/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 1997 Wolfgang Helbig
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
 */

#include <sys/cdefs.h>
#include <calendar.h>
#include <ctype.h>
#include <err.h>
#include <langinfo.h>
#include <libgen.h>
#include <locale.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdbool.h>
#include <sysexits.h>
#include <time.h>
#include <unistd.h>
#include <wchar.h>
#include <wctype.h>
#include <term.h>
#undef lines                    /* term.h defines this */

/* Width of one month with backward compatibility and in regular mode*/
#define MONTH_WIDTH_B_J 27
#define MONTH_WIDTH_B 20

#define MONTH_WIDTH_R_J 24
#define MONTH_WIDTH_R 18

#define MAX_WIDTH 64

typedef struct date date;

struct monthlines {
        wchar_t name[MAX_WIDTH + 1];
        char lines[7][MAX_WIDTH + 1];
        char weeks[MAX_WIDTH + 1];
        unsigned int extralen[7];
};

struct weekdays {
        wchar_t names[7][4];
};

/* The switches from Julian to Gregorian in some countries */
static struct djswitch {
        const char *cc; /* Country code according to ISO 3166 */
        const char *nm; /* Name of country */
        date dt;        /* Last day of Julian calendar */
} switches[] = {
        {"AL", "Albania",       {1912, 11, 30}},
        {"AT", "Austria",       {1583, 10,  5}},
        {"AU", "Australia",     {1752,  9,  2}},
        {"BE", "Belgium",       {1582, 12, 14}},
        {"BG", "Bulgaria",      {1916,  3, 31}},
        {"CA", "Canada",        {1752,  9,  2}},
        {"CH", "Switzerland",   {1655,  2, 28}},
        {"CN", "China",         {1911, 12, 18}},
        {"CZ", "Czech Republic",{1584,  1,  6}},
        {"DE", "Germany",       {1700,  2, 18}},
        {"DK", "Denmark",       {1700,  2, 18}},
        {"ES", "Spain",         {1582, 10,  4}},
        {"FI", "Finland",       {1753,  2, 17}},
        {"FR", "France",        {1582, 12,  9}},
        {"GB", "United Kingdom",{1752,  9,  2}},
        {"GR", "Greece",        {1924,  3,  9}},
        {"HU", "Hungary",       {1587, 10, 21}},
        {"IS", "Iceland",       {1700, 11, 16}},
        {"IT", "Italy",         {1582, 10,  4}},
        {"JP", "Japan",         {1918, 12, 18}},
        {"LT", "Lithuania",     {1918,  2,  1}},
        {"LU", "Luxembourg",    {1582, 12, 14}},
        {"LV", "Latvia",        {1918,  2,  1}},
        {"NL", "Netherlands",   {1582, 12, 14}},
        {"NO", "Norway",        {1700,  2, 18}},
        {"PL", "Poland",        {1582, 10,  4}},
        {"PT", "Portugal",      {1582, 10,  4}},
        {"RO", "Romania",       {1919,  3, 31}},
        {"RU", "Russia",        {1918,  1, 31}},
        {"SI", "Slovenia",      {1919,  3,  4}},
        {"SE", "Sweden",        {1753,  2, 17}},
        {"TR", "Turkey",        {1926, 12, 18}},
        {"US", "United States", {1752,  9,  2}},
        {"YU", "Yugoslavia",    {1919,  3,  4}}
};

static struct djswitch *dftswitch =
    switches + sizeof(switches) / sizeof(struct djswitch) - 2;
    /* default switch (should be "US") */

/* Table used to print day of month and week numbers */
static char daystr[] = "     1  2  3  4  5  6  7  8  9 10 11 12 13 14 15"
                       " 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31"
                       " 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47"
                       " 48 49 50 51 52 53";

/* Table used to print day of year and week numbers */
static char jdaystr[] = "       1   2   3   4   5   6   7   8   9"
                        "  10  11  12  13  14  15  16  17  18  19"
                        "  20  21  22  23  24  25  26  27  28  29"
                        "  30  31  32  33  34  35  36  37  38  39"
                        "  40  41  42  43  44  45  46  47  48  49"
                        "  50  51  52  53  54  55  56  57  58  59"
                        "  60  61  62  63  64  65  66  67  68  69"
                        "  70  71  72  73  74  75  76  77  78  79"
                        "  80  81  82  83  84  85  86  87  88  89"
                        "  90  91  92  93  94  95  96  97  98  99"
                        " 100 101 102 103 104 105 106 107 108 109"
                        " 110 111 112 113 114 115 116 117 118 119"
                        " 120 121 122 123 124 125 126 127 128 129"
                        " 130 131 132 133 134 135 136 137 138 139"
                        " 140 141 142 143 144 145 146 147 148 149"
                        " 150 151 152 153 154 155 156 157 158 159"
                        " 160 161 162 163 164 165 166 167 168 169"
                        " 170 171 172 173 174 175 176 177 178 179"
                        " 180 181 182 183 184 185 186 187 188 189"
                        " 190 191 192 193 194 195 196 197 198 199"
                        " 200 201 202 203 204 205 206 207 208 209"
                        " 210 211 212 213 214 215 216 217 218 219"
                        " 220 221 222 223 224 225 226 227 228 229"
                        " 230 231 232 233 234 235 236 237 238 239"
                        " 240 241 242 243 244 245 246 247 248 249"
                        " 250 251 252 253 254 255 256 257 258 259"
                        " 260 261 262 263 264 265 266 267 268 269"
                        " 270 271 272 273 274 275 276 277 278 279"
                        " 280 281 282 283 284 285 286 287 288 289"
                        " 290 291 292 293 294 295 296 297 298 299"
                        " 300 301 302 303 304 305 306 307 308 309"
                        " 310 311 312 313 314 315 316 317 318 319"
                        " 320 321 322 323 324 325 326 327 328 329"
                        " 330 331 332 333 334 335 336 337 338 339"
                        " 340 341 342 343 344 345 346 347 348 349"
                        " 350 351 352 353 354 355 356 357 358 359"
                        " 360 361 362 363 364 365 366";

static int flag_highlight;      /* highlighted today */
static int flag_weeks;          /* user wants number of week */
static int nswitch;             /* user defined switch date */
static int nswitchb;            /* switch date for backward compatibility */
static int highlightdate;
static bool flag_monday;        /* user wants week starts on Monday */

static char     *center(char *s, char *t, int w);
static wchar_t *wcenter(wchar_t *s, wchar_t *t, int w);
static int      firstday(int y, int m);
static void     highlight(char *dst, char *src, int len, int *extraletters);
static void     mkmonthr(int year, int month, int jd_flag,
    struct monthlines * monthl);
static void     mkmonthb(int year, int month, int jd_flag,
    struct monthlines * monthl);
static void     mkweekdays(struct weekdays * wds);
static void     monthranger(int year, int m, int jd_flag,
    int before, int after);
static void     monthrangeb(int year, int m, int jd_flag,
    int before, int after);
static int      parsemonth(const char *s, int *m, int *y);
static void     printcc(void);
static void     printeaster(int year, int julian, int orthodox);
static date     *sdater(int ndays, struct date * d);
static date     *sdateb(int ndays, struct date * d);
static int      sndaysr(struct date * d);
static int      sndaysb(struct date * d);
static void     usage(void);

int
main(int argc, char *argv[])
{
        struct  djswitch *p, *q;        /* to search user defined switch date */
        date    never = {10000, 1, 1};  /* outside valid range of dates */
        date    ukswitch = {1752, 9, 2};/* switch date for Great Britain */
        date    dt;
        int     ch;                     /* holds the option character */
        int     m = 0;                  /* month */
        int     y = 0;                  /* year */
        int     flag_backward = 0;      /* user called cal--backward compat. */
        int     flag_wholeyear = 0;     /* user wants the whole year */
        int     flag_julian_cal = 0;    /* user wants Julian Calendar */
        int     flag_julian_day = 0;    /* user wants the Julian day numbers */
        int     flag_orthodox = 0;      /* user wants Orthodox easter */
        int     flag_easter = 0;        /* user wants easter date */
        int     flag_3months = 0;       /* user wants 3 month display (-3) */
        int     flag_after = 0;         /* user wants to see months after */
        int     flag_before = 0;        /* user wants to see months before */
        int     flag_specifiedmonth = 0;/* user wants to see this month (-m) */
        int     flag_givenmonth = 0;    /* user has specified month [n] */
        int     flag_givenyear = 0;     /* user has specified year [n] */
        char    *cp;                    /* character pointer */
        char    *flag_today = NULL;     /* debug: use date as being today */
        char    *flag_month = NULL;     /* requested month as string */
        char    *flag_highlightdate = NULL; /* debug: date to highlight */
        int     before, after;
        const char    *locale;          /* locale to get country code */

        flag_highlight = isatty(STDOUT_FILENO);
        flag_weeks = 0;
        flag_monday = false;

        /*
         * Use locale to determine the country code,
         * and use the country code to determine the default
         * switchdate and date format from the switches table.
         */
        if (setlocale(LC_ALL, "") == NULL)
                warn("setlocale");
        locale = setlocale(LC_TIME, NULL);
        if (locale == NULL ||
            strcmp(locale, "C") == 0 ||
            strcmp(locale, "POSIX") == 0 ||
            strcmp(locale, "ASCII") == 0 ||
            strcmp(locale, "US-ASCII") == 0)
                locale = "_US";
        q = switches + sizeof(switches) / sizeof(struct djswitch);
        for (p = switches; p != q; p++)
                if ((cp = strstr(locale, p->cc)) != NULL && *(cp - 1) == '_')
                        break;
        if (p == q) {
                nswitch = ndaysj(&dftswitch->dt);
        } else {
                nswitch = ndaysj(&p->dt);
                dftswitch = p;
        }


        /*
         * Get the filename portion of argv[0] and set flag_backward if
         * this program is called "cal".
         */
        if (strncmp(basename(argv[0]), "cal", strlen("cal")) == 0)
                flag_backward = 1;

        /* Set the switch date to United Kingdom if backwards compatible */
        if (flag_backward)
                nswitchb = ndaysj(&ukswitch);

        before = after = -1;

        while ((ch = getopt(argc, argv, "3A:B:Cd:eH:hjJm:Nops:wyM")) != -1)
                switch (ch) {
                case '3':
                        flag_3months = 1;
                        break;
                case 'A':
                        if (flag_after > 0)
                                errx(EX_USAGE, "Double -A specified");
                        flag_after = strtol(optarg, NULL, 10);
                        if (flag_after <= 0)
                                errx(EX_USAGE,
                                    "Argument to -A must be positive");
                        break;
                case 'B':
                        if (flag_before > 0)
                                errx(EX_USAGE, "Double -B specified");
                        flag_before = strtol(optarg, NULL, 10);
                        if (flag_before <= 0)
                                errx(EX_USAGE,
                                    "Argument to -B must be positive");
                        break;
                case 'J':
                        if (flag_backward)
                                usage();
                        nswitch = ndaysj(&never);
                        flag_julian_cal = 1;
                        break;
                case 'C':
                        flag_backward = 1;
                        break;
                case 'N':
                        flag_backward = 0;
                        break;
                case 'd':
                        flag_today = optarg;
                        break;
                case 'H':
                        flag_highlightdate = optarg;
                        break;
                case 'h':
                        flag_highlight = !flag_highlight;
                        break;
                case 'e':
                        if (flag_backward)
                                usage();
                        flag_easter = 1;
                        break;
                case 'j':
                        flag_julian_day = 1;
                        break;
                case 'M':
                        flag_monday = true;
                        break;
                case 'm':
                        if (flag_specifiedmonth)
                                errx(EX_USAGE, "Double -m specified");
                        flag_month = optarg;
                        flag_specifiedmonth = 1;
                        break;
                case 'o':
                        if (flag_backward)
                                usage();
                        flag_orthodox = 1;
                        flag_easter = 1;
                        break;
                case 'p':
                        if (flag_backward)
                                usage();
                        printcc();
                        return (0);
                        break;
                case 's':
                        if (flag_backward)
                                usage();
                        q = switches +
                            sizeof(switches) / sizeof(struct djswitch);
                        for (p = switches;
                             p != q && strcmp(p->cc, optarg) != 0; p++)
                                ;
                        if (p == q)
                                errx(EX_USAGE,
                                    "%s: invalid country code", optarg);
                        nswitch = ndaysj(&(p->dt));
                        break;
                case 'w':
                        if (flag_backward)
                                usage();
                        flag_weeks = 1;
                        break;
                case 'y':
                        flag_wholeyear = 1;
                        break;
                default:
                        usage();
                }

        argc -= optind;
        argv += optind;

        switch (argc) {
        case 2:
                if (flag_easter)
                        usage();
                flag_month = *argv++;
                flag_givenmonth = 1;
                m = strtol(flag_month, NULL, 10);
                /* FALLTHROUGH */
        case 1:
                y = atoi(*argv);
                if (y < 1 || y > 9999)
                        errx(EX_USAGE, "year `%s' not in range 1..9999", *argv);
                argv++;
                flag_givenyear = 1;
                break;
        case 0:
                if (flag_today != NULL) {
                        y = strtol(flag_today, NULL, 10);
                        m = strtol(flag_today + 5, NULL, 10);
                } else {
                        time_t t;
                        struct tm *tm;

                        t = time(NULL);
                        tm = localtime(&t);
                        y = tm->tm_year + 1900;
                        m = tm->tm_mon + 1;
                }
                break;
        default:
                usage();
        }

        if (flag_month != NULL) {
                if (parsemonth(flag_month, &m, &y)) {
                        errx(EX_USAGE,
                            "%s is neither a month number (1..12) nor a name",
                            flag_month);
                }
        }

        /*
         * What is not supported:
         * -3 with -A or -B
         *      -3 displays 3 months, -A and -B change that behaviour.
         * -3 with -y
         *      -3 displays 3 months, -y says display a whole year.
         * -3 with a given year but no given month or without -m
         *      -3 displays 3 months, no month specified doesn't make clear
         *      which three months.
         * -m with a given month
         *      conflicting arguments, both specify the same field.
         * -y with -m
         *      -y displays the whole year, -m displays a single month.
         * -y with a given month
         *      -y displays the whole year, the given month displays a single
         *      month.
         * -y with -A or -B
         *      -y displays the whole year, -A and -B display extra months.
         */

        /* -3 together with -A or -B. */
        if (flag_3months && (flag_after || flag_before))
                errx(EX_USAGE, "-3 together with -A and -B is not supported.");
        /* -3 together with -y. */
        if (flag_3months && flag_wholeyear)
                errx(EX_USAGE, "-3 together with -y is not supported.");
        /* -3 together with givenyear but no givenmonth. */
        if (flag_3months && flag_givenyear &&
            !(flag_givenmonth || flag_specifiedmonth))
                errx(EX_USAGE,
                    "-3 together with a given year but no given month is "
                    "not supported.");
        /* -m together with xx xxxx. */
        if (flag_specifiedmonth && flag_givenmonth)
                errx(EX_USAGE,
                    "-m together with a given month is not supported.");
        /* -y together with -m. */
        if (flag_wholeyear && flag_specifiedmonth)
                errx(EX_USAGE, "-y together with -m is not supported.");
        /* -y together with xx xxxx. */
        if (flag_wholeyear && flag_givenmonth)
                errx(EX_USAGE, "-y together a given month is not supported.");
        /* -y together with -A or -B. */
        if (flag_wholeyear && (flag_before > 0 || flag_after > 0))
                errx(EX_USAGE, "-y together a -A or -B is not supported.");
        /* The rest should be fine. */

        /* Select the period to display, in order of increasing priority .*/
        if (flag_wholeyear ||
            (flag_givenyear && !(flag_givenmonth || flag_specifiedmonth))) {
                m = 1;
                before = 0;
                after = 11;
        }
        if (flag_givenyear && flag_givenmonth) {
                before = 0;
                after = 0;
        }
        if (flag_specifiedmonth) {
                before = 0;
                after = 0;
        }
        if (flag_before) {
                before = flag_before;
        }
        if (flag_after) {
                after = flag_after;
        }
        if (flag_3months) {
                before = 1;
                after = 1;
        }
        if (after == -1)
                after = 0;
        if (before == -1)
                before = 0;

        /* Highlight a specified day or today .*/
        if (flag_highlightdate != NULL) {
                dt.y = strtol(flag_highlightdate, NULL, 10);
                dt.m = strtol(flag_highlightdate + 5, NULL, 10);
                dt.d = strtol(flag_highlightdate + 8, NULL, 10);
        } else {
                time_t t;
                struct tm *tm1;

                t = time(NULL);
                tm1 = localtime(&t);
                dt.y = tm1->tm_year + 1900;
                dt.m = tm1->tm_mon + 1;
                dt.d = tm1->tm_mday;
        }
        highlightdate = sndaysb(&dt);

        /* And now we finally start to calculate and output calendars. */
        if (flag_easter)
                printeaster(y, flag_julian_cal, flag_orthodox);
        else
                if (flag_backward)
                        monthrangeb(y, m, flag_julian_day, before, after);
                else
                        monthranger(y, m, flag_julian_day, before, after);
        if (ferror(stdout) != 0 || fflush(stdout) != 0)
                err(1, "stdout");
        return (0);
}

static void
usage(void)
{

        fputs(
"Usage: cal [general options] [-hjy] [[month] year]\n"
"       cal [general options] [-hj] [-m month] [year]\n"
"       ncal [general options] [-hJjpwy] [-s country_code] [[month] year]\n"
"       ncal [general options] [-hJeo] [year]\n"
"General options: [-NCM3] [-A months] [-B months]\n"
"For debug the highlighting: [-H yyyy-mm-dd] [-d yyyy-mm]\n",
            stderr);
        exit(EX_USAGE);
}

/* Print the assumed switches for all countries. */
static void
printcc(void)
{
        struct djswitch *p;
        int n;  /* number of lines to print */
        int m;  /* offset from left to right table entry on the same line */

#define FSTR "%c%s %-15s%4d-%02d-%02d"
#define DFLT(p) ((p) == dftswitch ? '*' : ' ')
#define FSTRARG(p) DFLT(p), (p)->cc, (p)->nm, (p)->dt.y, (p)->dt.m, (p)->dt.d

        n = sizeof(switches) / sizeof(struct djswitch);
        m = (n + 1) / 2;
        n /= 2;
        for (p = switches; p != switches + n; p++)
                printf(FSTR"     "FSTR"\n", FSTRARG(p), FSTRARG(p+m));
        if (m != n)
                printf(FSTR"\n", FSTRARG(p));
}

/* Print the date of easter sunday. */
static void
printeaster(int y, int julian, int orthodox)
{
        date    dt;
        struct tm tm;
        char    buf[MAX_WIDTH];
        static int d_first = -1;

        if (d_first < 0)
                d_first = (*nl_langinfo(D_MD_ORDER) == 'd');
        /* force orthodox easter for years before 1583 */
        if (y < 1583)
                orthodox = 1;

        if (orthodox)
                if (julian)
                        easteroj(y, &dt);
                else
                        easterog(y, &dt);
        else
                easterg(y, &dt);

        memset(&tm, 0, sizeof(tm));
        tm.tm_year = dt.y - 1900;
        tm.tm_mon  = dt.m - 1;
        tm.tm_mday = dt.d;
        strftime(buf, sizeof(buf), d_first ? "%e %B %Y" : "%B %e %Y",  &tm);
        printf("%s\n", buf);
}

#define MW(mw, me)              ((mw) + me)
#define DECREASEMONTH(m, y)             \
                if (--m == 0) {         \
                        m = 12;         \
                        y--;            \
                }
#define INCREASEMONTH(m, y)             \
                if (++(m) == 13) {      \
                        (m) = 1;        \
                        (y)++;          \
                }
#define M2Y(m)  ((m) / 12)
#define M2M(m)  (1 + (m) % 12)

/* Print all months for the period in the range [ before .. y-m .. after ]. */
static void
monthrangeb(int y, int m, int jd_flag, int before, int after)
{
        struct monthlines year[12];
        struct weekdays wds;
        char    s[MAX_WIDTH], t[MAX_WIDTH];
        wchar_t ws[MAX_WIDTH], ws1[MAX_WIDTH];
        const char      *wdss;
        int     i, j;
        int     mpl;
        int     mw;
        int     m1, m2;
        int     printyearheader;
        int     prevyear = -1;

        mpl = jd_flag ? 2 : 3;
        mw = jd_flag ? MONTH_WIDTH_B_J : MONTH_WIDTH_B;
        wdss = (mpl == 2) ? " " : "";

        while (before != 0) {
                DECREASEMONTH(m, y);
                before--;
                after++;
        }
        m1 = y * 12 + m - 1;
        m2 = m1 + after;

        mkweekdays(&wds);

        /*
         * The year header is printed when there are more than 'mpl' months
         * and if the first month is a multitude of 'mpl'.
         * If not, it will print the year behind every month.
         */
        printyearheader = (after >= mpl - 1) && (M2M(m1) - 1) % mpl == 0;

        m = m1;
        while (m <= m2) {
                int count = 0;
                for (i = 0; i != mpl && m + i <= m2; i++) {
                        mkmonthb(M2Y(m + i), M2M(m + i) - 1, jd_flag, year + i);
                        count++;
                }

                /* Empty line between two rows of months */
                if (m != m1)
                        printf("\n");

                /* Year at the top. */
                if (printyearheader && M2Y(m) != prevyear) {
                        sprintf(s, "%d", M2Y(m));
                        printf("%s\n", center(t, s, mpl * mw));
                        prevyear = M2Y(m);
                }

                /* Month names. */
                for (i = 0; i < count; i++)
                        if (printyearheader)
                                wprintf(L"%-*ls  ",
                                    mw, wcenter(ws, year[i].name, mw));
                        else {
                                swprintf(ws, sizeof(ws)/sizeof(ws[0]),
                                    L"%-ls %d", year[i].name, M2Y(m + i));
                                wprintf(L"%-*ls  ", mw, wcenter(ws1, ws, mw));
                        }
                printf("\n");

                /* Day of the week names. */
                for (i = 0; i < count; i++) {
                        wprintf(L"%s%ls%s%ls%s%ls%s%ls%s%ls%s%ls%s%ls ",
                                wdss, wds.names[flag_monday ? 0 : 6],
                                wdss, wds.names[flag_monday ? 1 : 0],
                                wdss, wds.names[flag_monday ? 2 : 1],
                                wdss, wds.names[flag_monday ? 3 : 2],
                                wdss, wds.names[flag_monday ? 4 : 3],
                                wdss, wds.names[flag_monday ? 5 : 4],
                                wdss, wds.names[flag_monday ? 6 : 5]);
                }
                printf("\n");

                /* And the days of the month. */
                for (i = 0; i != 6; i++) {
                        for (j = 0; j < count; j++)
                                printf("%-*s  ",
                                    MW(mw, year[j].extralen[i]),
                                        year[j].lines[i]+1);
                        printf("\n");
                }

                m += mpl;
        }
}

static void
monthranger(int y, int m, int jd_flag, int before, int after)
{
        struct monthlines year[12];
        struct weekdays wds;
        char    s[MAX_WIDTH], t[MAX_WIDTH];
        int     i, j;
        int     mpl;
        int     mw;
        int     m1, m2;
        int     prevyear = -1;
        int     printyearheader;

        mpl = jd_flag ? 3 : 4;
        mw = jd_flag ? MONTH_WIDTH_R_J : MONTH_WIDTH_R;

        while (before != 0) {
                DECREASEMONTH(m, y);
                before--;
                after++;
        }
        m1 = y * 12 + m - 1;
        m2 = m1 + after;

        mkweekdays(&wds);

        /*
         * The year header is printed when there are more than 'mpl' months
         * and if the first month is a multitude of 'mpl'.
         * If not, it will print the year behind every month.
         */
        printyearheader = (after >= mpl - 1) && (M2M(m1) - 1) % mpl == 0;

        m = m1;
        while (m <= m2) {
                int count = 0;
                for (i = 0; i != mpl && m + i <= m2; i++) {
                        mkmonthr(M2Y(m + i), M2M(m + i) - 1, jd_flag, year + i);
                        count++;
                }

                /* Empty line between two rows of months. */
                if (m != m1)
                        printf("\n");

                /* Year at the top. */
                if (printyearheader && M2Y(m) != prevyear) {
                        sprintf(s, "%d", M2Y(m));
                        printf("%s\n", center(t, s, mpl * mw));
                        prevyear = M2Y(m);
                }

                /* Month names. */
                wprintf(L"    ");
                for (i = 0; i < count; i++)
                        if (printyearheader)
                                wprintf(L"%-*ls", mw, year[i].name);
                        else
                                wprintf(L"%-ls %-*d", year[i].name,
                                    mw - wcslen(year[i].name) - 1, M2Y(m + i));
                printf("\n");

                /* And the days of the month. */
                for (i = 0; i != 7; i++) {
                        /* Week day */
                        wprintf(L"%.2ls", wds.names[i]);

                        /* Full months */
                        for (j = 0; j < count; j++)
                                printf("%-*s",
                                    MW(mw, year[j].extralen[i]),
                                        year[j].lines[i]);
                        printf("\n");
                }

                /* Week numbers. */
                if (flag_weeks) {
                        printf("  ");
                        for (i = 0; i < count; i++)
                                printf("%-*s", mw, year[i].weeks);
                        printf("\n");
                }

                m += mpl;
        }
        return;
}

static void
mkmonthr(int y, int m, int jd_flag, struct monthlines *mlines)
{

        struct tm tm;           /* for strftime printing local names of
                                 * months */
        date    dt;             /* handy date */
        int     dw;             /* width of numbers */
        int     first;          /* first day of month */
        int     firstm;         /* first day of first week of month */
        int     i, j, k, l;     /* just indices */
        int     last;           /* the first day of next month */
        int     jan1 = 0;       /* the first day of this year */
        char   *ds;             /* pointer to day strings (daystr or
                                 * jdaystr) */

        /* Set name of month. */
        memset(&tm, 0, sizeof(tm));
        tm.tm_mon = m;
        wcsftime(mlines->name, sizeof(mlines->name) / sizeof(mlines->name[0]),
                 L"%OB", &tm);
        mlines->name[0] = towupper(mlines->name[0]);

        /*
         * Set first and last to the day number of the first day of this
         * month and the first day of next month respectively. Set jan1 to
         * the day number of the first day of this year.
         */
        first = firstday(y, m + 1);
        if (m == 11)
                last = firstday(y + 1, 1);
        else
                last = firstday(y, m + 2);

        if (jd_flag)
                jan1 = firstday(y, 1);

        /*
         * Set firstm to the day number of monday of the first week of
         * this month. (This might be in the last month)
         */
        firstm = first - weekday(first);

        /* Set ds (daystring) and dw (daywidth) according to the jd_flag. */
        if (jd_flag) {
                ds = jdaystr;
                dw = 4;
        } else {
                ds = daystr;
                dw = 3;
        }

        /*
         * Fill the lines with day of month or day of year (julian day)
         * line index: i, each line is one weekday. column index: j, each
         * column is one day number. print column index: k.
         */
        for (i = 0; i != 7; i++) {
                l = 0;
                for (j = firstm + i, k = 0; j < last; j += 7, k += dw) {
                        if (j >= first) {
                                if (jd_flag)
                                        dt.d = j - jan1 + 1;
                                else
                                        sdater(j, &dt);
                                if (j == highlightdate && flag_highlight)
                                        highlight(mlines->lines[i] + k,
                                            ds + dt.d * dw, dw, &l);
                                else
                                        memcpy(mlines->lines[i] + k + l,
                                               ds + dt.d * dw, dw);
                        } else
                                memcpy(mlines->lines[i] + k + l, "    ", dw);
                }
                mlines->lines[i][k + l] = '\0';
                mlines->extralen[i] = l;
        }

        /* fill the weeknumbers. */
        if (flag_weeks) {
                for (j = firstm, k = 0; j < last;  k += dw, j += 7)
                        if (j <= nswitch)
                                memset(mlines->weeks + k, ' ', dw);
                        else
                                memcpy(mlines->weeks + k,
                                    ds + week(j, &i)*dw, dw);
                mlines->weeks[k] = '\0';
        }
}

static void
mkmonthb(int y, int m, int jd_flag, struct monthlines *mlines)
{

        struct tm tm;           /* for strftime printing local names of
                                 * months */
        date    dt;             /* handy date */
        int     dw;             /* width of numbers */
        int     first;          /* first day of month */
        int     firstsm;        /* sunday or monday of first week of month */
        int     i, j, k, l;     /* just indices */
        int     jan1 = 0;       /* the first day of this year */
        int     last;           /* the first day of next month */
        char   *ds;             /* pointer to day strings (daystr or
                                 * jdaystr) */

        /* Set ds (daystring) and dw (daywidth) according to the jd_flag */
        if (jd_flag) {
                ds = jdaystr;
                dw = 4;
        } else {
                ds = daystr;
                dw = 3;
        }

        /* Set name of month centered. */
        memset(&tm, 0, sizeof(tm));
        tm.tm_mon = m;
        wcsftime(mlines->name, sizeof(mlines->name) / sizeof(mlines->name[0]),
                 L"%OB", &tm);
        mlines->name[0] = towupper(mlines->name[0]);

        /*
         * Set first and last to the day number of the first day of this
         * month and the first day of next month respectively. Set jan1 to
         * the day number of Jan 1st of this year.
         */
        dt.y = y;
        dt.m = m + 1;
        dt.d = 1;
        first = sndaysb(&dt);
        if (m == 11) {
                dt.y = y + 1;
                dt.m = 1;
                dt.d = 1;
        } else {
                dt.y = y;
                dt.m = m + 2;
                dt.d = 1;
        }
        last = sndaysb(&dt);

        if (jd_flag) {
                dt.y = y;
                dt.m = 1;
                dt.d = 1;
                jan1 = sndaysb(&dt);
        }

        /*
         * Set firstsm to the day number of sunday or monday of the first week
         * of this month. (This might be in the last month)
         */
        if (flag_monday)
                firstsm = first - weekday(first);
        else
                firstsm = first - (weekday(first) + 1) % 7;

        /*
         * Fill the lines with day of month or day of year (Julian day)
         * line index: i, each line is one week. column index: j, each
         * column is one day number. print column index: k.
         */
        for (i = 0; i != 6; i++) {
                l = 0;
                for (j = firstsm + 7 * i, k = 0; j < last && k != dw * 7;
                    j++, k += dw) {
                        if (j >= first) {
                                if (jd_flag)
                                        dt.d = j - jan1 + 1;
                                else
                                        sdateb(j, &dt);
                                if (j == highlightdate && flag_highlight)
                                        highlight(mlines->lines[i] + k,
                                            ds + dt.d * dw, dw, &l);
                                else
                                        memcpy(mlines->lines[i] + k + l,
                                               ds + dt.d * dw, dw);
                        } else
                                memcpy(mlines->lines[i] + k + l, "    ", dw);
                }
                if (k == 0)
                        mlines->lines[i][1] = '\0';
                else
                        mlines->lines[i][k + l] = '\0';
                mlines->extralen[i] = l;
        }
}

/* Put the local names of weekdays into the wds. */
static void
mkweekdays(struct weekdays *wds)
{
        int i, len, width = 0;
        struct tm tm;
        wchar_t buf[20];

        memset(&tm, 0, sizeof(tm));

        for (i = 0; i != 7; i++) {
                tm.tm_wday = (i+1) % 7;
                wcsftime(buf, sizeof(buf)/sizeof(buf[0]), L"%a", &tm);
                for (len = 2; len > 0; --len) {
                        if ((width = wcswidth(buf, len)) <= 2)
                                break;
                }
                wmemset(wds->names[i], L'\0', 4);
                if (width == 1)
                        wds->names[i][0] = L' ';
                wcsncat(wds->names[i], buf, len);
                wcsncat(wds->names[i], L" ", 1);
        }
}

/*
 * Compute the day number of the first existing date after the first day in
 * month. (the first day in month and even the month might not exist!)
 */
static int
firstday(int y, int m)
{
        date dt;
        int nd;

        dt.y = y;
        dt.m = m;
        dt.d = 1;
        nd = sndaysr(&dt);
        for (;;) {
                sdater(nd, &dt);
                if ((dt.m >= m && dt.y == y) || dt.y > y)
                        return (nd);
                else
                        nd++;
        }
        /* NEVER REACHED */
}

/*
 * Compute the number of days from date, obey the local switch from
 * Julian to Gregorian if specified by the user.
 */
static int
sndaysr(struct date *d)
{

        if (nswitch != 0)
                if (nswitch < ndaysj(d))
                        return (ndaysg(d));
                else
                        return (ndaysj(d));
        else
                return ndaysg(d);
}

/*
 * Compute the number of days from date, obey the switch from
 * Julian to Gregorian as used by UK and her colonies.
 */
static int
sndaysb(struct date *d)
{

        if (nswitchb < ndaysj(d))
                return (ndaysg(d));
        else
                return (ndaysj(d));
}

/* Inverse of sndays. */
static struct date *
sdater(int nd, struct date *d)
{

        if (nswitch < nd)
                return (gdate(nd, d));
        else
                return (jdate(nd, d));
}

/* Inverse of sndaysb. */
static struct date *
sdateb(int nd, struct date *d)
{

        if (nswitchb < nd)
                return (gdate(nd, d));
        else
                return (jdate(nd, d));
}

/* Center string t in string s of length w by putting enough leading blanks. */
static char *
center(char *s, char *t, int w)
{
        char blanks[MAX_WIDTH];

        memset(blanks, ' ', sizeof(blanks));
        sprintf(s, "%.*s%s", (int)(w - strlen(t)) / 2, blanks, t);
        return (s);
}

/* Center string t in string s of length w by putting enough leading blanks. */
static wchar_t *
wcenter(wchar_t *s, wchar_t *t, int w)
{
        char blanks[MAX_WIDTH];

        memset(blanks, ' ', sizeof(blanks));
        swprintf(s, MAX_WIDTH, L"%.*s%ls", (int)(w - wcslen(t)) / 2, blanks, t);
        return (s);
}

static int
parsemonth(const char *s, int *m, int *y)
{
        int nm, ny;
        char *cp;
        struct tm tm;

        nm = (int)strtol(s, &cp, 10);
        if (cp != s) {
                ny = *y;
                if (*cp == '\0') {
                        ;       /* no special action */
                } else if (*cp == 'f' || *cp == 'F') {
                        if (nm <= *m)
                                ny++;
                } else if (*cp == 'p' || *cp == 'P') {
                        if (nm >= *m)
                                ny--;
                } else
                        return (1);
                if (nm < 1 || nm > 12)
                        return 1;
                *m = nm;
                *y = ny;
                return (0);
        }
        if (strptime(s, "%B", &tm) != NULL || strptime(s, "%b", &tm) != NULL) {
                *m = tm.tm_mon + 1;
                return (0);
        }
        return (1);
}

static void
highlight(char *dst, char *src, int len, int *extralen)
{
        static int first = 1;
        static const char *term_so, *term_se;

        if (first) {
                static char cbuf[512];
                char tbuf[1024], *b;

                term_se = term_so = NULL;

                /* On how to highlight on this type of terminal (if any). */
                if (isatty(STDOUT_FILENO) && tgetent(tbuf, NULL) == 1) {
                        b = cbuf;
                        term_so = tgetstr("so", &b);
                        term_se = tgetstr("se", &b);
                }

                first = 0;
        }

        /*
         * This check is not necessary, should have been handled before calling
         * this function.
         */
        if (!flag_highlight) {
                memcpy(dst, src, len);
                return;
        }

        /*
         * If it is a real terminal, use the data from the termcap database.
         */
        if (term_so != NULL && term_se != NULL) {
                /* separator. */
                dst[0] = ' ';
                dst++;
                /* highlight on. */
                memcpy(dst, term_so, strlen(term_so));
                dst += strlen(term_so);
                /* the actual text. (minus leading space) */
                len--;
                src++;
                memcpy(dst, src, len);
                dst += len;
                /* highlight off. */
                memcpy(dst, term_se, strlen(term_se));
                *extralen = strlen(term_so) + strlen(term_se);
                return;
        }

        /*
         * Otherwise, print a _, backspace and the letter.
         */
        *extralen = 0;
        /* skip leading space. */
        src++;
        len--;
        /* separator. */
        dst[0] = ' ';
        dst++;
        while (len > 0) {
                /* _ and backspace. */
                memcpy(dst, "_\010", 2);
                dst += 2;
                *extralen += 2;
                /* the character. */
                *dst++ = *src++;
                len--;
        }
        return;
}