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/* See LICENSE file for copyright and license details. */
#include <limits.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include "util.h"
enum { JAN, FEB, MAR, APR, MAY, JUN, JUL, AUG, SEP, OCT, NOV, DEC };
enum caltype { JULIAN, GREGORIAN };
enum { TRANS_YEAR = 1752, TRANS_MONTH = SEP, TRANS_DAY = 2 };
static struct tm *ltime;
static int
isleap(size_t year, enum caltype cal)
{
if (cal == GREGORIAN) {
if (year % 400 == 0)
return 1;
if (year % 100 == 0)
return 0;
return (year % 4 == 0);
}
else { /* cal == Julian */
return (year % 4 == 0);
}
}
static int
monthlength(size_t year, int month, enum caltype cal)
{
int mdays[] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
return (month == FEB && isleap(year, cal)) ? 29 : mdays[month];
}
/* From http://www.tondering.dk/claus/cal/chrweek.php#calcdow */
static int
dayofweek(size_t year, int month, int dom, enum caltype cal)
{
size_t y;
int m, a;
a = (13 - month) / 12;
y = year - a;
m = month + 12 * a - 1;
if (cal == GREGORIAN)
return (dom + y + y / 4 - y / 100 + y / 400 + (31 * m) / 12) % 7;
else /* cal == Julian */
return (5 + dom + y + y / 4 + (31 * m) / 12) % 7;
}
static void
printgrid(size_t year, int month, int fday, int line)
{
enum caltype cal;
int offset, dom, d = 0, trans; /* are we in the transition from Julian to Gregorian? */
int today = 0;
cal = (year < TRANS_YEAR || (year == TRANS_YEAR && month <= TRANS_MONTH)) ? JULIAN : GREGORIAN;
trans = (year == TRANS_YEAR && month == TRANS_MONTH);
offset = dayofweek(year, month, 1, cal) - fday;
if (offset < 0)
offset += 7;
if (line == 1) {
for (; d < offset; ++d)
printf(" ");
dom = 1;
} else {
dom = 8 - offset + (line - 2) * 7;
if (trans && !(line == 2 && fday == 3))
dom += 11;
}
if (ltime && year == ltime->tm_year + 1900 && month == ltime->tm_mon)
today = ltime->tm_mday;
for (; d < 7 && dom <= monthlength(year, month, cal); ++d, ++dom) {
if (dom == today)
printf("\x1b[7m%2d\x1b[0m ", dom); /* highlight today's date */
else
printf("%2d ", dom);
if (trans && dom == TRANS_DAY)
dom += 11;
}
for (; d < 7; ++d)
printf(" ");
}
static void
drawcal(size_t year, int month, size_t ncols, size_t nmons, int fday)
{
char *smon[] = { "January", "February", "March", "April",
"May", "June", "July", "August",
"September", "October", "November", "December" };
char *days[] = { "Su", "Mo", "Tu", "We", "Th", "Fr", "Sa", };
size_t m, n, col, cur_year, cur_month, dow;
int line, pad;
char month_year[sizeof("Su Mo Tu We Th Fr Sa")];
for (m = 0; m < nmons; ) {
n = m;
for (col = 0; m < nmons && col < ncols; ++col, ++m) {
cur_year = year + m / 12;
cur_month = month + m % 12;
if (cur_month > 11) {
cur_month -= 12;
cur_year += 1;
}
snprintf(month_year, sizeof(month_year), "%s %zu", smon[cur_month], cur_year);
pad = sizeof(month_year) - 1 - strlen(month_year);
printf("%*s%s%*s ", pad / 2 + pad % 2, "", month_year, pad / 2, "");
}
putchar('\n');
for (col = 0, m = n; m < nmons && col < ncols; ++col, ++m) {
for (dow = fday; dow < (fday + 7); ++dow)
printf("%s ", days[dow % 7]);
printf(" ");
}
putchar('\n');
for (line = 1; line <= 6; ++line) {
for (col = 0, m = n; m < nmons && col < ncols; ++col, ++m) {
cur_year = year + m / 12;
cur_month = month + m % 12;
if (cur_month > 11) {
cur_month -= 12;
cur_year += 1;
}
printgrid(cur_year, cur_month, fday, line);
printf(" ");
}
putchar('\n');
}
}
}
static void
usage(void)
{
eprintf("usage: %s [-1 | -3 | -y | -n num] "
"[-s | -m | -f num] [-c num] [[month] year]\n", argv0);
}
int
main(int argc, char *argv[])
{
time_t now;
size_t year, ncols, nmons;
int fday, month;
now = time(NULL);
ltime = localtime(&now);
year = ltime->tm_year + 1900;
month = ltime->tm_mon + 1;
fday = 0;
if (!isatty(STDOUT_FILENO))
ltime = NULL; /* don't highlight today's date */
ncols = 3;
nmons = 0;
ARGBEGIN {
case '1':
nmons = 1;
break;
case '3':
nmons = 3;
if (--month == 0) {
month = 12;
year--;
}
break;
case 'c':
ncols = estrtonum(EARGF(usage()), 0, MIN(SIZE_MAX, LLONG_MAX));
break;
case 'f':
fday = estrtonum(EARGF(usage()), 0, 6);
break;
case 'm': /* Monday */
fday = 1;
break;
case 'n':
nmons = estrtonum(EARGF(usage()), 1, MIN(SIZE_MAX, LLONG_MAX));
break;
case 's': /* Sunday */
fday = 0;
break;
case 'y':
month = 1;
nmons = 12;
break;
default:
usage();
} ARGEND
if (nmons == 0) {
if (argc == 1) {
month = 1;
nmons = 12;
} else {
nmons = 1;
}
}
switch (argc) {
case 2:
month = estrtonum(argv[0], 1, 12);
argv++;
case 1: /* fallthrough */
year = estrtonum(argv[0], 0, INT_MAX);
break;
case 0:
break;
default:
usage();
}
drawcal(year, month - 1, ncols, nmons, fday);
return fshut(stdout, "<stdout>");
}