/*
 * Copyright (C) 2021  P. J. McDermott
 *
 * This file is part of @
 *
 * @ is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * @ is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with @.  If not, see <http://www.gnu.org/licenses/>.
 */

#define _XOPEN_SOURCE

#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include "datetime.h"

static const char *DATETIME_FMTS_[] = {
#include "datetime-formats.c"
	NULL
};

int
datetime_parse(const char *input, time_t *arg_sec)
{
	int        i;
	char      *end;
	struct tm  arg_tm;
	time_t     now_sec;
	struct tm *now_tm;

	arg_tm.tm_mday = INT_MIN;  /* Sentinel */
	arg_tm.tm_sec  = 0;        /* Default */
	arg_tm.tm_isdst = -1;

	for (i = 0; DATETIME_FMTS_[i] != NULL; ++i) {
		end = strptime(input, DATETIME_FMTS_[i], &arg_tm);
		if (end != NULL && *end == '\0') {
			goto found;
		}
	}

	fprintf(stderr, "Unknown date format\n");
	return -1;

 found:
	/* TODO: Support %a-only dates and optional years */
	if (arg_tm.tm_mday == INT_MIN) {
		/* No date specified; try today. */
		now_sec = time(NULL);
		now_tm = localtime(&now_sec);
		arg_tm.tm_year = now_tm->tm_year;
		arg_tm.tm_mon  = now_tm->tm_mon;
		arg_tm.tm_mday = now_tm->tm_mday;
		*arg_sec = mktime(&arg_tm);
		if (*arg_sec <= mktime(now_tm)) {
			/* Specified time already happened today; use tomorrow.
			 * Adding the number of seconds in a day is a shortcut
			 * that ignores leap seconds.  One better method would
			 * be to increment tm_mday % days in tm_mon, etc. */
			*arg_sec += 60 * 60 * 24;
			now_tm = localtime(arg_sec);
			arg_tm.tm_year = now_tm->tm_year;
			arg_tm.tm_mon  = now_tm->tm_mon;
			arg_tm.tm_mday = now_tm->tm_mday;
			*arg_sec = mktime(&arg_tm);
		}
	} else {
		*arg_sec = mktime(&arg_tm);
	}

	return 0;
}