/* -------------------------------------------------------------------------
 *
 * findtimezone.c
 *	  Functions for determining the default timezone to use.
 *
 * Portions Copyright (c) 1996-2012, PostgreSQL Global Development Group
 *
 * IDENTIFICATION
 *	  src/bin/initdb/findtimezone.c
 *
 * -------------------------------------------------------------------------
 */
#include "postgres_fe.h"
#include <time.h>
#include <fcntl.h>

#include "pgtz.h"
#include "bin/elog.h"

#define TZNAME_LENGTH 128
#define LOCAL_TZNAME_LENGTH 256

/* Ideally this would be in a .h file, but it hardly seems worth the trouble */
extern const char* select_default_timezone(const char* share_path);

#ifndef SYSTEMTZDIR
static char tzdirpath[MAXPGPATH];
#endif

#ifndef ERROR_LIMIT_LEN
#define ERROR_LIMIT_LEN 256
#endif

/*
 * Return full pathname of timezone data directory
 *
 * In this file, tzdirpath is assumed to be set up by select_default_timezone.
 */
static const char* pg_TZDIR(void)
{
#ifndef SYSTEMTZDIR
    /* normal case: timezone stuff is under our share dir */
    return tzdirpath;
#else
    /* we're configured to use system's timezone database */
    return SYSTEMTZDIR;
#endif
}

/*
 * Given a timezone name, open() the timezone data file.  Return the
 * file descriptor if successful, -1 if not.
 *
 * This is simpler than the backend function of the same name because
 * we assume that the input string has the correct case already, so there
 * is no need for case-folding.  (This is obviously true if we got the file
 * name from the filesystem to start with.	The only other place it can come
 * from is the environment variable TZ, and there seems no need to allow
 * case variation in that; other programs aren't likely to.)
 *
 * If "canonname" is not NULL, then on success the canonical spelling of the
 * given name is stored there (the buffer must be > TZ_STRLEN_MAX bytes!).
 * This is redundant but kept for compatibility with the backend code.
 */
int pg_open_tzfile(const char* name, char* canonname)
{
    char fullname[MAXPGPATH];
    errno_t rc = 0;

    if (canonname != NULL) {
        rc = strncpy_s(canonname, TZ_STRLEN_MAX + 1, name, TZ_STRLEN_MAX);
        securec_check_c(rc, "\0", "\0");
    }

    rc = strcpy_s(fullname, MAXPGPATH, pg_TZDIR());
    securec_check_c(rc, "\0", "\0");
    if (strlen(fullname) + 1 + strlen(name) >= MAXPGPATH)
        return -1; /* not gonna fit */
    rc = strcat_s(fullname, MAXPGPATH, "/");
    securec_check_c(rc, "\0", "\0");
    rc = strcat_s(fullname, MAXPGPATH, name);
    securec_check_c(rc, "\0", "\0");

    return open(fullname, O_RDONLY | PG_BINARY, 0);
}

/*
 * Load a timezone definition.
 * Does not verify that the timezone is acceptable!
 *
 * This corresponds to the backend's pg_tzset(), except that we only support
 * one loaded timezone at a time.
 */
static pg_tz* pg_load_tz(const char* name)
{
    static pg_tz tz;
    errno_t rc = 0;

    if (strlen(name) > TZ_STRLEN_MAX)
        return NULL; /* not going to fit */

    /*
     * "GMT" is always sent to tzparse(); see comments for pg_tzset().
     */
    if (strcmp(name, "GMT") == 0) {
        if (tzparse(name, &tz.state, TRUE) != 0) {
            /* This really, really should not happen ... */
            return NULL;
        }
    } else if (tzload(name, NULL, &tz.state, TRUE) != 0) {
        if (name[0] == ':' || tzparse(name, &tz.state, FALSE) != 0) {
            return NULL; /* unknown timezone */
        }
    }

    rc = strcpy_s(tz.TZname, (TZ_STRLEN_MAX + 1), name);
    securec_check_c(rc, "\0", "\0");

    return &tz;
}

/*
 * The following block of code attempts to determine which timezone in our
 * timezone database is the best match for the active system timezone.
 *
 * On most systems, we rely on trying to match the observable behavior of
 * the C library's localtime() function.  The database zone that matches
 * furthest into the past is the one to use.  Often there will be several
 * zones with identical rankings (since the Olson database assigns multiple
 * names to many zones).  We break ties arbitrarily by preferring shorter,
 * then alphabetically earlier zone names.
 *
 * Win32's native knowledge about timezones appears to be too incomplete
 * and too different from the Olson database for the above matching strategy
 * to be of any use. But there is just a limited number of timezones
 * available, so we can rely on a handmade mapping table instead.
 */

#ifndef WIN32

#define T_DAY ((time_t)(60 * 60 * 24))
#define T_WEEK ((time_t)(60 * 60 * 24 * 7))
#define T_MONTH ((time_t)(60 * 60 * 24 * 31))

#define MAX_TEST_TIMES (52 * 100) /* 100 years */

struct tztry {
    int n_test_times;
    time_t test_times[MAX_TEST_TIMES];
};

/*
 * Get GMT offset from a system struct tm
 */
static int get_timezone_offset(struct tm* tm_val)
{
#if defined(HAVE_STRUCT_TM_TM_ZONE)
    return tm_val->tm_gmtoff;
#elif defined(HAVE_INT_TIMEZONE)
    return -TIMEZONE_GLOBAL;
#else
#error No way to determine TZ? Can this happen?
#endif
}

/*
 * Convenience subroutine to convert y/m/d to time_t (NOT pg_time_t)
 */
static time_t build_time_t(int year, int month, int day)
{
    struct tm tm_val;
    errno_t rc = 0;

    rc = memset_s(&tm_val, sizeof(tm_val), 0, sizeof(tm_val));
    securec_check_c(rc, "\0", "\0");
    tm_val.tm_mday = day;
    tm_val.tm_mon = month - 1;
    tm_val.tm_year = year - 1900;

    return mktime(&tm_val);
}

/*
 * Does a system tm value match one we computed ourselves?
 */
static bool compare_tm(struct tm* s, struct pg_tm* p)
{
    if (s->tm_sec != p->tm_sec || s->tm_min != p->tm_min || s->tm_hour != p->tm_hour || s->tm_mday != p->tm_mday ||
        s->tm_mon != p->tm_mon || s->tm_year != p->tm_year || s->tm_wday != p->tm_wday || s->tm_yday != p->tm_yday ||
        s->tm_isdst != p->tm_isdst)
        return false;
    return true;
}

/*
 * See how well a specific timezone setting matches the system behavior
 *
 * We score a timezone setting according to the number of test times it
 * matches.  (The test times are ordered later-to-earlier, but this routine
 * doesn't actually know that; it just scans until the first non-match.)
 *
 * We return -1 for a completely unusable setting; this is worse than the
 * score of zero for a setting that works but matches not even the first
 * test time.
 */
static int score_timezone(const char* tz_name, struct tztry* tt)
{
    int i;
    pg_time_t pgtt;
    struct tm* systm = NULL;
    struct pg_tm* pgtm = NULL;
    char cbuf[TZ_STRLEN_MAX + 1];
    pg_tz* tz = NULL;
    errno_t rc = 0;

    /* Load timezone definition */
    tz = pg_load_tz(tz_name);
    if (tz == NULL)
        return -1; /* unrecognized zone name */

    /* Reject if leap seconds involved */
    if (!pg_tz_acceptable(tz)) {
#ifdef DEBUG_IDENTIFY_TIMEZONE
        write_stderr("Reject TZ \"%s\": uses leap seconds\n", tz_name);
#endif
        return -1;
    }

    /* Check for match at all the test times */
    for (i = 0; i < tt->n_test_times; i++) {
        pgtt = (pg_time_t)(tt->test_times[i]);
        pgtm = pg_localtime(&pgtt, tz);
        if (pgtm == NULL) {
            return -1; /* probably shouldn't happen */
        }
        systm = localtime(&(tt->test_times[i]));
        if (systm == NULL) {
#ifdef DEBUG_IDENTIFY_TIMEZONE
            write_stderr("TZ \"%s\" scores %d: at %ld %04d-%02d-%02d %02d:%02d:%02d %s, system had no data\n",
                tz_name,
                i,
                (long)pgtt,
                pgtm->tm_year + 1900,
                pgtm->tm_mon + 1,
                pgtm->tm_mday,
                pgtm->tm_hour,
                pgtm->tm_min,
                pgtm->tm_sec,
                pgtm->tm_isdst ? "dst" : "std");
#endif
            return i;
        }
        if (!compare_tm(systm, pgtm)) {
#ifdef DEBUG_IDENTIFY_TIMEZONE
            write_stderr("TZ \"%s\" scores %d: at %ld %04d-%02d-%02d %02d:%02d:%02d %s versus %04d-%02d-%02d "
                         "%02d:%02d:%02d %s\n",
                tz_name,
                i,
                (long)pgtt,
                pgtm->tm_year + 1900,
                pgtm->tm_mon + 1,
                pgtm->tm_mday,
                pgtm->tm_hour,
                pgtm->tm_min,
                pgtm->tm_sec,
                pgtm->tm_isdst ? "dst" : "std",
                systm->tm_year + 1900,
                systm->tm_mon + 1,
                systm->tm_mday,
                systm->tm_hour,
                systm->tm_min,
                systm->tm_sec,
                systm->tm_isdst ? "dst" : "std");
#endif
            return i;
        }
        if (systm->tm_isdst >= 0) {
            /* Check match of zone names, too */
            if (pgtm->tm_zone == NULL)
                return -1; /* probably shouldn't happen */
            rc = memset_s(cbuf, (TZ_STRLEN_MAX + 1), 0, sizeof(cbuf));
            securec_check_c(rc, "\0", "\0");
            (void)strftime(cbuf, sizeof(cbuf) - 1, "%Z", systm); /* zone abbr */
            if (strcmp(cbuf, pgtm->tm_zone) != 0) {
#ifdef DEBUG_IDENTIFY_TIMEZONE
                write_stderr(
                    "TZ \"%s\" scores %d: at %ld \"%s\" versus \"%s\"\n", tz_name, i, (long)pgtt, pgtm->tm_zone, cbuf);
#endif
                return i;
            }
        }
    }

#ifdef DEBUG_IDENTIFY_TIMEZONE
    write_stderr("TZ \"%s\" gets max score %d\n", tz_name, i);
#endif

    return i;
}

/*
 * Try to identify a timezone name (in our terminology) that best matches the
 * observed behavior of the system timezone library.  We cannot assume that
 * the system TZ environment setting (if indeed there is one) matches our
 * terminology, so we ignore it and just look at what localtime() returns.
 */
const char* identify_system_timezone(void)
{
    static char resultbuf[TZ_STRLEN_MAX + 1];
    time_t tnow;
    time_t t;
    struct tztry tt = {0};
    struct tm* tm_val = NULL;
    int thisyear;
    int bestscore;
    char tmptzdir[MAXPGPATH];
    int std_ofs;
    char std_zone_name[TZ_STRLEN_MAX + 1], dst_zone_name[TZ_STRLEN_MAX + 1];
    char cbuf[TZ_STRLEN_MAX + 1];
    errno_t rc = 0;
    int nRet = 0;

    /* Initialize OS timezone library */
    tzset();

    /*
     * Set up the list of dates to be probed to see how well our timezone
     * matches the system zone.  We first probe January and July of the
     * current year; this serves to quickly eliminate the vast majority of the
     * TZ database entries.  If those dates match, we probe every week for 100
     * years backwards from the current July.  (Weekly resolution is good
     * enough to identify DST transition rules, since everybody switches on
     * Sundays.)  This is sufficient to cover most of the Unix time_t range,
     * and we don't want to look further than that since many systems won't
     * have sane TZ behavior further back anyway.  The further back the zone
     * matches, the better we score it.  This may seem like a rather random
     * way of doing things, but experience has shown that system-supplied
     * timezone definitions are likely to have DST behavior that is right for
     * the recent past and not so accurate further back. Scoring in this way
     * allows us to recognize zones that have some commonality with the Olson
     * database, without insisting on exact match. (Note: we probe Thursdays,
     * not Sundays, to avoid triggering DST-transition bugs in localtime
     * itself.)
     */
    tnow = time(NULL);
    tm_val = localtime(&tnow);
    if (tm_val == NULL) {
        return NULL; /* give up if localtime is broken... */
    }
    thisyear = tm_val->tm_year + 1900;

    t = build_time_t(thisyear, 1, 15);

    /*
     * Round back to GMT midnight Thursday.  This depends on the knowledge
     * that the time_t origin is Thu Jan 01 1970.  (With a different origin
     * we'd be probing some other day of the week, but it wouldn't matter
     * anyway unless localtime() had DST-transition bugs.)
     */
    t -= (t % T_WEEK);

    tt.n_test_times = 0;
    tt.test_times[tt.n_test_times++] = t;

    t = build_time_t(thisyear, 7, 15);
    t -= (t % T_WEEK);

    tt.test_times[tt.n_test_times++] = t;

    while (tt.n_test_times < MAX_TEST_TIMES) {
        t -= T_WEEK;
        tt.test_times[tt.n_test_times++] = t;
    }

    /* Search for the best-matching timezone file */
    rc = strncpy_s(tmptzdir, MAXPGPATH, pg_TZDIR(), MAXPGPATH - 1);
    securec_check_c(rc, "\0", "\0");
    bestscore = -1;
    resultbuf[0] = '\0';
    scan_available_timezones(tmptzdir, tmptzdir + strlen(tmptzdir) + 1, &tt, &bestscore, resultbuf);
    if (bestscore > 0) {
        /* Ignore Olson's rather silly "Factory" zone; use GMT instead */
        if (strcmp(resultbuf, "Factory") == 0)
            return NULL;
        return resultbuf;
    }

    /*
     * Couldn't find a match in the database, so next we try constructed zone
     * names (like "PST8PDT").
     *
     * First we need to determine the names of the local standard and daylight
     * zones.  The idea here is to scan forward from today until we have seen
     * both zones, if both are in use.
     */
    rc = memset_s(std_zone_name, (TZ_STRLEN_MAX + 1), 0, sizeof(std_zone_name));
    securec_check_c(rc, "\0", "\0");
    rc = memset_s(dst_zone_name, (TZ_STRLEN_MAX + 1), 0, sizeof(dst_zone_name));
    securec_check_c(rc, "\0", "\0");
    std_ofs = 0;

    tnow = time(NULL);

    /*
     * Round back to a GMT midnight so results don't depend on local time of
     * day
     */
    tnow -= (tnow % T_DAY);

    /*
     * We have to look a little further ahead than one year, in case today is
     * just past a DST boundary that falls earlier in the year than the next
     * similar boundary.  Arbitrarily scan up to 14 months.
     */
    for (t = tnow; t <= tnow + T_MONTH * 14; t += T_MONTH) {
        tm_val = localtime(&t);
        if (tm_val == NULL) {
            continue;
        }
        if (tm_val->tm_isdst < 0) {
            continue;
        }
        if (tm_val->tm_isdst == 0 && std_zone_name[0] == '\0') {
            /* found STD zone */
            rc = memset_s(cbuf, (TZ_STRLEN_MAX + 1), 0, sizeof(cbuf));
            securec_check_c(rc, "\0", "\0");
            (void)strftime(cbuf, sizeof(cbuf) - 1, "%Z", tm_val); /* zone abbr */
            rc = strcpy_s(std_zone_name, (TZ_STRLEN_MAX + 1), cbuf);
            securec_check_c(rc, "\0", "\0");
            std_ofs = get_timezone_offset(tm_val);
        }
        if (tm_val->tm_isdst > 0 && dst_zone_name[0] == '\0') {
            /* found DST zone */
            rc = memset_s(cbuf, (TZ_STRLEN_MAX + 1), 0, sizeof(cbuf));
            securec_check_c(rc, "\0", "\0");
            (void)strftime(cbuf, sizeof(cbuf) - 1, "%Z", tm_val); /* zone abbr */
            rc = strcpy_s(dst_zone_name, (TZ_STRLEN_MAX + 1), cbuf);
            securec_check_c(rc, "\0", "\0");
        }
        /* Done if found both */
        if (std_zone_name[0] && dst_zone_name[0])
            break;
    }

    /* We should have found a STD zone name by now... */
    if (std_zone_name[0] == '\0') {
#ifdef DEBUG_IDENTIFY_TIMEZONE
        write_stderr("could not determine system time zone\n");
#endif
        return NULL; /* go to GMT */
    }

    /* If we found DST then try STD<ofs>DST */
    if (dst_zone_name[0] != '\0') {
        nRet = snprintf_s(resultbuf,
            sizeof(resultbuf),
            sizeof(resultbuf) - 1,
            "%s%d%s",
            std_zone_name,
            -std_ofs / 3600,
            dst_zone_name);
        securec_check_ss_c(nRet, "\0", "\0");
        if (score_timezone(resultbuf, &tt) > 0)
            return resultbuf;
    }

    /* Try just the STD timezone (works for GMT at least) */
    rc = strcpy_s(resultbuf, (TZ_STRLEN_MAX + 1), std_zone_name);
    securec_check_c(rc, "\0", "\0");
    if (score_timezone(resultbuf, &tt) > 0)
        return resultbuf;

    /* Try STD<ofs> */
    nRet = snprintf_s(resultbuf, sizeof(resultbuf), sizeof(resultbuf) - 1, "%s%d", std_zone_name, -std_ofs / 3600);
    securec_check_ss_c(nRet, "\0", "\0");
    if (score_timezone(resultbuf, &tt) > 0)
        return resultbuf;

    /*
     * Did not find the timezone.  Fallback to use a GMT zone.	Note that the
     * Olson timezone database names the GMT-offset zones in POSIX style: plus
     * is west of Greenwich.  It's unfortunate that this is opposite of SQL
     * conventions.  Should we therefore change the names? Probably not...
     */
    nRet = snprintf_s(
        resultbuf, sizeof(resultbuf), sizeof(resultbuf) - 1, "Etc/GMT%s%d", (-std_ofs > 0) ? "+" : "", -std_ofs / 3600);
    securec_check_ss_c(nRet, "\0", "\0");

#ifdef DEBUG_IDENTIFY_TIMEZONE
    write_stderr("could not recognize system time zone, using \"%s\"\n", resultbuf);
#endif
    return resultbuf;
}

/*
 * Recursively scan the timezone database looking for the best match to
 * the system timezone behavior.
 *
 * tzdir points to a buffer of size MAXPGPATH.	On entry, it holds the
 * pathname of a directory containing TZ files.  We internally modify it
 * to hold pathnames of sub-directories and files, but must restore it
 * to its original contents before exit.
 *
 * tzdirsub points to the part of tzdir that represents the subfile name
 * (ie, tzdir + the original directory name length, plus one for the
 * first added '/').
 *
 * tt tells about the system timezone behavior we need to match.
 *
 * *bestscore and *bestzonename on entry hold the best score found so far
 * and the name of the best zone.  We overwrite them if we find a better
 * score.  bestzonename must be a buffer of length TZ_STRLEN_MAX + 1.
 */
void scan_available_timezones(char* tzdir, char* tzdirsub, struct tztry* tt, int* bestscore, char* bestzonename)
{
    int tzdir_orig_len = strlen(tzdir);
    char** names;
    char** namep;

    names = pgfnames(tzdir);
    if (names == NULL) {
        return;
    }

    for (namep = names; *namep != NULL; namep++) {
        char* name = *namep;
        struct stat statbuf;
        int nRet = 0;

        /* Ignore . and .., plus any other "hidden" files */
        if (name[0] == '.') {
            continue;
        }

        nRet = snprintf_s(
            tzdir + tzdir_orig_len, (MAXPGPATH - tzdir_orig_len), MAXPGPATH - tzdir_orig_len - 1, "/%s", name);
        securec_check_ss_c(nRet, "\0", "\0");

        if (stat(tzdir, &statbuf) != 0) {
#ifdef DEBUG_IDENTIFY_TIMEZONE
            char errBuffer[ERROR_LIMIT_LEN];
            write_stderr("could not stat \"%s\": %s\n", tzdir, pqStrerror(errno, errBuffer, ERROR_LIMIT_LEN));
#endif
            tzdir[tzdir_orig_len] = '\0';
            continue;
        }

        if (S_ISDIR(statbuf.st_mode)) {
            /* Recurse into subdirectory */
            scan_available_timezones(tzdir, tzdirsub, tt, bestscore, bestzonename);
        } else {
            /* Load and test this file */
            int score = score_timezone(tzdirsub, tt);

            if (score > *bestscore) {
                *bestscore = score;
                nRet = strncpy_s(bestzonename, TZ_STRLEN_MAX + 1, tzdirsub, TZ_STRLEN_MAX);
                securec_check_ss_c(nRet, "\0", "\0");
            } else if (score == *bestscore) {
                /* Consider how to break a tie */
                if (strlen(tzdirsub) < strlen(bestzonename) ||
                    (strlen(tzdirsub) == strlen(bestzonename) && strcmp(tzdirsub, bestzonename) < 0)) {
                    nRet = strncpy_s(bestzonename, TZ_STRLEN_MAX + 1, tzdirsub, TZ_STRLEN_MAX);
                    securec_check_ss_c(nRet, "\0", "\0");
                }
            }
        }

        /* Restore tzdir */
        tzdir[tzdir_orig_len] = '\0';
    }

    pgfnames_cleanup(names);
}
#else /* WIN32 */

static const struct {
    const char* stdname;  /* Windows name of standard timezone */
    const char* dstname;  /* Windows name of daylight timezone */
    const char* pgtzname; /* Name of pgsql timezone to map to */
} win32_tzmap[] =

    {
        /*
         * This list was built from the contents of the registry at
         * HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Time
         * Zones on Windows 2003 R2.
         *
         * The zones have been matched to Olson timezones by looking at the cities
         * listed in the win32 display name (in the comment here) in most cases.
         */
        {"Afghanistan Standard Time", "Afghanistan Daylight Time", "Asia/Kabul"}, /* (GMT+04:30) Kabul */
        {"Alaskan Standard Time", "Alaskan Daylight Time", "US/Alaska"},          /* (GMT-09:00) Alaska */
        {"Arab Standard Time", "Arab Daylight Time", "Asia/Kuwait"},              /* (GMT+03:00) Kuwait, Riyadh */
        {"Arabian Standard Time", "Arabian Daylight Time", "Asia/Muscat"},        /* (GMT+04:00) Abu Dhabi, Muscat */
        {"Arabic Standard Time", "Arabic Daylight Time", "Asia/Baghdad"},         /* (GMT+03:00) Baghdad */
        {"Argentina Standard Time", "Argentina Daylight Time", "America/Buenos_Aires"}, /* (GMT-03:00) Buenos Aires */
        {"Armenian Standard Time", "Armenian Daylight Time", "Asia/Yerevan"},           /* (GMT+04:00) Yerevan */
        {"Atlantic Standard Time",
            "Atlantic Daylight Time",
            "Canada/Atlantic"}, /* (GMT-04:00) Atlantic Time (Canada) */
        {"AUS Central Standard Time", "AUS Central Daylight Time", "Australia/Darwin"}, /* (GMT+09:30) Darwin */
        {"AUS Eastern Standard Time",
            "AUS Eastern Daylight Time",
            "Australia/Canberra"}, /* (GMT+10:00) Canberra, Melbourne, Sydney */
        {"Azerbaijan Standard Time", "Azerbaijan Daylight Time", "Asia/Baku"},  /* (GMT+04:00) Baku */
        {"Azores Standard Time", "Azores Daylight Time", "Atlantic/Azores"},    /* (GMT-01:00) Azores */
        {"Bangladesh Standard Time", "Bangladesh Daylight Time", "Asia/Dhaka"}, /* (GMT+06:00) Dhaka */
        {"Canada Central Standard Time",
            "Canada Central Daylight Time",
            "Canada/Saskatchewan"}, /* (GMT-06:00) Saskatchewan */
        {"Cape Verde Standard Time",
            "Cape Verde Daylight Time",
            "Atlantic/Cape_Verde"},                                        /* (GMT-01:00) Cape Verde Is. */
        {"Caucasus Standard Time", "Caucasus Daylight Time", "Asia/Baku"}, /* (GMT+04:00) Baku, Tbilisi, Yerevan */
        {"Cen. Australia Standard Time",
            "Cen. Australia Daylight Time",
            "Australia/Adelaide"}, /* (GMT+09:30) Adelaide */
        /* Central America (other than Mexico) generally does not observe DST */
        {"Central America Standard Time", "Central America Daylight Time", "CST6"}, /* (GMT-06:00) Central America */
        {"Central Asia Standard Time", "Central Asia Daylight Time", "Asia/Dhaka"}, /* (GMT+06:00) Astana, Dhaka */
        {"Central Brazilian Standard Time",
            "Central Brazilian Daylight Time",
            "America/Cuiaba"}, /* (GMT-04:00) Cuiaba */
        {"Central Europe Standard Time",
            "Central Europe Daylight Time",
            "Europe/Belgrade"}, /* (GMT+01:00) Belgrade, Bratislava, Budapest,
                                 * Ljubljana, Prague */
        {"Central European Standard Time",
            "Central European Daylight Time",
            "Europe/Sarajevo"}, /* (GMT+01:00) Sarajevo, Skopje, Warsaw,
                                 * Zagreb */
        {"Central Pacific Standard Time",
            "Central Pacific Daylight Time",
            "Pacific/Noumea"},                                            /* (GMT+11:00) Magadan, Solomon Is., New
                                                                           * Caledonia */
        {"Central Standard Time", "Central Daylight Time", "US/Central"}, /* (GMT-06:00) Central Time (US & Canada) */
        {"Central Standard Time (Mexico)",
            "Central Daylight Time (Mexico)",
            "America/Mexico_City"},                                       /* (GMT-06:00) Guadalajara, Mexico City,
                                                                           * Monterrey - New */
        {"China Standard Time", "China Daylight Time", "Asia/Hong_Kong"}, /* (GMT+08:00) Beijing, Chongqing, Hong Kong,
                                                                           * Urumqi */
        {"Dateline Standard Time",
            "Dateline Daylight Time",
            "Etc/GMT+12"}, /* (GMT-12:00) International Date Line West */
        {"E. Africa Standard Time", "E. Africa Daylight Time", "Africa/Nairobi"},           /* (GMT+03:00) Nairobi */
        {"E. Australia Standard Time", "E. Australia Daylight Time", "Australia/Brisbane"}, /* (GMT+10:00) Brisbane */
        {"E. Europe Standard Time", "E. Europe Daylight Time", "Europe/Bucharest"},         /* (GMT+02:00) Bucharest */
        {"E. South America Standard Time",
            "E. South America Daylight Time",
            "America/Araguaina"},                                         /* (GMT-03:00) Brasilia */
        {"Eastern Standard Time", "Eastern Daylight Time", "US/Eastern"}, /* (GMT-05:00) Eastern Time (US & Canada) */
        {"Egypt Standard Time", "Egypt Daylight Time", "Africa/Cairo"},   /* (GMT+02:00) Cairo */
        {"Ekaterinburg Standard Time",
            "Ekaterinburg Daylight Time",
            "Asia/Yekaterinburg"},                                     /* (GMT+05:00) Ekaterinburg */
        {"Fiji Standard Time", "Fiji Daylight Time", "Pacific/Fiji"},  /* (GMT+12:00) Fiji, Kamchatka, Marshall Is. */
        {"FLE Standard Time", "FLE Daylight Time", "Europe/Helsinki"}, /* (GMT+02:00) Helsinki, Kyiv, Riga, Sofia,
                                                                        * Tallinn, Vilnius */
        {"Georgian Standard Time", "Georgian Daylight Time", "Asia/Tbilisi"}, /* (GMT+03:00) Tbilisi */
        {"GMT Standard Time", "GMT Daylight Time", "Europe/London"},          /* (GMT) Greenwich Mean Time : Dublin,
                                                                               * Edinburgh, Lisbon, London */
        {"Greenland Standard Time", "Greenland Daylight Time", "America/Godthab"},   /* (GMT-03:00) Greenland */
        {"Greenwich Standard Time", "Greenwich Daylight Time", "Africa/Casablanca"}, /* (GMT) Casablanca, Monrovia */
        {"GTB Standard Time", "GTB Daylight Time", "Europe/Athens"},       /* (GMT+02:00) Athens, Istanbul, Minsk */
        {"Hawaiian Standard Time", "Hawaiian Daylight Time", "US/Hawaii"}, /* (GMT-10:00) Hawaii */
        {"India Standard Time", "India Daylight Time", "Asia/Calcutta"},   /* (GMT+05:30) Chennai, Kolkata, Mumbai, New
                                                                            * Delhi */
        {"Iran Standard Time", "Iran Daylight Time", "Asia/Tehran"},       /* (GMT+03:30) Tehran */
        {"Jerusalem Standard Time", "Jerusalem Daylight Time", "Asia/Jerusalem"}, /* (GMT+02:00) Jerusalem */
        {"Jordan Standard Time", "Jordan Daylight Time", "Asia/Amman"},           /* (GMT+02:00) Amman */
        {"Kamchatka Standard Time",
            "Kamchatka Daylight Time",
            "Asia/Kamchatka"},                                        /* (GMT+12:00) Petropavlovsk-Kamchatsky */
        {"Korea Standard Time", "Korea Daylight Time", "Asia/Seoul"}, /* (GMT+09:00) Seoul */
        {"Mauritius Standard Time", "Mauritius Daylight Time", "Indian/Mauritius"}, /* (GMT+04:00) Port Louis */
        {"Mexico Standard Time", "Mexico Daylight Time", "America/Mexico_City"},    /* (GMT-06:00) Guadalajara, Mexico
                                                                                     * City,    Monterrey */
        {"Mexico Standard Time 2",
            "Mexico Daylight Time 2",
            "America/Chihuahua"}, /* (GMT-07:00) Chihuahua, La Paz, Mazatlan */
        {"Mid-Atlantic Standard Time",
            "Mid-Atlantic Daylight Time",
            "Atlantic/South_Georgia"},                                                  /* (GMT-02:00) Mid-Atlantic */
        {"Middle East Standard Time", "Middle East Daylight Time", "Asia/Beirut"},      /* (GMT+02:00) Beirut */
        {"Montevideo Standard Time", "Montevideo Daylight Time", "America/Montevideo"}, /* (GMT-03:00) Montevideo */
        {"Morocco Standard Time", "Morocco Daylight Time", "Africa/Casablanca"},        /* (GMT) Casablanca */
        {"Mountain Standard Time",
            "Mountain Daylight Time",
            "US/Mountain"}, /* (GMT-07:00) Mountain Time (US & Canada) */
        {"Mountain Standard Time (Mexico)",
            "Mountain Daylight Time (Mexico)",
            "America/Chihuahua"},                                           /* (GMT-07:00) Chihuahua, La Paz, Mazatlan -
                                                                             * New */
        {"Myanmar Standard Time", "Myanmar Daylight Time", "Asia/Rangoon"}, /* (GMT+06:30) Rangoon */
        {"N. Central Asia Standard Time",
            "N. Central Asia Daylight Time",
            "Asia/Novosibirsk"},                                               /* (GMT+06:00) Novosibirsk */
        {"Namibia Standard Time", "Namibia Daylight Time", "Africa/Windhoek"}, /* (GMT+02:00) Windhoek */
        {"Nepal Standard Time", "Nepal Daylight Time", "Asia/Katmandu"},       /* (GMT+05:45) Kathmandu */
        {"New Zealand Standard Time",
            "New Zealand Daylight Time",
            "Pacific/Auckland"}, /* (GMT+12:00) Auckland, Wellington */
        {"Newfoundland Standard Time",
            "Newfoundland Daylight Time",
            "Canada/Newfoundland"}, /* (GMT-03:30) Newfoundland */
        {"North Asia East Standard Time",
            "North Asia East Daylight Time",
            "Asia/Irkutsk"}, /* (GMT+08:00) Irkutsk, Ulaan Bataar */
        {"North Asia Standard Time", "North Asia Daylight Time", "Asia/Krasnoyarsk"}, /* (GMT+07:00) Krasnoyarsk */
        {"Pacific SA Standard Time", "Pacific SA Daylight Time", "America/Santiago"}, /* (GMT-04:00) Santiago */
        {"Pacific Standard Time", "Pacific Daylight Time", "US/Pacific"}, /* (GMT-08:00) Pacific Time (US & Canada);
                                                                           * Tijuana */
        {"Pacific Standard Time (Mexico)",
            "Pacific Daylight Time (Mexico)",
            "America/Tijuana"},                                               /* (GMT-08:00) Tijuana, Baja California */
        {"Pakistan Standard Time", "Pakistan Daylight Time", "Asia/Karachi"}, /* (GMT+05:00) Islamabad, Karachi */
        {"Paraguay Standard Time", "Paraguay Daylight Time", "America/Asuncion"}, /* (GMT-04:00) Asuncion */
        {"Romance Standard Time", "Romance Daylight Time", "Europe/Brussels"},    /* (GMT+01:00) Brussels, Copenhagen,
                                                                                   * Madrid,    Paris */
        {"Russian Standard Time", "Russian Daylight Time", "Europe/Moscow"},      /* (GMT+03:00) Moscow, St. Petersburg,
                                                                                   * Volgograd */
        {"SA Eastern Standard Time",
            "SA Eastern Daylight Time",
            "America/Buenos_Aires"}, /* (GMT-03:00) Buenos Aires, Georgetown */
        {"SA Pacific Standard Time",
            "SA Pacific Daylight Time",
            "America/Bogota"}, /* (GMT-05:00) Bogota, Lima, Quito */
        {"SA Western Standard Time", "SA Western Daylight Time", "America/Caracas"}, /* (GMT-04:00) Caracas, La Paz */
        {"Samoa Standard Time", "Samoa Daylight Time", "Pacific/Midway"},   /* (GMT-11:00) Midway Island, Samoa */
        {"SE Asia Standard Time", "SE Asia Daylight Time", "Asia/Bangkok"}, /* (GMT+07:00) Bangkok, Hanoi, Jakarta */
        {"Malay Peninsula Standard Time",
            "Malay Peninsula Daylight Time",
            "Asia/Kuala_Lumpur"}, /* (GMT+08:00) Kuala Lumpur, Singapore */
        {"South Africa Standard Time",
            "South Africa Daylight Time",
            "Africa/Harare"},                                                     /* (GMT+02:00) Harare, Pretoria */
        {"Sri Lanka Standard Time", "Sri Lanka Daylight Time", "Asia/Colombo"},   /* (GMT+06:00) Sri Jayawardenepura */
        {"Taipei Standard Time", "Taipei Daylight Time", "Asia/Taipei"},          /* (GMT+08:00) Taipei */
        {"Tasmania Standard Time", "Tasmania Daylight Time", "Australia/Hobart"}, /* (GMT+10:00) Hobart */
        {"Tokyo Standard Time", "Tokyo Daylight Time", "Asia/Tokyo"},        /* (GMT+09:00) Osaka, Sapporo, Tokyo */
        {"Tonga Standard Time", "Tonga Daylight Time", "Pacific/Tongatapu"}, /* (GMT+13:00) Nuku'alofa */
        {
            "Ulaanbaatar Standard Time",
            "Ulaanbaatar Daylight Time",
            "Asia/Ulaanbaatar",
        },                                                                        /* (GMT+08:00) Ulaanbaatar */
        {"US Eastern Standard Time", "US Eastern Daylight Time", "US/Eastern"},   /* (GMT-05:00) Indiana (East) */
        {"US Mountain Standard Time", "US Mountain Daylight Time", "US/Arizona"}, /* (GMT-07:00) Arizona */
        {"Coordinated Universal Time", "Coordinated Universal Time", "UTC"},      /* (GMT) Coordinated Universal Time */
        {"UTC+12", "UTC+12", "Etc/GMT+12"}, /* (GMT+12:00) Coordinated Universal Time+12 */
        {"UTC-02", "UTC-02", "Etc/GMT-02"}, /* (GMT-02:00) Coordinated Universal Time-02 */
        {"UTC-11", "UTC-11", "Etc/GMT-11"}, /* (GMT-11:00) Coordinated Universal Time-11 */
        {
            "Venezuela Standard Time",
            "Venezuela Daylight Time",
            "America/Caracas",
        },                                                                               /* (GMT-04:30) Caracas */
        {"Vladivostok Standard Time", "Vladivostok Daylight Time", "Asia/Vladivostok"},  /* (GMT+10:00) Vladivostok */
        {"W. Australia Standard Time", "W. Australia Daylight Time", "Australia/Perth"}, /* (GMT+08:00) Perth */
#ifdef NOT_USED
        /* Could not find a match for this one (just a guess). Excluded for now. */
        {"W. Central Africa Standard Time",
            "W. Central Africa Daylight Time",
            "WAT"},                                                    /* (GMT+01:00) West Central Africa */
#endif
        {"W. Europe Standard Time", "W. Europe Daylight Time", "CET"}, /* (GMT+01:00) Amsterdam, Berlin, Bern, Rome,
                                                                        * Stockholm, Vienna */
        {"West Asia Standard Time",
            "West Asia Daylight Time",
            "Asia/Karachi"}, /* (GMT+05:00) Islamabad, Karachi, Tashkent */
        {"West Pacific Standard Time",
            "West Pacific Daylight Time",
            "Pacific/Guam"},                                                /* (GMT+10:00) Guam, Port Moresby */
        {"Yakutsk Standard Time", "Yakutsk Daylight Time", "Asia/Yakutsk"}, /* (GMT+09:00) Yakutsk */
        {NULL, NULL, NULL}};

const char* identify_system_timezone(void)
{
    int i;
    char tzname[TZNAME_LENGTH];
    char localtzname[LOCAL_TZNAME_LENGTH];
    time_t t = time(NULL);
    struct tm* tm = localtime(&t);
    HKEY rootKey = NULL;
    int idx;
    errno_t rc = 0;

    if (tm == NULL) {
#ifdef DEBUG_IDENTIFY_TIMEZONE
        write_stderr("could not identify system time zone: localtime() failed\n");
#endif
        return NULL; /* go to GMT */
    }

    rc = memset_s(tzname, TZNAME_LENGTH, 0, sizeof(tzname));
    securec_check_c(rc, "\0", "\0");
    (void)strftime(tzname, sizeof(tzname) - 1, "%Z", tm);

    for (i = 0; win32_tzmap[i].stdname != NULL; i++) {
        if (strcmp(tzname, win32_tzmap[i].stdname) == 0 || strcmp(tzname, win32_tzmap[i].dstname) == 0) {
#ifdef DEBUG_IDENTIFY_TIMEZONE
            write_stderr("TZ \"%s\" matches system time zone \"%s\"\n", win32_tzmap[i].pgtzname, tzname);
#endif
            return win32_tzmap[i].pgtzname;
        }
    }

    /*
     * Localized Windows versions return localized names for the timezone.
     * Scan the registry to find the English name, and then try matching
     * against our table again.
     */
    rc = memset_s(localtzname, LOCAL_TZNAME_LENGTH, 0, sizeof(localtzname));
    securec_check_c(rc, "\0", "\0");
    if (RegOpenKeyEx(
            HKEY_LOCAL_MACHINE, "SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion\\Time Zones", 0, KEY_READ, &rootKey) !=
        ERROR_SUCCESS) {
#ifdef DEBUG_IDENTIFY_TIMEZONE
        write_stderr("could not open registry key to identify system time zone: error code %lu\n", GetLastError());
#endif
        return NULL; /* go to GMT */
    }

    for (idx = 0;; idx++) {
        char keyname[LOCAL_TZNAME_LENGTH];
        char zonename[LOCAL_TZNAME_LENGTH];
        DWORD namesize;
        FILETIME lastwrite;
        HKEY key = NULL;
        LONG r;

        rc = memset_s(keyname, LOCAL_TZNAME_LENGTH, 0, sizeof(keyname));
        securec_check_c(rc, "\0", "\0");
        namesize = sizeof(keyname);
        if ((r = RegEnumKeyEx(rootKey, idx, keyname, &namesize, NULL, NULL, NULL, &lastwrite)) != ERROR_SUCCESS) {
            if (r == ERROR_NO_MORE_ITEMS)
                break;
#ifdef DEBUG_IDENTIFY_TIMEZONE
            write_stderr("could not enumerate registry subkeys to identify system time zone: %d\n", (int)r);
#endif
            break;
        }

        if ((r = RegOpenKeyEx(rootKey, keyname, 0, KEY_READ, &key)) != ERROR_SUCCESS) {
#ifdef DEBUG_IDENTIFY_TIMEZONE
            write_stderr("could not open registry subkey to identify system time zone: %d\n", (int)r);
#endif
            break;
        }

        rc = memset_s(zonename, LOCAL_TZNAME_LENGTH, 0, sizeof(zonename));
        securec_check_c(rc, "\0", "\0");
        namesize = sizeof(zonename);
        if ((r = RegQueryValueEx(key, "Std", NULL, NULL, (unsigned char*)zonename, &namesize)) != ERROR_SUCCESS) {
#ifdef DEBUG_IDENTIFY_TIMEZONE
            write_stderr(
                "could not query value for key \"std\" to identify system time zone \"%s\": %d\n", keyname, (int)r);
#endif
            RegCloseKey(key);
            continue; /* Proceed to look at the next timezone */
        }
        if (strcmp(tzname, zonename) == 0) {
            /* Matched zone */
            rc = strcpy_s(localtzname, LOCAL_TZNAME_LENGTH, keyname);
            securec_check_c(rc, "\0", "\0");
            RegCloseKey(key);
            break;
        }
        rc = memset_s(zonename, LOCAL_TZNAME_LENGTH, 0, sizeof(zonename));
        securec_check_c(rc, "\0", "\0");
        namesize = sizeof(zonename);
        if ((r = RegQueryValueEx(key, "Dlt", NULL, NULL, (unsigned char*)zonename, &namesize)) != ERROR_SUCCESS) {
#ifdef DEBUG_IDENTIFY_TIMEZONE
            write_stderr(
                "could not query value for key \"dlt\" to identify system time zone \"%s\": %d\n", keyname, (int)r);
#endif
            RegCloseKey(key);
            continue; /* Proceed to look at the next timezone */
        }
        if (strcmp(tzname, zonename) == 0) {
            /* Matched DST zone */
            rc = strcpy_s(localtzname, LOCAL_TZNAME_LENGTH, keyname);
            securec_check_c(rc, "\0", "\0");
            RegCloseKey(key);
            break;
        }

        RegCloseKey(key);
    }

    RegCloseKey(rootKey);

    if (localtzname[0]) {
        /* Found a localized name, so scan for that one too */
        for (i = 0; win32_tzmap[i].stdname != NULL; i++) {
            if (strcmp(localtzname, win32_tzmap[i].stdname) == 0 || strcmp(localtzname, win32_tzmap[i].dstname) == 0) {
#ifdef DEBUG_IDENTIFY_TIMEZONE
                write_stderr("TZ \"%s\" matches localized system time zone \"%s\" (\"%s\")\n",
                    win32_tzmap[i].pgtzname,
                    tzname,
                    localtzname);
#endif
                return win32_tzmap[i].pgtzname;
            }
        }
    }

#ifdef DEBUG_IDENTIFY_TIMEZONE
    write_stderr("could not find a match for system time zone \"%s\"\n", tzname);
#endif
    return NULL; /* go to GMT */
}
#endif /* WIN32 */

/*
 * Return true if the given zone name is valid and is an "acceptable" zone.
 */
static bool validate_zone(const char* tz_name)
{
    pg_tz* tz = NULL;

    if ((tz_name == NULL) || !tz_name[0]) {
        return false;
    }

    tz = pg_load_tz(tz_name);
    if (tz == NULL) {
        return false;
    }

    if (!pg_tz_acceptable(tz)) {
        return false;
    }

    return true;
}

/*
 * Identify a suitable default timezone setting based on the environment.
 *
 * The installation share_path must be passed in, as that is the default
 * location for the timezone database directory.
 *
 * We first look to the TZ environment variable.  If not found or not
 * recognized by our own code, we see if we can identify the timezone
 * from the behavior of the system timezone library.  When all else fails,
 * return NULL, indicating that we should default to GMT.
 */
const char* select_default_timezone(const char* share_path)
{
    const char* tz_name = NULL;
    int nRet = 0;

    /* Initialize timezone directory path, if needed */
#ifndef SYSTEMTZDIR
    nRet = snprintf_s(tzdirpath, sizeof(tzdirpath), sizeof(tzdirpath) - 1, "%s/timezone", share_path);
    securec_check_ss_c(nRet, "\0", "\0");
#endif

    /* Check TZ environment variable */
    tz_name = getenv("TZ");
    if (validate_zone(tz_name))
        return tz_name;

    /* Nope, so try to identify the system timezone */
    tz_name = identify_system_timezone();
    if (validate_zone(tz_name))
        return tz_name;

    return NULL;
}