//
// VMime library (http://www.vmime.org)
// Copyright (C) 2002 Vincent Richard <vincent@vmime.org>
//
// 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, write to the Free Software Foundation, Inc.,
// 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
//
// Linking this library statically or dynamically with other modules is making
// a combined work based on this library.  Thus, the terms and conditions of
// the GNU General Public License cover the whole combination.
//

#include "vmime/utility/datetimeUtils.hpp"

#include <stdexcept>


namespace vmime {
namespace utility {


#ifndef VMIME_BUILDING_DOC

static inline void nextMonth(datetime& d) {

	if (d.getMonth() >= 12) {
		d.setMonth(1);
		d.setYear(d.getYear() + 1);
	} else {
		d.setMonth(d.getMonth() + 1);
	}
}


static inline void prevMonth(datetime& d) {

	if (d.getMonth() <= 1) {
		d.setYear(d.getYear() - 1);
		d.setMonth(12);
	} else {
		d.setMonth(d.getMonth() - 1);
	}
}


static inline void nextDay(datetime& d) {

	if (d.getDay() >= datetimeUtils::getDaysInMonth(d.getYear(), d.getMonth())) {
		d.setDay(1);
		nextMonth(d);
	} else {
		d.setDay(d.getDay() + 1);
	}
}


static inline void prevDay(datetime& d) {

	if (d.getDay() <= 1) {
		prevMonth(d);
		d.setDay(datetimeUtils::getDaysInMonth(d.getYear(), d.getMonth()));
	} else {
		d.setDay(d.getDay() - 1);
	}
}


static inline void nextHour(datetime& d) {

	if (d.getHour() >= 23) {
		d.setHour(0);
		nextDay(d);
	} else {
		d.setHour(d.getHour() + 1);
	}
}


static inline void prevHour(datetime& d) {

	if (d.getHour() <= 0) {
		d.setHour(23);
		prevDay(d);
	} else {
		d.setHour(d.getHour() - 1);
	}
}


static inline void addHoursAndMinutes(datetime& d, const int h, const int m) {

	d.setMinute(d.getMinute() + m);

	if (d.getMinute() >= 60) {
		d.setMinute(d.getMinute() - 60);
		nextHour(d);
	}

	d.setHour(d.getHour() + h);

	if (d.getHour() >= 24) {
		d.setHour(d.getHour() - 24);
		nextDay(d);
	}
}


static inline void substractHoursAndMinutes(datetime& d, const int h, const int m) {

	if (m > d.getMinute()) {
		d.setMinute(60 - (m - d.getMinute()));
		prevHour(d);
	} else {
		d.setMinute(d.getMinute() - m);
	}

	if (h > d.getHour()) {
		d.setHour(24 - (h - d.getHour()));
		prevDay(d);
	} else {
		d.setHour(d.getHour() - h);
	}
}

#endif // VMIME_BUILDING_DOC


const datetime datetimeUtils::toUniversalTime(const datetime& date) {

	if (date.getZone() == datetime::GMT) {
		return date; // no conversion needed
	}

	datetime nd(date);
	nd.setZone(datetime::GMT);

	const int z = date.getZone();
	const int h = (z < 0) ? (-z / 60) : (z / 60);
	const int m = (z < 0) ? (-z - h * 60) : (z - h * 60);

	if (z < 0) {  // GMT-hhmm: add hours and minutes to date
		addHoursAndMinutes(nd, h, m);
	} else {      // GMT+hhmm: substract hours and minutes from date
		substractHoursAndMinutes(nd, h, m);
	}

	return nd;
}


const datetime datetimeUtils::toLocalTime(const datetime& date, const int zone) {

	datetime utcDate(date);

	if (utcDate.getZone() != datetime::GMT) {
		utcDate = toUniversalTime(date); // convert to UT before
	}

	datetime nd(utcDate);
	nd.setZone(zone);

	const int h = (zone < 0) ? (-zone / 60) : (zone / 60);
	const int m = (zone < 0) ? (-zone - h * 60) : (zone - h * 60);

	if (zone < 0) {  // GMT+hhmm: substract hours and minutes from date
		substractHoursAndMinutes(nd, h, m);
	} else {         // GMT-hhmm: add hours and minutes to date
		addHoursAndMinutes(nd, h, m);
	}

	return nd;
}


bool datetimeUtils::isLeapYear(const int year) {

	// From RFC 3339 - Appendix C. Leap Years:
	return ((year % 4) == 0 && (year % 100 != 0 || year % 400 == 0));
}


int datetimeUtils::getDaysInMonth(const int year, const int month) {

	static const int daysInMonth[12] = {
		31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
	};
	static const int daysInMonthLeapYear[12] = {
		31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
	};

	if (month < 1 || month > 12) {
		throw std::out_of_range("Invalid month number");
	}

	return isLeapYear(year) ? daysInMonthLeapYear[month - 1] : daysInMonth[month - 1];
}


int datetimeUtils::getDayOfWeek(const int year, const int month, const int day) {

	int y = year;
	int m = month;

	if (month < 1 || month > 12) {
		throw std::out_of_range("Invalid month number");
	} else if (day < 1 || day > getDaysInMonth(year, month)) {
		throw std::out_of_range("Invalid day number");
	}

	// From RFC-3339 - Appendix B. Day of the Week

	// Adjust months so February is the last one
	m -= 2;

	if (m < 1) {
		m += 12;
		--y;
	}

	// Split by century
	const int cent = y / 100;
	y %= 100;

	return ((26 * m - 2) / 10 + day + y + (y >> 2) + (cent >> 2) + 5 * cent) % 7;
}


int datetimeUtils::getWeekOfYear(const int year, const int month, const int day, const bool iso) {

	// Algorithm from http://personal.ecu.edu/mccartyr/ISOwdALG.txt

	const bool leapYear = ((year % 4) == 0 && (year % 100) != 0) || (year % 400) == 0;
	const bool leapYear_1 = (((year - 1) % 4) == 0 && ((year - 1) % 100) != 0) || ((year - 1) % 400) == 0;

	// 4. Find the DayOfYearNumber for Y M D
	static const int DAY_OF_YEAR_NUMBER_MAP[12] = {
		0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334
	};

	int DayOfYearNumber = day + DAY_OF_YEAR_NUMBER_MAP[month - 1];

	if (leapYear && month > 2) {
		DayOfYearNumber += 1;
	}

	// 5. Find the Jan1Weekday for Y (Monday=1, Sunday=7)
	const int YY = (year - 1) % 100;
	const int C = (year - 1) - YY;
	const int G = YY + YY / 4;
	const int Jan1Weekday = 1 + (((((C / 100) % 4) * 5) + G) % 7);

	// 6. Find the Weekday for Y M D
	const int H = DayOfYearNumber + (Jan1Weekday - 1);
	const int Weekday = 1 + ((H - 1) % 7);

	// 7. Find if Y M D falls in YearNumber Y-1, WeekNumber 52 or 53
	int YearNumber = 0, WeekNumber = 0;

	if (DayOfYearNumber <= (8 - Jan1Weekday) && Jan1Weekday > 4) {

		YearNumber = year - 1;

		if (Jan1Weekday == 5 || (Jan1Weekday == 6 && leapYear_1)) {
			WeekNumber = 53;
		} else {
			WeekNumber = 52;
		}

	} else {

		YearNumber = year;
	}

	// 8. Find if Y M D falls in YearNumber Y+1, WeekNumber 1
	if (YearNumber == year) {

		const int I = (leapYear ? 366 : 365);

		if ((I - DayOfYearNumber) < (4 - Weekday)) {
			YearNumber = year + 1;
			WeekNumber = 1;
		}
	}

	// 9. Find if Y M D falls in YearNumber Y, WeekNumber 1 through 53
	if (YearNumber == year) {

		const int J = DayOfYearNumber + (7 - Weekday) + (Jan1Weekday - 1);

		WeekNumber = J / 7;

		if (Jan1Weekday > 4) {
			WeekNumber -= 1;
		}
	}

	if (!iso && (WeekNumber == 1 && month == 12)) {
		WeekNumber = 53;
	}

	return WeekNumber;
}


} // utility
} // vmime