path: root/src/ui-calendar.c

/*
 * Calcurse - text-based organizer
 *
 * Copyright (c) 2004-2013 calcurse Development Team <misc@calcurse.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *      - Redistributions of source code must retain the above
 *        copyright notice, this list of conditions and the
 *        following disclaimer.
 *
 *      - 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 COPYRIGHT HOLDERS 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 COPYRIGHT
 * OWNER 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.
 *
 * Send your feedback or comments to : misc@calcurse.org
 * Calcurse home page : http://calcurse.org
 *
 */

#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <time.h>
#include <math.h>

#include "calcurse.h"

#ifndef M_PI
#define	M_PI	  3.14159265358979323846
#endif

#define	EPOCH	  90
#define	EPSILONg  279.403303	/* solar ecliptic long at EPOCH */
#define	RHOg	  282.768422	/* solar ecliptic long of perigee at EPOCH */
#define	ECCEN	  0.016713	/* solar orbit eccentricity */
#define	lzero	  318.351648	/* lunar mean long at EPOCH */
#define	Pzero	  36.340410	/* lunar mean long of perigee at EPOCH */
#define	Nzero	  318.510107	/* lunar mean long of node at EPOCH */

#define ISLEAP(y) ((((y) % 4) == 0 && ((y) % 100) != 0) || ((y) % 400) == 0)

enum pom {
	NO_POM,
	FIRST_QUARTER,
	FULL_MOON,
	LAST_QUARTER,
	NEW_MOON,
	MOON_PHASES
};

static struct date today, slctd_day;
static unsigned ui_calendar_view, week_begins_on_monday;
static pthread_mutex_t date_thread_mutex = PTHREAD_MUTEX_INITIALIZER;
static pthread_t ui_calendar_t_date;

static void draw_monthly_view(struct window *, struct date *, unsigned);
static void draw_weekly_view(struct window *, struct date *, unsigned);
static void (*draw_calendar[CAL_VIEWS]) (struct window *, struct date *,
					 unsigned) = {
draw_monthly_view, draw_weekly_view};

static int monthly_view_cache[MAXDAYSPERMONTH];
static int monthly_view_cache_valid = 0;
static int monthly_view_cache_month = 0;

/* Switch between calendar views (monthly view is selected by default). */
void ui_calendar_view_next(void)
{
	ui_calendar_view++;
	if (ui_calendar_view == CAL_VIEWS)
		ui_calendar_view = 0;
}

void ui_calendar_view_prev(void)
{
	if (ui_calendar_view == 0)
		ui_calendar_view = CAL_VIEWS;
	ui_calendar_view--;
}

void ui_calendar_set_view(int view)
{
	ui_calendar_view = (view < 0
			    || view >= CAL_VIEWS) ? CAL_MONTH_VIEW : view;
}

int ui_calendar_get_view(void)
{
	return (int)ui_calendar_view;
}

/* Thread needed to update current date in calendar. */
/* ARGSUSED0 */
static void *ui_calendar_date_thread(void *arg)
{
	time_t actual, tomorrow;

	for (;;) {
		tomorrow = (time_t) (get_today() + DAYINSEC);

		while ((actual = time(NULL)) < tomorrow)
			sleep(tomorrow - actual);

		ui_calendar_set_current_date();
		ui_calendar_update_panel(&win[CAL]);
	}

	return NULL;
}

/* Launch the calendar date thread. */
void ui_calendar_start_date_thread(void)
{
	pthread_create(&ui_calendar_t_date, NULL, ui_calendar_date_thread,
		       NULL);
}

/* Stop the calendar date thread. */
void ui_calendar_stop_date_thread(void)
{
	if (ui_calendar_t_date) {
		pthread_cancel(ui_calendar_t_date);
		pthread_join(ui_calendar_t_date, NULL);
	}
}

/* Set static variable today to current date */
void ui_calendar_set_current_date(void)
{
	time_t timer;
	struct tm tm;

	timer = time(NULL);
	localtime_r(&timer, &tm);

	pthread_mutex_lock(&date_thread_mutex);
	today.dd = tm.tm_mday;
	today.mm = tm.tm_mon + 1;
	today.yyyy = tm.tm_year + 1900;
	pthread_mutex_unlock(&date_thread_mutex);
}

/* Needed to display sunday or monday as the first day of week in calendar. */
void ui_calendar_set_first_day_of_week(enum wday first_day)
{
	switch (first_day) {
	case SUNDAY:
		week_begins_on_monday = 0;
		break;
	case MONDAY:
		week_begins_on_monday = 1;
		break;
	default:
		ERROR_MSG(_("ERROR setting first day of week"));
		week_begins_on_monday = 0;
		/* NOTREACHED */
	}
}

/* Swap first day of week in calendar. */
void ui_calendar_change_first_day_of_week(void)
{
	week_begins_on_monday = !week_begins_on_monday;
}

/* Return 1 if week begins on monday, 0 otherwise. */
unsigned ui_calendar_week_begins_on_monday(void)
{
	return week_begins_on_monday;
}

/* Fill in the given variable with the current date. */
void ui_calendar_store_current_date(struct date *date)
{
	pthread_mutex_lock(&date_thread_mutex);
	*date = today;
	pthread_mutex_unlock(&date_thread_mutex);
}

/* This is to start at the current date in calendar. */
void ui_calendar_init_slctd_day(void)
{
	ui_calendar_store_current_date(&slctd_day);
}

/* Return the selected day in calendar */
struct date *ui_calendar_get_slctd_day(void)
{
	return &slctd_day;
}

/* Returned value represents the selected day in calendar (in seconds) */
long ui_calendar_get_slctd_day_sec(void)
{
	return date2sec(slctd_day, 0, 0);
}

static int ui_calendar_get_wday(struct date *date)
{
	struct tm t;

	memset(&t, 0, sizeof(struct tm));
	t.tm_mday = date->dd;
	t.tm_mon = date->mm - 1;
	t.tm_year = date->yyyy - 1900;

	mktime(&t);

	return t.tm_wday;
}

static unsigned months_to_days(unsigned month)
{
	return (month * 3057 - 3007) / 100;
}

static long years_to_days(unsigned year)
{
	return year * 365L + year / 4 - year / 100 + year / 400;
}

static long ymd_to_scalar(unsigned year, unsigned month, unsigned day)
{
	long scalar;

	scalar = day + months_to_days(month);
	if (month > 2)
		scalar -= ISLEAP(year) ? 1 : 2;
	year--;
	scalar += years_to_days(year);

	return scalar;
}

/*
 * Used to change date by adding a certain amount of days or weeks.
 * Returns 0 on success, 1 otherwise.
 */
static int date_change(struct tm *date, int delta_month, int delta_day)
{
	struct tm t;

	t = *date;
	t.tm_mon += delta_month;
	t.tm_mday += delta_day;

	if (mktime(&t) == -1) {
		return 1;
	} else {
		*date = t;
		return 0;
	}
}

void ui_calendar_monthly_view_cache_set_invalid(void)
{
	monthly_view_cache_valid = 0;
}

/* Draw the monthly view inside calendar panel. */
static void
draw_monthly_view(struct window *cwin, struct date *current_day,
		  unsigned sunday_first)
{
	const int OFFY = CALHEIGHT / 2 - (conf.compact_panels ? 3 : 1);
	struct date check_day;
	int c_day, c_day_1, day_1_sav, numdays, j;
	unsigned yr, mo;
	int OFFX, SBAR_WIDTH, ofs_x, ofs_y;
	int item_this_day = 0;

	mo = slctd_day.mm;
	yr = slctd_day.yyyy;

	/* offset for centering calendar in window */
	SBAR_WIDTH = wins_sbar_width();
	OFFX = (SBAR_WIDTH - 27) / 2;
	ofs_y = OFFY;
	ofs_x = OFFX;

	/* checking the number of days in february */
	numdays = days[mo - 1];
	if (2 == mo && ISLEAP(yr))
		++numdays;

	/*
	 * the first calendar day will be monday or sunday, depending on
	 * 'week_begins_on_monday' value
	 */
	c_day_1 =
	    (int)((ymd_to_scalar(yr, mo, 1 + sunday_first) -
		   (long)1) % 7L);

	/* Write the current month and year on top of the calendar */
	WINS_CALENDAR_LOCK;
	custom_apply_attr(cwin->p, ATTR_HIGHEST);
	mvwprintw(cwin->p, ofs_y,
		  (SBAR_WIDTH - (strlen(_(monthnames[mo - 1])) + 5)) / 2,
		  "%s %d", _(monthnames[mo - 1]), slctd_day.yyyy);
	custom_remove_attr(cwin->p, ATTR_HIGHEST);
	++ofs_y;

	/* print the days, with regards to the first day of the week */
	custom_apply_attr(cwin->p, ATTR_HIGHEST);
	for (j = 0; j < WEEKINDAYS; j++) {
		mvwaddstr(cwin->p, ofs_y, ofs_x + 4 * j,
			  _(daynames[1 + j - sunday_first]));
	}
	custom_remove_attr(cwin->p, ATTR_HIGHEST);
	WINS_CALENDAR_UNLOCK;

	day_1_sav = (c_day_1 + 1) * 3 + c_day_1 - 7;

	/* invalidate cache if a new month is selected */
	if (yr * YEARINMONTHS + mo != monthly_view_cache_month) {
		monthly_view_cache_month = yr * YEARINMONTHS + mo;
		monthly_view_cache_valid = 0;
	}

	for (c_day = 1; c_day <= numdays; ++c_day, ++c_day_1, c_day_1 %= 7) {
		check_day.dd = c_day;
		check_day.mm = slctd_day.mm;
		check_day.yyyy = slctd_day.yyyy;

		/* check if the day contains an event or an appointment */
		if (monthly_view_cache_valid) {
			item_this_day = monthly_view_cache[c_day - 1];
		} else {
			item_this_day = monthly_view_cache[c_day - 1] =
			    day_check_if_item(check_day);
		}

		/* Go to next line, the week is over. */
		if (!c_day_1 && 1 != c_day) {
			ofs_y++;
			ofs_x = OFFX - day_1_sav - 4 * c_day;
		}

		WINS_CALENDAR_LOCK;
		if (c_day == current_day->dd
		    && current_day->mm == slctd_day.mm
		    && current_day->yyyy == slctd_day.yyyy
		    && current_day->dd != slctd_day.dd) {
			/* This is today, so print it in yellow. */
			custom_apply_attr(cwin->p, ATTR_LOWEST);
			mvwprintw(cwin->p, ofs_y + 1,
				  ofs_x + day_1_sav + 4 * c_day + 1, "%2d",
				  c_day);
			custom_remove_attr(cwin->p, ATTR_LOWEST);
		} else if (c_day == slctd_day.dd) {
			/* This is the selected day, print it according to user's theme. */
			custom_apply_attr(cwin->p, ATTR_HIGHEST);
			mvwprintw(cwin->p, ofs_y + 1,
				  ofs_x + day_1_sav + 4 * c_day + 1, "%2d",
				  c_day);
			custom_remove_attr(cwin->p, ATTR_HIGHEST);
		} else if (item_this_day) {
			custom_apply_attr(cwin->p, ATTR_LOW);
			mvwprintw(cwin->p, ofs_y + 1,
				  ofs_x + day_1_sav + 4 * c_day + 1, "%2d",
				  c_day);
			custom_remove_attr(cwin->p, ATTR_LOW);
		} else {
			/* otherwise, print normal days in black */
			mvwprintw(cwin->p, ofs_y + 1,
				  ofs_x + day_1_sav + 4 * c_day + 1, "%2d",
				  c_day);
		}
		WINS_CALENDAR_UNLOCK;
	}

	monthly_view_cache_valid = 1;
}

static int weeknum(const struct tm *t, int firstweekday)
{
	int wday, wnum;

	wday = t->tm_wday;
	if (firstweekday == MONDAY) {
		if (wday == SUNDAY)
			wday = 6;
		else
			wday--;
	}
	wnum = ((t->tm_yday + WEEKINDAYS - wday) / WEEKINDAYS);
	if (wnum < 0)
		wnum = 0;

	return wnum;
}

/*
 * Compute the week number according to ISO 8601.
 */
static int ISO8601weeknum(const struct tm *t)
{
	int wnum, jan1day;

	wnum = weeknum(t, MONDAY);

	jan1day = t->tm_wday - (t->tm_yday % WEEKINDAYS);
	if (jan1day < 0)
		jan1day += WEEKINDAYS;

	switch (jan1day) {
	case MONDAY:
		break;
	case TUESDAY:
	case WEDNESDAY:
	case THURSDAY:
		wnum++;
		break;
	case FRIDAY:
	case SATURDAY:
	case SUNDAY:
		if (wnum == 0) {
			/* Get week number of last week of last year. */
			struct tm dec31ly;	/* 12/31 last year */

			dec31ly = *t;
			dec31ly.tm_year--;
			dec31ly.tm_mon = 11;
			dec31ly.tm_mday = 31;
			dec31ly.tm_wday =
			    (jan1day == SUNDAY) ? 6 : jan1day - 1;
			dec31ly.tm_yday =
			    364 + ISLEAP(dec31ly.tm_year + 1900);
			wnum = ISO8601weeknum(&dec31ly);
		}
		break;
	}

	if (t->tm_mon == 11) {
		int wday, mday;

		wday = t->tm_wday;
		mday = t->tm_mday;
		if ((wday == MONDAY && (mday >= 29 && mday <= 31))
		    || (wday == TUESDAY && (mday == 30 || mday == 31))
		    || (wday == WEDNESDAY && mday == 31))
			wnum = 1;
	}

	return wnum;
}

/* Draw the weekly view inside calendar panel. */
static void
draw_weekly_view(struct window *cwin, struct date *current_day,
		 unsigned sunday_first)
{
#define DAYSLICESNO  6
	const int WCALWIDTH = 30;
	const int OFFY = CALHEIGHT / 2 - (conf.compact_panels ? 3 : 1);
	struct tm t;
	int OFFX, j, c_wday, days_to_remove, weeknum;

	OFFX = (wins_sbar_width() - WCALWIDTH) / 2 + 1;

	/* Fill in a tm structure with the first day of the selected week. */
	c_wday = ui_calendar_get_wday(&slctd_day);
	if (sunday_first)
		days_to_remove = c_wday;
	else
		days_to_remove = c_wday == 0 ? WEEKINDAYS - 1 : c_wday - 1;

	memset(&t, 0, sizeof(struct tm));
	t.tm_mday = slctd_day.dd;
	t.tm_mon = slctd_day.mm - 1;
	t.tm_year = slctd_day.yyyy - 1900;
	mktime(&t);
	date_change(&t, 0, -days_to_remove);

	/* Print the week number. */
	weeknum = ISO8601weeknum(&t);
	WINS_CALENDAR_LOCK;
	custom_apply_attr(cwin->p, ATTR_HIGHEST);
	mvwprintw(cwin->p, conf.compact_panels ? 0 : 2, cwin->w - 9,
		  "(# %02d)", weeknum);
	custom_remove_attr(cwin->p, ATTR_HIGHEST);
	WINS_CALENDAR_UNLOCK;

	/* Now draw calendar view. */
	for (j = 0; j < WEEKINDAYS; j++) {
		struct date date;
		unsigned attr, item_this_day;
		int i, slices[DAYSLICESNO];

		/* print the day names, with regards to the first day of the week */
		custom_apply_attr(cwin->p, ATTR_HIGHEST);
		mvwaddstr(cwin->p, OFFY, OFFX + 4 * j,
			  _(daynames[1 + j - sunday_first]));
		custom_remove_attr(cwin->p, ATTR_HIGHEST);

		/* Check if the day to be printed has an item or not. */
		date.dd = t.tm_mday;
		date.mm = t.tm_mon + 1;
		date.yyyy = t.tm_year + 1900;
		item_this_day = day_check_if_item(date);

		/* Print the day numbers with appropriate decoration. */
		if (t.tm_mday == current_day->dd
		    && current_day->mm == slctd_day.mm
		    && current_day->yyyy == slctd_day.yyyy
		    && current_day->dd != slctd_day.dd)
			attr = ATTR_LOWEST;	/* today, but not selected */
		else if (t.tm_mday == slctd_day.dd)
			attr = ATTR_HIGHEST;	/* selected day */
		else if (item_this_day)
			attr = ATTR_LOW;
		else
			attr = 0;

		WINS_CALENDAR_LOCK;
		if (attr)
			custom_apply_attr(cwin->p, attr);
		mvwprintw(cwin->p, OFFY + 1, OFFX + 1 + 4 * j, "%02d",
			  t.tm_mday);
		if (attr)
			custom_remove_attr(cwin->p, attr);
		WINS_CALENDAR_UNLOCK;

		/* Draw slices indicating appointment times. */
		memset(slices, 0, DAYSLICESNO * sizeof *slices);
		if (day_chk_busy_slices(date, DAYSLICESNO, slices)) {
			for (i = 0; i < DAYSLICESNO; i++) {
				if (j != WEEKINDAYS - 1
				    && i != DAYSLICESNO - 1) {
					WINS_CALENDAR_LOCK;
					mvwhline(cwin->p, OFFY + 2 + i,
						 OFFX + 3 + 4 * j, ACS_S9,
						 2);
					WINS_CALENDAR_UNLOCK;
				}
				if (slices[i]) {
					int highlight;

					highlight =
					    (t.tm_mday ==
					     slctd_day.dd) ? 1 : 0;
					WINS_CALENDAR_LOCK;
					if (highlight)
						custom_apply_attr(cwin->p,
								  attr);
					wattron(cwin->p, A_REVERSE);
					mvwaddstr(cwin->p, OFFY + 2 + i,
						  OFFX + 1 + 4 * j, " ");
					mvwaddstr(cwin->p, OFFY + 2 + i,
						  OFFX + 2 + 4 * j, " ");
					wattroff(cwin->p, A_REVERSE);
					if (highlight)
						custom_remove_attr(cwin->p,
								   attr);
					WINS_CALENDAR_UNLOCK;
				}
			}
		}

		/* get next day */
		date_change(&t, 0, 1);
	}

	/* Draw marks to indicate midday on the sides of the calendar. */
	WINS_CALENDAR_LOCK;
	custom_apply_attr(cwin->p, ATTR_HIGHEST);
	mvwhline(cwin->p, OFFY + 1 + DAYSLICESNO / 2, OFFX, ACS_S9, 1);
	mvwhline(cwin->p, OFFY + 1 + DAYSLICESNO / 2,
		 OFFX + WCALWIDTH - 3, ACS_S9, 1);
	custom_remove_attr(cwin->p, ATTR_HIGHEST);
	WINS_CALENDAR_UNLOCK;

#undef DAYSLICESNO
}

/* Function used to display the calendar panel. */
void ui_calendar_update_panel(struct window *cwin)
{
	struct date current_day;
	unsigned sunday_first;

	ui_calendar_store_current_date(&current_day);

	WINS_CALENDAR_LOCK;
	erase_window_part(cwin->p, 1, conf.compact_panels ? 1 : 3,
			  cwin->w - 2, cwin->h - 2);
	if (!conf.compact_panels)
		mvwhline(cwin->p, 2, 1, ACS_HLINE, cwin->w - 2);
	WINS_CALENDAR_UNLOCK;

	sunday_first = ui_calendar_week_begins_on_monday()? 0 : 1;

	draw_calendar[ui_calendar_view] (cwin, &current_day, sunday_first);

	wnoutrefresh(cwin->p);
}

/* Set the selected day in calendar to current day. */
void ui_calendar_goto_today(void)
{
	struct date today;

	ui_calendar_store_current_date(&today);
	slctd_day.dd = today.dd;
	slctd_day.mm = today.mm;
	slctd_day.yyyy = today.yyyy;
}

/*
 * Ask for a date to jump to, then check the correctness of that date
 * and jump to it.
 * If the entered date is empty, automatically jump to the current date.
 * slctd_day is updated with the newly selected date.
 */
void ui_calendar_change_day(int datefmt)
{
#define LDAY 11
	char selected_day[LDAY] = "";
	char outstr[BUFSIZ];
	int dday, dmonth, dyear;
	int wrong_day = 1;
	const char *mesg_line1 =
	    _("The day you entered is not valid "
	      "(should be between 01/01/1902 and 12/31/2037)");
	const char *mesg_line2 = _("Press [ENTER] to continue");
	const char *request_date =
	    _("Enter the day to go to [ENTER for today] : %s");

	while (wrong_day) {
		snprintf(outstr, BUFSIZ, request_date,
			 DATEFMT_DESC(datefmt));
		status_mesg(outstr, "");
		if (getstring(win[STA].p, selected_day, LDAY, 0, 1) ==
		    GETSTRING_ESC) {
			return;
		} else {
			if (strlen(selected_day) == 0) {
				wrong_day = 0;
				ui_calendar_goto_today();
			} else
			    if (parse_date
				(selected_day, datefmt, &dyear, &dmonth,
				 &dday, ui_calendar_get_slctd_day())) {
				wrong_day = 0;
				/* go to chosen day */
				slctd_day.dd = dday;
				slctd_day.mm = dmonth;
				slctd_day.yyyy = dyear;
			}
			if (wrong_day) {
				status_mesg(mesg_line1, mesg_line2);
				wgetch(win[KEY].p);
			}
		}
	}

	return;
}

void ui_calendar_move(enum move move, int count)
{
	int ret, days_to_remove, days_to_add;
	struct tm t;

	memset(&t, 0, sizeof(struct tm));
	t.tm_mday = slctd_day.dd;
	t.tm_mon = slctd_day.mm - 1;
	t.tm_year = slctd_day.yyyy - 1900;

	switch (move) {
	case DAY_PREV:
		ret = date_change(&t, 0, -count);
		break;
	case DAY_NEXT:
		ret = date_change(&t, 0, count);
		break;
	case WEEK_PREV:
		ret = date_change(&t, 0, -count * WEEKINDAYS);
		break;
	case WEEK_NEXT:
		ret = date_change(&t, 0, count * WEEKINDAYS);
		break;
	case MONTH_PREV:
		ret = date_change(&t, -count, 0);
		break;
	case MONTH_NEXT:
		ret = date_change(&t, count, 0);
		break;
	case YEAR_PREV:
		ret = date_change(&t, -count * YEARINMONTHS, 0);
		break;
	case YEAR_NEXT:
		ret = date_change(&t, count * YEARINMONTHS, 0);
		break;
	case WEEK_START:
		/* Normalize struct tm to get week day number. */
		mktime(&t);
		if (ui_calendar_week_begins_on_monday())
			days_to_remove =
			    ((t.tm_wday ==
			      0) ? WEEKINDAYS - 1 : t.tm_wday - 1);
		else
			days_to_remove =
			    ((t.tm_wday == 0) ? 0 : t.tm_wday);
		days_to_remove += (count - 1) * WEEKINDAYS;
		ret = date_change(&t, 0, -days_to_remove);
		break;
	case WEEK_END:
		mktime(&t);
		if (ui_calendar_week_begins_on_monday())
			days_to_add =
			    ((t.tm_wday ==
			      0) ? 0 : WEEKINDAYS - t.tm_wday);
		else
			days_to_add = ((t.tm_wday == 0) ?
				       WEEKINDAYS - 1 : WEEKINDAYS - 1 -
				       t.tm_wday);
		days_to_add += (count - 1) * WEEKINDAYS;
		ret = date_change(&t, 0, days_to_add);
		break;
	default:
		ret = 1;
		/* NOTREACHED */
	}

	if (ret == 0) {
		if (t.tm_year < 2) {
			t.tm_mday = 1;
			t.tm_mon = 0;
			t.tm_year = 2;
		} else if (t.tm_year > 137) {
			t.tm_mday = 31;
			t.tm_mon = 11;
			t.tm_year = 137;
		}

		slctd_day.dd = t.tm_mday;
		slctd_day.mm = t.tm_mon + 1;
		slctd_day.yyyy = t.tm_year + 1900;
	}
}

/* Returns the beginning of current year as a long. */
long ui_calendar_start_of_year(void)
{
	time_t timer;
	struct tm tm;

	timer = time(NULL);
	localtime_r(&timer, &tm);
	tm.tm_mon = 0;
	tm.tm_mday = 1;
	tm.tm_hour = 0;
	tm.tm_min = 0;
	tm.tm_sec = 0;
	timer = mktime(&tm);

	return (long)timer;
}

long ui_calendar_end_of_year(void)
{
	time_t timer;
	struct tm tm;

	timer = time(NULL);
	localtime_r(&timer, &tm);
	tm.tm_mon = 0;
	tm.tm_mday = 1;
	tm.tm_hour = 0;
	tm.tm_min = 0;
	tm.tm_sec = 0;
	tm.tm_year++;
	timer = mktime(&tm);

	return (long)(timer - 1);
}

/*
 * The pom, potm, dotr, adj360 are used to compute the current
 * phase of the moon.
 * The code is based on the OpenBSD version of pom(6).
 * Below is reported the copyright notice.
 */
/*
 * Copyright (c) 1989, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software posted to USENET.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/*
 * dtor --
 *	convert degrees to radians
 */
static double dtor(double deg)
{
	return deg * M_PI / 180;
}

/*
 * adj360 --
 *	adjust value so 0 <= deg <= 360
 */
static void adj360(double *deg)
{
	for (;;)
		if (*deg < 0.0)
			*deg += 360.0;
		else if (*deg > 360.0)
			*deg -= 360.0;
		else
			break;
}

/*
 * potm --
 *	return phase of the moon
 */
static double potm(double days)
{
	double N, Msol, Ec, LambdaSol, l, Mm, Ev, Ac, A3, Mmprime;
	double A4, lprime, V, ldprime, D, Nm;

	N = 360.0 * days / 365.242191;	/* sec 46 #3 */
	adj360(&N);
	Msol = N + EPSILONg - RHOg;	/* sec 46 #4 */
	adj360(&Msol);
	Ec = 360 / M_PI * ECCEN * sin(dtor(Msol));	/* sec 46 #5 */
	LambdaSol = N + Ec + EPSILONg;	/* sec 46 #6 */
	adj360(&LambdaSol);
	l = 13.1763966 * days + lzero;	/* sec 65 #4 */
	adj360(&l);
	Mm = l - (0.1114041 * days) - Pzero;	/* sec 65 #5 */
	adj360(&Mm);
	Nm = Nzero - (0.0529539 * days);	/* sec 65 #6 */
	adj360(&Nm);
	Ev = 1.2739 * sin(dtor(2 * (l - LambdaSol) - Mm));	/* sec 65 #7 */
	Ac = 0.1858 * sin(dtor(Msol));	/* sec 65 #8 */
	A3 = 0.37 * sin(dtor(Msol));
	Mmprime = Mm + Ev - Ac - A3;	/* sec 65 #9 */
	Ec = 6.2886 * sin(dtor(Mmprime));	/* sec 65 #10 */
	A4 = 0.214 * sin(dtor(2 * Mmprime));	/* sec 65 #11 */
	lprime = l + Ev + Ec - Ac + A4;	/* sec 65 #12 */
	V = 0.6583 * sin(dtor(2 * (lprime - LambdaSol)));	/* sec 65 #13 */
	ldprime = lprime + V;	/* sec 65 #14 */
	D = ldprime - LambdaSol;	/* sec 67 #2 */
	return 50.0 * (1 - cos(dtor(D)));	/* sec 67 #3 */
}

/*
 * Phase of the Moon.  Calculates the current phase of the moon.
 * Based on routines from `Practical Astronomy with Your Calculator',
 * by Duffett-Smith.  Comments give the section from the book that
 * particular piece of code was adapted from.
 *
 * -- Keith E. Brandt  VIII 1984
 *
 * Updated to the Third Edition of Duffett-Smith's book, IX 1998
 *
 */
static double pom(time_t tmpt)
{
	struct tm *GMT;
	double days;
	int cnt;

	GMT = gmtime(&tmpt);
	days = (GMT->tm_yday + 1) + ((GMT->tm_hour + (GMT->tm_min / 60.0) +
				      (GMT->tm_sec / 3600.0)) / 24.0);
	for (cnt = EPOCH; cnt < GMT->tm_year; ++cnt)
		days += ISLEAP(cnt + TM_YEAR_BASE) ? 366 : 365;
	/* Selected time could be before EPOCH */
	for (cnt = GMT->tm_year; cnt < EPOCH; ++cnt)
		days -= ISLEAP(cnt + TM_YEAR_BASE) ? 366 : 365;

	return potm(days);
}

/*
 * Return a pictogram representing the current phase of the moon.
 * Careful: date is the selected day in calendar at 00:00, so it represents
 * the phase of the moon for previous day.
 */
const char *ui_calendar_get_pom(time_t date)
{
	const char *pom_pict[MOON_PHASES] =
	    { "   ", "|) ", "(|)", "(| ", " | " };
	enum pom phase = NO_POM;
	double pom_today, relative_pom, pom_yesterday, pom_tomorrow;
	const double half = 50.0;

	pom_yesterday = pom(date);
	pom_today = pom(date + DAYINSEC);
	relative_pom = abs(pom_today - half);
	pom_tomorrow = pom(date + 2 * DAYINSEC);
	if (pom_today > pom_yesterday && pom_today > pom_tomorrow)
		phase = FULL_MOON;
	else if (pom_today < pom_yesterday && pom_today < pom_tomorrow)
		phase = NEW_MOON;
	else if (relative_pom < abs(pom_yesterday - half)
		 && relative_pom < abs(pom_tomorrow - half))
		phase =
		    (pom_tomorrow >
		     pom_today) ? FIRST_QUARTER : LAST_QUARTER;

	return pom_pict[phase];
}