1/*
2 * Copyright (c) 1989, 1993
3 *	The Regents of the University of California.  All rights reserved.
4 *
5 * This code is derived from software posted to USENET.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 *    notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 *    notice, this list of conditions and the following disclaimer in the
14 *    documentation and/or other materials provided with the distribution.
15 * 3. Neither the name of the University nor the names of its contributors
16 *    may be used to endorse or promote products derived from this software
17 *    without specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * SUCH DAMAGE.
30 */
31
32/*
33 * Phase of the Moon.  Calculates the current phase of the moon.
34 * Based on routines from `Practical Astronomy with Your Calculator',
35 * by Duffett-Smith.  Comments give the section from the book that
36 * particular piece of code was adapted from.
37 *
38 * -- Keith E. Brandt  VIII 1984
39 *
40 */
41
42#include <sys/capsicum.h>
43#include <capsicum_helpers.h>
44
45#include <err.h>
46#include <errno.h>
47#include <stdio.h>
48#include <stdlib.h>
49#include <math.h>
50#include <string.h>
51#include <sysexits.h>
52#include <time.h>
53#include <unistd.h>
54
55#ifndef	PI
56#define	PI	  3.14159265358979323846
57#endif
58#define	EPOCH	  85
59#define	EPSILONg  279.611371	/* solar ecliptic long at EPOCH */
60#define	RHOg	  282.680403	/* solar ecliptic long of perigee at EPOCH */
61#define	ECCEN	  0.01671542	/* solar orbit eccentricity */
62#define	lzero	  18.251907	/* lunar mean long at EPOCH */
63#define	Pzero	  192.917585	/* lunar mean long of perigee at EPOCH */
64#define	Nzero	  55.204723	/* lunar mean long of node at EPOCH */
65#define isleap(y) ((((y) % 4) == 0 && ((y) % 100) != 0) || ((y) % 400) == 0)
66
67static void	adj360(double *);
68static double	dtor(double);
69static double	potm(double);
70static void	usage(char *progname);
71
72int
73main(int argc, char **argv)
74{
75	time_t tt;
76	struct tm GMT, tmd;
77	double days, today, tomorrow;
78	int ch, cnt, pflag = 0;
79	char *odate = NULL, *otime = NULL;
80	char *progname = argv[0];
81
82	if (caph_limit_stdio() < 0)
83		err(1, "unable to limit capabitilities for stdio");
84
85	caph_cache_catpages();
86	if (caph_enter() < 0)
87		err(1, "unable to enter capability mode");
88
89	while ((ch = getopt(argc, argv, "d:pt:")) != -1)
90		switch (ch) {
91		case 'd':
92			odate = optarg;
93			break;
94		case 'p':
95			pflag = 1;
96			break;
97		case 't':
98			otime = optarg;
99			break;
100		default:
101			usage(progname);
102		}
103
104        argc -= optind;
105	argv += optind;
106
107	if (argc)
108		usage(progname);
109
110	/* Adjust based on users preferences */
111	time(&tt);
112	if (otime != NULL || odate != NULL) {
113		/* Save today in case -d isn't specified */
114		localtime_r(&tt, &tmd);
115
116		if (odate != NULL) {
117			tmd.tm_year = strtol(odate, NULL, 10) - 1900;
118			tmd.tm_mon = strtol(odate + 5, NULL, 10) - 1;
119			tmd.tm_mday = strtol(odate + 8, NULL, 10);
120			/* Use midnight as the middle of the night */
121			tmd.tm_hour = 0;
122			tmd.tm_min = 0;
123			tmd.tm_sec = 0;
124			tmd.tm_isdst = -1;
125		}
126		if (otime != NULL) {
127			tmd.tm_hour = strtol(otime, NULL, 10);
128			tmd.tm_min = strtol(otime + 3, NULL, 10);
129			tmd.tm_sec = strtol(otime + 6, NULL, 10);
130			tmd.tm_isdst = -1;
131		}
132		tt = mktime(&tmd);
133	}
134
135	gmtime_r(&tt, &GMT);
136	days = (GMT.tm_yday + 1) + ((GMT.tm_hour +
137	    (GMT.tm_min / 60.0) + (GMT.tm_sec / 3600.0)) / 24.0);
138	for (cnt = EPOCH; cnt < GMT.tm_year; ++cnt)
139		days += isleap(1900 + cnt) ? 366 : 365;
140	today = potm(days);
141	if (pflag) {
142		(void)printf("%1.0f\n", today);
143		return (0);
144	}
145	(void)printf("The Moon is ");
146	if (today >= 99.5)
147		(void)printf("Full\n");
148	else if (today < 0.5)
149		(void)printf("New\n");
150	else {
151		tomorrow = potm(days + 1);
152		if (today >= 49.5 && today < 50.5)
153			(void)printf("%s\n", tomorrow > today ?
154			    "at the First Quarter" : "at the Last Quarter");
155		else {
156			(void)printf("%s ", tomorrow > today ?
157			    "Waxing" : "Waning");
158			if (today > 50)
159				(void)printf("Gibbous (%1.0f%% of Full)\n",
160				    today);
161			else if (today < 50)
162				(void)printf("Crescent (%1.0f%% of Full)\n",
163				    today);
164		}
165	}
166
167	return 0;
168}
169
170/*
171 * potm --
172 *	return phase of the moon
173 */
174static double
175potm(double days)
176{
177	double N, Msol, Ec, LambdaSol, l, Mm, Ev, Ac, A3, Mmprime;
178	double A4, lprime, V, ldprime, D, Nm;
179
180	N = 360 * days / 365.2422;				/* sec 42 #3 */
181	adj360(&N);
182	Msol = N + EPSILONg - RHOg;				/* sec 42 #4 */
183	adj360(&Msol);
184	Ec = 360 / PI * ECCEN * sin(dtor(Msol));		/* sec 42 #5 */
185	LambdaSol = N + Ec + EPSILONg;				/* sec 42 #6 */
186	adj360(&LambdaSol);
187	l = 13.1763966 * days + lzero;				/* sec 61 #4 */
188	adj360(&l);
189	Mm = l - (0.1114041 * days) - Pzero;			/* sec 61 #5 */
190	adj360(&Mm);
191	Nm = Nzero - (0.0529539 * days);			/* sec 61 #6 */
192	adj360(&Nm);
193	Ev = 1.2739 * sin(dtor(2*(l - LambdaSol) - Mm));	/* sec 61 #7 */
194	Ac = 0.1858 * sin(dtor(Msol));				/* sec 61 #8 */
195	A3 = 0.37 * sin(dtor(Msol));
196	Mmprime = Mm + Ev - Ac - A3;				/* sec 61 #9 */
197	Ec = 6.2886 * sin(dtor(Mmprime));			/* sec 61 #10 */
198	A4 = 0.214 * sin(dtor(2 * Mmprime));			/* sec 61 #11 */
199	lprime = l + Ev + Ec - Ac + A4;				/* sec 61 #12 */
200	V = 0.6583 * sin(dtor(2 * (lprime - LambdaSol)));	/* sec 61 #13 */
201	ldprime = lprime + V;					/* sec 61 #14 */
202	D = ldprime - LambdaSol;				/* sec 63 #2 */
203	return(50 * (1 - cos(dtor(D))));			/* sec 63 #3 */
204}
205
206/*
207 * dtor --
208 *	convert degrees to radians
209 */
210static double
211dtor(double deg)
212{
213
214	return(deg * PI / 180);
215}
216
217/*
218 * adj360 --
219 *	adjust value so 0 <= deg <= 360
220 */
221static void
222adj360(double *deg)
223{
224
225	for (;;)
226		if (*deg < 0)
227			*deg += 360;
228		else if (*deg > 360)
229			*deg -= 360;
230		else
231			break;
232}
233
234static void
235usage(char *progname)
236{
237
238	fprintf(stderr, "Usage: %s [-p] [-d yyyy.mm.dd] [-t hh:mm:ss]\n",
239	    progname);
240	exit(EX_USAGE);
241}
242