/*  Copyright (C) 2017 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>

    This program 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.

    This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#include <assert.h>
#include <time.h>

#include "knot/conf/conf.h"
#include "knot/zone/serial.h"

static const serial_cmp_result_t diffbrief2result[4] = {
	[0] = SERIAL_EQUAL,
	[1] = SERIAL_GREATER,
	[2] = SERIAL_INCOMPARABLE,
	[3] = SERIAL_LOWER,
};

serial_cmp_result_t serial_compare(uint32_t s1, uint32_t s2)
{
	uint64_t diff = ((uint64_t)s1 + ((uint64_t)1 << 32) - s2) & 0xffffffff;
	int diffbrief = (diff >> 31 << 1) | ((diff & 0x7fffffff) ? 1 : 0);
	assert(diffbrief > -1 && diffbrief < 4);
	return diffbrief2result[diffbrief];
}

static uint32_t serial_next_date(uint32_t current)
{
	uint32_t next = current + 1;

	struct tm now;
	time_t current_time = time(NULL);
	struct tm *gmtime_result = gmtime_r(&current_time, &now);
	if (gmtime_result == NULL) {
		return next;
	}

	uint32_t yyyyMMdd00 = (1900 + now.tm_year) * 1000000 +
	                      (   1 + now.tm_mon ) *   10000 +
	                      (       now.tm_mday) *     100;

	if (next < yyyyMMdd00) {
		next = yyyyMMdd00;
	}

	return next;
}

uint32_t serial_next(uint32_t current, int policy)
{
	switch (policy) {
	case SERIAL_POLICY_INCREMENT:
		return current + 1;
	case SERIAL_POLICY_UNIXTIME:
		return time(NULL);
	case SERIAL_POLICY_DATESERIAL:
		return serial_next_date(current);
	default:
		assert(0);
		return 0;
	}
}

serial_cmp_result_t kserial_cmp(kserial_t a, kserial_t b)
{
	return ((a.valid && b.valid) ? serial_compare(a.serial, b.serial) : SERIAL_INCOMPARABLE);
}