cpp-utilities/chrono/datetime.cpp

#include "./datetime.h"

#include "../conversion/stringbuilder.h"
#include "../conversion/stringconversion.h"

#include <iomanip>
#include <sstream>
#include <stdexcept>

using namespace std;
using namespace ChronoUtilities;
using namespace ConversionUtilities;

const int DateTime::m_daysPerYear = 365;
const int DateTime::m_daysPer4Years = 1461;
const int DateTime::m_daysPer100Years = 36524;
const int DateTime::m_daysPer400Years = 146097;
const int DateTime::m_daysTo1601 = 584388;
const int DateTime::m_daysTo1899 = 693593;
const int DateTime::m_daysTo10000 = 3652059;
const int DateTime::m_daysToMonth365[13] = { 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365 };
const int DateTime::m_daysToMonth366[13] = { 0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366 };
const int DateTime::m_daysInMonth365[12] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
const int DateTime::m_daysInMonth366[12] = { 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };

template <typename num1, typename num2, typename num3> constexpr bool inRangeInclMax(num1 val, num2 min, num3 max)
{
    return (val) >= (min) && (val) <= (max);
}

template <typename num1, typename num2, typename num3> constexpr bool inRangeExclMax(num1 val, num2 min, num3 max)
{
    return (val) >= (min) && (val) < (max);
}

/*!
 * \class ChronoUtilities::DateTime
 * \brief Represents an instant in time, typically expressed as a date and time of day.
 * \remarks
 *  - Time values are measured in 100-nanosecond units called ticks,
 *    and a particular date is the number of ticks since 12:00 midnight, January 1,
 *    0001 A.D. (C.E.) in the GregorianCalendar calendar (excluding ticks that would
 *    be added by leap seconds).
 *  - There is no time zone information associated. Hence different time zones are
 *    not taken into account when comparing two instances. For instance, the
 *    expression (DateTime::now() - DateTime::gmtNow()) returns one hour in Germany during winter
 *    time (instead of zero).
 * \todo
 * - Add method for parsing custom string formats.
 * - Add method for printing to custom string formats.
 * - Allow to determine the date part for each compontent at once to prevent multiple
 *   invocations of getDatePart().
 * - Make more methods constexpr.
 */

/*!
 * \brief Constructs a new DateTime object with the local time from the specified UNIX \a timeStamp.
 */
DateTime DateTime::fromTimeStamp(time_t timeStamp)
{
    if (timeStamp) {
        struct tm *timeinfo = localtime(&timeStamp);
        return DateTime::fromDateAndTime(timeinfo->tm_year + 1900, timeinfo->tm_mon + 1, timeinfo->tm_mday, timeinfo->tm_hour, timeinfo->tm_min,
            timeinfo->tm_sec < 60 ? timeinfo->tm_sec : 59, 0);
    } else {
        return DateTime();
    }
}

/*!
 * \brief Constructs a new DateTime object with the GMT time from the specified UNIX \a timeStamp.
 */
DateTime DateTime::fromTimeStampGmt(time_t timeStamp)
{
    return DateTime(DateTime::unixEpochStart().totalTicks() + static_cast<uint64>(timeStamp) * TimeSpan::m_ticksPerSecond);
}

/*!
 * \brief Parses the given C-style string as DateTime.
 * \throws Throws a ConversionException if the specified \a str does not match the expected time format.
 *
 * The expected format is something like "2012-02-29 15:34:20.033" or "2012/02/29 15:34:20.033". The
 * delimiters '-', ':' and '/' are exchangeable.
 *
 * \sa DateTime::fromIsoString()
 */
DateTime DateTime::fromString(const char *str)
{
    int values[6] = { 0 };
    int *const dayIndex = values + 2;
    int *const secondsIndex = values + 5;
    int *valueIndex = values;
    int *const valuesEnd = values + 7;
    double miliSecondsFact = 100.0, miliSeconds = 0.0;
    for (const char *strIndex = str;; ++strIndex) {
        const char c = *strIndex;
        if (c <= '9' && c >= '0') {
            if (valueIndex > secondsIndex) {
                miliSeconds += (c - '0') * miliSecondsFact;
                miliSecondsFact /= 10;
            } else {
                *valueIndex *= 10;
                *valueIndex += c - '0';
            }
        } else if ((c == '-' || c == ':' || c == '/') || (c == '.' && (valueIndex == secondsIndex)) || (c == ' ' && (valueIndex == dayIndex))) {
            if (++valueIndex == valuesEnd) {
                break; // just ignore further values for now
            }
        } else if (c == '\0') {
            break;
        } else {
            throw ConversionException(argsToString("unexpected ", c));
        }
    }
    return DateTime::fromDateAndTime(values[0], values[1], *dayIndex, values[3], values[4], *secondsIndex, miliSeconds);
}

/*!
 * \brief Parses the specified ISO date time denotation provided as C-style string.
 * \returns Returns a pair where the first value is the parsed date time and the second value
 *          a time span which can be subtracted from the first value to get the UTC time.
 * \remarks Not all variants allowed by ISO 8601 are supported right now, eg. delimiters can not
 *          be omitted.
 *          The common form (something like "2016-08-29T21:32:31.588539814+02:00") is supported of course.
 * \sa https://en.wikipedia.org/wiki/ISO_8601
 */
std::pair<DateTime, TimeSpan> DateTime::fromIsoString(const char *str)
{
    int values[9] = { 0 };
    int *const dayIndex = values + 2;
    int *const hourIndex = values + 3;
    int *const secondsIndex = values + 5;
    int *const miliSecondsIndex = values + 6;
    int *const deltaHourIndex = values + 7;
    int *valueIndex = values;
    bool deltaNegative = false;
    double miliSecondsFact = 100.0, miliSeconds = 0.0;
    for (const char *strIndex = str;; ++strIndex) {
        const char c = *strIndex;
        if (c <= '9' && c >= '0') {
            if (valueIndex == miliSecondsIndex) {
                miliSeconds += (c - '0') * miliSecondsFact;
                miliSecondsFact /= 10;
            } else {
                *valueIndex *= 10;
                *valueIndex += c - '0';
            }
        } else if (c == 'T') {
            if (++valueIndex != hourIndex) {
                throw ConversionException("\"T\" expected before hour");
            }
        } else if (c == '-') {
            if (valueIndex < dayIndex) {
                ++valueIndex;
            } else if (++valueIndex == deltaHourIndex) {
                deltaNegative = true;
            } else {
                throw ConversionException("unexpected \"-\" after day");
            }
        } else if (c == '.') {
            if (valueIndex != secondsIndex) {
                throw ConversionException("unexpected \".\"");
            } else {
                ++valueIndex;
            }
        } else if (c == ':') {
            if (valueIndex < hourIndex) {
                throw ConversionException("unexpected \":\" before hour");
            } else if (valueIndex == secondsIndex) {
                throw ConversionException("unexpected \":\" after second");
            } else {
                ++valueIndex;
            }
        } else if ((c == '+') && (++valueIndex == deltaHourIndex)) {
            deltaNegative = false;
        } else if ((c == 'Z') && (++valueIndex == deltaHourIndex)) {
            valueIndex += 2;
        } else if (c == '\0') {
            break;
        } else {
            throw ConversionException(argsToString("unexpected \"", c, '\"'));
        }
    }
    auto delta(TimeSpan::fromMinutes(*deltaHourIndex * 60 + values[8]));
    if (deltaNegative) {
        delta = TimeSpan(-delta.totalTicks());
    }
    return make_pair(DateTime::fromDateAndTime(values[0], values[1], *dayIndex, *hourIndex, values[4], *secondsIndex, miliSeconds), delta);
}

/*!
 * \brief Returns the string representation of the current instance using the specified \a format.
 * \remarks If \a noMilliseconds is true the date will be rounded to full seconds.
 * \sa toIsoString() for ISO format
 */
string DateTime::toString(DateTimeOutputFormat format, bool noMilliseconds) const
{
    string result;
    toString(result, format, noMilliseconds);
    return result;
}

/*!
 * \brief Returns the string representation of the current instance using the specified \a format.
 * \remarks If \a noMilliseconds is true the date will be rounded to full seconds.
 * \sa toIsoString() for ISO format
 */
void DateTime::toString(string &result, DateTimeOutputFormat format, bool noMilliseconds) const
{
    stringstream s(stringstream::in | stringstream::out);
    s << setfill('0');
    if (format == DateTimeOutputFormat::DateTimeAndWeekday || format == DateTimeOutputFormat::DateTimeAndShortWeekday)
        s << printDayOfWeek(dayOfWeek(), format == DateTimeOutputFormat::DateTimeAndShortWeekday) << ' ';
    if (format == DateTimeOutputFormat::DateOnly || format == DateTimeOutputFormat::DateAndTime || format == DateTimeOutputFormat::DateTimeAndWeekday
        || format == DateTimeOutputFormat::DateTimeAndShortWeekday)
        s << setw(4) << year() << '-' << setw(2) << month() << '-' << setw(2) << day();
    if (format == DateTimeOutputFormat::DateAndTime || format == DateTimeOutputFormat::DateTimeAndWeekday
        || format == DateTimeOutputFormat::DateTimeAndShortWeekday)
        s << " ";
    if (format == DateTimeOutputFormat::TimeOnly || format == DateTimeOutputFormat::DateAndTime || format == DateTimeOutputFormat::DateTimeAndWeekday
        || format == DateTimeOutputFormat::DateTimeAndShortWeekday) {
        s << setw(2) << hour() << ':' << setw(2) << minute() << ':' << setw(2) << second();
        int ms = millisecond();
        if (!noMilliseconds && ms > 0) {
            s << '.' << setw(3) << ms;
        }
    }
    result = s.str();
}

/*!
 * \brief Returns the string representation of the current instance in the ISO format,
 *        eg. 2016-08-29T21:32:31.588539814+02:00.
 */
string DateTime::toIsoString(TimeSpan timeZoneDelta) const
{
    stringstream s(stringstream::in | stringstream::out);
    s << setfill('0');
    s << setw(4) << year() << '-' << setw(2) << month() << '-' << setw(2) << day() << 'T' << setw(2) << hour() << ':' << setw(2) << minute() << ':'
      << setw(2) << second();
    const int milli(millisecond());
    const int micro(microsecond());
    const int nano(nanosecond());
    if (milli || micro || nano) {
        s << '.' << setw(3) << milli;
        if (micro || nano) {
            s << setw(3) << micro;
            if (nano) {
                s << nano / TimeSpan::nanosecondsPerTick;
            }
        }
    }
    if (!timeZoneDelta.isNull()) {
        if (timeZoneDelta.isNegative()) {
            s << '-';
            timeZoneDelta = TimeSpan(-timeZoneDelta.totalTicks());
        } else {
            s << '+';
        }
        s << setw(2) << timeZoneDelta.hours() << ':' << setw(2) << timeZoneDelta.minutes();
    }
    return s.str();
}

/*!
 * \brief Returns the string representation as C-style string for the given day of week.
 *
 * If \a abbreviation is true, only the first three letters of the string will
 * be returned.
 * \sa DayOfWeek
 */
const char *DateTime::printDayOfWeek(DayOfWeek dayOfWeek, bool abbreviation)
{
    if (abbreviation) {
        switch (dayOfWeek) {
        case DayOfWeek::Monday:
            return "Mon";
        case DayOfWeek::Tuesday:
            return "Tue";
        case DayOfWeek::Wednesday:
            return "Wed";
        case DayOfWeek::Thursday:
            return "Thu";
        case DayOfWeek::Friday:
            return "Fri";
        case DayOfWeek::Saturday:
            return "Sat";
        case DayOfWeek::Sunday:
            return "Sun";
        }
    } else {
        switch (dayOfWeek) {
        case DayOfWeek::Monday:
            return "Monday";
        case DayOfWeek::Tuesday:
            return "Tuesday";
        case DayOfWeek::Wednesday:
            return "Wednesday";
        case DayOfWeek::Thursday:
            return "Thursday";
        case DayOfWeek::Friday:
            return "Friday";
        case DayOfWeek::Saturday:
            return "Saturday";
        case DayOfWeek::Sunday:
            return "Sunday";
        }
    }
    return "";
}

#if defined(PLATFORM_UNIX) && !defined(PLATFORM_MAC)
/*!
 * \brief Returns a DateTime object that is set to the current date and time on this computer, expressed as the GMT time.
 * \remarks Only available under UNIX-like systems supporting clock_gettime().
 */
DateTime DateTime::exactGmtNow()
{
    struct timespec t;
    clock_gettime(CLOCK_REALTIME, &t);
    return DateTime(
        DateTime::unixEpochStart().totalTicks() + static_cast<uint64>(t.tv_sec) * TimeSpan::m_ticksPerSecond + static_cast<uint64>(t.tv_nsec) / 100);
}
#endif

/*!
 * \brief Converts the given date expressed in \a year, \a month and \a day to ticks.
 */
uint64 DateTime::dateToTicks(int year, int month, int day)
{
    if (!inRangeInclMax(year, 1, 9999)) {
        throw ConversionException("year is out of range");
    }
    if (!inRangeInclMax(month, 1, 12)) {
        throw ConversionException("month is out of range");
    }
    const auto *const daysToMonth = reinterpret_cast<const int *>(isLeapYear(year) ? m_daysToMonth366 : m_daysToMonth365);
    const int passedMonth = month - 1;
    if (!inRangeInclMax(day, 1, daysToMonth[month] - daysToMonth[passedMonth])) {
        throw ConversionException("day is out of range");
    }
    const auto passedYears = static_cast<unsigned int>(year - 1);
    const auto passedDays = static_cast<unsigned int>(day - 1);
    return (passedYears * m_daysPerYear + passedYears / 4 - passedYears / 100 + passedYears / 400
               + static_cast<unsigned int>(daysToMonth[passedMonth]) + passedDays)
        * TimeSpan::m_ticksPerDay;
}

/*!
 * \brief Converts the given time expressed in \a hour, \a minute, \a second and \a millisecond to ticks.
 */
uint64 DateTime::timeToTicks(int hour, int minute, int second, double millisecond)
{
    if (!inRangeExclMax(hour, 0, 24)) {
        throw ConversionException("hour is out of range");
    }
    if (!inRangeExclMax(minute, 0, 60)) {
        throw ConversionException("minute is out of range");
    }
    if (!inRangeExclMax(second, 0, 60)) {
        throw ConversionException("second is out of range");
    }
    if (!inRangeExclMax(millisecond, 0.0, 1000.0)) {
        throw ConversionException("millisecond is out of range");
    }
    return static_cast<uint64>(hour * TimeSpan::m_ticksPerHour) + static_cast<uint64>(minute * TimeSpan::m_ticksPerMinute)
        + static_cast<uint64>(second * TimeSpan::m_ticksPerSecond) + static_cast<uint64>(millisecond * TimeSpan::m_ticksPerMillisecond);
}

/*!
 * \brief Returns the specified date part.
 * \sa DatePart
 */
int DateTime::getDatePart(DatePart part) const
{
    const int fullDays = m_ticks / TimeSpan::m_ticksPerDay;
    const int full400YearBlocks = fullDays / m_daysPer400Years;
    const int daysMinusFull400YearBlocks = fullDays - full400YearBlocks * m_daysPer400Years;
    int full100YearBlocks = daysMinusFull400YearBlocks / m_daysPer100Years;
    if (full100YearBlocks == 4) {
        full100YearBlocks = 3;
    }
    const int daysMinusFull100YearBlocks = daysMinusFull400YearBlocks - full100YearBlocks * m_daysPer100Years;
    const int full4YearBlocks = daysMinusFull100YearBlocks / m_daysPer4Years;
    const int daysMinusFull4YearBlocks = daysMinusFull100YearBlocks - full4YearBlocks * m_daysPer4Years;
    int full1YearBlocks = daysMinusFull4YearBlocks / m_daysPerYear;
    if (full1YearBlocks == 4) {
        full1YearBlocks = 3;
    }
    if (part == DatePart::Year) {
        return full400YearBlocks * 400 + full100YearBlocks * 100 + full4YearBlocks * 4 + full1YearBlocks + 1;
    }
    const int restDays = daysMinusFull4YearBlocks - full1YearBlocks * m_daysPerYear;
    if (part == DatePart::DayOfYear) { // day
        return restDays + 1;
    }
    const int *const daysToMonth = (full1YearBlocks == 3 && (full4YearBlocks != 24 || full100YearBlocks == 3)) ? m_daysToMonth366 : m_daysToMonth365;
    int month = 1;
    while (restDays >= daysToMonth[month]) {
        ++month;
    }
    if (part == DatePart::Month) {
        return month;
    } else if (part == DatePart::Day) {
        return restDays - daysToMonth[month - 1] + 1;
    }
    return 0;
}