/*
 * COPYRIGHT:         See COPYING in the top level directory
 * PROJECT:           ReactOS system libraries
 * FILE:              lib/rtl/time.c
 * PURPOSE:           Conversion between Time and TimeFields
 * PROGRAMMER:        Rex Jolliff (rex@lvcablemodem.com)
 */

/* INCLUDES *****************************************************************/

#include <rtl.h>

#define NDEBUG
#include <debug.h>

#define TICKSPERMIN        600000000
#define TICKSPERSEC        10000000
#define TICKSPERMSEC       10000
#define SECSPERDAY         86400
#define SECSPERHOUR        3600
#define SECSPERMIN         60
#define MINSPERHOUR        60
#define HOURSPERDAY        24
#define EPOCHWEEKDAY       1
#define DAYSPERWEEK        7
#define EPOCHYEAR          1601
#define DAYSPERNORMALYEAR  365
#define DAYSPERLEAPYEAR    366
#define MONSPERYEAR        12

#if defined(__GNUC__)
#define TICKSTO1970         0x019db1ded53e8000LL
#define TICKSTO1980         0x01a8e79fe1d58000LL
#else
#define TICKSTO1970         0x019db1ded53e8000i64
#define TICKSTO1980         0x01a8e79fe1d58000i64
#endif


static const int YearLengths[2] =
{
    DAYSPERNORMALYEAR, DAYSPERLEAPYEAR
};
static const UCHAR MonthLengths[2][MONSPERYEAR] =
{
    { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 },
    { 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 }
};

static __inline int IsLeapYear(int Year)
{
   return Year % 4 == 0 && (Year % 100 != 0 || Year % 400 == 0) ? 1 : 0;
}

static int DaysSinceEpoch(int Year)
{
   int Days;
   Year--; /* Don't include a leap day from the current year */
   Days = Year * DAYSPERNORMALYEAR + Year / 4 - Year / 100 + Year / 400;
   Days -= (EPOCHYEAR - 1) * DAYSPERNORMALYEAR + (EPOCHYEAR - 1) / 4 - (EPOCHYEAR - 1) / 100 + (EPOCHYEAR - 1) / 400;
   return Days;
}

/* FUNCTIONS *****************************************************************/

/*
 * @implemented
 */
BOOLEAN NTAPI
RtlCutoverTimeToSystemTime(IN PTIME_FIELDS CutoverTimeFields,
                           OUT PLARGE_INTEGER SystemTime,
                           IN PLARGE_INTEGER CurrentTime,
                           IN BOOLEAN ThisYearsCutoverOnly)
{
  TIME_FIELDS AdjustedTimeFields;
  TIME_FIELDS CurrentTimeFields;
  TIME_FIELDS CutoverSystemTimeFields;
  LARGE_INTEGER CutoverSystemTime;
  UCHAR MonthLength;
  CSHORT Days;
  BOOLEAN NextYearsCutover = FALSE;

  /* Check fixed cutover time */
  if (CutoverTimeFields->Year != 0)
  {
    if (!RtlTimeFieldsToTime(CutoverTimeFields, SystemTime))
      return FALSE;

    if (SystemTime->QuadPart < CurrentTime->QuadPart)
      return FALSE;

    return TRUE;
  }

  /*
   * Compute recurring cutover time
   */

  /* Day must be between 1(first) and 5(last) */
  if (CutoverTimeFields->Day == 0 || CutoverTimeFields->Day > 5)
    return FALSE;

  RtlTimeToTimeFields(CurrentTime, &CurrentTimeFields);

  while (TRUE)
  {
    /* Compute the cutover time of the first day of the current month */
    AdjustedTimeFields.Year = CurrentTimeFields.Year;
    if (NextYearsCutover == TRUE)
      AdjustedTimeFields.Year++;

    AdjustedTimeFields.Month = CutoverTimeFields->Month;
    AdjustedTimeFields.Day = 1;
    AdjustedTimeFields.Hour = CutoverTimeFields->Hour;
    AdjustedTimeFields.Minute = CutoverTimeFields->Minute;
    AdjustedTimeFields.Second = CutoverTimeFields->Second;
    AdjustedTimeFields.Milliseconds = CutoverTimeFields->Milliseconds;

    if (!RtlTimeFieldsToTime(&AdjustedTimeFields, &CutoverSystemTime))
      return FALSE;

    RtlTimeToTimeFields(&CutoverSystemTime, &CutoverSystemTimeFields);

    /* Adjust day to first matching weekday */
    if (CutoverSystemTimeFields.Weekday != CutoverTimeFields->Weekday)
    {
      if (CutoverSystemTimeFields.Weekday < CutoverTimeFields->Weekday)
        Days = CutoverTimeFields->Weekday - CutoverSystemTimeFields.Weekday;
      else
        Days = DAYSPERWEEK - (CutoverSystemTimeFields.Weekday - CutoverTimeFields->Weekday);

      AdjustedTimeFields.Day += Days;
    }

    /* Adjust the number of weeks */
    if (CutoverTimeFields->Day > 1)
    {
      Days = DAYSPERWEEK * (CutoverTimeFields->Day - 1);
      MonthLength = MonthLengths[IsLeapYear(AdjustedTimeFields.Year)][AdjustedTimeFields.Month - 1];
      if ((AdjustedTimeFields.Day + Days) > MonthLength)
        Days -= DAYSPERWEEK;

      AdjustedTimeFields.Day += Days;
    }

    if (!RtlTimeFieldsToTime(&AdjustedTimeFields, &CutoverSystemTime))
      return FALSE;

    if (ThisYearsCutoverOnly == TRUE ||
        NextYearsCutover == TRUE ||
        CutoverSystemTime.QuadPart >= CurrentTime->QuadPart)
    {
      break;
    }

    NextYearsCutover = TRUE;
  }

  SystemTime->QuadPart = CutoverSystemTime.QuadPart;

  return TRUE;
}


/*
 * @implemented
 */
BOOLEAN
NTAPI
RtlTimeFieldsToTime(
   IN PTIME_FIELDS TimeFields,
   OUT PLARGE_INTEGER Time)
{
   int CurMonth;
   TIME_FIELDS IntTimeFields;

   memcpy(&IntTimeFields,
          TimeFields,
          sizeof(TIME_FIELDS));

   if (TimeFields->Milliseconds < 0 || TimeFields->Milliseconds > 999 ||
       TimeFields->Second < 0 || TimeFields->Second > 59 ||
       TimeFields->Minute < 0 || TimeFields->Minute > 59 ||
       TimeFields->Hour < 0 || TimeFields->Hour > 23 ||
       TimeFields->Month < 1 || TimeFields->Month > 12 ||
       TimeFields->Day < 1 ||
       TimeFields->Day >
           MonthLengths[IsLeapYear(TimeFields->Year)][TimeFields->Month - 1] ||
       TimeFields->Year < 1601)
   {
       return FALSE;
   }

   /* Compute the time */
   Time->QuadPart = DaysSinceEpoch(IntTimeFields.Year);
   for (CurMonth = 1; CurMonth < IntTimeFields.Month; CurMonth++)
   {
      Time->QuadPart += MonthLengths[IsLeapYear(IntTimeFields.Year)][CurMonth - 1];
   }
   Time->QuadPart += IntTimeFields.Day - 1;
   Time->QuadPart *= SECSPERDAY;
   Time->QuadPart += IntTimeFields.Hour * SECSPERHOUR + IntTimeFields.Minute * SECSPERMIN +
                     IntTimeFields.Second;
   Time->QuadPart *= TICKSPERSEC;
   Time->QuadPart += IntTimeFields.Milliseconds * TICKSPERMSEC;

   return TRUE;
}


/*
 * @implemented
 */
VOID
NTAPI
RtlTimeToElapsedTimeFields(IN PLARGE_INTEGER Time,
                           OUT PTIME_FIELDS TimeFields)
{
   ULONGLONG ElapsedSeconds;
   ULONG SecondsInDay;
   ULONG SecondsInMinute;

   /* Extract millisecond from time */
   TimeFields->Milliseconds = (CSHORT)((Time->QuadPart % TICKSPERSEC) / TICKSPERMSEC);

   /* Compute elapsed seconds */
   ElapsedSeconds = (ULONGLONG)Time->QuadPart / TICKSPERSEC;

   /* Compute seconds within the day */
   SecondsInDay = ElapsedSeconds % SECSPERDAY;

   /* Compute elapsed minutes within the day */
   SecondsInMinute = SecondsInDay % SECSPERHOUR;

   /* Compute elapsed time of day */
   TimeFields->Hour = (CSHORT)(SecondsInDay / SECSPERHOUR);
   TimeFields->Minute = (CSHORT)(SecondsInMinute / SECSPERMIN);
   TimeFields->Second = (CSHORT)(SecondsInMinute % SECSPERMIN);

   /* Compute elapsed days */
   TimeFields->Day = (CSHORT)(ElapsedSeconds / SECSPERDAY);

   /* The elapsed number of months and days cannot be calculated */
   TimeFields->Month = 0;
   TimeFields->Year = 0;
}


/*
 * @implemented
 */
VOID
NTAPI
RtlTimeToTimeFields(
   IN PLARGE_INTEGER Time,
   OUT PTIME_FIELDS TimeFields)
{
   const UCHAR *Months;
   ULONG SecondsInDay, CurYear;
   ULONG LeapYear, CurMonth;
   ULONG Days;
   ULONGLONG IntTime = Time->QuadPart;

   /* Extract millisecond from time and convert time into seconds */
   TimeFields->Milliseconds = (CSHORT) ((IntTime % TICKSPERSEC) / TICKSPERMSEC);
   IntTime = IntTime / TICKSPERSEC;

   /* Split the time into days and seconds within the day */
   Days = (ULONG)(IntTime / SECSPERDAY);
   SecondsInDay = IntTime % SECSPERDAY;

   /* compute time of day */
   TimeFields->Hour = (CSHORT) (SecondsInDay / SECSPERHOUR);
   SecondsInDay = SecondsInDay % SECSPERHOUR;
   TimeFields->Minute = (CSHORT) (SecondsInDay / SECSPERMIN);
   TimeFields->Second = (CSHORT) (SecondsInDay % SECSPERMIN);

   /* compute day of week */
   TimeFields->Weekday = (CSHORT) ((EPOCHWEEKDAY + Days) % DAYSPERWEEK);

   /* compute year */
   CurYear = EPOCHYEAR;
   CurYear += Days / DAYSPERLEAPYEAR;
   Days -= DaysSinceEpoch(CurYear);
   while (1)
   {
      LeapYear = IsLeapYear(CurYear);
      if (Days < YearLengths[LeapYear])
      {
         break;
      }
      CurYear++;
      Days = Days - YearLengths[LeapYear];
   }
   TimeFields->Year = (CSHORT) CurYear;

   /* Compute month of year */
   LeapYear = IsLeapYear(CurYear);
   Months = MonthLengths[LeapYear];
   for (CurMonth = 0; Days >= Months[CurMonth]; CurMonth++)
      Days = Days - Months[CurMonth];
   TimeFields->Month = (CSHORT) (CurMonth + 1);
   TimeFields->Day = (CSHORT) (Days + 1);
}


/*
 * @implemented
 */
BOOLEAN
NTAPI
RtlTimeToSecondsSince1970(
   IN PLARGE_INTEGER Time,
   OUT PULONG SecondsSince1970)
{
   LARGE_INTEGER IntTime;

   IntTime.QuadPart = Time->QuadPart - TICKSTO1970;
   IntTime.QuadPart = IntTime.QuadPart / TICKSPERSEC;

   if (IntTime.u.HighPart != 0)
      return FALSE;

   *SecondsSince1970 = IntTime.u.LowPart;

   return TRUE;
}


/*
 * @implemented
 */
BOOLEAN
NTAPI
RtlTimeToSecondsSince1980(
   IN PLARGE_INTEGER Time,
   OUT PULONG SecondsSince1980)
{
   LARGE_INTEGER IntTime;

   IntTime.QuadPart = Time->QuadPart - TICKSTO1980;
   IntTime.QuadPart = IntTime.QuadPart / TICKSPERSEC;

   if (IntTime.u.HighPart != 0)
      return FALSE;

   *SecondsSince1980 = IntTime.u.LowPart;

   return TRUE;
}


/*
 * @implemented
 */
NTSTATUS
NTAPI
RtlLocalTimeToSystemTime(IN PLARGE_INTEGER LocalTime,
                         OUT PLARGE_INTEGER SystemTime)
{
   SYSTEM_TIMEOFDAY_INFORMATION TimeInformation;
   NTSTATUS Status;

   Status = ZwQuerySystemInformation(SystemTimeOfDayInformation,
                                     &TimeInformation,
                                     sizeof(SYSTEM_TIMEOFDAY_INFORMATION),
                                     NULL);
   if (!NT_SUCCESS(Status))
      return Status;

   SystemTime->QuadPart = LocalTime->QuadPart +
                          TimeInformation.TimeZoneBias.QuadPart;

   return STATUS_SUCCESS;
}


/*
 * @implemented
 */
NTSTATUS
NTAPI
RtlSystemTimeToLocalTime(IN PLARGE_INTEGER SystemTime,
                         OUT PLARGE_INTEGER LocalTime)
{
   SYSTEM_TIMEOFDAY_INFORMATION TimeInformation;
   NTSTATUS Status;

   Status = ZwQuerySystemInformation(SystemTimeOfDayInformation,
                                     &TimeInformation,
                                     sizeof(SYSTEM_TIMEOFDAY_INFORMATION),
                                     NULL);
   if (!NT_SUCCESS(Status))
      return Status;

   LocalTime->QuadPart = SystemTime->QuadPart -
                         TimeInformation.TimeZoneBias.QuadPart;

   return STATUS_SUCCESS;
}


/*
 * @implemented
 */
VOID NTAPI
RtlSecondsSince1970ToTime(
   IN ULONG SecondsSince1970,
   OUT PLARGE_INTEGER Time)
{
  Time->QuadPart = ((LONGLONG)SecondsSince1970 * TICKSPERSEC) + TICKSTO1970;
}


/*
 * @implemented
 */
VOID NTAPI
RtlSecondsSince1980ToTime(
   IN ULONG SecondsSince1980,
   OUT PLARGE_INTEGER Time)
{
   Time->QuadPart = ((LONGLONG)SecondsSince1980 * TICKSPERSEC) + TICKSTO1980;
}

/* EOF */
