/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1988 University of Utah.
 * Copyright (c) 1982, 1990, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * the Systems Programming Group of the University of Utah Computer
 * Science Department.
 *
 * 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.
 *
 *      from: Utah $Hdr: clock.c 1.18 91/01/21$
 *      from: NetBSD: clock_subr.c,v 1.6 2001/07/07 17:04:02 thorpej Exp
 *      and
 *      from: src/sys/i386/isa/clock.c,v 1.176 2001/09/04
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/bus.h>
#include <sys/clock.h>
#include <sys/limits.h>
#include <sys/sysctl.h>
#include <sys/timetc.h>

/*
 * The adjkerntz and wall_cmos_clock sysctls are in the "machdep" sysctl
 * namespace because they were misplaced there originally.
 */
static int adjkerntz;
static int
sysctl_machdep_adjkerntz(SYSCTL_HANDLER_ARGS)
{
        int error;
        error = sysctl_handle_int(oidp, oidp->oid_arg1, oidp->oid_arg2, req);
        if (!error && req->newptr)
                resettodr();
        return (error);
}
SYSCTL_PROC(_machdep, OID_AUTO, adjkerntz, CTLTYPE_INT | CTLFLAG_RW |
    CTLFLAG_MPSAFE, &adjkerntz, 0, sysctl_machdep_adjkerntz, "I",
    "Local offset from UTC in seconds");

static int ct_debug;
SYSCTL_INT(_debug, OID_AUTO, clocktime, CTLFLAG_RWTUN,
    &ct_debug, 0, "Enable printing of clocktime debugging");

static int wall_cmos_clock;
SYSCTL_INT(_machdep, OID_AUTO, wall_cmos_clock, CTLFLAG_RW,
    &wall_cmos_clock, 0, "Enables application of machdep.adjkerntz");

/*--------------------------------------------------------------------*
 * Generic routines to convert between a POSIX date
 * (seconds since 1/1/1970) and yr/mo/day/hr/min/sec
 * Derived from NetBSD arch/hp300/hp300/clock.c
 */

#define FEBRUARY        2
#define days_in_year(y)         (leapyear(y) ? 366 : 365)
#define days_in_month(y, m) \
        (month_days[(m) - 1] + (m == FEBRUARY ? leapyear(y) : 0))
/* Day of week. Days are counted from 1/1/1970, which was a Thursday */
#define day_of_week(days)       (((days) + 4) % 7)

static const int month_days[12] = {
        31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
};

/*
 * Optimization: using a precomputed count of days between POSIX_BASE_YEAR and
 * some recent year avoids lots of unnecessary loop iterations in conversion.
 * recent_base_days is the number of days before the start of recent_base_year.
 */
static const int recent_base_year = 2017;
static const int recent_base_days = 17167;

/*
 * Table to 'calculate' pow(10, 9 - nsdigits) via lookup of nsdigits.
 * Before doing the lookup, the code asserts 0 <= nsdigits <= 9.
 */
static u_int nsdivisors[] = {
    1000000000, 100000000, 10000000, 1000000, 100000, 10000, 1000, 100, 10, 1
};

/*
 * This inline avoids some unnecessary modulo operations
 * as compared with the usual macro:
 *   ( ((year % 4) == 0 &&
 *      (year % 100) != 0) ||
 *     ((year % 400) == 0) )
 * It is otherwise equivalent.
 */
static int
leapyear(int year)
{
        int rv = 0;

        if ((year & 3) == 0) {
                rv = 1;
                if ((year % 100) == 0) {
                        rv = 0;
                        if ((year % 400) == 0)
                                rv = 1;
                }
        }
        return (rv);
}

int
clock_ct_to_ts(const struct clocktime *ct, struct timespec *ts)
{
        int i, year, days;

        if (ct_debug) {
                printf("ct_to_ts([");
                clock_print_ct(ct, 9);
                printf("])");
        }

        /*
         * Many realtime clocks store the year as 2-digit BCD; pivot on 70 to
         * determine century.  Some clocks have a "century bit" and drivers do
         * year += 100, so interpret values between 70-199 as relative to 1900.
         */
        year = ct->year;
        if (year < 70)
                year += 2000;
        else if (year < 200)
                year += 1900;

        /* Sanity checks. */
        if (ct->mon < 1 || ct->mon > 12 || ct->day < 1 ||
            ct->day > days_in_month(year, ct->mon) ||
            ct->hour > 23 ||  ct->min > 59 || ct->sec > 59 || year < 1970 ||
            (sizeof(time_t) == 4 && year > 2037)) {     /* time_t overflow */
                if (ct_debug)
                        printf(" = EINVAL\n");
                return (EINVAL);
        }

        /*
         * Compute days since start of time
         * First from years, then from months.
         */
        if (year >= recent_base_year) {
                i = recent_base_year;
                days = recent_base_days;
        } else {
                i = POSIX_BASE_YEAR;
                days = 0;
        }
        for (; i < year; i++)
                days += days_in_year(i);

        /* Months */
        for (i = 1; i < ct->mon; i++)
                days += days_in_month(year, i);
        days += (ct->day - 1);

        ts->tv_sec = (((time_t)days * 24 + ct->hour) * 60 + ct->min) * 60 +
            ct->sec;
        ts->tv_nsec = ct->nsec;

        if (ct_debug)
                printf(" = %jd.%09ld\n", (intmax_t)ts->tv_sec, ts->tv_nsec);
        return (0);
}

int
clock_bcd_to_ts(const struct bcd_clocktime *bct, struct timespec *ts, bool ampm)
{
        struct clocktime ct;
        int bcent, byear;

        /*
         * Year may come in as 2-digit or 4-digit BCD.  Split the value into
         * separate BCD century and year values for validation and conversion.
         */
        bcent = bct->year >> 8;
        byear = bct->year & 0xff;

        /*
         * Ensure that all values are valid BCD numbers, to avoid assertions in
         * the BCD-to-binary conversion routines.  clock_ct_to_ts() will further
         * validate the field ranges (such as 0 <= min <= 59) during conversion.
         */
        if (!validbcd(bcent) || !validbcd(byear) || !validbcd(bct->mon) ||
            !validbcd(bct->day) || !validbcd(bct->hour) ||
            !validbcd(bct->min) || !validbcd(bct->sec)) {
                if (ct_debug)
                        printf("clock_bcd_to_ts: bad BCD: "
                            "[%04x-%02x-%02x %02x:%02x:%02x]\n",
                            bct->year, bct->mon, bct->day,
                            bct->hour, bct->min, bct->sec);
                return (EINVAL);
        }

        ct.year = FROMBCD(byear) + FROMBCD(bcent) * 100;
        ct.mon  = FROMBCD(bct->mon);
        ct.day  = FROMBCD(bct->day);
        ct.hour = FROMBCD(bct->hour);
        ct.min  = FROMBCD(bct->min);
        ct.sec  = FROMBCD(bct->sec);
        ct.dow  = bct->dow;
        ct.nsec = bct->nsec;

        /* If asked to handle am/pm, convert from 12hr+pmflag to 24hr. */
        if (ampm) {
                if (ct.hour == 12)
                        ct.hour = 0;
                if (bct->ispm)
                        ct.hour += 12;
        }

        return (clock_ct_to_ts(&ct, ts));
}

void
clock_ts_to_ct(const struct timespec *ts, struct clocktime *ct)
{
        time_t i, year, days;
        time_t rsec;    /* remainder seconds */
        time_t secs;

        secs = ts->tv_sec;
        days = secs / SECDAY;
        rsec = secs % SECDAY;

        ct->dow = day_of_week(days);

        /* Subtract out whole years. */
        if (days >= recent_base_days) {
                year = recent_base_year;
                days -= recent_base_days;
        } else {
                year = POSIX_BASE_YEAR;
        }
        for (; days >= days_in_year(year); year++)
                days -= days_in_year(year);
        ct->year = year;

        /* Subtract out whole months, counting them in i. */
        for (i = 1; days >= days_in_month(year, i); i++)
                days -= days_in_month(year, i);
        ct->mon = i;

        /* Days are what is left over (+1) from all that. */
        ct->day = days + 1;

        /* Hours, minutes, seconds are easy */
        ct->hour = rsec / 3600;
        rsec = rsec % 3600;
        ct->min  = rsec / 60;
        rsec = rsec % 60;
        ct->sec  = rsec;
        ct->nsec = ts->tv_nsec;
        if (ct_debug) {
                printf("ts_to_ct(%jd.%09ld) = [",
                    (intmax_t)ts->tv_sec, ts->tv_nsec);
                clock_print_ct(ct, 9);
                printf("]\n");
        }

        KASSERT(ct->year >= 0 && ct->year < 10000,
            ("year %d isn't a 4 digit year", ct->year));
        KASSERT(ct->mon >= 1 && ct->mon <= 12,
            ("month %d not in 1-12", ct->mon));
        KASSERT(ct->day >= 1 && ct->day <= 31,
            ("day %d not in 1-31", ct->day));
        KASSERT(ct->hour >= 0 && ct->hour <= 23,
            ("hour %d not in 0-23", ct->hour));
        KASSERT(ct->min >= 0 && ct->min <= 59,
            ("minute %d not in 0-59", ct->min));
        /* Not sure if this interface needs to handle leapseconds or not. */
        KASSERT(ct->sec >= 0 && ct->sec <= 60,
            ("seconds %d not in 0-60", ct->sec));
}

void
clock_ts_to_bcd(const struct timespec *ts, struct bcd_clocktime *bct, bool ampm)
{
        struct clocktime ct;

        clock_ts_to_ct(ts, &ct);

        /* If asked to handle am/pm, convert from 24hr to 12hr+pmflag. */
        bct->ispm = false;
        if (ampm) {
                if (ct.hour >= 12) {
                        ct.hour -= 12;
                        bct->ispm = true;
                }
                if (ct.hour == 0)
                        ct.hour = 12;
        }

        bct->year = TOBCD(ct.year % 100) | (TOBCD(ct.year / 100) << 8);
        bct->mon  = TOBCD(ct.mon);
        bct->day  = TOBCD(ct.day);
        bct->hour = TOBCD(ct.hour);
        bct->min  = TOBCD(ct.min);
        bct->sec  = TOBCD(ct.sec);
        bct->dow  = ct.dow;
        bct->nsec = ct.nsec;
}

void
clock_print_bcd(const struct bcd_clocktime *bct, int nsdigits)
{

        KASSERT(nsdigits >= 0 && nsdigits <= 9, ("bad nsdigits %d", nsdigits));

        if (nsdigits > 0) {
                printf("%4.4x-%2.2x-%2.2x %2.2x:%2.2x:%2.2x.%*.*ld",
                    bct->year, bct->mon, bct->day,
                    bct->hour, bct->min, bct->sec,
                    nsdigits, nsdigits, bct->nsec / nsdivisors[nsdigits]);
        } else {
                printf("%4.4x-%2.2x-%2.2x %2.2x:%2.2x:%2.2x",
                    bct->year, bct->mon, bct->day,
                    bct->hour, bct->min, bct->sec);
        }
}

void
clock_print_ct(const struct clocktime *ct, int nsdigits)
{

        KASSERT(nsdigits >= 0 && nsdigits <= 9, ("bad nsdigits %d", nsdigits));

        if (nsdigits > 0) {
                printf("%04d-%02d-%02d %02d:%02d:%02d.%*.*ld",
                    ct->year, ct->mon, ct->day,
                    ct->hour, ct->min, ct->sec,
                    nsdigits, nsdigits, ct->nsec / nsdivisors[nsdigits]);
        } else {
                printf("%04d-%02d-%02d %02d:%02d:%02d",
                    ct->year, ct->mon, ct->day,
                    ct->hour, ct->min, ct->sec);
        }
}

void
clock_print_ts(const struct timespec *ts, int nsdigits)
{
        struct clocktime ct;

        clock_ts_to_ct(ts, &ct);
        clock_print_ct(&ct, nsdigits);
}

int
utc_offset(void)
{

        return (wall_cmos_clock ? adjkerntz : 0);
}