#include "entry.h"

#include <assert.h>

static int sub_inc_year(struct tm *t, int n)
{
	if (n == 0)
		return 0;

	t->tm_year += n;

	if (mktime(t) == -1)
		return -1;

	return 0;
}

static int sub_inc_month(struct tm *t, int n)
{
	unsigned i;

	if (n == 0)
		return 0;

	for (i = 0; i < n; i++) {
		t->tm_mon++;
		if (mktime(t) == -1) {
			t->tm_mon = 0;
			if (sub_inc_year(t, 1) == -1)
				return -1;
		}
	}

	return 0;
}

static int sub_inc_day(struct tm *t, int n)
{
	unsigned i;

	if (n == 0)
		return 0;

	for (i = 0; i < n; i++) {
		t->tm_mday++;
		if (mktime(t) == -1) {
			t->tm_mday = 1;
			if (sub_inc_month(t, 1) == -1)
				return -1;
		}
	}

	return 0;
}

static int sub_inc_hour(struct tm *t, int n)
{
	unsigned i;

	if (n == 0)
		return 0;

	for (i = 0; i < n; i++) {
		t->tm_hour++;
		if (mktime(t) == -1) {
			t->tm_hour = 0;
			if (sub_inc_day(t, 1) == -1)
				return -1;
		}
	}

	return 0;
}

static int sub_inc_minute(struct tm *t, int n)
{
	unsigned i;

	if (n == 0)
		return 0;

	for (i = 0; i < n; i++) {
		t->tm_min++;
		if (mktime(t) == -1) {
			t->tm_min = 0;
			if (sub_inc_hour(t, 1) == -1)
				return -1;
		}
	}

	return 0;
}

static int sub_inc_second(struct tm *t, int n)
{
	time_t rt;
	struct tm *tmp;

	if (n == 0)
		return 0;

	rt = mktime(t);

	if (rt + n <= rt)
		return -1;
	rt += n;

	tmp = localtime(&rt);
	*t = *tmp;

	return 0;
}

/* super inefficient, but should best-possible avoid any weird leap
 * years/seconds/dst-problems/other future changes */
bool entry_is_active(struct entry_s *e, time_t now)
{
	struct tm t, *tmp;
	time_t rt, now_plus_warn;
	
	assert(e != NULL);

	tmp = localtime(&now);
	assert(tmp != NULL);
	t = *tmp;

	if (sub_inc_year(&t, e->warn.year))
		return false;
	if (sub_inc_month(&t, e->warn.month))
		return false;
	if (sub_inc_day(&t, e->warn.day))
		return false;
	if (sub_inc_hour(&t, e->warn.hour))
		return false;
	if (sub_inc_minute(&t, e->warn.minute))
		return false;
	if (sub_inc_second(&t, e->warn.second))
		return false;

	now_plus_warn = mktime(&t);

	if (e->type == ENTRY_TYPE_ON) {
		if (e->start >= now && e->start <= now_plus_warn)
			return true;

		return false;
	}

	tmp = localtime(&(e->start));
	assert(tmp != NULL);
	t = *tmp;

	if (e->has_end && now > e->end)
		return false;

	for (rt = e->start;;) {
		rt = mktime(&t);

		if (rt > now_plus_warn)
			return false;

		if (rt >= now)
			return true;

		if (sub_inc_year(&t, e->every.year))
			return false;
		if (sub_inc_month(&t, e->every.month))
			return false;
		if (sub_inc_day(&t, e->every.day))
			return false;
		if (sub_inc_hour(&t, e->every.hour))
			return false;
		if (sub_inc_minute(&t, e->every.minute))
			return false;
		if (sub_inc_second(&t, e->every.second))
			return false;
	}
}