/*      $NetBSD: parsetime.c,v 1.20 2019/02/16 17:56:57 kre Exp $       */

/*
 * parsetime.c - parse time for at(1)
 * Copyright (C) 1993, 1994  Thomas Koenig
 *
 * modifications for english-language times
 * Copyright (C) 1993  David Parsons
 *
 * 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. The name of the author(s) may not be used to endorse or promote
 *    products derived from this software without specific prior written
 *    permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``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 AUTHOR(S) 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, WETHER 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.
 *
 *  at [NOW] PLUS NUMBER MINUTES|HOURS|DAYS|WEEKS
 *     /NUMBER [DOT NUMBER] [AM|PM]\ /[MONTH NUMBER [NUMBER]]             \
 *     |NOON                       | |[TOMORROW]                          |
 *     |MIDNIGHT                   | |[DAY OF WEEK]                       |
 *     \TEATIME                    / |NUMBER [SLASH NUMBER [SLASH NUMBER]]|
 *                                   \PLUS NUMBER MINUTES|HOURS|DAYS|WEEKS/
 */

/* System Headers */

#include <sys/types.h>
#include <err.h>
#include <ctype.h>
#include <errno.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <tzfile.h>
#include <unistd.h>

/* Local headers */

#include "at.h"
#include "panic.h"
#include "parsetime.h"
#include "stime.h"

/* Structures and unions */

typedef enum { /* symbols */
        MIDNIGHT, NOON, TEATIME,
        PM, AM, TOMORROW, TODAY, NOW,
        MINUTES, HOURS, DAYS, WEEKS, MONTHS, YEARS,
        NUMBER, PLUS, DOT, SLASH, ID, JUNK,
        JAN, FEB, MAR, APR, MAY, JUN,
        JUL, AUG, SEP, OCT, NOV, DEC,
        SUN, MON, TUE, WED, THU, FRI, SAT,
        TOKEOF  /* EOF marker */
} tokid_t;

/*
 * parse translation table - table driven parsers can be your FRIEND!
 */
static const struct {
        const char *name;       /* token name */
        tokid_t value;          /* token id */
        bool plural;            /* is this plural? */
} Specials[] = {
        {"midnight", MIDNIGHT, false},  /* 00:00:00 of today or tomorrow */
        {"noon", NOON, false},          /* 12:00:00 of today or tomorrow */
        {"teatime", TEATIME, false},    /* 16:00:00 of today or tomorrow */
        {"am", AM, false},              /* morning times for 0-12 clock */
        {"pm", PM, false},              /* evening times for 0-12 clock */
        {"tomorrow", TOMORROW, false},  /* execute 24 hours from time */
        {"today", TODAY, false},                /* execute today - don't advance time */
        {"now", NOW, false},            /* opt prefix for PLUS */

        {"minute", MINUTES, false},     /* minutes multiplier */
        {"min", MINUTES, false},
        {"m", MINUTES, false},
        {"minutes", MINUTES, true},     /* (pluralized) */
        {"hour", HOURS, false},         /* hours ... */
        {"hr", HOURS, false},           /* abbreviated */
        {"h", HOURS, false},
        {"hours", HOURS, true},         /* (pluralized) */
        {"day", DAYS, false},           /* days ... */
        {"d", DAYS, false},
        {"days", DAYS, true},           /* (pluralized) */
        {"week", WEEKS, false},         /* week ... */
        {"w", WEEKS, false},
        {"weeks", WEEKS, true},         /* (pluralized) */
        { "month", MONTHS, 0 },         /* month ... */
        { "months", MONTHS, 1 },        /* (pluralized) */
        { "year", YEARS, 0 },           /* year ... */
        { "years", YEARS, 1 },          /* (pluralized) */
        {"jan", JAN, false},
        {"feb", FEB, false},
        {"mar", MAR, false},
        {"apr", APR, false},
        {"may", MAY, false},
        {"jun", JUN, false},
        {"jul", JUL, false},
        {"aug", AUG, false},
        {"sep", SEP, false},
        {"oct", OCT, false},
        {"nov", NOV, false},
        {"dec", DEC, false},
        {"january", JAN, false},
        {"february", FEB, false},
        {"march", MAR, false},
        {"april", APR, false},
        {"may", MAY, false},
        {"june", JUN, false},
        {"july", JUL, false},
        {"august", AUG, false},
        {"september", SEP, false},
        {"october", OCT, false},
        {"november", NOV, false},
        {"december", DEC, false},
        {"sunday", SUN, false},
        {"sun", SUN, false},
        {"monday", MON, false},
        {"mon", MON, false},
        {"tuesday", TUE, false},
        {"tue", TUE, false},
        {"wednesday", WED, false},
        {"wed", WED, false},
        {"thursday", THU, false},
        {"thu", THU, false},
        {"friday", FRI, false},
        {"fri", FRI, false},
        {"saturday", SAT, false},
        {"sat", SAT, false}
};

/* File scope variables */

static char **scp;      /* scanner - pointer at arglist */
static char scc;        /* scanner - count of remaining arguments */
static char *sct;       /* scanner - next char pointer in current argument */
static bool need;       /* scanner - need to advance to next argument */

static char *sc_token;  /* scanner - token buffer */
static size_t sc_len;   /* scanner - length of token buffer */
static tokid_t sc_tokid;/* scanner - token id */
static bool sc_tokplur; /* scanner - is token plural? */

#ifndef lint
#if 0
static char rcsid[] = "$OpenBSD: parsetime.c,v 1.4 1997/03/01 23:40:10 millert Exp $";
#else
__RCSID("$NetBSD: parsetime.c,v 1.20 2019/02/16 17:56:57 kre Exp $");
#endif
#endif

/* Local functions */
static void     assign_date(struct tm *, int, int, int);
static void     expect(tokid_t);
static void     init_scanner(int, char **);
static void     month(struct tm *);
static tokid_t  parse_token(char *);
static void     plonk(tokid_t) __dead;
static void     plus(struct tm *);
static void     tod(struct tm *);
static tokid_t  token(void);

/*
 * parse a token, checking if it's something special to us
 */
static tokid_t
parse_token(char *arg)
{
        size_t i;

        for (i=0; i < __arraycount(Specials); i++) {
                if (strcasecmp(Specials[i].name, arg) == 0) {
                        sc_tokplur = Specials[i].plural;
                        return sc_tokid = Specials[i].value;
                }
        }

        /* not special - must be some random id */
        return ID;
}

/*
 * init_scanner() sets up the scanner to eat arguments
 */
static void
init_scanner(int argc, char **argv)
{

        scp = argv;
        scc = argc;
        need = true;
        sc_len = 1;
        while (argc-- > 0)
                sc_len += strlen(*argv++);

        if ((sc_token = malloc(sc_len)) == NULL)
                panic("Insufficient virtual memory");
}

/*
 * token() fetches a token from the input stream
 */
static tokid_t
token(void)
{
        int idx;

        for(;;) {
                (void)memset(sc_token, 0, sc_len);
                sc_tokid = TOKEOF;
                sc_tokplur = false;
                idx = 0;

                /*
                 * if we need to read another argument, walk along the
                 * argument list; when we fall off the arglist, we'll
                 * just return TOKEOF forever
                 */
                if (need) {
                        if (scc < 1)
                                return sc_tokid;
                        sct = *scp;
                        scp++;
                        scc--;
                        need = false;
                }
                /*
                 * eat whitespace now - if we walk off the end of the argument,
                 * we'll continue, which puts us up at the top of the while loop
                 * to fetch the next argument in
                 */
                while (isspace((unsigned char)*sct))
                        ++sct;
                if (!*sct) {
                        need = true;
                        continue;
                }

                /*
                 * preserve the first character of the new token
                 */
                sc_token[0] = *sct++;

                /*
                 * then see what it is
                 */
                if (isdigit((unsigned char)sc_token[0])) {
                        while (isdigit((unsigned char)*sct))
                                sc_token[++idx] = *sct++;
                        sc_token[++idx] = 0;
                        return sc_tokid = NUMBER;
                } else if (isalpha((unsigned char)sc_token[0])) {
                        while (isalpha((unsigned char)*sct))
                                sc_token[++idx] = *sct++;
                        sc_token[++idx] = 0;
                        return parse_token(sc_token);
                }
                else if (sc_token[0] == ':' || sc_token[0] == '.')
                        return sc_tokid = DOT;
                else if (sc_token[0] == '+')
                        return sc_tokid = PLUS;
                else if (sc_token[0] == '/')
                        return sc_tokid = SLASH;
                else
                        return sc_tokid = JUNK;
        }
}

/*
 * plonk() gives an appropriate error message if a token is incorrect
 */
__dead
static void
plonk(tokid_t tok)
{

        panic(tok == TOKEOF ? "incomplete time" : "garbled time");
}

/*
 * expect() gets a token and dies most horribly if it's not the token we want
 */
static void
expect(tokid_t desired)
{

        if (token() != desired)
                plonk(sc_tokid);        /* and we die here... */
}

/*
 * plus() parses a now + time
 *
 *  at [NOW] PLUS NUMBER [MINUTES|HOURS|DAYS|WEEKS|MONTHS|YEARS]
 *
 */
static void
plus(struct tm *tm)
{
        int delay;
        int expectplur;

        expect(NUMBER);

        delay = atoi(sc_token);
        expectplur = delay != 1;

        switch (token()) {
        case YEARS:
                tm->tm_year += delay;
                break;
        case MONTHS:
                tm->tm_mon += delay;
                break;
        case WEEKS:
                delay *= 7;
                /*FALLTHROUGH*/
        case DAYS:
                tm->tm_mday += delay;
                break;
        case HOURS:
                tm->tm_hour += delay;
                break;
        case MINUTES:
                tm->tm_min += delay;
                break;
        default:
                plonk(sc_tokid);
                break;
        }

        if (expectplur != sc_tokplur)
                warnx("pluralization is wrong");

        tm->tm_isdst = -1;
        if (mktime(tm) == -1)
                plonk(sc_tokid);
}

/*
 * tod() computes the time of day
 *     [NUMBER [DOT NUMBER] [AM|PM]]
 */
static void
tod(struct tm *tm)
{
        int hour, minute;
        size_t tlen;

        minute = 0;
        hour = atoi(sc_token);
        tlen = strlen(sc_token);

        /*
         * first pick out the time of day - if it's 4 digits, we assume
         * a HHMM time, otherwise it's HH DOT MM time
         */
        if (token() == DOT) {
                expect(NUMBER);
                minute = atoi(sc_token);
                (void)token();
        } else if (tlen == 4) {
                minute = hour % 100;
                hour = hour / 100;
        }

        if (minute > 59)
                panic("garbled time");

        /*
         * check if an AM or PM specifier was given
         */
        if (sc_tokid == AM || sc_tokid == PM) {
                if (hour > 12)
                        panic("garbled time");

                if (sc_tokid == PM) {
                        if (hour != 12) /* 12:xx PM is 12:xx, not 24:xx */
                                hour += 12;
                } else {
                        if (hour == 12) /* 12:xx AM is 00:xx, not 12:xx */
                                hour = 0;
                }
                (void)token();
        } else if (hour > 23)
                panic("garbled time");

        /*
         * if we specify an absolute time, we don't want to bump the day even
         * if we've gone past that time - but if we're specifying a time plus
         * a relative offset, it's okay to bump things
         */
        if ((sc_tokid == TOKEOF || sc_tokid == PLUS) && (tm->tm_hour > hour ||
            (tm->tm_hour == hour && tm->tm_min > minute))) {
                tm->tm_mday++;
                tm->tm_wday++;
        }

        tm->tm_hour = hour;
        tm->tm_min = minute;
}

/*
 * assign_date() assigns a date, wrapping to next year if needed.
 * Accept years in 4-digit, 2-digit, or current year (-1).
 */
static void
assign_date(struct tm *tm, int mday, int mon, int year)
{

        if (year > 99) {        /* four digit year */
                if (year >= TM_YEAR_BASE)
                        tm->tm_year = year - TM_YEAR_BASE;
                else
                        panic("garbled time");
        }
        else if (year >= 0) {   /* two digit year */
                tm->tm_year = conv_2dig_year(year) - TM_YEAR_BASE;
        }
        else if (year == -1) {  /* year not given (use default in tm) */
                /* allow for 1 year range from current date */
                if (tm->tm_mon > mon ||
                    (tm->tm_mon == mon && tm->tm_mday > mday))
                        tm->tm_year++;
        }
        else
                panic("invalid year");

        tm->tm_mday = mday;
        tm->tm_mon = mon;
}

/*
 * month() picks apart a month specification
 *
 *  /[<month> NUMBER [NUMBER]]           \
 *  |[TOMORROW]                          |
 *  |[DAY OF WEEK]                       |
 *  |NUMBER [SLASH NUMBER [SLASH NUMBER]]|
 *  \PLUS NUMBER MINUTES|HOURS|DAYS|WEEKS/
 */
static void
month(struct tm *tm)
{
        int year;
        int mday, wday, mon;
        size_t tlen;

        year = -1;
        mday = 0;
        switch (sc_tokid) {
        case PLUS:
                plus(tm);
                break;

        case TOMORROW:
                /* do something tomorrow */
                tm->tm_mday++;
                tm->tm_wday++;
                /*FALLTHROUGH*/
        case TODAY:
                /* force ourselves to stay in today - no further processing */
                (void)token();
                break;

        case JAN: case FEB: case MAR: case APR: case MAY: case JUN:
        case JUL: case AUG: case SEP: case OCT: case NOV: case DEC:
                /*
                 * do month mday [year]
                 */
                mon = sc_tokid - JAN;
                expect(NUMBER);
                mday = atoi(sc_token);
                if (token() == NUMBER) {
                        year = atoi(sc_token);
                        (void)token();
                }
                assign_date(tm, mday, mon, year);
                break;

        case SUN: case MON: case TUE:
        case WED: case THU: case FRI:
        case SAT:
                /* do a particular day of the week */
                wday = sc_tokid - SUN;

                mday = tm->tm_mday;

                /* if this day is < today, then roll to next week */
                if (wday < tm->tm_wday)
                        mday += 7 - (tm->tm_wday - wday);
                else
                        mday += (wday - tm->tm_wday);

                tm->tm_wday = wday;

                assign_date(tm, mday, tm->tm_mon, tm->tm_year + TM_YEAR_BASE);
                break;

        case NUMBER:
                /*
                 * get numeric MMDDYY, mm/dd/yy, or dd.mm.yy
                 */
                tlen = strlen(sc_token);
                mon = atoi(sc_token);
                (void)token();

                if (sc_tokid == SLASH || sc_tokid == DOT) {
                        tokid_t sep;

                        sep = sc_tokid;
                        expect(NUMBER);
                        mday = atoi(sc_token);
                        if (token() == sep) {
                                expect(NUMBER);
                                year = atoi(sc_token);
                                (void)token();
                        }

                        /*
                         * flip months and days for european timing
                         */
                        if (sep == DOT) {
                                int x = mday;
                                mday = mon;
                                mon = x;
                        }
                } else if (tlen == 6 || tlen == 8) {
                        if (tlen == 8) {
                                year = (mon % 10000) - 1900;
                                mon /= 10000;
                        } else {
                                year = mon % 100;
                                mon /= 100;
                        }
                        mday = mon % 100;
                        mon /= 100;
                } else
                        panic("garbled time");

                mon--;
                if (mon < 0 || mon > 11 || mday < 1 || mday > 31)
                        panic("garbled time");

                assign_date(tm, mday, mon, year);
                break;
        default:
                /* plonk(sc_tokid); */  /* XXX - die here? */
                break;
        }
}


/* Global functions */

time_t
parsetime(int argc, char **argv)
{
        /*
         * Do the argument parsing, die if necessary, and return the
         * time the job should be run.
         */
        time_t nowtimer, runtimer;
        struct tm nowtime, runtime;
        int hr = 0; /* this MUST be initialized to zero for
                       midnight/noon/teatime */

        nowtimer = time(NULL);
        nowtime = *localtime(&nowtimer);

        runtime = nowtime;
        runtime.tm_sec = 0;

        if (argc <= optind)
                usage();

        init_scanner(argc - optind, argv + optind);

        switch (token()) {
        case NOW:
                if (scc < 1)
                        return nowtimer;

                /* now is optional prefix for PLUS tree */
                expect(PLUS);
                /*FALLTHROUGH*/
        case PLUS:
                plus(&runtime);
                break;

        case NUMBER:
                tod(&runtime);
                month(&runtime);
                break;

                /*
                 * evil coding for TEATIME|NOON|MIDNIGHT - we've initialised
                 * hr to zero up above, then fall into this case in such a
                 * way so we add +12 +4 hours to it for teatime, +12 hours
                 * to it for noon, and nothing at all for midnight, then
                 * set our runtime to that hour before leaping into the
                 * month scanner
                 */
        case TEATIME:
                hr += 4;
                /*FALLTHROUGH*/
        case NOON:
                hr += 12;
                /*FALLTHROUGH*/
        case MIDNIGHT:
                if (runtime.tm_hour >= hr) {
                        runtime.tm_mday++;
                        runtime.tm_wday++;
                }
                runtime.tm_hour = hr;
                runtime.tm_min = 0;
                (void)token();
                /*FALLTHROUGH*/ /* fall through to month setting */
        default:
                month(&runtime);
                break;
        }
        expect(TOKEOF);

        /*
         * adjust for daylight savings time
         */
        runtime.tm_isdst = -1;
        runtimer = mktime(&runtime);

        if (runtimer == (time_t)-1)
                panic("Invalid time");

        if (nowtimer > runtimer)
                panic("Trying to travel back in time");

        return runtimer;
}