/* Convert a broken-down timestamp to a string.  */

/*
 * Copyright 1989 The Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *	  notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *	  notice, this list of conditions and the following disclaimer in the
 *	  documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *	  may be used to endorse or promote products derived from this software
 *	  without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/*
 * Based on the UCB version with the copyright notice appearing above.
 *
 * This is ANSIish only when "multibyte character == plain character".
 *
 * IDENTIFICATION
 *	  src/timezone/strftime.c
 */

#include "postgres.h"

#include <fcntl.h>

#include "private.h"


struct lc_time_T
{
	const char *mon[MONSPERYEAR];
	const char *month[MONSPERYEAR];
	const char *wday[DAYSPERWEEK];
	const char *weekday[DAYSPERWEEK];
	const char *X_fmt;
	const char *x_fmt;
	const char *c_fmt;
	const char *am;
	const char *pm;
	const char *date_fmt;
};

#define Locale	(&C_time_locale)

static const struct lc_time_T C_time_locale = {
	{
		"Jan", "Feb", "Mar", "Apr", "May", "Jun",
		"Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
	}, {
		"January", "February", "March", "April", "May", "June",
		"July", "August", "September", "October", "November", "December"
	}, {
		"Sun", "Mon", "Tue", "Wed",
		"Thu", "Fri", "Sat"
	}, {
		"Sunday", "Monday", "Tuesday", "Wednesday",
		"Thursday", "Friday", "Saturday"
	},

	/* X_fmt */
	"%H:%M:%S",

	/*
	 * x_fmt
	 *
	 * C99 and later require this format. Using just numbers (as here) makes
	 * Quakers happier; it's also compatible with SVR4.
	 */
	"%m/%d/%y",

	/*
	 * c_fmt
	 *
	 * C99 and later require this format. Previously this code used "%D %X",
	 * but we now conform to C99. Note that "%a %b %d %H:%M:%S %Y" is used by
	 * Solaris 2.3.
	 */
	"%a %b %e %T %Y",

	/* am */
	"AM",

	/* pm */
	"PM",

	/* date_fmt */
	"%a %b %e %H:%M:%S %Z %Y"
};

enum warn
{
	IN_NONE, IN_SOME, IN_THIS, IN_ALL
};

static char *_add(const char *str, char *pt, const char *ptlim);
static char *_conv(int n, const char *format, char *pt, const char *ptlim);
static char *_fmt(const char *format, const struct pg_tm *t, char *pt, const char *ptlim,
				  enum warn *warnp);
static char *_yconv(int a, int b, bool convert_top, bool convert_yy, char *pt, char const *ptlim);


/*
 * Convert timestamp t to string s, a caller-allocated buffer of size maxsize,
 * using the given format pattern.
 *
 * Unlike standard strftime(), we guarantee to provide a null-terminated
 * result even on failure, so long as maxsize > 0.  If we overrun the buffer,
 * return an empty string rather than risking mis-encoded multibyte output.
 * (Since this module only supports C locale, you might think multibyte
 * characters are impossible --- but the time zone name printed by %Z comes
 * from outside and could contain such.)
 *
 * See also timestamptz_to_str.
 */
size_t
pg_strftime(char *s, size_t maxsize, const char *format, const struct pg_tm *t)
{
	char	   *p;
	int			saved_errno = errno;
	enum warn	warn = IN_NONE;

	p = _fmt(format, t, s, s + maxsize, &warn);
	if (!p)
	{
		errno = EOVERFLOW;
		if (maxsize > 0)
			*s = '\0';
		return 0;
	}
	if (p == s + maxsize)
	{
		errno = ERANGE;
		if (maxsize > 0)
			*s = '\0';
		return 0;
	}
	*p = '\0';
	errno = saved_errno;
	return p - s;
}

static char *
_fmt(const char *format, const struct pg_tm *t, char *pt,
	 const char *ptlim, enum warn *warnp)
{
	for (; *format; ++format)
	{
		if (*format == '%')
		{
	label:
			switch (*++format)
			{
				case '\0':
					--format;
					break;
				case 'A':
					pt = _add((t->tm_wday < 0 ||
							   t->tm_wday >= DAYSPERWEEK) ?
							  "?" : Locale->weekday[t->tm_wday],
							  pt, ptlim);
					continue;
				case 'a':
					pt = _add((t->tm_wday < 0 ||
							   t->tm_wday >= DAYSPERWEEK) ?
							  "?" : Locale->wday[t->tm_wday],
							  pt, ptlim);
					continue;
				case 'B':
					pt = _add((t->tm_mon < 0 ||
							   t->tm_mon >= MONSPERYEAR) ?
							  "?" : Locale->month[t->tm_mon],
							  pt, ptlim);
					continue;
				case 'b':
				case 'h':
					pt = _add((t->tm_mon < 0 ||
							   t->tm_mon >= MONSPERYEAR) ?
							  "?" : Locale->mon[t->tm_mon],
							  pt, ptlim);
					continue;
				case 'C':

					/*
					 * %C used to do a... _fmt("%a %b %e %X %Y", t);
					 * ...whereas now POSIX 1003.2 calls for something
					 * completely different. (ado, 1993-05-24)
					 */
					pt = _yconv(t->tm_year, TM_YEAR_BASE,
								true, false, pt, ptlim);
					continue;
				case 'c':
					{
						enum warn	warn2 = IN_SOME;

						pt = _fmt(Locale->c_fmt, t, pt, ptlim, &warn2);
						if (warn2 == IN_ALL)
							warn2 = IN_THIS;
						if (warn2 > *warnp)
							*warnp = warn2;
					}
					continue;
				case 'D':
					pt = _fmt("%m/%d/%y", t, pt, ptlim, warnp);
					continue;
				case 'd':
					pt = _conv(t->tm_mday, "%02d", pt, ptlim);
					continue;
				case 'E':
				case 'O':

					/*
					 * Locale modifiers of C99 and later. The sequences %Ec
					 * %EC %Ex %EX %Ey %EY %Od %oe %OH %OI %Om %OM %OS %Ou %OU
					 * %OV %Ow %OW %Oy are supposed to provide alternative
					 * representations.
					 */
					goto label;
				case 'e':
					pt = _conv(t->tm_mday, "%2d", pt, ptlim);
					continue;
				case 'F':
					pt = _fmt("%Y-%m-%d", t, pt, ptlim, warnp);
					continue;
				case 'H':
					pt = _conv(t->tm_hour, "%02d", pt, ptlim);
					continue;
				case 'I':
					pt = _conv((t->tm_hour % 12) ?
							   (t->tm_hour % 12) : 12,
							   "%02d", pt, ptlim);
					continue;
				case 'j':
					pt = _conv(t->tm_yday + 1, "%03d", pt, ptlim);
					continue;
				case 'k':

					/*
					 * This used to be... _conv(t->tm_hour % 12 ? t->tm_hour %
					 * 12 : 12, 2, ' '); ...and has been changed to the below
					 * to match SunOS 4.1.1 and Arnold Robbins' strftime
					 * version 3.0. That is, "%k" and "%l" have been swapped.
					 * (ado, 1993-05-24)
					 */
					pt = _conv(t->tm_hour, "%2d", pt, ptlim);
					continue;
#ifdef KITCHEN_SINK
				case 'K':

					/*
					 * After all this time, still unclaimed!
					 */
					pt = _add("kitchen sink", pt, ptlim);
					continue;
#endif							/* defined KITCHEN_SINK */
				case 'l':

					/*
					 * This used to be... _conv(t->tm_hour, 2, ' '); ...and
					 * has been changed to the below to match SunOS 4.1.1 and
					 * Arnold Robbin's strftime version 3.0. That is, "%k" and
					 * "%l" have been swapped. (ado, 1993-05-24)
					 */
					pt = _conv((t->tm_hour % 12) ?
							   (t->tm_hour % 12) : 12,
							   "%2d", pt, ptlim);
					continue;
				case 'M':
					pt = _conv(t->tm_min, "%02d", pt, ptlim);
					continue;
				case 'm':
					pt = _conv(t->tm_mon + 1, "%02d", pt, ptlim);
					continue;
				case 'n':
					pt = _add("\n", pt, ptlim);
					continue;
				case 'p':
					pt = _add((t->tm_hour >= (HOURSPERDAY / 2)) ?
							  Locale->pm :
							  Locale->am,
							  pt, ptlim);
					continue;
				case 'R':
					pt = _fmt("%H:%M", t, pt, ptlim, warnp);
					continue;
				case 'r':
					pt = _fmt("%I:%M:%S %p", t, pt, ptlim, warnp);
					continue;
				case 'S':
					pt = _conv(t->tm_sec, "%02d", pt, ptlim);
					continue;
				case 'T':
					pt = _fmt("%H:%M:%S", t, pt, ptlim, warnp);
					continue;
				case 't':
					pt = _add("\t", pt, ptlim);
					continue;
				case 'U':
					pt = _conv((t->tm_yday + DAYSPERWEEK -
								t->tm_wday) / DAYSPERWEEK,
							   "%02d", pt, ptlim);
					continue;
				case 'u':

					/*
					 * From Arnold Robbins' strftime version 3.0: "ISO 8601:
					 * Weekday as a decimal number [1 (Monday) - 7]" (ado,
					 * 1993-05-24)
					 */
					pt = _conv((t->tm_wday == 0) ?
							   DAYSPERWEEK : t->tm_wday,
							   "%d", pt, ptlim);
					continue;
				case 'V':		/* ISO 8601 week number */
				case 'G':		/* ISO 8601 year (four digits) */
				case 'g':		/* ISO 8601 year (two digits) */
/*
 * From Arnold Robbins' strftime version 3.0: "the week number of the
 * year (the first Monday as the first day of week 1) as a decimal number
 * (01-53)."
 * (ado, 1993-05-24)
 *
 * From <https://www.cl.cam.ac.uk/~mgk25/iso-time.html> by Markus Kuhn:
 * "Week 01 of a year is per definition the first week which has the
 * Thursday in this year, which is equivalent to the week which contains
 * the fourth day of January. In other words, the first week of a new year
 * is the week which has the majority of its days in the new year. Week 01
 * might also contain days from the previous year and the week before week
 * 01 of a year is the last week (52 or 53) of the previous year even if
 * it contains days from the new year. A week starts with Monday (day 1)
 * and ends with Sunday (day 7). For example, the first week of the year
 * 1997 lasts from 1996-12-30 to 1997-01-05..."
 * (ado, 1996-01-02)
 */
					{
						int			year;
						int			base;
						int			yday;
						int			wday;
						int			w;

						year = t->tm_year;
						base = TM_YEAR_BASE;
						yday = t->tm_yday;
						wday = t->tm_wday;
						for (;;)
						{
							int			len;
							int			bot;
							int			top;

							len = isleap_sum(year, base) ?
								DAYSPERLYEAR :
								DAYSPERNYEAR;

							/*
							 * What yday (-3 ... 3) does the ISO year begin
							 * on?
							 */
							bot = ((yday + 11 - wday) %
								   DAYSPERWEEK) - 3;

							/*
							 * What yday does the NEXT ISO year begin on?
							 */
							top = bot -
								(len % DAYSPERWEEK);
							if (top < -3)
								top += DAYSPERWEEK;
							top += len;
							if (yday >= top)
							{
								++base;
								w = 1;
								break;
							}
							if (yday >= bot)
							{
								w = 1 + ((yday - bot) /
										 DAYSPERWEEK);
								break;
							}
							--base;
							yday += isleap_sum(year, base) ?
								DAYSPERLYEAR :
								DAYSPERNYEAR;
						}
						if (*format == 'V')
							pt = _conv(w, "%02d",
									   pt, ptlim);
						else if (*format == 'g')
						{
							*warnp = IN_ALL;
							pt = _yconv(year, base,
										false, true,
										pt, ptlim);
						}
						else
							pt = _yconv(year, base,
										true, true,
										pt, ptlim);
					}
					continue;
				case 'v':

					/*
					 * From Arnold Robbins' strftime version 3.0: "date as
					 * dd-bbb-YYYY" (ado, 1993-05-24)
					 */
					pt = _fmt("%e-%b-%Y", t, pt, ptlim, warnp);
					continue;
				case 'W':
					pt = _conv((t->tm_yday + DAYSPERWEEK -
								(t->tm_wday ?
								 (t->tm_wday - 1) :
								 (DAYSPERWEEK - 1))) / DAYSPERWEEK,
							   "%02d", pt, ptlim);
					continue;
				case 'w':
					pt = _conv(t->tm_wday, "%d", pt, ptlim);
					continue;
				case 'X':
					pt = _fmt(Locale->X_fmt, t, pt, ptlim, warnp);
					continue;
				case 'x':
					{
						enum warn	warn2 = IN_SOME;

						pt = _fmt(Locale->x_fmt, t, pt, ptlim, &warn2);
						if (warn2 == IN_ALL)
							warn2 = IN_THIS;
						if (warn2 > *warnp)
							*warnp = warn2;
					}
					continue;
				case 'y':
					*warnp = IN_ALL;
					pt = _yconv(t->tm_year, TM_YEAR_BASE,
								false, true,
								pt, ptlim);
					continue;
				case 'Y':
					pt = _yconv(t->tm_year, TM_YEAR_BASE,
								true, true,
								pt, ptlim);
					continue;
				case 'Z':
					if (t->tm_zone != NULL)
						pt = _add(t->tm_zone, pt, ptlim);

					/*
					 * C99 and later say that %Z must be replaced by the empty
					 * string if the time zone abbreviation is not
					 * determinable.
					 */
					continue;
				case 'z':
					{
						long		diff;
						char const *sign;
						bool		negative;

						if (t->tm_isdst < 0)
							continue;
						diff = t->tm_gmtoff;
						negative = diff < 0;
						if (diff == 0)
						{
							if (t->tm_zone != NULL)
								negative = t->tm_zone[0] == '-';
						}
						if (negative)
						{
							sign = "-";
							diff = -diff;
						}
						else
							sign = "+";
						pt = _add(sign, pt, ptlim);
						diff /= SECSPERMIN;
						diff = (diff / MINSPERHOUR) * 100 +
							(diff % MINSPERHOUR);
						pt = _conv(diff, "%04d", pt, ptlim);
					}
					continue;
				case '+':
					pt = _fmt(Locale->date_fmt, t, pt, ptlim,
							  warnp);
					continue;
				case '%':

					/*
					 * X311J/88-090 (4.12.3.5): if conversion char is
					 * undefined, behavior is undefined. Print out the
					 * character itself as printf(3) also does.
					 */
				default:
					break;
			}
		}
		if (pt == ptlim)
			break;
		*pt++ = *format;
	}
	return pt;
}

static char *
_conv(int n, const char *format, char *pt, const char *ptlim)
{
	char		buf[INT_STRLEN_MAXIMUM(int) + 1];

	sprintf(buf, format, n);
	return _add(buf, pt, ptlim);
}

static char *
_add(const char *str, char *pt, const char *ptlim)
{
	while (pt < ptlim && (*pt = *str++) != '\0')
		++pt;
	return pt;
}

/*
 * POSIX and the C Standard are unclear or inconsistent about
 * what %C and %y do if the year is negative or exceeds 9999.
 * Use the convention that %C concatenated with %y yields the
 * same output as %Y, and that %Y contains at least 4 bytes,
 * with more only if necessary.
 */

static char *
_yconv(int a, int b, bool convert_top, bool convert_yy,
	   char *pt, const char *ptlim)
{
	int			lead;
	int			trail;

#define DIVISOR	100
	trail = a % DIVISOR + b % DIVISOR;
	lead = a / DIVISOR + b / DIVISOR + trail / DIVISOR;
	trail %= DIVISOR;
	if (trail < 0 && lead > 0)
	{
		trail += DIVISOR;
		--lead;
	}
	else if (lead < 0 && trail > 0)
	{
		trail -= DIVISOR;
		++lead;
	}
	if (convert_top)
	{
		if (lead == 0 && trail < 0)
			pt = _add("-0", pt, ptlim);
		else
			pt = _conv(lead, "%02d", pt, ptlim);
	}
	if (convert_yy)
		pt = _conv(((trail < 0) ? -trail : trail), "%02d", pt, ptlim);
	return pt;
}
