# include	<stdio.h>
# include	<time.h>
# include	<math.h>

#define EPOCH   1985
#define EPSILONg 279.611371     /* solar ecliptic long at EPOCH */
#define RHOg     282.680403     /* solar ecliptic long of perigee at EPOCH */
#define e          0.01671542   /* solar orbit eccentricity */
#define lzero     18.251907     /* lunar mean long at EPOCH */
#define Pzero    192.917585     /* lunar mean long of perigee at EPOCH */
#define Nzero     55.204723     /* lunar mean long of node at EPOCH */
#define	PI         3.141592654  /* an extremely crude approximation */

char	result[64];

int day_month[] = {			/* Needed for dotexttime()      */
	0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
};

main()
{
    long tmnow;
    struct tm *today;

    tmnow = time(0);
    today = localtime(&tmnow);

    moontxt(result, today->tm_year+1900, today->tm_mon+1, today->tm_mday,
	    today->tm_hour, today->tm_min, today->tm_sec);
    printf("\n        ***  The moon is%s  ***\n", result+11);
    exit(0);
}




/****************************************************************************
     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   M.I.T.  VIII 1984

 ****************************************************************************/

double dtor();
double adj360();
double potm();

moontxt(buf, year, month, day, hour, minute, second)
char	buf[];
int     year;                           /* Year		1900 = 1900	*/
int     month;                          /* Month	January = 1	*/
int     day;                            /* Day		1 = 1		*/
int	hour;				/* Hour		0 .. 23		*/
int	minute;				/* Minute	0 .. 59		*/
int	second;				/* Second	0 .. 59		*/
{
    char *cp=buf;


double days;   /* days since EPOCH */
double phase;  /* percent of lunar surface illuminated */
double phase2; /* percent of lunar surface illuminated one day later */
int i = EPOCH;

/* calculate days since EPOCH */

days = 0;
while (--month)
    days += day_month[month];

days += day + ((hour + (minute / 60.0)
       + (second / 3600.0)) / 24.0);
while (i < year)
   days = days + 365 + ly(i++);


phase = potm(days);
sprintf(cp,"The Moon is ");
cp += strlen(buf);
if ((int)(phase + .5) == 100) {
   sprintf(cp,"Full");
   }
else if ((int)(phase + 0.5) == 0) 
   sprintf(cp,"New");
else if ((int)(phase + 0.5) == 50)  {
   phase2 = potm(++days);
   if (phase2 > phase)
      sprintf(cp,"at the First Quarter");
   else 
      sprintf(cp,"at the Last Quarter");
   }
else if ((int)(phase + 0.5) > 50) {
   phase2 = potm(++days);
   if (phase2 > phase)
      sprintf(cp,"Waxing ");
   else 
      sprintf(cp,"Waning ");
   cp = buf + strlen(buf);
   sprintf(cp,"Gibbous (%1.0f%% of Full)", phase);
   }
else if ((int)(phase + 0.5) < 50) {
   phase2 = potm(++days);
   if (phase2 > phase)
      sprintf(cp,"Waxing ");
   else
      sprintf(cp,"Waning ");
   cp = buf + strlen(buf);
   sprintf(cp,"Crescent (%1.0f%% of Full)", phase);
   }
}

double potm(days)
double days;
{
double N;
double Msol;
double Ec;
double LambdaSol;
double l;
double Mm;
double Ev;
double Ac;
double A3;
double Mmprime;
double A4;
double lprime;
double V;
double ldprime;
double D;
double Nm;

N = 360 * days / 365.2422;  /* sec 42 #3 */
adj360(&N);

Msol = N + EPSILONg - RHOg; /* sec 42 #4 */
adj360(&Msol);

Ec = 360 / PI * e * sin(dtor(Msol)); /* sec 42 #5 */

LambdaSol = N + Ec + EPSILONg;       /* sec 42 #6 */
adj360(&LambdaSol);

l = 13.1763966 * days + lzero;       /* sec 61 #4 */
adj360(&l);

Mm = l - (0.1114041 * days) - Pzero; /* sec 61 #5 */
adj360(&Mm);

Nm = Nzero - (0.0529539 * days);     /* sec 61 #6 */
adj360(&Nm);

Ev = 1.2739 * sin(dtor(2*(l - LambdaSol) - Mm)); /* sec 61 #7 */

Ac = 0.1858 * sin(dtor(Msol));       /* sec 61 #8 */
A3 = 0.37 * sin(dtor(Msol));

Mmprime = Mm + Ev - Ac - A3;         /* sec 61 #9 */

Ec = 6.2886 * sin(dtor(Mmprime));    /* sec 61 #10 */

A4 = 0.214 * sin(dtor(2 * Mmprime)); /* sec 61 #11 */

lprime = l + Ev + Ec - Ac + A4;      /* sec 61 #12 */

V = 0.6583 * sin(dtor(2 * (lprime - LambdaSol))); /* sec 61 #13 */

ldprime = lprime + V;                /* sec 61 #14 */

D = ldprime - LambdaSol;             /* sec 63 #2 */

return (50 * (1 - cos(dtor(D))));    /* sec 63 #3 */
}

ly(yr)
int yr;
{
/* returns 1 if leapyear, 0 otherwise */
return (yr % 4 == 0 && yr % 100 != 0 || yr % 400 == 0);
}

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

double adj360(deg)
double *deg;
{
/* adjust value so 0 <= deg <= 360 */
do if (*deg < 0)
   *deg += 360;
else if (*deg > 360)
   *deg -= 360;
while (*deg < 0 || *deg > 360);
}