/*-
 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
 *
 * 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>
__FBSDID("$FreeBSD: head/usr.bin/ncal/ncal.c 359419 2020-03-29 04:18:27Z grog $");

#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 <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}},
	{"LI", "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_nohighlight;	/* user doesn't want a 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 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_nohighlight = 0;
	flag_weeks = 0;

	/*
	 * 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:wy")) != -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 -A 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_nohighlight = 1;
			break;
		case 'e':
			if (flag_backward)
				usage();
			flag_easter = 1;
			break;
		case 'j':
			flag_julian_day = 1;
			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);
	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: [-NC3] [-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[6], wdss, wds.names[0],
				wdss, wds.names[1], wdss, wds.names[2],
				wdss, wds.names[3], wdss, wds.names[4],
				wdss, wds.names[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_nohighlight
				 && isatty(STDOUT_FILENO))
					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     firsts;		/* sunday 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 firsts to the day number of sunday of the first week of
	 * this month. (This might be in the last month)
	 */
	firsts = 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 = firsts + 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_nohighlight)
					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_nohighlight) {
		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;
}
