libepoch/datetime.c

/*                 _,.---._    .-._        .--.-. ,--.--------.
 *   _,..---._   ,-.' , -  `. /==/ \  .-._/==/  //==/,  -   , -\
 * /==/,   -  \ /==/_,  ,  - \|==|, \/ /, |==\ -\\==\.-.  - ,-./
 * |==|   _   _\==|   .=.     |==|-  \|  | \==\- \`--`\==\- \
 * |==|  .=.   |==|_ : ;=:  - |==| ,  | -|  `--`-'     \==\_ \
 * |==|,|   | -|==| , '='     |==| -   _ |             |==|- |
 * |==|  '='   /\==\ -    ,_ /|==|  /\ , |             |==|, |
 * |==|-,   _`/  '.='. -   .' /==/, | |- |             /==/ -/
 * `-.`.____.'     `--`--''   `--`./  `--`             `--`--`
 *                    _ __    ,---.      .-._         .=-.-.  _,.----.
 *                 .-`.' ,`..--.'  \    /==/ \  .-._ /==/_ /.' .' -   \
 *                /==/, -   \==\-/\ \   |==|, \/ /, /==|, |/==/  ,  ,-'
 *               |==| _ .=. /==/-|_\ |  |==|-  \|  ||==|  ||==|-   |  .
 *               |==| , '=',\==\,   - \ |==| ,  | -||==|- ||==|_   `-' \
 *               |==|-  '..'/==/ -   ,| |==| -   _ ||==| ,||==|   _  , |
 *               |==|,  |  /==/-  /\ - \|==|  /\ , ||==|- |\==\.       /
 *               /==/ - |  \==\ _.\=\.-'/==/, | |- |/==/. / `-.`.___.-'
 *               `--`---'   `--`        `--`./  `--``--`-`
 *
 *	@(#)Copyright (c) 2024, Nathan D. Fisher.
 *
 *      This is free software.  It comes with NO WARRANTY.
 *      Permission to use, modify and distribute this source code
 *      is granted subject to the following conditions.
 *      1/ that the above copyright notice and this notice
 *      are preserved in all copies and that due credit be given
 *      to the author.
 *      2/ that any changes to this code are clearly commented
 *      as such so that the author does not get blamed for bugs
 *      other than his own.
 */

#include "epoch.h"
#include <stdint.h>
#include <time.h>

int32_t dateTimeGetYear(DateTime *self) {
    return self->year.year;
}

int64_t dateTimeGetTimestampNaive(DateTime *self) {
    int64_t seconds = 0;
    Year    year    = (Year){ .tag = normalYear, .year = 1970 };
    Month   month   = January;
    int32_t oldyear = yearGetInner(&self->year);

    if (oldyear < 1970) {
        while (yearGetInner(&year) > oldyear) {
            yearDecrement(&year);
            seconds -= yearGetSeconds(&year);
        }
    } else if (oldyear > 1970) {
        while (yearGetInner(&year) < oldyear) {
            seconds += yearGetSeconds(&year);
            yearIncrement(&year);
        }
    }
    while (month < self->month) {
        seconds += monthGetSeconds(month, &self->year);
        monthIncrement(&month);
    }
    seconds += ((int64_t)self->day - 1) * SECONDS_PER_DAY;
    seconds += (int64_t)self->hour * SECONDS_PER_HOUR;
    seconds += (int64_t)self->minute * 60;
    seconds += (int64_t)self->second;
    return seconds;
}

int64_t dateTimeGetTimestamp(DateTime *self) {
    int64_t seconds = dateTimeGetTimestampNaive(self);
    seconds += timezoneAsSeconds(&self->zone);
    return seconds;
}

void dateTimeGetTimespec(DateTime *self, struct timespec * ts) {
    ts->tv_nsec = self->nanoseconds;
    ts->tv_sec  = (time_t)dateTimeGetTimestamp(self);
}

Weekday dateTimeGetWeekday(DateTime *self) {
    int64_t ts = dateTimeGetTimestampNaive(self);
    ts /= SECONDS_PER_DAY;
    return ts % 7;
}

void dateTimeFromTimestampParts(DateTime *self, int64_t seconds, int64_t nanoseconds) {
    int     ret = 0;
    
    self->nanoseconds = nanoseconds;
    self->zone.tag = UTC;
    if (seconds < 0) {
        yearNew(&self->year, 1969);
        while (seconds < yearGetSeconds(&self->year)) {
            seconds += yearGetSeconds(&self->year);
            yearDecrement(&self->year);
        }
        self->month = December;
        while (ret == 0) {
            if (-seconds < monthGetSeconds(self->month, &self->year)) break;
            seconds += monthGetSeconds(self->month, &self->year);
            ret = monthDecrement(&self->month);
        }
        ret = 0;
        self->day = monthGetDays(self->month, &self->year);
        while (self->day > 0 && seconds < -SECONDS_PER_DAY) {
            seconds += SECONDS_PER_DAY;
            self->day -=1;
        }
        self->hour = 23;
        while (self->hour > 0 && seconds < -SECONDS_PER_HOUR) {
            seconds += SECONDS_PER_HOUR;
            self->hour -= 1;
        }
        self->minute = 59;
        while (self->minute > 0 && seconds < -60) {
            seconds += 60;
            self->minute -= 1;
        }
        self->second = seconds + 60;
    } else if (seconds > 0) {
        yearNew(&self->year, 1970);
        while (yearGetSeconds(&self->year) < seconds) {
            seconds -= yearGetSeconds(&self->year);
            yearIncrement(&self->year);
        }
        self->month = January;
        while (ret == 0 && monthGetSeconds(self->month, &self->year) < seconds) {
            seconds -= (int64_t)monthGetSeconds(self->month, &self->year);
            ret = monthIncrement(&self->month);
        }
        self->day = seconds / SECONDS_PER_DAY + 1;
        seconds %= SECONDS_PER_DAY;
        self->hour = seconds / SECONDS_PER_HOUR;
        seconds %= SECONDS_PER_HOUR;
        self->minute = seconds / 60;
        seconds %= 60;
        self->second = seconds;
    } else {
        yearNew(&self->year, 1970);
        self->month = January;
        self->day = 1;
        self->hour = 0;
        self->minute = 0;
        self->second = 0;
    }
}

void dateTimeFromTimespec(DateTime *self, struct timespec *ts) {
    dateTimeFromTimestampParts(self, ts->tv_sec, ts->tv_nsec);
}