/*

 * Copyright (C) 1999-2000 Harri Porten (porten@kde.org)

 * Copyright (C) 2006, 2007 Apple Inc. All rights reserved.

 *

 * The Original Code is Mozilla Communicator client code, released

 * March 31, 1998.

 *

 * The Initial Developer of the Original Code is

 * Netscape Communications Corporation.

 * Portions created by the Initial Developer are Copyright (C) 1998

 * the Initial Developer. All Rights Reserved.

 *

 * This library is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public

 * License as published by the Free Software Foundation; either

 * version 2.1 of the License, or (at your option) any later version.

 *

 * This library 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

 * Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public

 * License along with this library; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA

 *

 * Alternatively, the contents of this file may be used under the terms

 * of either the Mozilla Public License Version 1.1, found at

 * http://www.mozilla.org/MPL/ (the "MPL") or the GNU General Public

 * License Version 2.0, found at http://www.fsf.org/copyleft/gpl.html

 * (the "GPL"), in which case the provisions of the MPL or the GPL are

 * applicable instead of those above.  If you wish to allow use of your

 * version of this file only under the terms of one of those two

 * licenses (the MPL or the GPL) and not to allow others to use your

 * version of this file under the LGPL, indicate your decision by

 * deletingthe provisions above and replace them with the notice and

 * other provisions required by the MPL or the GPL, as the case may be.

 * If you do not delete the provisions above, a recipient may use your

 * version of this file under any of the LGPL, the MPL or the GPL.

 */

#include "config.h"

#include "DateMath.h"

#include <math.h>

#include <stdint.h>

#include <value.h>

#include <wtf/Assertions.h>

#if PLATFORM(DARWIN)

#include <notify.h>

#endif

#if HAVE(SYS_TIME_H)

#include <sys/time.h>

#endif

#if HAVE(SYS_TIMEB_H)

#include <sys/timeb.h>

#endif

namespace KJS {

/* Constants */

static const double minutesPerDay = 24.0 * 60.0;

static const double secondsPerDay = 24.0 * 60.0 * 60.0;

static const double secondsPerYear = 24.0 * 60.0 * 60.0 * 365.0;

static const double usecPerSec = 1000000.0;

static const double maxUnixTime = 2145859200.0; // 12/31/2037

// Day of year for the first day of each month, where index 0 is January, and day 0 is January 1.

// First for non-leap years, then for leap years.

static const int firstDayOfMonth[2][12] = {

    {0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334},

    {0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335}

};

static inline bool isLeapYear(int year)

{

    if (year % 4 != 0)

        return false;

    if (year % 400 == 0)

        return true;

    if (year % 100 == 0)

        return false;

    return true;

}

static inline int daysInYear(int year)

{

    return 365 + isLeapYear(year);

}

static inline double daysFrom1970ToYear(int year)

{

    return 365.0 * (year - 1970)

        + floor((year - 1969) / 4.0)

        - floor((year - 1901) / 100.0)

        + floor((year - 1601) / 400.0);

}

static inline double msFrom1970ToYear(int year)

{

    return msPerDay * daysFrom1970ToYear(year);

}

static inline double msToDays(double ms)

{

    return floor(ms / msPerDay);

}

static inline int msToYear(double ms)

{

    int y = static_cast<int>(floor(ms / (msPerDay * 365.2425)) + 1970);

    double t2 = msFrom1970ToYear(y);

    if (t2 > ms) {

        y--;

    } else {

        if (t2 + msPerDay * daysInYear(y) <= ms)

            y++;

    }

    return y;

}

static inline bool isInLeapYear(double ms)

{

    return isLeapYear(msToYear(ms));

}

static inline int dayInYear(double ms, int year)

{

    return static_cast<int>(msToDays(ms) - daysFrom1970ToYear(year));

}

static inline double msToMilliseconds(double ms)

{

    double result = fmod(ms, msPerDay);

    if (result < 0)

        result += msPerDay;

    return result;

}

// 0: Sunday, 1: Monday, etc.

static inline int msToWeekDay(double ms)

{

    int wd = (static_cast<int>(msToDays(ms)) + 4) % 7;

    if (wd < 0)

        wd += 7;

    return wd;

}

static inline int msToSeconds(double ms)

{

    double result = fmod(floor(ms / msPerSecond), secondsPerMinute);

    if (result < 0)

        result += secondsPerMinute;

    return static_cast<int>(result);

}

static inline int msToMinutes(double ms)

{

    double result = fmod(floor(ms / msPerMinute), minutesPerHour);

    if (result < 0)

        result += minutesPerHour;

    return static_cast<int>(result);

}

static inline int msToHours(double ms)

{

    double result = fmod(floor(ms/msPerHour), hoursPerDay);

    if (result < 0)

        result += hoursPerDay;

    return static_cast<int>(result);

}

static inline int msToMonth(double ms)

{

    int step;

    int year = msToYear(ms);

    int d = dayInYear(ms, year);

    if (d < (step = 31))

        return 0;

    step += (isInLeapYear(ms) ? 29 : 28);

    if (d < step)

        return 1;

    if (d < (step += 31))

        return 2;

    if (d < (step += 30))

        return 3;

    if (d < (step += 31))

        return 4;

    if (d < (step += 30))

        return 5;

    if (d < (step += 31))

        return 6;

    if (d < (step += 31))

        return 7;

    if (d < (step += 30))

        return 8;

    if (d < (step += 31))

        return 9;

    if (d < (step += 30))

        return 10;

    return 11;

}

static inline int msToDayInMonth(double ms)

{

    int step, next;

    int year = msToYear(ms);

    int d = dayInYear(ms, year);

    if (d <= (next = 30))

        return d + 1;

    step = next;

    next += (isInLeapYear(ms) ? 29 : 28);

    if (d <= next)

        return d - step;

    step = next;

    if (d <= (next += 31))

        return d - step;

    step = next;

    if (d <= (next += 30))

        return d - step;

    step = next;

    if (d <= (next += 31))

        return d - step;

    step = next;

    if (d <= (next += 30))

        return d - step;

    step = next;

    if (d <= (next += 31))

        return d - step;

    step = next;

    if (d <= (next += 31))

        return d - step;

    step = next;

    if (d <= (next += 30))

        return d - step;

    step = next;

    if (d <= (next += 31))

        return d - step;

    step = next;

    if (d <= (next += 30))

        return d - step;

    step = next;

    return d - step;

}

static inline int monthToDayInYear(int month, bool isLeapYear)

{

    return firstDayOfMonth[isLeapYear][month];

}

static inline double timeToMS(double hour, double min, double sec, double ms)

{

    return (((hour * minutesPerHour + min) * secondsPerMinute + sec) * msPerSecond + ms);

}

static int dateToDayInYear(int year, int month, int day)

{

    year += month / 12;

    month %= 12;

    if (month < 0) {

        month += 12;

        --year;

    }

    int yearday = static_cast<int>(floor(msFrom1970ToYear(year) / msPerDay));

    int monthday = monthToDayInYear(month, isLeapYear(year));

    return yearday + monthday + day - 1;

}

double getCurrentUTCTime()

{

#if PLATFORM(WIN_OS)

#if COMPILER(BORLAND)

    struct timeb timebuffer;

    ftime(&timebuffer);

#else

    struct _timeb timebuffer;

    _ftime(&timebuffer);

#endif

    double utc = timebuffer.time * msPerSecond + timebuffer.millitm;

#else

    struct timeval tv;

    gettimeofday(&tv, 0);

    double utc = floor(tv.tv_sec * msPerSecond + tv.tv_usec / 1000);

#endif

    return utc;

}

// There is a hard limit at 2038 that we currently do not have a workaround

// for (rdar://problem/5052975).

static inline int maximumYearForDST()

{

    return 2037;

}

// It is ok if the cached year is not the current year (e.g. Dec 31st)

// so long as the rules for DST did not change between the two years, if it does

// the app would need to be restarted.

static int mimimumYearForDST()

{

    // Because of the 2038 issue (see maximumYearForDST) if the current year is

    // greater than the max year minus 27 (2010), we want to use the max year

    // minus 27 instead, to ensure there is a range of 28 years that all years

    // can map to.

    static int minYear = std::min(msToYear(getCurrentUTCTime()), maximumYearForDST()-27) ;

    return minYear;

}

/*

 * Find an equivalent year for the one given, where equivalence is deterined by

 * the two years having the same leapness and the first day of the year, falling

 * on the same day of the week.

 *

 * This function returns a year between this current year and 2037, however this

 * function will potentially return incorrect results if the current year is after

 * 2010, (rdar://problem/5052975), if the year passed in is before 1900 or after

 * 2100, (rdar://problem/5055038).

 */

int equivalentYearForDST(int year)

{

    static int minYear = mimimumYearForDST();

    static int maxYear = maximumYearForDST();

    int difference;

    if (year > maxYear)

        difference = minYear - year;

    else if (year < minYear)

        difference = maxYear - year;

    else

        return year;

    int quotient = difference / 28;

    int product = (quotient) * 28;

    year += product;

    ASSERT((year >= minYear && year <= maxYear) || (product - year == static_cast<int>(NaN)));

    return year;

}

/*

 * Get the difference in milliseconds between this time zone and UTC (GMT)

 * NOT including DST.

 */

double getUTCOffset()

{

#if PLATFORM(DARWIN)

    // Register for a notification whenever the time zone changes.

    static bool triedToRegister = false;

    static bool haveNotificationToken = false;

    static int notificationToken;

    if (!triedToRegister) {

        triedToRegister = true;

        uint32_t status = notify_register_check("com.apple.system.timezone", &notificationToken);

        if (status == NOTIFY_STATUS_OK)

            haveNotificationToken = true;

    }

    // If we can verify that we have not received a time zone notification,

    // then use the cached offset from the last time this function was called.

    static bool haveCachedOffset = false;

    static double cachedOffset;

    if (haveNotificationToken && haveCachedOffset) {

        int notified;

        uint32_t status = notify_check(notificationToken, &notified);

        if (status == NOTIFY_STATUS_OK && !notified)

            return cachedOffset;

    }

#endif

    tm localt;

    memset(&localt, 0, sizeof(localt));

    // get the difference between this time zone and UTC on Jan 01, 2000 12:00:00 AM

    localt.tm_mday = 1;

    localt.tm_year = 100;

    double utcOffset = 946684800.0 - mktime(&localt);

    utcOffset *= msPerSecond;

#if PLATFORM(DARWIN)

    haveCachedOffset = true;

    cachedOffset = utcOffset;

#endif

    return utcOffset;

}

/*

 * Get the DST offset for the time passed in.  Takes

 * seconds (not milliseconds) and cannot handle dates before 1970

 * on some OS'

 */

static double getDSTOffsetSimple(double localTimeSeconds)

{

    if (localTimeSeconds > maxUnixTime)

        localTimeSeconds = maxUnixTime;

    else if(localTimeSeconds < 0) // Go ahead a day to make localtime work (does not work with 0)

        localTimeSeconds += secondsPerDay;

    //input is UTC so we have to shift back to local time to determine DST thus the + getUTCOffset()

    double offsetTime = (localTimeSeconds * msPerSecond) + getUTCOffset();

    // Offset from UTC but doesn't include DST obviously

    int offsetHour =  msToHours(offsetTime);

    int offsetMinute =  msToMinutes(offsetTime);

    // FIXME: time_t has a potential problem in 2038

    time_t localTime = static_cast<time_t>(localTimeSeconds);

    tm localTM;

#if PLATFORM(QT)

    // ### this is not threadsafe but we don't use multiple threads anyway

    // in the Qt build

#if USE(MULTIPLE_THREADS)

#error Mulitple threads are currently not supported in the Qt/mingw build

#endif

    localTM = *localtime(&localTime);

#elif PLATFORM(WIN_OS)

    localtime_s(&localTM, &localTime);

#else

    localtime_r(&localTime, &localTM);

#endif

    double diff = ((localTM.tm_hour - offsetHour) * secondsPerHour) + ((localTM.tm_min - offsetMinute) * 60);

    if(diff < 0)

        diff += secondsPerDay;

    return (diff * msPerSecond);

}

// Get the DST offset, given a time in UTC

static double getDSTOffset(double ms)

{

#if PLATFORM(SYMBIAN)

    // Symbian does not support DST

    return User::UTCOffset().Int() * msPerSecond;

#else

    // On Mac OS X, the call to localtime (see getDSTOffsetSimple) will return historically accurate

    // DST information (e.g. New Zealand did not have DST from 1946 to 1974) however the JavaScript

    // standard explicitly dictates that historical information should not be considered when

    // determining DST. For this reason we shift away from years that localtime can handle but would

    // return historically accurate information.

    int year = msToYear(ms);

    int equvalentYear = equivalentYearForDST(year);

    if (year != equvalentYear) {

        int day = dateToDayInYear(equvalentYear, msToMonth(ms), msToDayInMonth(ms));

        ms = (day * msPerDay) + msToMilliseconds(ms);

    }

    return getDSTOffsetSimple(ms / msPerSecond);

#endif

}

double gregorianDateTimeToMS(const GregorianDateTime& t, double milliSeconds, bool inputIsUTC)

{

    int day = dateToDayInYear(t.year + 1900, t.month, t.monthDay);

    double ms = timeToMS(t.hour, t.minute, t.second, milliSeconds);

    double result = (day * msPerDay) + ms;

    if (!inputIsUTC) { // convert to UTC

        result -= getUTCOffset();       

        result -= getDSTOffset(result);

    }

    return result;

}

void msToGregorianDateTime(double ms, bool outputIsUTC, GregorianDateTime& tm)

{

    // input is UTC

    double dstOff = 0.0;

    if (!outputIsUTC) {  // convert to local time

        dstOff = getDSTOffset(ms);

        ms += dstOff + getUTCOffset();

    }

    tm.second   =  msToSeconds(ms);

    tm.minute   =  msToMinutes(ms);

    tm.hour     =  msToHours(ms);

    tm.weekDay  =  msToWeekDay(ms);

    tm.monthDay =  msToDayInMonth(ms);

    tm.yearDay  =  dayInYear(ms, msToYear(ms));

    tm.month    =  msToMonth(ms);

    tm.year     =  msToYear(ms) - 1900;

    tm.isDST    =  dstOff != 0.0;

    tm.utcOffset = static_cast<long>((dstOff + getUTCOffset()) / msPerSecond);

    tm.timeZone = NULL;

}

} // namespace KJS