricDefinition::LOCAL));
  }
}

TEST(DatetimeUtilTest, TimePointToHourIdWithUtcConverter) {
  UtcTimeConverter converter = UtcTimeConverter();
  MetricDefinition utc_metric = MetricWithTimeZonePolicy(MetricDefinition::UTC);
  MetricDefinition local_metric = MetricWithTimeZonePolicy(MetricDefinition::LOCAL);
  MetricDefinition other_tz_metric = MetricWithTimeZonePolicy(MetricDefinition::OTHER_TIME_ZONE);

  std::tm kSummerExactHourTime = {
      .tm_sec = 0,
      .tm_min = 0,
      .tm_hour = 0,
      .tm_mday = 6,    // 6th
      .tm_mon = 7,     // August
      .tm_year = 119,  // 2019
  };
  // This Unix time point corresponds to:
  // UTC:  00:00:00 on August 6, 2019
  // PDT:  00:00:00 on August 5, 2019
  const std::chrono::time_point<std::chrono::system_clock> kSummerExactHourTimePoint =
      std::chrono::system_clock::from_time_t(timegm(&kSummerExactHourTime));
  static const uint32_t kUtcSummerExactHourId =
      (18114 /* Days */ * kHourIdsPerDay) + 1 /* Not DST */;
  static const uint32_t kPacificSummerExactHourId =
      (18113 /* Days */ * kHourIdsPerDay) + (17 * 2) /* DST */;

  std::tm kSummerOffHourTime = {
      .tm_sec = 7,
      .tm_min = 42,
      .tm_hour = 13,
      .tm_mday = 6,    // 6th
      .tm_mon = 7,     // August
      .tm_year = 119,  // 2019
  };
  // This Unix time point corresponds to:
  // UTC:  13:42:07 on August 6, 2019
  // PDT:  06:42:07 on August 6, 2019
  const std::chrono::time_point<std::chrono::system_clock> kSummerOffHourTimePoint =
      std::chrono::system_clock::from_time_t(timegm(&kSummerOffHourTime));
  static const uint32_t kUtcSummerOffHourId =
      (18114 /* Days */ * kHourIdsPerDay) + (13 * 2) + 1 /* Not DST */;
  static const uint32_t kPacificSummerOffHourId =
      (18114 /* Days */ * kHourIdsPerDay) + (6 * 2) /* DST */;

  std::tm kWinterTime = {
      .tm_sec = 0,
      .tm_min = 0,
      .tm_hour = 0,
      .tm_mday = 6,    // 6th
      .tm_mon = 0,     // January
      .tm_year = 119,  // 2019
  };
  // This Unix time point corresponds to:
  // UTC:  00:00:00 on January 6, 2019
  // PST:  16:00:00 on January 5, 2019
  const std::chrono::time_point<std::chrono::system_clock> kWinterTimePoint =
      std::chrono::system_clock::from_time_t(timegm(&kWinterTime));
  static const uint32_t kUtcWinterHourId = (17902 /* Days */ * kHourIdsPerDay) + 1 /* Not DST */;
  static const uint32_t kPacificWinterHourId =
      (17901 /* Days */ * kHourIdsPerDay) + (16 * 2) + 1 /* Not DST*/;

  CB_ASSERT_OK_AND_ASSIGN(uint32_t summer_exact_hour,
                          TimePointToHourId(kSummerExactHourTimePoint, converter, utc_metric));
  EXPECT_EQ(kUtcSummerExactHourId, summer_exact_hour);

  CB_ASSERT_OK_AND_ASSIGN(uint32_t summer_off_hour,
                          TimePointToHourId(kSummerOffHourTimePoint, converter, utc_metric));
  EXPECT_EQ(kUtcSummerOffHourId, summer_off_hour);

  CB_ASSERT_OK_AND_ASSIGN(uint32_t winter,
                          TimePointToHourId(kWinterTimePoint, converter, utc_metric));
  EXPECT_EQ(kUtcWinterHourId, winter);

  // Only perform the following check when running this test in the Pacific
  // timezone. Note that |timezone| is a global variable defined in <ctime>
  // that stores difference between UTC and the latest local standard time, in
  // seconds west of UTC. This value is not adjusted for daylight saving.
  // See https://www.gnu.org/software/libc/manual/html_node/ \
  //                              Time-Zone-Functions.html#Time-Zone-Functions
  if (timezone / 3600 == 8) {
    CB_ASSERT_OK_AND_ASSIGN(uint32_t pacific_summer_exact_hour,
                            TimePointToHourId(kSummerExactHourTimePoint, converter, local_metric));
    EXPECT_EQ(kPacificSummerExactHourId, pacific_summer_exact_hour);

    CB_ASSERT_OK_AND_ASSIGN(uint32_t pacific_summer_off_hour,
                            TimePointToHourId(kSummerOffHourTimePoint, converter, local_metric));
    EXPECT_EQ(kPacificSummerOffHourId, pacific_summer_off_hour);

    CB_ASSERT_OK_AND_ASSIGN(uint32_t pacific_winter,
                            TimePointToHourId(kWinterTimePoint, converter, local_metric));
    EXPECT_EQ(kPacificWinterHourId, pacific_winter);
  }

  // Since |converter| converts time points to time structs with respect to UTC, the hour IDs for
  // |other_tz_metric| should agree with those for |utc_metric|.
  CB_ASSERT_OK_AND_ASSIGN(uint32_t other_summer_exact_hour,
                          TimePointToHourId(kSummerExactHourTimePoint, converter, other_tz_metric));
  EXPECT_EQ(kUtcSummerExactHourId, other_summer_exact_hour);

  CB_ASSERT_OK_AND_ASSIGN(uint32_t other_summer_off_hour,
                          TimePointToHourId(kSummerOffHourTimePoint, converter, other_tz_metric));
  EXPECT_EQ(kUtcSummerOffHourId, other_summer_off_hour);

  CB_ASSERT_OK_AND_ASSIGN(uint32_t other_winter,
                          TimePointToHourId(kWinterTimePoint, converter, other_tz_metric));
  EXPECT_EQ(kUtcWinterHourId, other_winter);
}

TEST(DatetimeUtilTest, TimePointToHourIdWithOffsetConverter) {
  // A CivilTimeConverterInterface that mimics conversion of a time_point to a time struct with
  // respect to Pacific Daylight Time.
  FakeCivilTimeConverter summer_converter = FakeCivilTimeConverter(-7, true);
  // A CivilTimeConverterInterface that mimics conversion of a time_point to a time struct with
  // respect to Pacific Standard Time.
  FakeCivilTimeConverter winter_converter = FakeCivilTimeConverter(-8, false);
  MetricDefinition other_tz_metric = MetricWithTimeZonePolicy(MetricDefinition::OTHER_TIME_ZONE);

  std::tm kSummerExactHourTime = {
      .tm_sec = 0,
      .tm_min = 0,
      .tm_hour = 0,
      .tm_mday = 6,    // 6th
      .tm_mon = 7,     // August
      .tm_year = 119,  // 2019
  };
  // This Unix time point corresponds to:
  // UTC:  00:00:00 on August 6, 2019
  // PDT:  00:00:00 on August 5, 2019
  const std::chrono::time_point<std::chrono::system_clock> kSummerExactHourTimePoint =
      std::chrono::system_clock::from_time_t(timegm(&kSummerExactHourTime));
  static const uint32_t kPacificSummerExactHourId =
      (18113 /* Days */ * kHourIdsPerDay) + (17 * 2) /* DST */;

  std::tm kSummerOffHourTime = {
      .tm_sec = 7,
      .tm_min = 42,
      .tm_hour = 13,
      .tm_mday = 6,    // 6th
      .tm_mon = 7,     // August
      .tm_year = 119,  // 2019
  };
  // This Unix time point corresponds to:
  // UTC:  13:42:07 on August 6, 2019
  // PDT:  06:42:07 on August 6, 2019
  const std::chrono::time_point<std::chrono::system_clock> kSummerOffHourTimePoint =
      std::chrono::system_clock::from_time_t(timegm(&kSummerOffHourTime));
  static const uint32_t kPacificSummerOffHourId =
      (18114 /* Days */ * kHourIdsPerDay) + (6 * 2) /* DST */;

  std::tm kWinterTime = {
      .tm_sec = 0,
      .tm_min = 0,
      .tm_hour = 0,
      .tm_mday = 6,    // 6th
      .tm_mon = 0,     // January
      .tm_year = 119,  // 2019
  };
  // This Unix time point corresponds to:
  // UTC:  00:00:00 on January 6, 2019
  // PST:  16:00:00 on January 5, 2019
  const std::chrono::time_point<std::chrono::system_clock> kWinterTimePoint =
      std::chrono::system_clock::from_time_t(timegm(&kWinterTime));
  static const uint32_t kPacificWinterHourId =
      (17901 /* Days */ * kHourIdsPerDay) + (16 * 2) + 1 /* Not DST*/;

  CB_ASSERT_OK_AND_ASSIGN(
      uint32_t summer_exact_hour,
      TimePointToHourId(kSummerExactHourTimePoint, summer_converter, other_tz_metric));
  EXPECT_EQ(kPacificSummerExactHourId, summer_exact_hour);

  CB_ASSERT_OK_AND_ASSIGN(
      uint32_t summer_off_hour,
      TimePointToHourId(kSummerOffHourTimePoint, summer_converter, other_tz_metric));
  EXPECT_EQ(kPacificSummerOffHourId, summer_off_hour);

  CB_ASSERT_OK_AND_ASSIGN(uint32_t winter,
                          TimePointToHourId(kWinterTimePoint, winter_converter, other_tz_metric));
  EXPECT_EQ(kPacificWinterHourId, winter);
}

TEST(DatetimeUtilTest, HourIdToDayIndexTest) {
  static const uint32_t kDayIndex = 18114;
  static const uint32_t kHourIdMidnight = kDayIndex * kHourIdsPerDay;
  static const uint32_t kHourIdNoon = (kDayIndex * kHourIdsPerDay) + (12 * 2);
  EXPECT_EQ(kDayIndex, HourIdToDayIndex(kHourIdMidnight));
  EXPECT_EQ(kDayIndex, HourIdToDayIndex(kHourIdNoon));
}

TEST(DatetimeUtilTest, TimeToDayIndexTest) {
  // This unix timestamp corresponds to Friday Dec 2, 2016 in UTC
  // and Thursday Dec 1, 2016 in Pacific time.
  static const time_t kSomeTimestamp = 1480647356;

  // This is the day index for Friday Dec 2, 2016
  static const uint32_t kUtcDayIndex = 17137;

  // This is the day index for Thurs Dec 1, 2016
  static const uint32_t kPacificDayIndex = 17136;

  EXPECT_EQ(kUtcDayIndex, TimeToDayIndex(kSomeTimestamp, MetricDefinition::UTC));
  // Only perform the following check when running this test in the Pacific
  // timezone. Note that |timezone| is a global variable defined in <ctime>
  // that stores difference between UTC and the latest local standard time, in
  // seconds west of UTC. This value is not adjusted for daylight saving.
  // See https://www.gnu.org/software/libc/manual/html_node/ \
  //                              Time-Zone-Functions.html#Time-Zone-Functions
  if (timezone / 3600 == 8) {
    EXPECT_EQ(kPacificDayIndex, TimeToDayIndex(kSomeTimestamp, MetricDefinition::LOCAL));
  }
}

TEST(DatetimeUtilTest, TimePointToDayIndexWithUtcConverterTest) {
  UtcTimeConverter converter = UtcTimeConverter();
  MetricDefinition utc_metric = MetricWithTimeZonePolicy(MetricDefinition::UTC);
  MetricDefinition local_metric = MetricWithTimeZonePolicy(MetricDefinition::LOCAL);
  MetricDefinition other_tz_metric = MetricWithTimeZonePolicy(MetricDefinition::OTHER_TIME_ZONE);

  std::tm kTimeStruct = {
      .tm_sec = 0,
      .tm_min = 0,
      .tm_hour = 0,
      .tm_mday = 2,    // 2nd
      .tm_mon = 11,    // December
      .tm_year = 116,  // 2016
  };
  // This unix timestamp corresponds to Friday Dec 2, 2016 in UTC
  // and Thursday Dec 1, 2016 in Pacific time.
  const std::chrono::time_point<std::chrono::system_clock> kTimePoint =
      std::chrono::system_clock::from_time_t(timegm(&kTimeStruct));

  // This is the day index for Friday Dec 2, 2016
  static const uint32_t kUtcDayIndex = 17137;

  // This is the day index for Thurs Dec 1, 2016
  static const uint32_t kPacificDayIndex = 17136;

  CB_ASSERT_OK_AND_ASSIGN(uint32_t utc_day_index,
                          TimePointToDayIndex(kTimePoint, converter, utc_metric));
  EXPECT_EQ(kUtcDayIndex, utc_day_index);

  // Only perform the following check when running this test in the Pacific
  // timezone. Note that |timezone| is a global variable defined in <ctime>
  // that stores difference between UTC and the latest local standard time, in
  // seconds west of UTC. This value is not adjusted for daylight saving.
  // See https://www.gnu.org/software/libc/manual/html_node/ \
  //                              Time-Zone-Functions.html#Time-Zone-Functions
  if (timezone / 3600 == 8) {
    CB_ASSERT_OK_AND_ASSIGN(uint32_t pacific_day_index,
                            TimePointToDayIndex(kTimePoint, converter, local_metric));
    EXPECT_EQ(kPacificDayIndex, pacific_day_index);
  }

  // Since |converter| converts time points to time structs with respect to UTC, the day index for
  // |other_tz_metric| should agree with that for |utc_metric|.
  CB_ASSERT_OK_AND_ASSIGN(uint32_t other_tz_day_index,
                          TimePointToDayIndex(kTimePoint, converter, other_tz_metric));
  EXPECT_EQ(kUtcDayIndex, other_tz_day_index);
}

TEST(DatetimeUtilTest, TimePointToDayIndexWithOffsetConverterTest) {
  // A CivilTimeConverterInterface that mimics conversion of a time_point to a time struct with
  // respect to Pacific Standard Time.
  FakeCivilTimeConverter converter = FakeCivilTimeConverter(-8, false);
  MetricDefinition other_tz_metric = MetricWithTimeZonePolicy(MetricDefinition::OTHER_TIME_ZONE);

  std::tm kTimeStruct = {
      .tm_sec = 0,
      .tm_min = 0,
      .tm_hour = 0,
      .tm_mday = 2,    // 2nd
      .tm_mon = 11,    // December
      .tm_year = 116,  // 2016
  };
  // This unix timestamp corresponds to Friday Dec 2, 2016 in UTC
  // and Thursday Dec 1, 2016 in Pacific time.
  const std::chrono::time_point<std::chrono::system_clock> kTimePoint =
      std::chrono::system_clock::from_time_t(timegm(&kTimeStruct));

  // This is the day index for Thurs Dec 1, 2016.
  static const uint32_t kPacificDayIndex = 17136;

  CB_ASSERT_OK_AND_ASSIGN(uint32_t pacific_day_index,
                          TimePointToDayIndex(kTimePoint, converter, other_tz_metric));
  EXPECT_EQ(kPacificDayIndex, pacific_day_index);
}

TEST(DatetimeUtilTest, TimeInfoFromTimePointUtcConverter) {
  UtcTimeConverter converter = UtcTimeConverter();
  MetricDefinition metric = MetricWithTimeZonePolicy(MetricDefinition::UTC);

  std::chrono::system_clock::time_point time =
      std::chrono::system_clock::time_point(std::chrono::hours(kNumHoursPerDay * 100));
  CB_ASSERT_OK_AND_ASSIGN(TimeInfo time_info_now, TimeInfo::FromTimePoint(time, converter, metric));

  EXPECT_EQ(time_info_now.day_index, 100u);
  EXPECT_EQ(time_info_now.hour_id, kNumHoursPerDay * kHourIdsPerHour * 100u + 1);
  EXPECT_EQ(TimePointToDayIndexUtc(time), 100u);
  EXPECT_EQ(TimePointToHourIdUtc(time), kNumHoursPerDay * kHourIdsPerHour * 100u + 1);
}

TEST(DatetimeUtilTest, TimeInfoFromTimePointFakeCivilTimeConverter) {
  MetricDefinition metric = MetricWithTimeZonePolicy(MetricDefinition::OTHER_TIME_ZONE);
  std::chrono::system_clock::time_point start =
      std::chrono::system_clock::time_point(std::chrono::hours(kNumHoursPerDay * 100));

  FakeCivilTimeConverter converter = FakeCivilTimeConverter(
      /*start_utc_offset=*/-8, /*start_isdst=*/false, /*end_utc_offset=*/-7, /*end_isdst=*/true,
      /*threshold=*/start + std::chrono::hours(1));

  CB_ASSERT_OK_AND_ASSIGN(TimeInfo start_time_info,
                          TimeInfo::FromTimePoint(start, converter, metric));
  ASSERT_EQ(start_time_info.day_index, 99u);
  ASSERT_EQ(start_time_info.hour_id, kHourIdsPerHour * (kNumHoursPerDay * 100u - 8u) + 1);

  CB_ASSERT_OK_AND_ASSIGN(
      TimeInfo end_time_info,
      TimeInfo::FromTimePoint(start + std::chrono::hours(1), converter, metric));
  ASSERT_EQ(end_time_info.day_index, 99u);
  ASSERT_EQ(end_time_info.hour_id, kHourIdsPerHour * (kNumHoursPerDay * 100u - 6u));
}

TEST(DatetimeUtilTest, FailingCivilTimeConverter) {
  MetricDefinition metric = MetricWithTimeZonePolicy(MetricDefinition::OTHER_TIME_ZONE);
  std::chrono::system_clock::time_point time =
      std::chrono::system_clock::time_point(std::chrono::hours(kNumHoursPerDay * 100));

  // A CivilTimeConverterInterface that always returns an error status.
  class FailingCivilTimeConverter : public util::CivilTimeConverterInterface {
    [[nodiscard]] lib::statusor::StatusOr<std::tm> civil_time(
        std::chrono::system_clock::time_point /*time*/,
        const std::string& /*time_zone*/) const override {
      return Status(StatusCode::INVALID_ARGUMENT, "failed to convert time");
    }
  };

  FailingCivilTimeConverter converter;
  ASSERT_FALSE(TimeInfo::FromTimePoint(time, converter, metric).ok());
}

TEST(DatetimeUtilTest, TimeInfoFromTimePointDeprecated) {
  const uint32_t day_index = 100;
  auto time = FromUnixSeconds(static_cast<int64_t>(day_index) * util::kNumUnixSecondsPerDay);

  auto time_info_now = TimeInfo::FromTimePoint(time, MetricDefinition::UTC);

  ASSERT_EQ(time_info_now.day_index, day_index);
  // Hour ID is 1 more than day_index * util::kHourIdsPerDay since UTC does
  // not have daylight savings time.
  ASSERT_EQ(time_info_now.hour_id, day_index * util::kHourIdsPerDay + 1);
}

}  // namespace cobalt::util