// Copyright 2018 The Abseil Authors.

//

// 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

//

//      https://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.

//

// -----------------------------------------------------------------------------

// File: civil_time.h

// -----------------------------------------------------------------------------

//

// This header file defines abstractions for computing with "civil time".

// The term "civil time" refers to the legally recognized human-scale time

// that is represented by the six fields `YYYY-MM-DD hh:mm:ss`. A "date"

// is perhaps the most common example of a civil time (represented here as

// an `absl::CivilDay`).

//

// Modern-day civil time follows the Gregorian Calendar and is a

// time-zone-independent concept: a civil time of "2015-06-01 12:00:00", for

// example, is not tied to a time zone. Put another way, a civil time does not

// map to a unique point in time; a civil time must be mapped to an absolute

// time *through* a time zone.

//

// Because a civil time is what most people think of as "time," it is common to

// map absolute times to civil times to present to users.

//

// Time zones define the relationship between absolute and civil times. Given an

// absolute or civil time and a time zone, you can compute the other time:

//

//   Civil Time = F(Absolute Time, Time Zone)

//   Absolute Time = G(Civil Time, Time Zone)

//

// The Abseil time library allows you to construct such civil times from

// absolute times; consult time.h for such functionality.

//

// This library provides six classes for constructing civil-time objects, and

// provides several helper functions for rounding, iterating, and performing

// arithmetic on civil-time objects, while avoiding complications like

// daylight-saving time (DST):

//

//   * `absl::CivilSecond`

//   * `absl::CivilMinute`

//   * `absl::CivilHour`

//   * `absl::CivilDay`

//   * `absl::CivilMonth`

//   * `absl::CivilYear`

//

// Example:

//

//   // Construct a civil-time object for a specific day

//   const absl::CivilDay cd(1969, 07, 20);

//

//   // Construct a civil-time object for a specific second

//   const absl::CivilSecond cd(2018, 8, 1, 12, 0, 1);

//

// Note: In C++14 and later, this library is usable in a constexpr context.

//

// Example:

//

//   // Valid in C++14

//   constexpr absl::CivilDay cd(1969, 07, 20);

#ifndef ABSL_TIME_CIVIL_TIME_H_

#define ABSL_TIME_CIVIL_TIME_H_

#include <iosfwd>

#include <string>

#include "absl/base/config.h"

#include "absl/strings/string_view.h"

#include "absl/time/internal/cctz/include/cctz/civil_time.h"

namespace absl {

ABSL_NAMESPACE_BEGIN

namespace time_internal {

struct second_tag : cctz::detail::second_tag {};

struct minute_tag : second_tag, cctz::detail::minute_tag {};

struct hour_tag : minute_tag, cctz::detail::hour_tag {};

struct day_tag : hour_tag, cctz::detail::day_tag {};

struct month_tag : day_tag, cctz::detail::month_tag {};

struct year_tag : month_tag, cctz::detail::year_tag {};

}  // namespace time_internal

// -----------------------------------------------------------------------------

// CivilSecond, CivilMinute, CivilHour, CivilDay, CivilMonth, CivilYear

// -----------------------------------------------------------------------------

//

// Each of these civil-time types is a simple value type with the same

// interface for construction and the same six accessors for each of the civil

// time fields (year, month, day, hour, minute, and second, aka YMDHMS). These

// classes differ only in their alignment, which is indicated by the type name

// and specifies the field on which arithmetic operates.

//

// CONSTRUCTION

//

// Each of the civil-time types can be constructed in two ways: by directly

// passing to the constructor up to six integers representing the YMDHMS fields,

// or by copying the YMDHMS fields from a differently aligned civil-time type.

// Omitted fields are assigned their minimum valid value. Hours, minutes, and

// seconds will be set to 0, month and day will be set to 1. Since there is no

// minimum year, the default is 1970.

//

// Examples:

//

//   absl::CivilDay default_value;               // 1970-01-01 00:00:00

//

//   absl::CivilDay a(2015, 2, 3);               // 2015-02-03 00:00:00

//   absl::CivilDay b(2015, 2, 3, 4, 5, 6);      // 2015-02-03 00:00:00

//   absl::CivilDay c(2015);                     // 2015-01-01 00:00:00

//

//   absl::CivilSecond ss(2015, 2, 3, 4, 5, 6);  // 2015-02-03 04:05:06

//   absl::CivilMinute mm(ss);                   // 2015-02-03 04:05:00

//   absl::CivilHour hh(mm);                     // 2015-02-03 04:00:00

//   absl::CivilDay d(hh);                       // 2015-02-03 00:00:00

//   absl::CivilMonth m(d);                      // 2015-02-01 00:00:00

//   absl::CivilYear y(m);                       // 2015-01-01 00:00:00

//

//   m = absl::CivilMonth(y);                    // 2015-01-01 00:00:00

//   d = absl::CivilDay(m);                      // 2015-01-01 00:00:00

//   hh = absl::CivilHour(d);                    // 2015-01-01 00:00:00

//   mm = absl::CivilMinute(hh);                 // 2015-01-01 00:00:00

//   ss = absl::CivilSecond(mm);                 // 2015-01-01 00:00:00

//

// Each civil-time class is aligned to the civil-time field indicated in the

// class's name after normalization. Alignment is performed by setting all the

// inferior fields to their minimum valid value (as described above). The

// following are examples of how each of the six types would align the fields

// representing November 22, 2015 at 12:34:56 in the afternoon. (Note: the

// string format used here is not important; it's just a shorthand way of

// showing the six YMDHMS fields.)

//

//   absl::CivilSecond   : 2015-11-22 12:34:56

//   absl::CivilMinute   : 2015-11-22 12:34:00

//   absl::CivilHour     : 2015-11-22 12:00:00

//   absl::CivilDay      : 2015-11-22 00:00:00

//   absl::CivilMonth    : 2015-11-01 00:00:00

//   absl::CivilYear     : 2015-01-01 00:00:00

//

// Each civil-time type performs arithmetic on the field to which it is

// aligned. This means that adding 1 to an absl::CivilDay increments the day

// field (normalizing as necessary), and subtracting 7 from an absl::CivilMonth

// operates on the month field (normalizing as necessary). All arithmetic

// produces a valid civil time. Difference requires two similarly aligned

// civil-time objects and returns the scalar answer in units of the objects'

// alignment. For example, the difference between two absl::CivilHour objects

// will give an answer in units of civil hours.

//

// ALIGNMENT CONVERSION

//

// The alignment of a civil-time object cannot change, but the object may be

// used to construct a new object with a different alignment. This is referred

// to as "realigning". When realigning to a type with the same or more

// precision (e.g., absl::CivilDay -> absl::CivilSecond), the conversion may be

// performed implicitly since no information is lost. However, if information

// could be discarded (e.g., CivilSecond -> CivilDay), the conversion must

// be explicit at the call site.

//

// Examples:

//

//   void UseDay(absl::CivilDay day);

//

//   absl::CivilSecond cs;

//   UseDay(cs);                  // Won't compile because data may be discarded

//   UseDay(absl::CivilDay(cs));  // OK: explicit conversion

//

//   absl::CivilDay cd;

//   UseDay(cd);                  // OK: no conversion needed

//

//   absl::CivilMonth cm;

//   UseDay(cm);                  // OK: implicit conversion to absl::CivilDay

//

// NORMALIZATION

//

// Normalization takes invalid values and adjusts them to produce valid values.

// Within the civil-time library, integer arguments passed to the Civil*

// constructors may be out-of-range, in which case they are normalized by

// carrying overflow into a field of courser granularity to produce valid

// civil-time objects. This normalization enables natural arithmetic on

// constructor arguments without worrying about the field's range.

//

// Examples:

//

//   // Out-of-range; normalized to 2016-11-01

//   absl::CivilDay d(2016, 10, 32);

//   // Out-of-range, negative: normalized to 2016-10-30T23

//   absl::CivilHour h1(2016, 10, 31, -1);

//   // Normalization is cumulative: normalized to 2016-10-30T23

//   absl::CivilHour h2(2016, 10, 32, -25);

//

// Note: If normalization is undesired, you can signal an error by comparing

// the constructor arguments to the normalized values returned by the YMDHMS

// properties.

//

// COMPARISON

//

// Comparison between civil-time objects considers all six YMDHMS fields,

// regardless of the type's alignment. Comparison between differently aligned

// civil-time types is allowed.

//

// Examples:

//

//   absl::CivilDay feb_3(2015, 2, 3);  // 2015-02-03 00:00:00

//   absl::CivilDay mar_4(2015, 3, 4);  // 2015-03-04 00:00:00

//   // feb_3 < mar_4

//   // absl::CivilYear(feb_3) == absl::CivilYear(mar_4)

//

//   absl::CivilSecond feb_3_noon(2015, 2, 3, 12, 0, 0);  // 2015-02-03 12:00:00

//   // feb_3 < feb_3_noon

//   // feb_3 == absl::CivilDay(feb_3_noon)

//

//   // Iterates all the days of February 2015.

//   for (absl::CivilDay d(2015, 2, 1); d < absl::CivilMonth(2015, 3); ++d) {

//     // ...

//   }

//

// ARITHMETIC

//

// Civil-time types support natural arithmetic operators such as addition,

// subtraction, and difference. Arithmetic operates on the civil-time field

// indicated in the type's name. Difference operators require arguments with

// the same alignment and return the answer in units of the alignment.

//

// Example:

//

//   absl::CivilDay a(2015, 2, 3);

//   ++a;                              // 2015-02-04 00:00:00

//   --a;                              // 2015-02-03 00:00:00

//   absl::CivilDay b = a + 1;         // 2015-02-04 00:00:00

//   absl::CivilDay c = 1 + b;         // 2015-02-05 00:00:00

//   int n = c - a;                    // n = 2 (civil days)

//   int m = c - absl::CivilMonth(c);  // Won't compile: different types.

//

// ACCESSORS

//

// Each civil-time type has accessors for all six of the civil-time fields:

// year, month, day, hour, minute, and second.

//

// civil_year_t year()

// int          month()

// int          day()

// int          hour()

// int          minute()

// int          second()

//

// Recall that fields inferior to the type's alignment will be set to their

// minimum valid value.

//

// Example:

//

//   absl::CivilDay d(2015, 6, 28);

//   // d.year() == 2015

//   // d.month() == 6

//   // d.day() == 28

//   // d.hour() == 0

//   // d.minute() == 0

//   // d.second() == 0

//

// CASE STUDY: Adding a month to January 31.

//

// One of the classic questions that arises when considering a civil time

// library (or a date library or a date/time library) is this:

//   "What is the result of adding a month to January 31?"

// This is an interesting question because it is unclear what is meant by a

// "month", and several different answers are possible, depending on context:

//

//   1. March 3 (or 2 if a leap year), if "add a month" means to add a month to

//      the current month, and adjust the date to overflow the extra days into

//      March. In this case the result of "February 31" would be normalized as

//      within the civil-time library.

//   2. February 28 (or 29 if a leap year), if "add a month" means to add a

//      month, and adjust the date while holding the resulting month constant.

//      In this case, the result of "February 31" would be truncated to the last

//      day in February.

//   3. An error. The caller may get some error, an exception, an invalid date

//      object, or perhaps return `false`. This may make sense because there is

//      no single unambiguously correct answer to the question.

//

// Practically speaking, any answer that is not what the programmer intended

// is the wrong answer.

//

// The Abseil time library avoids this problem by making it impossible to

// ask ambiguous questions. All civil-time objects are aligned to a particular

// civil-field boundary (such as aligned to a year, month, day, hour, minute,

// or second), and arithmetic operates on the field to which the object is

// aligned. This means that in order to "add a month" the object must first be

// aligned to a month boundary, which is equivalent to the first day of that

// month.

//

// Of course, there are ways to compute an answer the question at hand using

// this Abseil time library, but they require the programmer to be explicit

// about the answer they expect. To illustrate, let's see how to compute all

// three of the above possible answers to the question of "Jan 31 plus 1

// month":

//

// Example:

//

//   const absl::CivilDay d(2015, 1, 31);

//

//   // Answer 1:

//   // Add 1 to the month field in the constructor, and rely on normalization.

//   const auto normalized = absl::CivilDay(d.year(), d.month() + 1, d.day());

//   // normalized == 2015-03-03 (aka Feb 31)

//

//   // Answer 2:

//   // Add 1 to month field, capping to the end of next month.

//   const auto next_month = absl::CivilMonth(d) + 1;

//   const auto last_day_of_next_month = absl::CivilDay(next_month + 1) - 1;

//   const auto capped = std::min(normalized, last_day_of_next_month);

//   // capped == 2015-02-28

//

//   // Answer 3:

//   // Signal an error if the normalized answer is not in next month.

//   if (absl::CivilMonth(normalized) != next_month) {

//     // error, month overflow

//   }

//

using CivilSecond =

    time_internal::cctz::detail::civil_time<time_internal::second_tag>;

using CivilMinute =

    time_internal::cctz::detail::civil_time<time_internal::minute_tag>;

using CivilHour =

    time_internal::cctz::detail::civil_time<time_internal::hour_tag>;

using CivilDay =

    time_internal::cctz::detail::civil_time<time_internal::day_tag>;

using CivilMonth =

    time_internal::cctz::detail::civil_time<time_internal::month_tag>;

using CivilYear =

    time_internal::cctz::detail::civil_time<time_internal::year_tag>;

// civil_year_t

//

// Type alias of a civil-time year value. This type is guaranteed to (at least)

// support any year value supported by `time_t`.

//

// Example:

//

//   absl::CivilSecond cs = ...;

//   absl::civil_year_t y = cs.year();

//   cs = absl::CivilSecond(y, 1, 1, 0, 0, 0);  // CivilSecond(CivilYear(cs))

//

using civil_year_t = time_internal::cctz::year_t;

// civil_diff_t

//

// Type alias of the difference between two civil-time values.

// This type is used to indicate arguments that are not

// normalized (such as parameters to the civil-time constructors), the results

// of civil-time subtraction, or the operand to civil-time addition.

//

// Example:

//

//   absl::civil_diff_t n_sec = cs1 - cs2;             // cs1 == cs2 + n_sec;

//

using civil_diff_t = time_internal::cctz::diff_t;

// Weekday::monday, Weekday::tuesday, Weekday::wednesday, Weekday::thursday,

// Weekday::friday, Weekday::saturday, Weekday::sunday

//

// The Weekday enum class represents the civil-time concept of a "weekday" with

// members for all days of the week.

//

//   absl::Weekday wd = absl::Weekday::thursday;

//

using Weekday = time_internal::cctz::weekday;

// GetWeekday()

//

// Returns the absl::Weekday for the given (realigned) civil-time value.

//

// Example:

//

//   absl::CivilDay a(2015, 8, 13);

//   absl::Weekday wd = absl::GetWeekday(a);  // wd == absl::Weekday::thursday

//

inline Weekday GetWeekday(CivilSecond cs) {

  return time_internal::cctz::get_weekday(cs);

}

// NextWeekday()

// PrevWeekday()

//

// Returns the absl::CivilDay that strictly follows or precedes a given

// absl::CivilDay, and that falls on the given absl::Weekday.

//

// Example, given the following month:

//

//       August 2015

//   Su Mo Tu We Th Fr Sa

//                      1

//    2  3  4  5  6  7  8

//    9 10 11 12 13 14 15

//   16 17 18 19 20 21 22

//   23 24 25 26 27 28 29

//   30 31

//

//   absl::CivilDay a(2015, 8, 13);

//   // absl::GetWeekday(a) == absl::Weekday::thursday

//   absl::CivilDay b = absl::NextWeekday(a, absl::Weekday::thursday);

//   // b = 2015-08-20

//   absl::CivilDay c = absl::PrevWeekday(a, absl::Weekday::thursday);

//   // c = 2015-08-06

//

//   absl::CivilDay d = ...

//   // Gets the following Thursday if d is not already Thursday

//   absl::CivilDay thurs1 = absl::NextWeekday(d - 1, absl::Weekday::thursday);

//   // Gets the previous Thursday if d is not already Thursday

//   absl::CivilDay thurs2 = absl::PrevWeekday(d + 1, absl::Weekday::thursday);

//

inline CivilDay NextWeekday(CivilDay cd, Weekday wd) {

  return CivilDay(time_internal::cctz::next_weekday(cd, wd));

}

inline CivilDay PrevWeekday(CivilDay cd, Weekday wd) {

  return CivilDay(time_internal::cctz::prev_weekday(cd, wd));

}

// GetYearDay()

//

// Returns the day-of-year for the given (realigned) civil-time value.

//

// Example:

//

//   absl::CivilDay a(2015, 1, 1);

//   int yd_jan_1 = absl::GetYearDay(a);   // yd_jan_1 = 1

//   absl::CivilDay b(2015, 12, 31);

//   int yd_dec_31 = absl::GetYearDay(b);  // yd_dec_31 = 365

//

inline int GetYearDay(CivilSecond cs) {

  return time_internal::cctz::get_yearday(cs);

}

// FormatCivilTime()

//

// Formats the given civil-time value into a string value of the following

// format:

//

//  Type        | Format

//  ---------------------------------

//  CivilSecond | YYYY-MM-DDTHH:MM:SS

//  CivilMinute | YYYY-MM-DDTHH:MM

//  CivilHour   | YYYY-MM-DDTHH

//  CivilDay    | YYYY-MM-DD

//  CivilMonth  | YYYY-MM

//  CivilYear   | YYYY

//

// Example:

//

//   absl::CivilDay d = absl::CivilDay(1969, 7, 20);

//   std::string day_string = absl::FormatCivilTime(d);  // "1969-07-20"

//

std::string FormatCivilTime(CivilSecond c);

std::string FormatCivilTime(CivilMinute c);

std::string FormatCivilTime(CivilHour c);

std::string FormatCivilTime(CivilDay c);

std::string FormatCivilTime(CivilMonth c);

std::string FormatCivilTime(CivilYear c);

// Support for StrFormat(), StrCat(), etc

template <typename Sink>

void AbslStringify(Sink& sink, CivilSecond c) {

  sink.Append(FormatCivilTime(c));

}

template <typename Sink>

void AbslStringify(Sink& sink, CivilMinute c) {

  sink.Append(FormatCivilTime(c));

}

template <typename Sink>

void AbslStringify(Sink& sink, CivilHour c) {

  sink.Append(FormatCivilTime(c));

}

template <typename Sink>

void AbslStringify(Sink& sink, CivilDay c) {

  sink.Append(FormatCivilTime(c));

}

template <typename Sink>

void AbslStringify(Sink& sink, CivilMonth c) {

  sink.Append(FormatCivilTime(c));

}

template <typename Sink>

void AbslStringify(Sink& sink, CivilYear c) {

  sink.Append(FormatCivilTime(c));

}

// absl::ParseCivilTime()

//

// Parses a civil-time value from the specified `absl::string_view` into the

// passed output parameter. Returns `true` upon successful parsing.

//

// The expected form of the input string is as follows:

//

//  Type        | Format

//  ---------------------------------

//  CivilSecond | YYYY-MM-DDTHH:MM:SS

//  CivilMinute | YYYY-MM-DDTHH:MM

//  CivilHour   | YYYY-MM-DDTHH

//  CivilDay    | YYYY-MM-DD

//  CivilMonth  | YYYY-MM

//  CivilYear   | YYYY

//

// Example:

//

//   absl::CivilDay d;

//   bool ok = absl::ParseCivilTime("2018-01-02", &d); // OK

//

// Note that parsing will fail if the string's format does not match the

// expected type exactly. `ParseLenientCivilTime()` below is more lenient.

//

bool ParseCivilTime(absl::string_view s, CivilSecond* c);

bool ParseCivilTime(absl::string_view s, CivilMinute* c);

bool ParseCivilTime(absl::string_view s, CivilHour* c);

bool ParseCivilTime(absl::string_view s, CivilDay* c);

bool ParseCivilTime(absl::string_view s, CivilMonth* c);

bool ParseCivilTime(absl::string_view s, CivilYear* c);

// ParseLenientCivilTime()

//

// Parses any of the formats accepted by `absl::ParseCivilTime()`, but is more

// lenient if the format of the string does not exactly match the associated

// type.

//

// Example:

//

//   absl::CivilDay d;

//   bool ok = absl::ParseLenientCivilTime("1969-07-20", &d); // OK

//   ok = absl::ParseLenientCivilTime("1969-07-20T10", &d);   // OK: T10 floored

//   ok = absl::ParseLenientCivilTime("1969-07", &d);   // OK: day defaults to 1

//

bool ParseLenientCivilTime(absl::string_view s, CivilSecond* c);

bool ParseLenientCivilTime(absl::string_view s, CivilMinute* c);

bool ParseLenientCivilTime(absl::string_view s, CivilHour* c);

bool ParseLenientCivilTime(absl::string_view s, CivilDay* c);

bool ParseLenientCivilTime(absl::string_view s, CivilMonth* c);

bool ParseLenientCivilTime(absl::string_view s, CivilYear* c);

namespace time_internal {  // For functions found via ADL on civil-time tags.

// Streaming Operators

//

// Each civil-time type may be sent to an output stream using operator<<().

// The result matches the string produced by `FormatCivilTime()`.

//

// Example:

//

//   absl::CivilDay d = absl::CivilDay(1969, 7, 20);

//   std::cout << "Date is: " << d << "\n";

//

std::ostream& operator<<(std::ostream& os, CivilYear y);

std::ostream& operator<<(std::ostream& os, CivilMonth m);

std::ostream& operator<<(std::ostream& os, CivilDay d);

std::ostream& operator<<(std::ostream& os, CivilHour h);

std::ostream& operator<<(std::ostream& os, CivilMinute m);

std::ostream& operator<<(std::ostream& os, CivilSecond s);

// AbslParseFlag()

//

// Parses the command-line flag string representation `s` into a civil-time

// value. Flags must be specified in a format that is valid for

// `absl::ParseLenientCivilTime()`.

bool AbslParseFlag(absl::string_view s, CivilSecond* c, std::string* error);

bool AbslParseFlag(absl::string_view s, CivilMinute* c, std::string* error);

bool AbslParseFlag(absl::string_view s, CivilHour* c, std::string* error);

bool AbslParseFlag(absl::string_view s, CivilDay* c, std::string* error);

bool AbslParseFlag(absl::string_view s, CivilMonth* c, std::string* error);

bool AbslParseFlag(absl::string_view s, CivilYear* c, std::string* error);

// AbslUnparseFlag()

//

// Unparses a civil-time value into a command-line string representation using

// the format specified by `absl::ParseCivilTime()`.

std::string AbslUnparseFlag(CivilSecond c);

std::string AbslUnparseFlag(CivilMinute c);

std::string AbslUnparseFlag(CivilHour c);

std::string AbslUnparseFlag(CivilDay c);

std::string AbslUnparseFlag(CivilMonth c);

std::string AbslUnparseFlag(CivilYear c);

}  // namespace time_internal

ABSL_NAMESPACE_END

}  // namespace absl

#endif  // ABSL_TIME_CIVIL_TIME_H_