/*** dt-core-tz-glue.c -- gluing date/times and tzs
 *
 * Copyright (C) 2012-2024 Sebastian Freundt
 *
 * Author:  Sebastian Freundt <freundt@ga-group.nl>
 *
 * This file is part of dateutils.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * 3. Neither the name of the author nor the names of any contributors
 *    may be used to endorse or promote products derived from this
 *    software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR "AS IS" AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
 * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
 * IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 **/
/* dt-core-tz-glue.h implementation */
#if !defined INCLUDED_dt_core_tz_glue_c_
#define INCLUDED_dt_core_tz_glue_c_

#if defined HAVE_CONFIG_H
# include "config.h"
#endif	/* HAVE_CONFIG_H */
#include "nifty.h"
#include "dt-core-tz-glue.h"

#if !defined DEFUN
# define DEFUN
#endif	/* !DEFUN */


/**
 * Return a dt object that forgot about DT's zone and uses ZONE instead. */
DEFUN struct dt_dt_s
dtz_forgetz(struct dt_dt_s d, zif_t zone)
{
	dt_ssexy_t d_unix;
	dt_ssexy_t d_locl;
	int32_t zdiff;

	if (dt_unk_p(d) || dt_sandwich_only_d_p(d)) {
		/* we need date/times to do the conversion */
		return d;
	} else if (d.znfxd) {
		/* already forgotten about */
		return d;
	} else if (zone == NULL) {
		/* convert from UTC, great idea */
		return d;
	}

	/* convert date/time part to unix stamp */
	d_locl = dt_to_unix_epoch(d);
	d_unix = zif_utc_time(zone, d_locl);
	if (LIKELY((zdiff = d_unix - d_locl))) {
		/* let dt_dtadd() do the magic */
#if defined HAVE_ANON_STRUCTS_INIT
		d = dt_dtadd(d, (struct dt_dtdur_s){DT_DURS, .dv = zdiff});
#else
		{
			struct dt_dtdur_s tmp = {DT_DURS};
			tmp.dv = zdiff;
			d = dt_dtadd(d, tmp);
		}
#endif
		d.znfxd = 1;
		if (zdiff > 0) {
			d.neg = 1;
			d.zdiff = (uint16_t)(zdiff / ZDIFF_RES);
		} else if (zdiff < 0) {
			d.zdiff = (uint16_t)(-zdiff / ZDIFF_RES);
		}
	}
	return d;
}

/**
 * Return a dt object from a UTC'd DT that uses ZONE. */
DEFUN struct dt_dt_s
dtz_enrichz(struct dt_dt_s d, zif_t zone)
{
	dt_ssexy_t d_unix;
	dt_ssexy_t d_locl;
	int32_t zdiff;

	if (dt_sandwich_only_d_p(d)) {
		/* nah, we need a date/time for this */
		return d;
	} else if (zone == NULL) {
		/* UTC -> UTC? */
		return d;
	}

	/* convert date/time part to unix stamp */
	d_unix = dt_to_unix_epoch(d);
	d_locl = zif_local_time(zone, d_unix);
	if (LIKELY((zdiff = d_locl - d_unix))) {
		/* let dt_dtadd() do the magic */
#if defined HAVE_ANON_STRUCTS_INIT
		d = dt_dtadd(d, (struct dt_dtdur_s){DT_DURS, .dv = zdiff});
#else
		{
			struct dt_dtdur_s tmp = {DT_DURS};
			tmp.dv = zdiff;
			d = dt_dtadd(d, tmp);
		}
#endif
		if (zdiff > 0) {
			d.zdiff = (uint16_t)(zdiff / ZDIFF_RES);
		} else if (zdiff < 0) {
			d.neg = 1;
			d.zdiff = (uint16_t)(-zdiff / ZDIFF_RES);
		}
	} else {
		/* no difference to UTC means the offset is +00:00 */
		d.zdiff = 0U;
		d.neg = 0U;
	}
	return d;
}

#endif	/* INCLUDED_dt_core_tz_glue_c_ */
/* dt-core-tz-glue.c ends here */