/* The following methods were adapted from musl.
 * See musl/COPYRIGHT for license information. */

#include <errno.h>

#include "../musl/time/time_impl.h"


static long  __timezone = 0;
static int dst_off = 0;
const char __utc[] = "UTC";
static const char *__tzname[2] = { __utc, __utc };


static void
__secs_to_zone(long long t, int local, int *isdst, int *offset, long *oppoff, const char **zonename)
{
        *isdst = 0;
        *offset = -__timezone;
        if (oppoff) *oppoff = -dst_off;
        *zonename = __tzname[0];
}


struct tm *
__gmtime_r_fallback(const time_t *restrict t, struct tm *restrict tm)
{
        if (__secs_to_tm(*t, tm) < 0) {
                errno = EOVERFLOW;
                return 0;
        }
        tm->tm_isdst = 0;
        tm->__tm_gmtoff = 0;
        tm->__tm_zone = __utc;
        return tm;
}


time_t
__mktime_fallback(struct tm *tm)
{
        struct tm new;
        long opp;
        long long t = __tm_to_secs(tm);

        __secs_to_zone(t, 1, &new.tm_isdst, &new.__tm_gmtoff, &opp, &new.__tm_zone);

        if (tm->tm_isdst>=0 && new.tm_isdst!=tm->tm_isdst)
                t -= opp - new.__tm_gmtoff;

        t -= new.__tm_gmtoff;
        if ((time_t)t != t) goto error;

        __secs_to_zone(t, 0, &new.tm_isdst, &new.__tm_gmtoff, &opp, &new.__tm_zone);

        if (__secs_to_tm(t + new.__tm_gmtoff, &new) < 0) goto error;

        *tm = new;
        return t;

error:
        errno = EOVERFLOW;
        return -1;
}


time_t
__timegm_fallback(struct tm *tm)
{
        struct tm new;
        long long t = __tm_to_secs(tm);
        if (__secs_to_tm(t, &new) < 0) {
                errno = EOVERFLOW;
                return -1;
        }
        *tm = new;
        tm->tm_isdst = 0;
        tm->__tm_gmtoff = 0;
        tm->__tm_zone = __utc;
        return t;
}