#include <time.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#include <platon/misc/week.h>

#ifdef DOS
long timezone = -1*60*60;
#endif

/* Returns non-zero if it failed, zero if OK. */
int week(int year, int month, int day, int *aweek, int *weekday)
{
	struct tm timeCheck;
	time_t timeNowInSeconds;
	struct tm *timeNow;
	int yearNow;
	int WeekDay_I;
	int WeekNo_I;
	int FirstWeek_I;
	int YearDay_I;

	memset(&timeCheck, 0, sizeof(struct tm));

	timeCheck.tm_year=year;
	timeCheck.tm_mon=month;
	timeCheck.tm_mday=day;

	timeNowInSeconds = mktime(&timeCheck);

	timeNow = localtime(&timeNowInSeconds);

	if(timeNow->tm_mon != month) {
		return 1; /* this is no longer the same month! */
	}

	yearNow = timeNow->tm_year;
	/* struct tm stores yday 0 based, we need it 1 based */
	YearDay_I = timeNow->tm_yday + 1;

	/* silly americans begin the week on sundays. ISO doesn't */
	WeekDay_I = timeNow->tm_wday;
	if ( 0 == WeekDay_I )               /* if it's sunday, */
		WeekDay_I = 7;                  /* make it sunday! */

	WeekNo_I    = YearDay_I / 7;
	FirstWeek_I = YearDay_I % 7;

	FirstWeek_I -= WeekDay_I;
	if ( ( FirstWeek_I <= 0 ) && ( WeekNo_I > 0 ) ) {
		/* break up one week and add the days to FirstWeek_I */
		WeekNo_I--;
		FirstWeek_I += 7;
	}

	if ( FirstWeek_I > (-4) )
		WeekNo_I += 1;

	if ( FirstWeek_I > 3 )
		WeekNo_I += 1;

	if(0 == WeekNo_I) {
		/* same as previous year's last day: */
		int fool;

		week(year - 1, 11 /* December is 11 */, 31, &WeekNo_I, &fool);
	}
	else if(WeekNo_I > 52) {
		/* the last days of the year */
		if(WeekDay_I < 4 &&
				day > 28) {
			/* Three or less days of this year in 53 makes it week 1 instead! */
			WeekNo_I = 1;
		}
	}

	*aweek = WeekNo_I;
	*weekday = WeekDay_I;

	return 0;
}

/*
 * Mission: we have year and week number. What date does that week
 * start with? (i.e what's the date monday that week)
 */
int week_no(int year, int aweek, int *ret_month, int *ret_day)
{
	int month;
	int day=15;

	int getweek;
	int getday;

	while (aweek > 53)
		aweek -= 53;

	month = 11 * aweek / 53; /* assume 53 weeks a year */

	do {
		if (week(year, month, day, &getweek, &getday)) {
			month++;
			day=1;
			continue;
		}
#if 0
		printf("Year %d Month %d Day %d Week %d WDay %d\n",
				year, month+1, day, getweek, getday);
#endif

		if ((getweek>aweek-3) && (getweek<aweek+3)) {
			if ((getweek == aweek) && (getday == 1)) {
				break;
			}
			else if(getweek<aweek) {
				if(aweek-getweek>1)
					day+=7;
				else
					day+=(8-getday);
			}
			else {
				if(getweek-aweek>1)
					day-=7;
				else if(getweek==aweek) {
					day-=getday-1;
				}
				else
					day-=getday+6;
				if(day<=0) {
					day=28;
					month--;
				}
			}
		}
		else {
			if(++month>11) {
				day=0;
				month=0;
				break;
			}
		}
	} while(1);

	*ret_day=day;
	*ret_month=month+1;
	return 0;
}

#if defined(SELF) || defined(SELFTEST) || defined(SELF_WEEK)

int main(int argc, char **argv)
{
	int WeekNo_I, WeekDay_I;

	if (argc < 4) {
		puts("Enter [YYYY] [MM] [DD]");
		return 1;
	}

	if (! strcasecmp(argv[1], "week")) {
		week_no(atoi(argv[2])-1900, atoi(argv[3]),
				&WeekNo_I, &WeekDay_I);
		if(WeekDay_I>0) {
			printf("Month %02d Day %02d\n", WeekNo_I, WeekDay_I);
		}
		else {
			printf("No monday in such a week that year!\n");
		}
	}
	else {
		if (! week(atoi(argv[1])-1900, atoi(argv[2])-1, atoi(argv[3]),
					&WeekNo_I, &WeekDay_I)) {
			printf("Week %d Weekday %d\n", WeekNo_I, WeekDay_I);
		}
		else
			printf("Illegal date!\n");
	}

	return 0;
}

#endif