/*
   Unix SMB/Netbios implementation.
   Version 1.9.
   time handling functions

   Copyright (C) Andrew Tridgell 1992-1998

   Copyright (C) 2011-2021
   Free Software Foundation, Inc.

   This file is part of the Midnight Commander.

   The Midnight Commander 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.

   The Midnight Commander 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, see <http://www.gnu.org/licenses/>.
 */

#include "includes.h"

/*
   This stuff was largely rewritten by Paul Eggert <eggert@twinsun.com>
   in May 1996 
 */


int serverzone = 0;
int extra_time_offset = 0;

extern int DEBUGLEVEL;

#ifndef CHAR_BIT
#define CHAR_BIT 8
#endif

#ifndef TIME_T_MIN
#define TIME_T_MIN ((time_t)0 < (time_t) -1 ? (time_t) 0 \
		    : ~ (time_t) 0 << (sizeof (time_t) * CHAR_BIT - 1))
#endif
#ifndef TIME_T_MAX
#define TIME_T_MAX (~ (time_t) 0 - TIME_T_MIN)
#endif



/*******************************************************************
a gettimeofday wrapper
********************************************************************/
void
GetTimeOfDay (struct timeval *tval)
{
#ifdef HAVE_GETTIMEOFDAY_TZ
    gettimeofday (tval, NULL);
#else
    gettimeofday (tval);
#endif
}

#define TM_YEAR_BASE 1900

/*******************************************************************
yield the difference between *A and *B, in seconds, ignoring leap seconds
********************************************************************/
static int
tm_diff (struct tm *a, struct tm *b)
{
    int ay = a->tm_year + (TM_YEAR_BASE - 1);
    int by = b->tm_year + (TM_YEAR_BASE - 1);
    int intervening_leap_days = (ay / 4 - by / 4) - (ay / 100 - by / 100) + (ay / 400 - by / 400);
    int years = ay - by;
    int days = 365 * years + intervening_leap_days + (a->tm_yday - b->tm_yday);
    int hours = 24 * days + (a->tm_hour - b->tm_hour);
    int minutes = 60 * hours + (a->tm_min - b->tm_min);
    int seconds = 60 * minutes + (a->tm_sec - b->tm_sec);

    return seconds;
}

/*******************************************************************
  return the UTC offset in seconds west of UTC, or 0 if it cannot be determined
  ******************************************************************/
static int
TimeZone (time_t t)
{
    struct tm *tm = gmtime (&t);
    struct tm tm_utc;
    if (!tm)
        return 0;
    tm_utc = *tm;
    tm = localtime (&t);
    if (!tm)
        return 0;
    return tm_diff (&tm_utc, tm);

}


/*******************************************************************
init the time differences
********************************************************************/
void
TimeInit (void)
{
    serverzone = TimeZone (time (NULL));

    if ((serverzone % 60) != 0)
    {
        DEBUG (1, ("WARNING: Your timezone is not a multiple of 1 minute.\n"));
    }

    DEBUG (4, ("Serverzone is %d\n", serverzone));
}


/*******************************************************************
return the same value as TimeZone, but it should be more efficient.

We keep a table of DST offsets to prevent calling localtime() on each 
call of this function. This saves a LOT of time on many unixes.

Updated by Paul Eggert <eggert@twinsun.com>
********************************************************************/
static int
TimeZoneFaster (time_t t)
{
    static struct dst_table
    {
        time_t start, end;
        int zone;
    } *dst_table = NULL;
    static int table_size = 0;
    int i;
    int zone = 0;

    if (t == 0)
        t = time (NULL);

    /* Tunis has a 8 day DST region, we need to be careful ... */
#define MAX_DST_WIDTH (365*24*60*60)
#define MAX_DST_SKIP (7*24*60*60)

    for (i = 0; i < table_size; i++)
        if (t >= dst_table[i].start && t <= dst_table[i].end)
            break;

    if (i < table_size)
    {
        zone = dst_table[i].zone;
    }
    else
    {
        time_t low, high;

        zone = TimeZone (t);
        dst_table = (struct dst_table *) Realloc (dst_table, sizeof (dst_table[0]) * (i + 1));
        if (!dst_table)
        {
            table_size = 0;
        }
        else
        {
            table_size++;

            dst_table[i].zone = zone;
            dst_table[i].start = dst_table[i].end = t;

            /* no entry will cover more than 6 months */
            low = t - MAX_DST_WIDTH / 2;
            if (t < low)
                low = TIME_T_MIN;

            high = t + MAX_DST_WIDTH / 2;
            if (high < t)
                high = TIME_T_MAX;

            /* widen the new entry using two bisection searches */
            while (low + 60 * 60 < dst_table[i].start)
            {
                if (dst_table[i].start - low > MAX_DST_SKIP * 2)
                    t = dst_table[i].start - MAX_DST_SKIP;
                else
                    t = low + (dst_table[i].start - low) / 2;
                if (TimeZone (t) == zone)
                    dst_table[i].start = t;
                else
                    low = t;
            }

            while (high - 60 * 60 > dst_table[i].end)
            {
                if (high - dst_table[i].end > MAX_DST_SKIP * 2)
                    t = dst_table[i].end + MAX_DST_SKIP;
                else
                    t = high - (high - dst_table[i].end) / 2;
                if (TimeZone (t) == zone)
                    dst_table[i].end = t;
                else
                    high = t;
            }
#if 0
            DEBUG (1, ("Added DST entry from %s ", asctime (localtime (&dst_table[i].start))));
            DEBUG (1, ("to %s (%d)\n", asctime (localtime (&dst_table[i].end)), dst_table[i].zone));
#endif
        }
    }
    return zone;
}

/****************************************************************************
  return the UTC offset in seconds west of UTC, adjusted for extra time offset
  **************************************************************************/
int
TimeDiff (time_t t)
{
    return TimeZoneFaster (t) + 60 * extra_time_offset;
}


/****************************************************************************
  return the UTC offset in seconds west of UTC, adjusted for extra time
  offset, for a local time value.  If ut = lt + LocTimeDiff(lt), then
  lt = ut - TimeDiff(ut), but the converse does not necessarily hold near
  daylight savings transitions because some local times are ambiguous.
  LocTimeDiff(t) equals TimeDiff(t) except near daylight savings transitions.
  +**************************************************************************/
static int
LocTimeDiff (time_t lte)
{
    time_t lt = lte - 60 * extra_time_offset;
    int d = TimeZoneFaster (lt);
    time_t t = lt + d;

    /* if overflow occurred, ignore all the adjustments so far */
    if (((lte < lt) ^ (extra_time_offset < 0)) | ((t < lt) ^ (d < 0)))
        t = lte;

    /* now t should be close enough to the true UTC to yield the right answer */
    return TimeDiff (t);
}


/****************************************************************************
try to optimise the localtime call, it can be quite expensive on some machines
****************************************************************************/
struct tm *
LocalTime (time_t * t)
{
    time_t t2 = *t;

    t2 -= TimeDiff (t2);

    return (gmtime (&t2));
}

#define TIME_FIXUP_CONSTANT (369.0*365.25*24*60*60-(3.0*24*60*60+6.0*60*60))

/****************************************************************************
interpret an 8 byte "filetime" structure to a time_t
It's originally in "100ns units since jan 1st 1601"

It appears to be kludge-GMT (at least for file listings). This means
its the GMT you get by taking a localtime and adding the
serverzone. This is NOT the same as GMT in some cases. This routine
converts this to real GMT.
****************************************************************************/
time_t
nt_time_to_unix (NTTIME * nt)
{
    double d;
    time_t ret;
    /* The next two lines are a fix needed for the 
       broken SCO compiler. JRA. */
    time_t l_time_min = TIME_T_MIN;
    time_t l_time_max = TIME_T_MAX;

    if (nt->high == 0)
        return (0);

    d = ((double) nt->high) * 4.0 * (double) (1 << 30);
    d += (nt->low & 0xFFF00000);
    d *= 1.0e-7;

    /* now adjust by 369 years to make the secs since 1970 */
    d -= TIME_FIXUP_CONSTANT;

    if (!(l_time_min <= d && d <= l_time_max))
        return (0);

    ret = (time_t) (d + 0.5);

    /* this takes us from kludge-GMT to real GMT */
    ret -= serverzone;
    ret += LocTimeDiff (ret);

    return (ret);
}



/****************************************************************************
interprets an nt time into a unix time_t
****************************************************************************/
time_t
interpret_long_date (char *p)
{
    NTTIME nt;
    nt.low = IVAL (p, 0);
    nt.high = IVAL (p, 4);
    return nt_time_to_unix (&nt);
}

/****************************************************************************
put a 8 byte filetime from a time_t
This takes real GMT as input and converts to kludge-GMT
****************************************************************************/
void
unix_to_nt_time (NTTIME * nt, time_t t)
{
    double d;

    if (t == 0)
    {
        nt->low = 0;
        nt->high = 0;
        return;
    }

    /* this converts GMT to kludge-GMT */
    t -= LocTimeDiff (t) - serverzone;

    d = (double) (t);
    d += TIME_FIXUP_CONSTANT;
    d *= 1.0e7;

    nt->high = (uint32) (d * (1.0 / (4.0 * (double) (1 << 30))));
    nt->low = (uint32) (d - ((double) nt->high) * 4.0 * (double) (1 << 30));
}


/****************************************************************************
take an NTTIME structure, containing high / low time.  convert to unix time.
lkclXXXX this may need 2 SIVALs not a memcpy.  we'll see...
****************************************************************************/
void
put_long_date (char *p, time_t t)
{
    NTTIME nt;
    unix_to_nt_time (&nt, t);
    SIVAL (p, 0, nt.low);
    SIVAL (p, 4, nt.high);
}

/****************************************************************************
check if it's a null mtime
****************************************************************************/
BOOL
null_mtime (time_t mtime)
{
    if (mtime == (time_t) 0 || mtime == (time_t) 0xFFFFFFFF || mtime == (time_t) - 1)
        return (True);
    return (False);
}

/*******************************************************************
  create a 16 bit dos packed date
********************************************************************/
static uint16
make_dos_date1 (struct tm *t)
{
    uint16 ret = 0;
    ret = (((unsigned) (t->tm_mon + 1)) >> 3) | ((t->tm_year - 80) << 1);
    ret = ((ret & 0xFF) << 8) | (t->tm_mday | (((t->tm_mon + 1) & 0x7) << 5));
    return (ret);
}

/*******************************************************************
  create a 16 bit dos packed time
********************************************************************/
static uint16
make_dos_time1 (struct tm *t)
{
    uint16 ret = 0;
    ret = ((((unsigned) t->tm_min >> 3) & 0x7) | (((unsigned) t->tm_hour) << 3));
    ret = ((ret & 0xFF) << 8) | ((t->tm_sec / 2) | ((t->tm_min & 0x7) << 5));
    return (ret);
}

/*******************************************************************
  create a 32 bit dos packed date/time from some parameters
  This takes a GMT time and returns a packed localtime structure
********************************************************************/
static uint32
make_dos_date (time_t unixdate)
{
    struct tm *t;
    uint32 ret = 0;

    t = LocalTime (&unixdate);
    if (!t)
        return 0xFFFFFFFF;

    ret = make_dos_date1 (t);
    ret = ((ret & 0xFFFF) << 16) | make_dos_time1 (t);

    return (ret);
}

/*******************************************************************
put a dos date into a buffer (time/date format)
This takes GMT time and puts local time in the buffer
********************************************************************/
void
put_dos_date (char *buf, int offset, time_t unixdate)
{
    uint32 x = make_dos_date (unixdate);
    SIVAL (buf, offset, x);
}

#if 0
/*******************************************************************
put a dos date into a buffer (date/time format)
This takes GMT time and puts local time in the buffer
********************************************************************/
void
put_dos_date2 (char *buf, int offset, time_t unixdate)
{
    uint32 x = make_dos_date (unixdate);
    x = ((x & 0xFFFF) << 16) | ((x & 0xFFFF0000) >> 16);
    SIVAL (buf, offset, x);
}
#endif /* 0 */

/*******************************************************************
put a dos 32 bit "unix like" date into a buffer. This routine takes
GMT and converts it to LOCAL time before putting it (most SMBs assume
localtime for this sort of date)
********************************************************************/
void
put_dos_date3 (char *buf, int offset, time_t unixdate)
{
    if (!null_mtime (unixdate))
        unixdate -= TimeDiff (unixdate);
    SIVAL (buf, offset, unixdate);
}

/*******************************************************************
  interpret a 32 bit dos packed date/time to some parameters
********************************************************************/
static void
interpret_dos_date (uint32 date, int *year, int *month, int *day, int *hour, int *minute,
                    int *second)
{
    uint32 p0, p1, p2, p3;

    p0 = date & 0xFF;
    p1 = ((date & 0xFF00) >> 8) & 0xFF;
    p2 = ((date & 0xFF0000) >> 16) & 0xFF;
    p3 = ((date & 0xFF000000) >> 24) & 0xFF;

    *second = 2 * (p0 & 0x1F);
    *minute = ((p0 >> 5) & 0xFF) + ((p1 & 0x7) << 3);
    *hour = (p1 >> 3) & 0xFF;
    *day = (p2 & 0x1F);
    *month = ((p2 >> 5) & 0xFF) + ((p3 & 0x1) << 3) - 1;
    *year = ((p3 >> 1) & 0xFF) + 80;
}

/*******************************************************************
  create a unix date (int GMT) from a dos date (which is actually in
  localtime)
********************************************************************/
time_t
make_unix_date (void *date_ptr)
{
    uint32 dos_date = 0;
    struct tm t;
    time_t ret;

    dos_date = IVAL (date_ptr, 0);

    if (dos_date == 0)
        return (0);

    interpret_dos_date (dos_date, &t.tm_year, &t.tm_mon,
                        &t.tm_mday, &t.tm_hour, &t.tm_min, &t.tm_sec);
    t.tm_isdst = -1;

    /* mktime() also does the local to GMT time conversion for us */
    ret = mktime (&t);

    return (ret);
}

/*******************************************************************
like make_unix_date() but the words are reversed
********************************************************************/
time_t
make_unix_date2 (void *date_ptr)
{
    uint32 x, x2;

    x = IVAL (date_ptr, 0);
    x2 = ((x & 0xFFFF) << 16) | ((x & 0xFFFF0000) >> 16);
    SIVAL (&x, 0, x2);

    return (make_unix_date ((void *) &x));
}

/*******************************************************************
  create a unix GMT date from a dos date in 32 bit "unix like" format
  these generally arrive as localtimes, with corresponding DST
  ******************************************************************/
time_t
make_unix_date3 (void *date_ptr)
{
    time_t t = (time_t) IVAL (date_ptr, 0);
    if (!null_mtime (t))
        t += LocTimeDiff (t);
    return (t);
}

#if 0
/***************************************************************************
return a HTTP/1.0 time string
  ***************************************************************************/
char *
http_timestring (time_t t)
{
    static fstring buf;
    struct tm *tm = LocalTime (&t);

    if (!tm)
        slprintf (buf, sizeof (buf) - 1, "%ld seconds since the Epoch", (long) t);
    else
        strftime (buf, sizeof (buf) - 1, "%a, %d %b %Y %H:%M:%S %Z", tm);
    return buf;
}
#endif /*0 */


/****************************************************************************
  return the date and time as a string
****************************************************************************/
char *
timestring (void)
{
    static fstring TimeBuf;
    time_t t = time (NULL);
    struct tm *tm = LocalTime (&t);

    if (!tm)
    {
        slprintf (TimeBuf, sizeof (TimeBuf) - 1, "%ld seconds since the Epoch", (long) t);
    }
    else
    {
        strftime (TimeBuf, 100, "%Y/%m/%d %H:%M:%S", tm);
    }
    return (TimeBuf);
}

/****************************************************************************
  return the best approximation to a 'create time' under UNIX from a stat
  structure.
****************************************************************************/

time_t
get_create_time (SMB_STRUCT_STAT * st, BOOL fake_dirs)
{
    time_t ret, ret1;

    if (S_ISDIR (st->st_mode) && fake_dirs)
        return (time_t) 315493200L;     /* 1/1/1980 */

    ret = MIN (st->st_ctime, st->st_mtime);
    ret1 = MIN (ret, st->st_atime);

    if (ret1 != (time_t) 0)
        return ret1;

    /*
     * One of ctime, mtime or atime was zero (probably atime).
     * Just return MIN(ctime, mtime).
     */
    return ret;
}
