text: // Copyright 2016 Google Inc. All Rights Reserved.
  //
  // Licensed under the Apache License, Version 2.0 (the "License");
  // you may not use this file except in compliance with the License.
  // You may obtain a copy of the License at
  //
  //   http://www.apache.org/licenses/LICENSE-2.0
  //
  //   Unless required by applicable law or agreed to in writing, software
  //   distributed under the License is distributed on an "AS IS" BASIS,
  //   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  //   See the License for the specific language governing permissions and
  //   limitations under the License.
  
  #include "absl/time/internal/cctz/include/cctz/civil_time.h"
  
  #include <iomanip>
  #include <limits>
  #include <sstream>
  #include <string>
  #include <type_traits>
  
  #include "gtest/gtest.h"
  
  namespace absl {
  inline namespace lts_2018_06_20 {
  namespace time_internal {
  namespace cctz {
  
  namespace {
  
  template <typename T>
  std::string Format(const T& t) {
    std::stringstream ss;
    ss << t;
    return ss.str();
  }
  
  }  // namespace
  
  #if __cpp_constexpr >= 201304 || _MSC_VER >= 1910
  // Construction constexpr tests
  
  TEST(CivilTime, Normal) {
    constexpr civil_second css(2016, 1, 28, 17, 14, 12);
    static_assert(css.second() == 12, "Normal.second");
    constexpr civil_minute cmm(2016, 1, 28, 17, 14);
    static_assert(cmm.minute() == 14, "Normal.minute");
    constexpr civil_hour chh(2016, 1, 28, 17);
    static_assert(chh.hour() == 17, "Normal.hour");
    constexpr civil_day cd(2016, 1, 28);
    static_assert(cd.day() == 28, "Normal.day");
    constexpr civil_month cm(2016, 1);
    static_assert(cm.month() == 1, "Normal.month");
    constexpr civil_year cy(2016);
    static_assert(cy.year() == 2016, "Normal.year");
  }
  
  TEST(CivilTime, Conversion) {
    constexpr civil_year cy(2016);
    static_assert(cy.year() == 2016, "Conversion.year");
    constexpr civil_month cm(cy);
    static_assert(cm.month() == 1, "Conversion.month");
    constexpr civil_day cd(cm);
    static_assert(cd.day() == 1, "Conversion.day");
    constexpr civil_hour chh(cd);
    static_assert(chh.hour() == 0, "Conversion.hour");
    constexpr civil_minute cmm(chh);
    static_assert(cmm.minute() == 0, "Conversion.minute");
    constexpr civil_second css(cmm);
    static_assert(css.second() == 0, "Conversion.second");
  }
  
  // Normalization constexpr tests
  
  TEST(CivilTime, Normalized) {
    constexpr civil_second cs(2016, 1, 28, 17, 14, 12);
    static_assert(cs.year() == 2016, "Normalized.year");
    static_assert(cs.month() == 1, "Normalized.month");
    static_assert(cs.day() == 28, "Normalized.day");
    static_assert(cs.hour() == 17, "Normalized.hour");
    static_assert(cs.minute() == 14, "Normalized.minute");
    static_assert(cs.second() == 12, "Normalized.second");
  }
  
  TEST(CivilTime, SecondOverflow) {
    constexpr civil_second cs(2016, 1, 28, 17, 14, 121);
    static_assert(cs.year() == 2016, "SecondOverflow.year");
    static_assert(cs.month() == 1, "SecondOverflow.month");
    static_assert(cs.day() == 28, "SecondOverflow.day");
    static_assert(cs.hour() == 17, "SecondOverflow.hour");
    static_assert(cs.minute() == 16, "SecondOverflow.minute");
    static_assert(cs.second() == 1, "SecondOverflow.second");
  }
  
  TEST(CivilTime, SecondUnderflow) {
    constexpr civil_second cs(2016, 1, 28, 17, 14, -121);
    static_assert(cs.year() == 2016, "SecondUnderflow.year");
    static_assert(cs.month() == 1, "SecondUnderflow.month");
    static_assert(cs.day() == 28, "SecondUnderflow.day");
    static_assert(cs.hour() == 17, "SecondUnderflow.hour");
    static_assert(cs.minute() == 11, "SecondUnderflow.minute");
    static_assert(cs.second() == 59, "SecondUnderflow.second");
  }
  
  TEST(CivilTime, MinuteOverflow) {
    constexpr civil_second cs(2016, 1, 28, 17, 121, 12);
    static_assert(cs.year() == 2016, "MinuteOverflow.year");
    static_assert(cs.month() == 1, "MinuteOverflow.month");
    static_assert(cs.day() == 28, "MinuteOverflow.day");
    static_assert(cs.hour() == 19, "MinuteOverflow.hour");
    static_assert(cs.minute() == 1, "MinuteOverflow.minute");
    static_assert(cs.second() == 12, "MinuteOverflow.second");
  }
  
  TEST(CivilTime, MinuteUnderflow) {
    constexpr civil_second cs(2016, 1, 28, 17, -121, 12);
    static_assert(cs.year() == 2016, "MinuteUnderflow.year");
    static_assert(cs.month() == 1, "MinuteUnderflow.month");
    static_assert(cs.day() == 28, "MinuteUnderflow.day");
    static_assert(cs.hour() == 14, "MinuteUnderflow.hour");
    static_assert(cs.minute() == 59, "MinuteUnderflow.minute");
    static_assert(cs.second() == 12, "MinuteUnderflow.second");
  }
  
  TEST(CivilTime, HourOverflow) {
    constexpr civil_second cs(2016, 1, 28, 49, 14, 12);
    static_assert(cs.year() == 2016, "HourOverflow.year");
    static_assert(cs.month() == 1, "HourOverflow.month");
    static_assert(cs.day() == 30, "HourOverflow.day");
    static_assert(cs.hour() == 1, "HourOverflow.hour");
    static_assert(cs.minute() == 14, "HourOverflow.minute");
    static_assert(cs.second() == 12, "HourOverflow.second");
  }
  
  TEST(CivilTime, HourUnderflow) {
    constexpr civil_second cs(2016, 1, 28, -49, 14, 12);
    static_assert(cs.year() == 2016, "HourUnderflow.year");
    static_assert(cs.month() == 1, "HourUnderflow.month");
    static_assert(cs.day() == 25, "HourUnderflow.day");
    static_assert(cs.hour() == 23, "HourUnderflow.hour");
    static_assert(cs.minute() == 14, "HourUnderflow.minute");
    static_assert(cs.second() == 12, "HourUnderflow.second");
  }
  
  TEST(CivilTime, MonthOverflow) {
    constexpr civil_second cs(2016, 25, 28, 17, 14, 12);
    static_assert(cs.year() == 2018, "MonthOverflow.year");
    static_assert(cs.month() == 1, "MonthOverflow.month");
    static_assert(cs.day() == 28, "MonthOverflow.day");
    static_assert(cs.hour() == 17, "MonthOverflow.hour");
    static_assert(cs.minute() == 14, "MonthOverflow.minute");
    static_assert(cs.second() == 12, "MonthOverflow.second");
  }
  
  TEST(CivilTime, MonthUnderflow) {
    constexpr civil_second cs(2016, -25, 28, 17, 14, 12);
    static_assert(cs.year() == 2013, "MonthUnderflow.year");
    static_assert(cs.month() == 11, "MonthUnderflow.month");
    static_assert(cs.day() == 28, "MonthUnderflow.day");
    static_assert(cs.hour() == 17, "MonthUnderflow.hour");
    static_assert(cs.minute() == 14, "MonthUnderflow.minute");
    static_assert(cs.second() == 12, "MonthUnderflow.second");
  }
  
  TEST(CivilTime, C4Overflow) {
    constexpr civil_second cs(2016, 1, 292195, 17, 14, 12);
    static_assert(cs.year() == 2816, "C4Overflow.year");
    static_assert(cs.month() == 1, "C4Overflow.month");
    static_assert(cs.day() == 1, "C4Overflow.day");
    static_assert(cs.hour() == 17, "C4Overflow.hour");
    static_assert(cs.minute() == 14, "C4Overflow.minute");
    static_assert(cs.second() == 12, "C4Overflow.second");
  }
  
  TEST(CivilTime, C4Underflow) {
    constexpr civil_second cs(2016, 1, -292195, 17, 14, 12);
    static_assert(cs.year() == 1215, "C4Underflow.year");
    static_assert(cs.month() == 12, "C4Underflow.month");
    static_assert(cs.day() == 30, "C4Underflow.day");
    static_assert(cs.hour() == 17, "C4Underflow.hour");
    static_assert(cs.minute() == 14, "C4Underflow.minute");
    static_assert(cs.second() == 12, "C4Underflow.second");
  }
  
  TEST(CivilTime, MixedNormalization) {
    constexpr civil_second cs(2016, -42, 122, 99, -147, 4949);
    static_assert(cs.year() == 2012, "MixedNormalization.year");
    static_assert(cs.month() == 10, "MixedNormalization.month");
    static_assert(cs.day() == 4, "MixedNormalization.day");
    static_assert(cs.hour() == 1, "MixedNormalization.hour");
    static_assert(cs.minute() == 55, "MixedNormalization.minute");
    static_assert(cs.second() == 29, "MixedNormalization.second");
  }
  
  // Relational constexpr tests
  
  TEST(CivilTime, Less) {
    constexpr civil_second cs1(2016, 1, 28, 17, 14, 12);
    constexpr civil_second cs2(2016, 1, 28, 17, 14, 13);
    constexpr bool less = cs1 < cs2;
    static_assert(less, "Less");
  }
  
  // Arithmetic constexpr tests
  
  TEST(CivilTime, Addition) {
    constexpr civil_second cs1(2016, 1, 28, 17, 14, 12);
    constexpr civil_second cs2 = cs1 + 50;
    static_assert(cs2.year() == 2016, "Addition.year");
    static_assert(cs2.month() == 1, "Addition.month");
    static_assert(cs2.day() == 28, "Addition.day");
    static_assert(cs2.hour() == 17, "Addition.hour");
    static_assert(cs2.minute() == 15, "Addition.minute");
    static_assert(cs2.second() == 2, "Addition.second");
  }
  
  TEST(CivilTime, Subtraction) {
    constexpr civil_second cs1(2016, 1, 28, 17, 14, 12);
    constexpr civil_second cs2 = cs1 - 50;
    static_assert(cs2.year() == 2016, "Subtraction.year");
    static_assert(cs2.month() == 1, "Subtraction.month");
    static_assert(cs2.day() == 28, "Subtraction.day");
    static_assert(cs2.hour() == 17, "Subtraction.hour");
    static_assert(cs2.minute() == 13, "Subtraction.minute");
    static_assert(cs2.second() == 22, "Subtraction.second");
  }
  
  TEST(CivilTime, Difference) {
    constexpr civil_day cd1(2016, 1, 28);
    constexpr civil_day cd2(2015, 1, 28);
    constexpr int diff = cd1 - cd2;
    static_assert(diff == 365, "Difference");
  }
  
  // NOTE: Run this with --copt=-ftrapv to detect overflow problems.
  TEST(CivilTime, DifferenceWithHugeYear) {
    {
      constexpr civil_day d1(9223372036854775807, 1, 1);
      constexpr civil_day d2(9223372036854775807, 12, 31);
      static_assert(d2 - d1 == 364, "DifferenceWithHugeYear");
    }
    {
      constexpr civil_day d1(-9223372036854775807 - 1, 1, 1);
      constexpr civil_day d2(-9223372036854775807 - 1, 12, 31);
      static_assert(d2 - d1 == 365, "DifferenceWithHugeYear");
    }
    {
      // Check the limits of the return value at the end of the year range.
      constexpr civil_day d1(9223372036854775807, 1, 1);
      constexpr civil_day d2(9198119301927009252, 6, 6);
      static_assert(d1 - d2 == 9223372036854775807, "DifferenceWithHugeYear");
      static_assert((d2 - 1) - d1 == -9223372036854775807 - 1,
                    "DifferenceWithHugeYear");
    }
    {
      // Check the limits of the return value at the start of the year range.
      constexpr civil_day d1(-9223372036854775807 - 1, 1, 1);
      constexpr civil_day d2(-9198119301927009254, 7, 28);
      static_assert(d2 - d1 == 9223372036854775807, "DifferenceWithHugeYear");
      static_assert(d1 - (d2 + 1) == -9223372036854775807 - 1,
                    "DifferenceWithHugeYear");
    }
    {
      // Check the limits of the return value from either side of year 0.
      constexpr civil_day d1(-12626367463883278, 9, 3);
      constexpr civil_day d2(12626367463883277, 3, 28);
      static_assert(d2 - d1 == 9223372036854775807, "DifferenceWithHugeYear");
      static_assert(d1 - (d2 + 1) == -9223372036854775807 - 1,
                    "DifferenceWithHugeYear");
    }
  }
  
  // NOTE: Run this with --copt=-ftrapv to detect overflow problems.
  TEST(CivilTime, DifferenceNoIntermediateOverflow) {
    {
      // The difference up to the minute field would be below the minimum
      // diff_t, but the 52 extra seconds brings us back to the minimum.
      constexpr civil_second s1(-292277022657, 1, 27, 8, 29 - 1, 52);
      constexpr civil_second s2(1970, 1, 1, 0, 0 - 1, 0);
      static_assert(s1 - s2 == -9223372036854775807 - 1,
                    "DifferenceNoIntermediateOverflow");
    }
    {
      // The difference up to the minute field would be above the maximum
      // diff_t, but the -53 extra seconds brings us back to the maximum.
      constexpr civil_second s1(292277026596, 12, 4, 15, 30, 7 - 7);
      constexpr civil_second s2(1970, 1, 1, 0, 0, 0 - 7);
      static_assert(s1 - s2 == 9223372036854775807,
                    "DifferenceNoIntermediateOverflow");
    }
  }
  
  // Helper constexpr tests
  
  TEST(CivilTime, WeekDay) {
    constexpr civil_day cd(2016, 1, 28);
    constexpr weekday wd = get_weekday(cd);
    static_assert(wd == weekday::thursday, "Weekday");
  }
  
  TEST(CivilTime, NextWeekDay) {
    constexpr civil_day cd(2016, 1, 28);
    constexpr civil_day next = next_weekday(cd, weekday::thursday);
    static_assert(next.year() == 2016, "NextWeekDay.year");
    static_assert(next.month() == 2, "NextWeekDay.month");
    static_assert(next.day() == 4, "NextWeekDay.day");
  }
  
  TEST(CivilTime, PrevWeekDay) {
    constexpr civil_day cd(2016, 1, 28);
    constexpr civil_day prev = prev_weekday(cd, weekday::thursday);
    static_assert(prev.year() == 2016, "PrevWeekDay.year");
    static_assert(prev.month() == 1, "PrevWeekDay.month");
    static_assert(prev.day() == 21, "PrevWeekDay.day");
  }
  
  TEST(CivilTime, YearDay) {
    constexpr civil_day cd(2016, 1, 28);
    constexpr int yd = get_yearday(cd);
    static_assert(yd == 28, "YearDay");
  }
  #endif  // __cpp_constexpr >= 201304 || _MSC_VER >= 1910
  
  // The remaining tests do not use constexpr.
  
  TEST(CivilTime, DefaultConstruction) {
    civil_second ss;
    EXPECT_EQ("1970-01-01T00:00:00", Format(ss));
  
    civil_minute mm;
    EXPECT_EQ("1970-01-01T00:00", Format(mm));
  
    civil_hour hh;
    EXPECT_EQ("1970-01-01T00", Format(hh));
  
    civil_day d;
    EXPECT_EQ("1970-01-01", Format(d));
  
    civil_month m;
    EXPECT_EQ("1970-01", Format(m));
  
    civil_year y;
    EXPECT_EQ("1970", Format(y));
  }
  
  TEST(CivilTime, StructMember) {
    struct S {
      civil_day day;
    };
    S s = {};
    EXPECT_EQ(civil_day{}, s.day);
  }
  
  TEST(CivilTime, FieldsConstruction) {
    EXPECT_EQ("2015-01-02T03:04:05", Format(civil_second(2015, 1, 2, 3, 4, 5)));
    EXPECT_EQ("2015-01-02T03:04:00", Format(civil_second(2015, 1, 2, 3, 4)));
    EXPECT_EQ("2015-01-02T03:00:00", Format(civil_second(2015, 1, 2, 3)));
    EXPECT_EQ("2015-01-02T00:00:00", Format(civil_second(2015, 1, 2)));
    EXPECT_EQ("2015-01-01T00:00:00", Format(civil_second(2015, 1)));
    EXPECT_EQ("2015-01-01T00:00:00", Format(civil_second(2015)));
  
    EXPECT_EQ("2015-01-02T03:04", Format(civil_minute(2015, 1, 2, 3, 4, 5)));
    EXPECT_EQ("2015-01-02T03:04", Format(civil_minute(2015, 1, 2, 3, 4)));
    EXPECT_EQ("2015-01-02T03:00", Format(civil_minute(2015, 1, 2, 3)));
    EXPECT_EQ("2015-01-02T00:00", Format(civil_minute(2015, 1, 2)));
    EXPECT_EQ("2015-01-01T00:00", Format(civil_minute(2015, 1)));
    EXPECT_EQ("2015-01-01T00:00", Format(civil_minute(2015)));
  
    EXPECT_EQ("2015-01-02T03", Format(civil_hour(2015, 1, 2, 3, 4, 5)));
    EXPECT_EQ("2015-01-02T03", Format(civil_hour(2015, 1, 2, 3, 4)));
    EXPECT_EQ("2015-01-02T03", Format(civil_hour(2015, 1, 2, 3)));
    EXPECT_EQ("2015-01-02T00", Format(civil_hour(2015, 1, 2)));
    EXPECT_EQ("2015-01-01T00", Format(civil_hour(2015, 1)));
    EXPECT_EQ("2015-01-01T00", Format(civil_hour(2015)));
  
    EXPECT_EQ("2015-01-02", Format(civil_day(2015, 1, 2, 3, 4, 5)));
    EXPECT_EQ("2015-01-02", Format(civil_day(2015, 1, 2, 3, 4)));
    EXPECT_EQ("2015-01-02", Format(civil_day(2015, 1, 2, 3)));
    EXPECT_EQ("2015-01-02", Format(civil_day(2015, 1, 2)));
    EXPECT_EQ("2015-01-01", Format(civil_day(2015, 1)));
    EXPECT_EQ("2015-01-01", Format(civil_day(2015)));
  
    EXPECT_EQ("2015-01", Format(civil_month(2015, 1, 2, 3, 4, 5)));
    EXPECT_EQ("2015-01", Format(civil_month(2015, 1, 2, 3, 4)));
    EXPECT_EQ("2015-01", Format(civil_month(2015, 1, 2, 3)));
    EXPECT_EQ("2015-01", Format(civil_month(2015, 1, 2)));
    EXPECT_EQ("2015-01", Format(civil_month(2015, 1)));
    EXPECT_EQ("2015-01", Format(civil_month(2015)));
  
    EXPECT_EQ("2015", Format(civil_year(2015, 1, 2, 3, 4, 5)));
    EXPECT_EQ("2015", Format(civil_year(2015, 1, 2, 3, 4)));
    EXPECT_EQ("2015", Format(civil_year(2015, 1, 2, 3)));
    EXPECT_EQ("2015", Format(civil_year(2015, 1, 2)));
    EXPECT_EQ("2015", Format(civil_year(2015, 1)));
    EXPECT_EQ("2015", Format(civil_year(2015)));
  }
  
  TEST(CivilTime, FieldsConstructionLimits) {
    const int kIntMax = std::numeric_limits<int>::max();
    EXPECT_EQ("2038-01-19T03:14:07",
              Format(civil_second(1970, 1, 1, 0, 0, kIntMax)));
    EXPECT_EQ("6121-02-11T05:21:07",
              Format(civil_second(1970, 1, 1, 0, kIntMax, kIntMax)));
    EXPECT_EQ("251104-11-20T12:21:07",
              Format(civil_second(1970, 1, 1, kIntMax, kIntMax, kIntMax)));
    EXPECT_EQ("6130715-05-30T12:21:07",
              Format(civil_second(1970, 1, kIntMax, kIntMax, kIntMax, kIntMax)));
    EXPECT_EQ(
        "185087685-11-26T12:21:07",
        Format(civil_second(1970, kIntMax, kIntMax, kIntMax, kIntMax, kIntMax)));
  
    const int kIntMin = std::numeric_limits<int>::min();
    EXPECT_EQ("1901-12-13T20:45:52",
              Format(civil_second(1970, 1, 1, 0, 0, kIntMin)));
    EXPECT_EQ("-2182-11-20T18:37:52",
              Format(civil_second(1970, 1, 1, 0, kIntMin, kIntMin)));
    EXPECT_EQ("-247165-02-11T10:37:52",
              Format(civil_second(1970, 1, 1, kIntMin, kIntMin, kIntMin)));
    EXPECT_EQ("-6126776-08-01T10:37:52",
              Format(civil_second(1970, 1, kIntMin, kIntMin, kIntMin, kIntMin)));
    EXPECT_EQ(
        "-185083747-10-31T10:37:52",
        Format(civil_second(1970, kIntMin, kIntMin, kIntMin, kIntMin, kIntMin)));
  }
  
  TEST(CivilTime, ImplicitCrossAlignment) {
    civil_year year(2015);
    civil_month month = year;
    civil_day day = month;
    civil_hour hour = day;
    civil_minute minute = hour;
    civil_second second = minute;
  
    second = year;
    EXPECT_EQ(second, year);
    second = month;
    EXPECT_EQ(second, month);
    second = day;
    EXPECT_EQ(second, day);
    second = hour;
    EXPECT_EQ(second, hour);
    second = minute;
    EXPECT_EQ(second, minute);
  
    minute = year;
    EXPECT_EQ(minute, year);
    minute = month;
    EXPECT_EQ(minute, month);
    minute = day;
    EXPECT_EQ(minute, day);
    minute = hour;
    EXPECT_EQ(minute, hour);
  
    hour = year;
    EXPECT_EQ(hour, year);
    hour = month;
    EXPECT_EQ(hour, month);
    hour = day;
    EXPECT_EQ(hour, day);
  
    day = year;
    EXPECT_EQ(day, year);
    day = month;
    EXPECT_EQ(day, month);
  
    month = year;
    EXPECT_EQ(month, year);
  
    // Ensures unsafe conversions are not allowed.
    EXPECT_FALSE((std::is_convertible<civil_second, civil_minute>::value));
    EXPECT_FALSE((std::is_convertible<civil_second, civil_hour>::value));
    EXPECT_FALSE((std::is_convertible<civil_second, civil_day>::value));
    EXPECT_FALSE((std::is_convertible<civil_second, civil_month>::value));
    EXPECT_FALSE((std::is_convertible<civil_second, civil_year>::value));
  
    EXPECT_FALSE((std::is_convertible<civil_minute, civil_hour>::value));
    EXPECT_FALSE((std::is_convertible<civil_minute, civil_day>::value));
    EXPECT_FALSE((std::is_convertible<civil_minute, civil_month>::value));
    EXPECT_FALSE((std::is_convertible<civil_minute, civil_year>::value));
  
    EXPECT_FALSE((std::is_convertible<civil_hour, civil_day>::value));
    EXPECT_FALSE((std::is_convertible<civil_hour, civil_month>::value));
    EXPECT_FALSE((std::is_convertible<civil_hour, civil_year>::value));
  
    EXPECT_FALSE((std::is_convertible<civil_day, civil_month>::value));
    EXPECT_FALSE((std::is_convertible<civil_day, civil_year>::value));
  
    EXPECT_FALSE((std::is_convertible<civil_month, civil_year>::value));
  }
  
  TEST(CivilTime, ExplicitCrossAlignment) {
    //
    // Assign from smaller units -> larger units
    //
  
    civil_second second(2015, 1, 2, 3, 4, 5);
    EXPECT_EQ("2015-01-02T03:04:05", Format(second));
  
    civil_minute minute(second);
    EXPECT_EQ("2015-01-02T03:04", Format(minute));
  
    civil_hour hour(minute);
    EXPECT_EQ("2015-01-02T03", Format(hour));
  
    civil_day day(hour);
    EXPECT_EQ("2015-01-02", Format(day));
  
    civil_month month(day);
    EXPECT_EQ("2015-01", Format(month));
  
    civil_year year(month);
    EXPECT_EQ("2015", Format(year));
  
    //
    // Now assign from larger units -> smaller units
    //
  
    month = civil_month(year);
    EXPECT_EQ("2015-01", Format(month));
  
    day = civil_day(month);
    EXPECT_EQ("2015-01-01", Format(day));
  
    hour = civil_hour(day);
    EXPECT_EQ("2015-01-01T00", Format(hour));
  
    minute = civil_minute(hour);
    EXPECT_EQ("2015-01-01T00:00", Format(minute));
  
    second = civil_second(minute);
    EXPECT_EQ("2015-01-01T00:00:00", Format(second));
  }
  
  // Metafunction to test whether difference is allowed between two types.
  template <typename T1, typename T2>
  struct HasDifference {
    template <typename U1, typename U2>
    static std::false_type test(...);
    template <typename U1, typename U2>
    static std::true_type test(decltype(std::declval<U1>() - std::declval<U2>()));
    static constexpr bool value = decltype(test<T1, T2>(0))::value;
  };
  
  TEST(CivilTime, DisallowCrossAlignedDifference) {
    // Difference is allowed between types with the same alignment.
    static_assert(HasDifference<civil_second, civil_second>::value, "");
    static_assert(HasDifference<civil_minute, civil_minute>::value, "");
    static_assert(HasDifference<civil_hour, civil_hour>::value, "");
    static_assert(HasDifference<civil_day, civil_day>::value, "");
    static_assert(HasDifference<civil_month, civil_month>::value, "");
    static_assert(HasDifference<civil_year, civil_year>::value, "");
  
    // Difference is disallowed between types with different alignments.
    static_assert(!HasDifference<civil_second, civil_minute>::value, "");
    static_assert(!HasDifference<civil_second, civil_hour>::value, "");
    static_assert(!HasDifference<civil_second, civil_day>::value, "");
    static_assert(!HasDifference<civil_second, civil_month>::value, "");
    static_assert(!HasDifference<civil_second, civil_year>::value, "");
  
    static_assert(!HasDifference<civil_minute, civil_hour>::value, "");
    static_assert(!HasDifference<civil_minute, civil_day>::value, "");
    static_assert(!HasDifference<civil_minute, civil_month>::value, "");
    static_assert(!HasDifference<civil_minute, civil_year>::value, "");
  
    static_assert(!HasDifference<civil_hour, civil_day>::value, "");
    static_assert(!HasDifference<civil_hour, civil_month>::value, "");
    static_assert(!HasDifference<civil_hour, civil_year>::value, "");
  
    static_assert(!HasDifference<civil_day, civil_month>::value, "");
    static_assert(!HasDifference<civil_day, civil_year>::value, "");
  
    static_assert(!HasDifference<civil_month, civil_year>::value, "");
  }
  
  TEST(CivilTime, ValueSemantics) {
    const civil_hour a(2015, 1, 2, 3);
    const civil_hour b = a;
    const civil_hour c(b);
    civil_hour d;
    d = c;
    EXPECT_EQ("2015-01-02T03", Format(d));
  }
  
  TEST(CivilTime, Relational) {
    // Tests that the alignment unit is ignored in comparison.
    const civil_year year(2014);
    const civil_month month(year);
    EXPECT_EQ(year, month);
  
  #define TEST_RELATIONAL(OLDER, YOUNGER) \
    do {                                  \
      EXPECT_FALSE(OLDER < OLDER);        \
      EXPECT_FALSE(OLDER > OLDER);        \
      EXPECT_TRUE(OLDER >= OLDER);        \
      EXPECT_TRUE(OLDER <= OLDER);        \
      EXPECT_FALSE(YOUNGER < YOUNGER);    \
      EXPECT_FALSE(YOUNGER > YOUNGER);    \
      EXPECT_TRUE(YOUNGER >= YOUNGER);    \
      EXPECT_TRUE(YOUNGER <= YOUNGER);    \
      EXPECT_EQ(OLDER, OLDER);            \
      EXPECT_NE(OLDER, YOUNGER);          \
      EXPECT_LT(OLDER, YOUNGER);          \
      EXPECT_LE(OLDER, YOUNGER);          \
      EXPECT_GT(YOUNGER, OLDER);          \
      EXPECT_GE(YOUNGER, OLDER);          \
    } while (0)
  
    // Alignment is ignored in comparison (verified above), so kSecond is used
    // to test comparison in all field positions.
    TEST_RELATIONAL(civil_second(2014, 1, 1, 0, 0, 0),
                    civil_second(2015, 1, 1, 0, 0, 0));
    TEST_RELATIONAL(civil_second(2014, 1, 1, 0, 0, 0),
                    civil_second(2014, 2, 1, 0, 0, 0));
    TEST_RELATIONAL(civil_second(2014, 1, 1, 0, 0, 0),
                    civil_second(2014, 1, 2, 0, 0, 0));
    TEST_RELATIONAL(civil_second(2014, 1, 1, 0, 0, 0),
                    civil_second(2014, 1, 1, 1, 0, 0));
    TEST_RELATIONAL(civil_second(2014, 1, 1, 1, 0, 0),
                    civil_second(2014, 1, 1, 1, 1, 0));
    TEST_RELATIONAL(civil_second(2014, 1, 1, 1, 1, 0),
                    civil_second(2014, 1, 1, 1, 1, 1));
  
    // Tests the relational operators of two different CivilTime types.
    TEST_RELATIONAL(civil_day(2014, 1, 1), civil_minute(2014, 1, 1, 1, 1));
    TEST_RELATIONAL(civil_day(2014, 1, 1), civil_month(2014, 2));
  
  #undef TEST_RELATIONAL
  }
  
  TEST(CivilTime, Arithmetic) {
    civil_second second(2015, 1, 2, 3, 4, 5);
    EXPECT_EQ("2015-01-02T03:04:06", Format(second += 1));
    EXPECT_EQ("2015-01-02T03:04:07", Format(second + 1));
    EXPECT_EQ("2015-01-02T03:04:08", Format(2 + second));
    EXPECT_EQ("2015-01-02T03:04:05", Format(second - 1));
    EXPECT_EQ("2015-01-02T03:04:05", Format(second -= 1));
    EXPECT_EQ("2015-01-02T03:04:05", Format(second++));
    EXPECT_EQ("2015-01-02T03:04:07", Format(++second));
    EXPECT_EQ("2015-01-02T03:04:07", Format(second--));
    EXPECT_EQ("2015-01-02T03:04:05", Format(--second));
  
    civil_minute minute(2015, 1, 2, 3, 4);
    EXPECT_EQ("2015-01-02T03:05", Format(minute += 1));
    EXPECT_EQ("2015-01-02T03:06", Format(minute + 1));
    EXPECT_EQ("2015-01-02T03:07", Format(2 + minute));
    EXPECT_EQ("2015-01-02T03:04", Format(minute - 1));
    EXPECT_EQ("2015-01-02T03:04", Format(minute -= 1));
    EXPECT_EQ("2015-01-02T03:04", Format(minute++));
    EXPECT_EQ("2015-01-02T03:06", Format(++minute));
    EXPECT_EQ("2015-01-02T03:06", Format(minute--));
    EXPECT_EQ("2015-01-02T03:04", Format(--minute));
  
    civil_hour hour(2015, 1, 2, 3);
    EXPECT_EQ("2015-01-02T04", Format(hour += 1));
    EXPECT_EQ("2015-01-02T05", Format(hour + 1));
    EXPECT_EQ("2015-01-02T06", Format(2 + hour));
    EXPECT_EQ("2015-01-02T03", Format(hour - 1));
    EXPECT_EQ("2015-01-02T03", Format(hour -= 1));
    EXPECT_EQ("2015-01-02T03", Format(hour++));
    EXPECT_EQ("2015-01-02T05", Format(++hour));
    EXPECT_EQ("2015-01-02T05", Format(hour--));
    EXPECT_EQ("2015-01-02T03", Format(--hour));
  
    civil_day day(2015, 1, 2);
    EXPECT_EQ("2015-01-03", Format(day += 1));
    EXPECT_EQ("2015-01-04", Format(day + 1));
    EXPECT_EQ("2015-01-05", Format(2 + day));
    EXPECT_EQ("2015-01-02", Format(day - 1));
    EXPECT_EQ("2015-01-02", Format(day -= 1));
    EXPECT_EQ("2015-01-02", Format(day++));
    EXPECT_EQ("2015-01-04", Format(++day));
    EXPECT_EQ("2015-01-04", Format(day--));
    EXPECT_EQ("2015-01-02", Format(--day));
  
    civil_month month(2015, 1);
    EXPECT_EQ("2015-02", Format(month += 1));
    EXPECT_EQ("2015-03", Format(month + 1));
    EXPECT_EQ("2015-04", Format(2 + month));
    EXPECT_EQ("2015-01", Format(month - 1));
    EXPECT_EQ("2015-01", Format(month -= 1));
    EXPECT_EQ("2015-01", Format(month++));
    EXPECT_EQ("2015-03", Format(++month));
    EXPECT_EQ("2015-03", Format(month--));
    EXPECT_EQ("2015-01", Format(--month));
  
    civil_year year(2015);
    EXPECT_EQ("2016", Format(year += 1));
    EXPECT_EQ("2017", Format(year + 1));
    EXPECT_EQ("2018", Format(2 + year));
    EXPECT_EQ("2015", Format(year - 1));
    EXPECT_EQ("2015", Format(year -= 1));
    EXPECT_EQ("2015", Format(year++));
    EXPECT_EQ("2017", Format(++year));
    EXPECT_EQ("2017", Format(year--));
    EXPECT_EQ("2015", Format(--year));
  }
  
  TEST(CivilTime, ArithmeticLimits) {
    const int kIntMax = std::numeric_limits<int>::max();
    const int kIntMin = std::numeric_limits<int>::min();
  
    civil_second second(1970, 1, 1, 0, 0, 0);
    second += kIntMax;
    EXPECT_EQ("2038-01-19T03:14:07", Format(second));
    second -= kIntMax;
    EXPECT_EQ("1970-01-01T00:00:00", Format(second));
    second += kIntMin;
    EXPECT_EQ("1901-12-13T20:45:52", Format(second));
    second -= kIntMin;
    EXPECT_EQ("1970-01-01T00:00:00", Format(second));
  
    civil_minute minute(1970, 1, 1, 0, 0);
    minute += kIntMax;
    EXPECT_EQ("6053-01-23T02:07", Format(minute));
    minute -= kIntMax;
    EXPECT_EQ("1970-01-01T00:00", Format(minute));
    minute += kIntMin;
    EXPECT_EQ("-2114-12-08T21:52", Format(minute));
    minute -= kIntMin;
    EXPECT_EQ("1970-01-01T00:00", Format(minute));
  
    civil_hour hour(1970, 1, 1, 0);
    hour += kIntMax;
    EXPECT_EQ("246953-10-09T07", Format(hour));
    hour -= kIntMax;
    EXPECT_EQ("1970-01-01T00", Format(hour));
    hour += kIntMin;
    EXPECT_EQ("-243014-03-24T16", Format(hour));
    hour -= kIntMin;
    EXPECT_EQ("1970-01-01T00", Format(hour));
  
    civil_day day(1970, 1, 1);
    day += kIntMax;
    EXPECT_EQ("5881580-07-11", Format(day));
    day -= kIntMax;
    EXPECT_EQ("1970-01-01", Format(day));
    day += kIntMin;
    EXPECT_EQ("-5877641-06-23", Format(day));
    day -= kIntMin;
    EXPECT_EQ("1970-01-01", Format(day));
  
    civil_month month(1970, 1);
    month += kIntMax;
    EXPECT_EQ("178958940-08", Format(month));
    month -= kIntMax;
    EXPECT_EQ("1970-01", Format(month));
    month += kIntMin;
    EXPECT_EQ("-178955001-05", Format(month));
    month -= kIntMin;
    EXPECT_EQ("1970-01", Format(month));
  
    civil_year year(0);
    year += kIntMax;
    EXPECT_EQ("2147483647", Format(year));
    year -= kIntMax;
    EXPECT_EQ("0", Format(year));
    year += kIntMin;
    EXPECT_EQ("-2147483648", Format(year));
    year -= kIntMin;
    EXPECT_EQ("0", Format(year));
  }
  
  TEST(CivilTime, ArithmeticDifference) {
    civil_second second(2015, 1, 2, 3, 4, 5);
    EXPECT_EQ(0, second - second);
    EXPECT_EQ(10, (second + 10) - second);
    EXPECT_EQ(-10, (second - 10) - second);
  
    civil_minute minute(2015, 1, 2, 3, 4);
    EXPECT_EQ(0, minute - minute);
    EXPECT_EQ(10, (minute + 10) - minute);
    EXPECT_EQ(-10, (minute - 10) - minute);
  
    civil_hour hour(2015, 1, 2, 3);
    EXPECT_EQ(0, hour - hour);
    EXPECT_EQ(10, (hour + 10) - hour);
    EXPECT_EQ(-10, (hour - 10) - hour);
  
    civil_day day(2015, 1, 2);
    EXPECT_EQ(0, day - day);
    EXPECT_EQ(10, (day + 10) - day);
    EXPECT_EQ(-10, (day - 10) - day);
  
    civil_month month(2015, 1);
    EXPECT_EQ(0, month - month);
    EXPECT_EQ(10, (month + 10) - month);
    EXPECT_EQ(-10, (month - 10) - month);
  
    civil_year year(2015);
    EXPECT_EQ(0, year - year);
    EXPECT_EQ(10, (year + 10) - year);
    EXPECT_EQ(-10, (year - 10) - year);
  }
  
  TEST(CivilTime, DifferenceLimits) {
    const int kIntMax = std::numeric_limits<int>::max();
    const int kIntMin = std::numeric_limits<int>::min();
  
    // Check day arithmetic at the end of the year range.
    const civil_day max_day(kIntMax, 12, 31);
    EXPECT_EQ(1, max_day - (max_day - 1));
    EXPECT_EQ(-1, (max_day - 1) - max_day);
  
    // Check day arithmetic at the end of the year range.
    const civil_day min_day(kIntMin, 1, 1);
    EXPECT_EQ(1, (min_day + 1) - min_day);
    EXPECT_EQ(-1, min_day - (min_day + 1));
  
    // Check the limits of the return value.
    const civil_day d1(1970, 1, 1);
    const civil_day d2(5881580, 7, 11);
    EXPECT_EQ(kIntMax, d2 - d1);
    EXPECT_EQ(kIntMin, d1 - (d2 + 1));
  }
  
  TEST(CivilTime, Properties) {
    civil_second ss(2015, 2, 3, 4, 5, 6);
    EXPECT_EQ(2015, ss.year());
    EXPECT_EQ(2, ss.month());
    EXPECT_EQ(3, ss.day());
    EXPECT_EQ(4, ss.hour());
    EXPECT_EQ(5, ss.minute());
    EXPECT_EQ(6, ss.second());
  
    civil_minute mm(2015, 2, 3, 4, 5, 6);
    EXPECT_EQ(2015, mm.year());
    EXPECT_EQ(2, mm.month());
    EXPECT_EQ(3, mm.day());
    EXPECT_EQ(4, mm.hour());
    EXPECT_EQ(5, mm.minute());
    EXPECT_EQ(0, mm.second());
  
    civil_hour hh(2015, 2, 3, 4, 5, 6);
    EXPECT_EQ(2015, hh.year());
    EXPECT_EQ(2, hh.month());
    EXPECT_EQ(3, hh.day());
    EXPECT_EQ(4, hh.hour());
    EXPECT_EQ(0, hh.minute());
    EXPECT_EQ(0, hh.second());
  
    civil_day d(2015, 2, 3, 4, 5, 6);
    EXPECT_EQ(2015, d.year());
    EXPECT_EQ(2, d.month());
    EXPECT_EQ(3, d.day());
    EXPECT_EQ(0, d.hour());
    EXPECT_EQ(0, d.minute());
    EXPECT_EQ(0, d.second());
    EXPECT_EQ(weekday::tuesday, get_weekday(d));
    EXPECT_EQ(34, get_yearday(d));
  
    civil_month m(2015, 2, 3, 4, 5, 6);
    EXPECT_EQ(2015, m.year());
    EXPECT_EQ(2, m.month());
    EXPECT_EQ(1, m.day());
    EXPECT_EQ(0, m.hour());
    EXPECT_EQ(0, m.minute());
    EXPECT_EQ(0, m.second());
  
    civil_year y(2015, 2, 3, 4, 5, 6);
    EXPECT_EQ(2015, y.year());
    EXPECT_EQ(1, y.month());
    EXPECT_EQ(1, y.day());
    EXPECT_EQ(0, y.hour());
    EXPECT_EQ(0, y.minute());
    EXPECT_EQ(0, y.second());
  }
  
  TEST(CivilTime, OutputStream) {
    // Tests formatting of civil_year, which does not pad.
    EXPECT_EQ("2016", Format(civil_year(2016)));
    EXPECT_EQ("123", Format(civil_year(123)));
    EXPECT_EQ("0", Format(civil_year(0)));
    EXPECT_EQ("-1", Format(civil_year(-1)));
  
    // Tests formatting of sub-year types, which pad to 2 digits
    EXPECT_EQ("2016-02", Format(civil_month(2016, 2)));
    EXPECT_EQ("2016-02-03", Format(civil_day(2016, 2, 3)));
    EXPECT_EQ("2016-02-03T04", Format(civil_hour(2016, 2, 3, 4)));
    EXPECT_EQ("2016-02-03T04:05", Format(civil_minute(2016, 2, 3, 4, 5)));
    EXPECT_EQ("2016-02-03T04:05:06", Format(civil_second(2016, 2, 3, 4, 5, 6)));
  
    // Tests formatting of weekday.
    EXPECT_EQ("Monday", Format(weekday::monday));
    EXPECT_EQ("Tuesday", Format(weekday::tuesday));
    EXPECT_EQ("Wednesday", Format(weekday::wednesday));
    EXPECT_EQ("Thursday", Format(weekday::thursday));
    EXPECT_EQ("Friday", Format(weekday::friday));
    EXPECT_EQ("Saturday", Format(weekday::saturday));
    EXPECT_EQ("Sunday", Format(weekday::sunday));
  }
  
  TEST(CivilTime, OutputStreamLeftFillWidth) {
    civil_second cs(2016, 2, 3, 4, 5, 6);
    {
      std::stringstream ss;
      ss << std::left << std::setfill('.');
      ss << std::setw(3) << 'X';
      ss << std::setw(21) << civil_year(cs);
      ss << std::setw(3) << 'X';
      EXPECT_EQ("X..2016.................X..", ss.str());
    }
    {
      std::stringstream ss;
      ss << std::left << std::setfill('.');
      ss << std::setw(3) << 'X';
      ss << std::setw(21) << civil_month(cs);
      ss << std::setw(3) << 'X';
      EXPECT_EQ("X..2016-02..............X..", ss.str());
    }
    {
      std::stringstream ss;
      ss << std::left << std::setfill('.');
      ss << std::setw(3) << 'X';
      ss << std::setw(21) << civil_day(cs);
      ss << std::setw(3) << 'X';
      EXPECT_EQ("X..2016-02-03...........X..", ss.str());
    }
    {
      std::stringstream ss;
      ss << std::left << std::setfill('.');
      ss << std::setw(3) << 'X';
      ss << std::setw(21) << civil_hour(cs);
      ss << std::setw(3) << 'X';
      EXPECT_EQ("X..2016-02-03T04........X..", ss.str());
    }
    {
      std::stringstream ss;
      ss << std::left << std::setfill('.');
      ss << std::setw(3) << 'X';
      ss << std::setw(21) << civil_minute(cs);
      ss << std::setw(3) << 'X';
      EXPECT_EQ("X..2016-02-03T04:05.....X..", ss.str());
    }
    {
      std::stringstream ss;
      ss << std::left << std::setfill('.');
      ss << std::setw(3) << 'X';
      ss << std::setw(21) << civil_second(cs);
      ss << std::setw(3) << 'X';
      EXPECT_EQ("X..2016-02-03T04:05:06..X..", ss.str());
    }
  }
  
  TEST(CivilTime, NextPrevWeekday) {
    // Jan 1, 1970 was a Thursday.
    const civil_day thursday(1970, 1, 1);
    EXPECT_EQ(weekday::thursday, get_weekday(thursday));
  
    // Thursday -> Thursday
    civil_day d = next_weekday(thursday, weekday::thursday);
    EXPECT_EQ(7, d - thursday) << Format(d);
    EXPECT_EQ(d - 14, prev_weekday(thursday, weekday::thursday));
  
    // Thursday -> Friday
    d = next_weekday(thursday, weekday::friday);
    EXPECT_EQ(1, d - thursday) << Format(d);
    EXPECT_EQ(d - 7, prev_weekday(thursday, weekday::friday));
  
    // Thursday -> Saturday
    d = next_weekday(thursday, weekday::saturday);
    EXPECT_EQ(2, d - thursday) << Format(d);
    EXPECT_EQ(d - 7, prev_weekday(thursday, weekday::saturday));
  
    // Thursday -> Sunday
    d = next_weekday(thursday, weekday::sunday);
    EXPECT_EQ(3, d - thursday) << Format(d);
    EXPECT_EQ(d - 7, prev_weekday(thursday, weekday::sunday));
  
    // Thursday -> Monday
    d = next_weekday(thursday, weekday::monday);
    EXPECT_EQ(4, d - thursday) << Format(d);
    EXPECT_EQ(d - 7, prev_weekday(thursday, weekday::monday));
  
    // Thursday -> Tuesday
    d = next_weekday(thursday, weekday::tuesday);
    EXPECT_EQ(5, d - thursday) << Format(d);
    EXPECT_EQ(d - 7, prev_weekday(thursday, weekday::tuesday));
  
    // Thursday -> Wednesday
    d = next_weekday(thursday, weekday::wednesday);
    EXPECT_EQ(6, d - thursday) << Format(d);
    EXPECT_EQ(d - 7, prev_weekday(thursday, weekday::wednesday));
  }
  
  TEST(CivilTime, NormalizeWithHugeYear) {
    civil_month c(9223372036854775807, 1);
    EXPECT_EQ("9223372036854775807-01", Format(c));
    c = c - 1;  // Causes normalization
    EXPECT_EQ("9223372036854775806-12", Format(c));
  
    c = civil_month(-9223372036854775807 - 1, 1);
    EXPECT_EQ("-9223372036854775808-01", Format(c));
    c = c + 12;  // Causes normalization
    EXPECT_EQ("-9223372036854775807-01", Format(c));
  }
  
  TEST(CivilTime, LeapYears) {
    // Test data for leap years.
    const struct {
      int year;
      int days;
      struct {
        int month;
        int day;
      } leap_day;  // The date of the day after Feb 28.
    } kLeapYearTable[]{
        {1900, 365, {3, 1}},
        {1999, 365, {3, 1}},
        {2000, 366, {2, 29}},  // leap year
        {2001, 365, {3, 1}},
        {2002, 365, {3, 1}},
        {2003, 365, {3, 1}},
        {2004, 366, {2, 29}},  // leap year
        {2005, 365, {3, 1}},
        {2006, 365, {3, 1}},
        {2007, 365, {3, 1}},
        {2008, 366, {2, 29}},  // leap year
        {2009, 365, {3, 1}},
        {2100, 365, {3, 1}},
    };
  
    for (const auto& e : kLeapYearTable) {
      // Tests incrementing through the leap day.
      const civil_day feb28(e.year, 2, 28);
      const civil_day next_day = feb28 + 1;
      EXPECT_EQ(e.leap_day.month, next_day.month());
      EXPECT_EQ(e.leap_day.day, next_day.day());
  
      // Tests difference in days of leap years.
      const civil_year year(feb28);
      const civil_year next_year = year + 1;
      EXPECT_EQ(e.days, civil_day(next_year) - civil_day(year));
    }
  }
  
  TEST(CivilTime, FirstThursdayInMonth) {
    const civil_day nov1(2014, 11, 1);
    const civil_day thursday = prev_weekday(nov1, weekday::thursday) + 7;
    EXPECT_EQ("2014-11-06", Format(thursday));
  
    // Bonus: Date of Thanksgiving in the United States
    // Rule: Fourth Thursday of November
    const civil_day thanksgiving = thursday + 7 * 3;
    EXPECT_EQ("2014-11-27", Format(thanksgiving));
  }
  
  }  // namespace cctz
  }  // namespace time_internal
  }  // inline namespace lts_2018_06_20
  }  // namespace absl
  