datetime.h

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#ifndef CHRONO_UTILITIES_DATETIME_H
#define CHRONO_UTILITIES_DATETIME_H
 
#include "./timespan.h"
 
#include "../misc/flagenumclass.h"
 
#include <cstdint>
#include <ctime>
#include <limits>
#include <string>
 
namespace CppUtilities {

enum class DateTimeOutputFormat {
    DateAndTime, 
    DateOnly, 
    TimeOnly, 
    DateTimeAndWeekday, 
    DateTimeAndShortWeekday, 
    Iso, 
    IsoOmittingDefaultComponents, 
};

enum class DayOfWeek {
    Monday, 
    Tuesday, 
    Wednesday, 
    Thursday, 
    Friday, 
    Saturday, 
    Sunday 
};

enum class DatePart {
    Year, 
    Month, 
    DayOfYear, 
    Day 
};
 
class CPP_UTILITIES_EXPORT DateTime {
public:
    using TickType = std::uint64_t;
 
    explicit constexpr DateTime();
    explicit constexpr DateTime(TickType ticks);
    static DateTime fromDate(int year = 1, int month = 1, int day = 1);
    static DateTime fromTime(int hour = 0, int minute = 0, int second = 0, double millisecond = 0.0);
    static DateTime fromDateAndTime(int year = 1, int month = 1, int day = 1, int hour = 0, int minute = 0, int second = 0, double millisecond = 0.0);
    static DateTime fromString(const std::string &str);
    static DateTime fromString(const char *str);
    static std::pair<DateTime, TimeSpan> fromIsoString(const char *str);
    static DateTime fromIsoStringGmt(const char *str);
    static DateTime fromIsoStringLocal(const char *str);
    static DateTime fromTimeStamp(std::time_t timeStamp);
    constexpr static DateTime fromTimeStampGmt(std::time_t timeStamp);
    template <typename TimePoint> static DateTime fromChronoTimePoint(TimePoint timePoint);
    template <typename TimePoint> constexpr static DateTime fromChronoTimePointGmt(TimePoint timePoint);
 
    constexpr TickType &ticks();
    constexpr TickType totalTicks() const;
    int year() const;
    int month() const;
    int day() const;
    int dayOfYear() const;
    constexpr DayOfWeek dayOfWeek() const;
    constexpr int hour() const;
    constexpr int minute() const;
    constexpr int second() const;
    constexpr int millisecond() const;
    constexpr int microsecond() const;
    constexpr int nanosecond() const;
    constexpr bool isNull() const;
    constexpr TimeSpan timeOfDay() const;
    bool isLeapYear() const;
    constexpr bool isEternity() const;
    constexpr bool isSameDay(const DateTime &other) const;
    std::string toString(DateTimeOutputFormat format = DateTimeOutputFormat::DateAndTime, bool noMilliseconds = false) const;
    void toString(std::string &result, DateTimeOutputFormat format = DateTimeOutputFormat::DateAndTime, bool noMilliseconds = false) const;
    std::string toIsoStringWithCustomDelimiters(
        TimeSpan timeZoneDelta = TimeSpan(), char dateDelimiter = '-', char timeDelimiter = ':', char timeZoneDelimiter = ':') const;
    std::string toIsoString(TimeSpan timeZoneDelta = TimeSpan()) const;
    constexpr std::time_t toTimeStamp() const;
    static const char *printDayOfWeek(DayOfWeek dayOfWeek, bool abbreviation = false);
 
    static constexpr DateTime eternity();
    static constexpr DateTime unixEpochStart();
    static DateTime now();
    static DateTime gmtNow();
    static DateTime exactGmtNow();
    constexpr static bool isLeapYear(int year);
    static int daysInMonth(int year, int month);
 
    constexpr bool operator==(const DateTime &other) const;
    constexpr bool operator!=(const DateTime &other) const;
    constexpr bool operator<(const DateTime &other) const;
    constexpr bool operator>(const DateTime &other) const;
    constexpr bool operator<=(const DateTime &other) const;
    constexpr bool operator>=(const DateTime &other) const;
    constexpr DateTime operator+(const TimeSpan &timeSpan) const;
    constexpr DateTime operator-(const TimeSpan &timeSpan) const;
    constexpr TimeSpan operator+(const DateTime &other) const;
    constexpr TimeSpan operator-(const DateTime &other) const;
    DateTime &operator+=(const TimeSpan &timeSpan);
    DateTime &operator-=(const TimeSpan &timeSpan);
 
private:
    static TickType dateToTicks(int year, int month, int day);
    static TickType timeToTicks(int hour, int minute, int second, double millisecond);
    int getDatePart(DatePart part) const;
 
    TickType m_ticks;
    static const int m_daysPerYear;
    static const int m_daysPer4Years;
    static const int m_daysPer100Years;
    static const int m_daysPer400Years;
    static const int m_daysTo1601;
    static const int m_daysTo1899;
    static const int m_daysTo10000;
    static const int m_daysToMonth365[13];
    static const int m_daysToMonth366[13];
    static const int m_daysInMonth365[12];
    static const int m_daysInMonth366[12];
};

enum class DateTimeParts : std::uint64_t {
    None = 0, 
    Year = (1 << 0), 
    Month = (1 << 1), 
    Day = (1 << 2), 
    Hour = (1 << 3), 
    Minute = (1 << 4), 
    Second = (1 << 5), 
    SubSecond = (1 << 6), 
    DeltaHour = (1 << 7), 
    DeltaMinute = (1 << 8), 
    Date = Year | Month | Day, 
    Time = Hour | Minute | Second | SubSecond, 
    DateTime = Date | Time, 
    TimeZoneDelta = DeltaHour | DeltaMinute, 
    All = DateTime | TimeZoneDelta, 
};
 
struct CPP_UTILITIES_EXPORT DateTimeExpression {
    DateTime value; 
    TimeSpan delta; 
    DateTimeParts parts = DateTimeParts::None; 
 
    constexpr DateTime gmt() const;
    constexpr bool operator==(const DateTimeExpression &other) const;
    std::string toIsoString(char dateDelimiter = '-', char timeDelimiter = ':', char timeZoneDelimiter = ':') const;
    static DateTimeExpression fromIsoString(const char *str);
    static DateTimeExpression fromString(const char *str);
};

constexpr DateTime DateTimeExpression::gmt() const
{
    return value - delta;
}

constexpr bool DateTimeExpression::operator==(const DateTimeExpression &other) const
{
    return value == other.value && delta == other.delta && parts == other.parts;
}

constexpr inline DateTime::DateTime()
    : m_ticks(0)
{
}

constexpr inline DateTime::DateTime(TickType ticks)
    : m_ticks(ticks)
{
}

inline DateTime DateTime::fromDate(int year, int month, int day)
{
    return DateTime(dateToTicks(year, month, day));
}

inline DateTime DateTime::fromTime(int hour, int minute, int second, double millisecond)
{
    return DateTime(timeToTicks(hour, minute, second, millisecond));
}

inline DateTime DateTime::fromDateAndTime(int year, int month, int day, int hour, int minute, int second, double millisecond)
{
    return DateTime(dateToTicks(year, month, day) + timeToTicks(hour, minute, second, millisecond));
}

inline DateTime DateTime::fromString(const std::string &str)
{
    return fromString(str.data());
}

inline DateTime DateTime::fromIsoStringGmt(const char *str)
{
    return DateTimeExpression::fromIsoString(str).gmt();
}

inline DateTime DateTime::fromIsoStringLocal(const char *str)
{
    return DateTimeExpression::fromIsoString(str).value;
}

constexpr inline DateTime DateTime::fromTimeStampGmt(std::time_t timeStamp)
{
    return DateTime(DateTime::unixEpochStart().totalTicks() + static_cast<std::uint64_t>(timeStamp) * TimeSpan::ticksPerSecond);
}

template <typename TimePoint> inline DateTime DateTime::fromChronoTimePoint(TimePoint timePoint)
{
    return DateTime::fromTimeStamp(decltype(timePoint)::clock::to_time_t(timePoint));
}

template <typename TimePoint> constexpr DateTime DateTime::fromChronoTimePointGmt(TimePoint timePoint)
{
    return DateTime::fromTimeStampGmt(decltype(timePoint)::clock::to_time_t(timePoint));
}

constexpr inline DateTime::TickType &DateTime::ticks()
{
    return m_ticks;
}

constexpr inline DateTime::TickType DateTime::totalTicks() const
{
    return m_ticks;
}

inline int DateTime::year() const
{
    return getDatePart(DatePart::Year);
}

inline int DateTime::month() const
{
    return getDatePart(DatePart::Month);
}

inline int DateTime::day() const
{
    return getDatePart(DatePart::Day);
}

inline int DateTime::dayOfYear() const
{
    return getDatePart(DatePart::DayOfYear);
}

constexpr inline DayOfWeek DateTime::dayOfWeek() const
{
    return static_cast<DayOfWeek>((m_ticks / TimeSpan::ticksPerDay) % 7l);
}

constexpr inline int DateTime::hour() const
{
    return static_cast<int>(m_ticks / TimeSpan::ticksPerHour % 24ul);
}

constexpr inline int DateTime::minute() const
{
    return static_cast<int>(m_ticks / TimeSpan::ticksPerMinute % 60ul);
}

constexpr inline int DateTime::second() const
{
    return static_cast<int>(m_ticks / TimeSpan::ticksPerSecond % 60ul);
}

constexpr inline int DateTime::millisecond() const
{
    return static_cast<int>(m_ticks / TimeSpan::ticksPerMillisecond % 1000ul);
}

constexpr inline int DateTime::microsecond() const
{
    return static_cast<int>(m_ticks / TimeSpan::ticksPerMicrosecond % 1000ul);
}

constexpr inline int DateTime::nanosecond() const
{
    return static_cast<int>(m_ticks % 10ul * TimeSpan::nanosecondsPerTick);
}

constexpr inline bool DateTime::isNull() const
{
    return m_ticks == 0;
}

constexpr inline TimeSpan DateTime::timeOfDay() const
{
    return TimeSpan(static_cast<TimeSpan::TickType>(m_ticks % TimeSpan::ticksPerDay));
}

inline bool DateTime::isLeapYear() const
{
    return isLeapYear(year());
}

constexpr inline bool DateTime::isEternity() const
{
    return m_ticks == std::numeric_limits<TickType>::max();
}

constexpr inline bool DateTime::isLeapYear(int year)
{
    return (year % 4 != 0) ? false : ((year % 100 == 0) ? (year % 400 == 0) : true);
}

inline int DateTime::daysInMonth(int year, int month)
{
    return (month >= 1 && month <= 12) ? (isLeapYear(year) ? m_daysInMonth366[month - 1] : m_daysInMonth365[month - 1]) : (0);
}

constexpr inline bool DateTime::isSameDay(const DateTime &other) const
{
    return (m_ticks / TimeSpan::ticksPerDay) == (other.m_ticks / TimeSpan::ticksPerDay);
}

inline std::string DateTime::toString(DateTimeOutputFormat format, bool noMilliseconds) const
{
    std::string result;
    toString(result, format, noMilliseconds);
    return result;
}

constexpr std::time_t DateTime::toTimeStamp() const
{
    return static_cast<std::time_t>((totalTicks() - DateTime::unixEpochStart().totalTicks()) / TimeSpan::ticksPerSecond);
}

constexpr inline DateTime DateTime::eternity()
{
    return DateTime(std::numeric_limits<TickType>::max());
}

constexpr inline DateTime DateTime::unixEpochStart()
{
    return DateTime(621355968000000000);
}

inline DateTime DateTime::now()
{
    return DateTime::fromTimeStamp(std::time(nullptr));
}

inline DateTime DateTime::gmtNow()
{
    return DateTime::fromTimeStampGmt(std::time(nullptr));
}

constexpr inline bool DateTime::operator==(const DateTime &other) const
{
    return m_ticks == other.m_ticks;
}

constexpr inline bool DateTime::operator!=(const DateTime &other) const
{
    return m_ticks != other.m_ticks;
}

constexpr inline bool DateTime::operator<(const DateTime &other) const
{
    return m_ticks < other.m_ticks;
}

constexpr inline bool DateTime::operator>(const DateTime &other) const
{
    return m_ticks > other.m_ticks;
}

constexpr inline bool DateTime::operator<=(const DateTime &other) const
{
    return m_ticks <= other.m_ticks;
}

constexpr inline bool DateTime::operator>=(const DateTime &other) const
{
    return m_ticks >= other.m_ticks;
}

constexpr inline DateTime DateTime::operator+(const TimeSpan &timeSpan) const
{
    return DateTime(m_ticks + static_cast<TickType>(timeSpan.m_ticks));
}

constexpr inline DateTime DateTime::operator-(const TimeSpan &timeSpan) const
{
    return DateTime(m_ticks - static_cast<TickType>(timeSpan.m_ticks));
}

constexpr inline TimeSpan DateTime::operator+(const DateTime &other) const
{
    return TimeSpan(static_cast<TimeSpan::TickType>(m_ticks + other.m_ticks));
}

constexpr inline TimeSpan DateTime::operator-(const DateTime &other) const
{
    return TimeSpan(static_cast<TimeSpan::TickType>(m_ticks - other.m_ticks));
}

inline DateTime &DateTime::operator+=(const TimeSpan &timeSpan)
{
    m_ticks += static_cast<TickType>(timeSpan.m_ticks);
    return *this;
}

inline DateTime &DateTime::operator-=(const TimeSpan &timeSpan)
{
    m_ticks += static_cast<TickType>(timeSpan.m_ticks);
    return *this;
}
} // namespace CppUtilities
 
namespace std {
template <> struct hash<CppUtilities::DateTime> {
    inline size_t operator()(const CppUtilities::DateTime &dateTime) const
    {
        return hash<CppUtilities::DateTime::TickType>()(dateTime.totalTicks());
    }
};
} // namespace std
 
CPP_UTILITIES_MARK_FLAG_ENUM_CLASS(CppUtilities, CppUtilities::DateTimeParts);
 
#endif // CHRONO_UTILITIES_DATETIME_H