/* comet_elements.c     enters comet elements	*/
/* Based upon Earl Spillar's  comets.c          */
/* 96/01/15  R. Howell  -- Modified to correct prompts */
/*                         Also allows years > 1999    */
/*                         Outputs info in new orbit catalog format */

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

double	cal_jd();				/* Convert date to JD   */
int		gtline();				/* Get line from input  */
void	trimstr();				/* Trim trailing spaces */


main()		/* Comets program */
{
	FILE *output_file;
	double perihel_jul_date,q,Omega,i;
	double equinox_jul_date,a,e,n,w,M=0.0,semdia=0.0,mag=0.0;
	char number[16], pnumber[18];	/* Short name or number, then same with quotes */
	char name[40],   pname[42];     /* Full name, then same with quotes. */
	char outfile[80],c='N';
	int		temp_day;		/* Temporarily holds day   of perihelion */
	double	temp_hr;		/* Temporarily holds hh.hh of perihelion */
	struct date{
		int year;
		int month;
		double day;
	}perihel,equinox;


	printf("Enter the equinox for the elements (yyyy mm dd)");
	printf("\nThis will probably by 1950 1 1 or 2000  1  1 : ");
	scanf("%d %d %lf",&equinox.year,&equinox.month,&equinox.day);

	/* Discard rest of line, in case limit caused end of input */
	while (c != EOF && c != '\n') c=getchar();

	printf("Enter the name of the comet: ");
	gtline(name, 40);
	name[39] = 0;			/* Make sure it is null terminated */
	
	printf("Enter the alternate name (such as 58p): ");
	gtline(number, 16);
	number[15] = 0;			/* Make sure it is null terminated */

	printf("Enter the date of perihelion passage (yyyy mm dd hh.hh):");
	scanf("%d %d %d %lf", &perihel.year, &perihel.month, &temp_day, &temp_hr);
	perihel.day = (double)temp_day + (temp_hr/24.);

	printf("Enter the distance at perihelion q: ");
	scanf("%lf",&q);
		
	printf("Enter the eccentricity e: ");
	scanf("%lf",&e);
		
	printf("Enter the argument of perihelion omega: ");
	scanf("%lf",&w);
		
	printf("Enter the longitude of ascending node Omega: ");
	scanf("%lf",&Omega);
		
	printf("Enter the inclination i: ");
	scanf("%lf",&i);
		
	printf("Enter the daily motion n or 0.0 if unknown: ");
	scanf("%lf",&n);
		
	perihel_jul_date = (double) cal_jd(perihel.year, perihel.month, perihel.day);

	equinox_jul_date = (double) cal_jd(equinox.year, equinox.month, equinox.day);
	a = q/(1-e);  /* convert perihelion to mean dist */

	printf("Orbit catalog file where elements will be appended: ");
	scanf("%s",outfile);
	output_file=fopen(outfile,"a");
	
	/* Add quotes around short and full name */
	trimstr(number);
	strcpy(pnumber, "\'");
	strcat(pnumber, number);
	strcat(pnumber, "\'");
	
	trimstr(name);
	strcpy(pname, "\'");
	strcat(pname, name);
	strcat(pname, "\'");
	
	
	fprintf(output_file,"%-6s %-20s %9.4f %10.5f %9.5f %9.5f %11.7f\n",
		pnumber, pname, perihel_jul_date,i,Omega,w,a);
	fprintf(output_file,"%10.5f %10.7f %10.7f %9.4f %7.3f %7.3f\n",
		n,e, M, equinox_jul_date,mag,semdia); 

	output_file=fopen(outfile,"a");
}

double cal_jd(yyyy, m, d)   /* Conversion routine */
int yyyy;
int m;
double d;
{
	double B,jul_date;

	if (m <= 2){
		m = m + 12;
		yyyy = yyyy - 1;
	}
	
/*	yyyy = yyyy + 1900.0;	New version uses full year. */

	B = -15.0;	/* approximation only good between 1 March 1900 and */
				/* 28 February 2100                                  */
	
	jul_date = ((floor(365.25 * yyyy))+(floor(30.6001*(m+1)))+(B)+
	(1720996.5)+(d));
    
	return((double)jul_date);    
}

int gtline(s, lim)
char s[];
int	lim;
{
/* Get line & return length, or EOF if FIRST character IS EOF        */
/* The limit is the FULL LENGTH, including the final '\n'.           */
/* This is very similar to K&R 1st ed. getline, except I also return */
/* EOF, and I don't return the final '\n'.                           */
/* Because I return EOF, I'm implicitly assuming that EOF is not the */
/* same as any valid integer.  Usually it is -1.                     */

        int c, i;
		int	found_eol = 0;
        
		/* Input characters till limit or EOL */
		for (i=0; i<lim-1; i++) {
			c = getchar();
			if (c==EOF || c == '\n') break;
			s[i] = (char) c;
		}
        s[i] = '\0';
        
		/* Discard rest of line, in case limit caused end of input */
		while (c != EOF && c != '\n') c=getchar();
		
		if (i==0 && c==EOF)
                return (EOF);
        else
                return(i);
}

/* Eliminate trailing spaces on a string */
void	trimstr(str)
char str[];
{
		int slen;
		int	i;
		slen = strlen(str);
		for (i=slen-1; i>=0; i--)
			if (str[i] == ' ') str[i] = '\0';
}