/*

 * prettydate - convert a time stamp to something readable

 */

#include <config.h>

#include <stdio.h>

#include "ntp_fp.h"

#include "ntp_unixtime.h" /* includes <sys/time.h> */

#include "lib_strbuf.h"

#include "ntp_stdlib.h"

#include "ntp_assert.h"

#include "ntp_calendar.h"

#if SIZEOF_TIME_T < 4

# error sizeof(time_t) < 4 -- this will not work!

#endif

static char *common_prettydate(l_fp *, int);

const char * const months[12] = {

  "Jan", "Feb", "Mar", "Apr", "May", "Jun",

  "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"

};

const char * const daynames[7] = {

  "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"

};

/* Helper function to handle possible wraparound of the ntp epoch.

 *

 * Works by periodic extension of the ntp time stamp in the UN*X epoch.

 * If the 'time_t' is 32 bit, use solar cycle warping to get the value

 * in a suitable range. Also uses solar cycle warping to work around

 * really buggy implementations of 'gmtime()' / 'localtime()' that

 * cannot work with a negative time value, that is, times before

 * 1970-01-01. (MSVCRT...)

 *

 * Apart from that we're assuming that the localtime/gmtime library

 * functions have been updated so that they work...

 *

 * An explanation: The julian calendar repeats ever 28 years, because

 * it's the LCM of 7 and 1461, the week and leap year cycles. This is

 * called a 'solar cycle'. The gregorian calendar does the same as

 * long as no centennial year (divisible by 100, but not 400) goes in

 * the way. So between 1901 and 2099 (inclusive) we can warp time

 * stamps by 28 years to make them suitable for localtime() and

 * gmtime() if we have trouble. Of course this will play hubbubb with

 * the DST zone switches, so we should do it only if necessary; but as

 * we NEED a proper conversion to dates via gmtime() we should try to

 * cope with as many idiosyncrasies as possible.

 *

 */

/*

 * solar cycle in unsigned secs and years, and the cycle limits.

 */

#define SOLAR_CYCLE_SECS   0x34AADC80UL  /* 7*1461*86400*/

#define SOLAR_CYCLE_YEARS  28

#define MINFOLD -3

#define MAXFOLD  3

static struct tm *

get_struct_tm(

  const vint64 *stamp,

  int       local)

{

  struct tm *tm  = NULL;

  int32    folds = 0;

  time_t     ts;

#ifdef HAVE_INT64

  int64 tl;

  ts = tl = stamp->q_s;

  /*

   * If there is chance of truncation, try to fix it. Let the

   * compiler find out if this can happen at all.

   */

  while (ts != tl) { /* truncation? */

    if (tl < 0) {

      if (--folds < MINFOLD)

        return NULL;

      tl += SOLAR_CYCLE_SECS;

    } else {

      if (++folds > MAXFOLD)

        return NULL;

      tl -= SOLAR_CYCLE_SECS;

    }

    ts = tl; /* next try... */

  }

#else

  /*

   * since we do not have 64-bit scalars, it's not likely we have

   * 64-bit time_t. Assume 32 bits and properly reduce the value.

   */

  u_int32 hi, lo;

  hi = stamp->D_s.hi;

  lo = stamp->D_s.lo;

  while ((hi && ~hi) || ((hi ^ lo) & 0x80000000u)) {

    if (M_ISNEG(hi, lo)) {

      if (--folds < MINFOLD)

        return NULL;

      M_ADD(hi, lo, 0, SOLAR_CYCLE_SECS);

    } else {

      if (++folds > MAXFOLD)

        return NULL;

      M_SUB(hi, lo, 0, SOLAR_CYCLE_SECS);

    }

  }

  ts = (int32)lo;

#endif

  /*

   * 'ts' should be a suitable value by now. Just go ahead, but

   * with care:

   *

   * There are some pathological implementations of 'gmtime()'

   * and 'localtime()' out there. No matter if we have 32-bit or

   * 64-bit 'time_t', try to fix this by solar cycle warping

   * again...

   *

   * At least the MSDN says that the (Microsoft) Windoze

   * versions of 'gmtime()' and 'localtime()' will bark on time

   * stamps < 0.

   */

  while ((tm = (*(local ? localtime : gmtime))(&ts)) == NULL)

    if (ts < 0) {

      if (--folds < MINFOLD)

        return NULL;

      ts += SOLAR_CYCLE_SECS;

    } else if (ts >= (time_t)SOLAR_CYCLE_SECS) {

      if (++folds > MAXFOLD)

        return NULL;

      ts -= SOLAR_CYCLE_SECS;

    } else

      return NULL; /* That's truly pathological! */

  /* 'tm' surely not NULL here! */

  INSIST(tm != NULL);

  if (folds != 0) {

    tm->tm_year += folds * SOLAR_CYCLE_YEARS;

    if (tm->tm_year <= 0 || tm->tm_year >= 200)

      return NULL; /* left warp range... can't help here! */

  }

  return tm;

}

static char *

common_prettydate(

  l_fp *ts,

  int local

  )

{

  static const char pfmt0[] =

      "%08lx.%08lx  %s, %s %2d %4d %2d:%02d:%02d.%03u";

  static const char pfmt1[] =

      "%08lx.%08lx [%s, %s %2d %4d %2d:%02d:%02d.%03u UTC]";

  char      *bp;

  struct tm   *tm;

  u_int      msec;

  u_int32      ntps;

  vint64       sec;

  LIB_GETBUF(bp);

  if (ts->l_ui == 0 && ts->l_uf == 0) {

    strlcpy (bp, "(no time)", LIB_BUFLENGTH);

    return (bp);

  }

  /* get & fix milliseconds */

  ntps = ts->l_ui;

  msec = ts->l_uf / 4294967;  /* fract / (2 ** 32 / 1000) */

  if (msec >= 1000u) {

    msec -= 1000u;

    ntps++;

  }

  sec = ntpcal_ntp_to_time(ntps, NULL);

  tm  = get_struct_tm(&sec, local);

  if (!tm) {

    /*

     * get a replacement, but always in UTC, using

     * ntpcal_time_to_date()

     */

    struct calendar jd;

    ntpcal_time_to_date(&jd, &sec);

    snprintf(bp, LIB_BUFLENGTH, local ? pfmt1 : pfmt0,

       (u_long)ts->l_ui, (u_long)ts->l_uf,

       daynames[jd.weekday], months[jd.month-1],

       jd.monthday, jd.year, jd.hour,

       jd.minute, jd.second, msec);

  } else    

    snprintf(bp, LIB_BUFLENGTH, pfmt0,

       (u_long)ts->l_ui, (u_long)ts->l_uf,

       daynames[tm->tm_wday], months[tm->tm_mon],

       tm->tm_mday, 1900 + tm->tm_year, tm->tm_hour,

       tm->tm_min, tm->tm_sec, msec);

  return bp;

}

char *

prettydate(

  l_fp *ts

  )

{

  return common_prettydate(ts, 1);

}

char *

gmprettydate(

  l_fp *ts

  )

{

  return common_prettydate(ts, 0);

}

struct tm *

ntp2unix_tm(

  u_int32 ntp, int local

  )

{

  vint64 vl;

  vl = ntpcal_ntp_to_time(ntp, NULL);

  return get_struct_tm(&vl, local);

}