/* ---------------------------------------------------------------------- */
/* ttime.c	return travel time for given depth and distance

26 Jan 98 dpa	Created.

		Use traveltimes.dat file for table lookup


		trav arg1 arg2 > delta distance traveltime

		arg1	depth in km
		arg2	distance in degrees


27 Jan 98 dpa	Added interpolation for time/distance.
		Modified to return "no_data" for invalid entries

11 Mar 98 dpa	tt.c  new function uses the table2.h travel times, including
		0 and 10 km depths and 0 distance.

26 Jul 98 dpa	callable as a subroutine, 
		Split into two files, tt.c and tt_obj.c

23 Apr 99 dpa	Moved "time" to "itime" so no collide with Unix.

17 May 99 dpa	Moved boundary condition tests to here
		Hand in pointers to itime and distance returned values.
		Hand in "out" flag to detemine ascii output to stdout

09 Oct 00 dpa	Corrected interpolation integer error

11 Oct 02 dpa	Added interpolation of depth

/* ---------------------------------------------------------------------- */

#define TTIME_VERSION "2.2"

/* ---------------------------------------------------------------------- */

#include "table2.h"

/* ---------------------------------------------------------------------- */

interpolate(depth, theta, time, distance)
float depth, theta;
float *time, *distance;
{
	int i,i2,j;
	float d,t;
	float a,b,s;

	i = (int)((depth/10)+.5);
	j = (int)theta;

	if ((j+1 < ENTRIES) && (i+1 < SIZE)) {

		/* interpolate depth and distance */
		s = (depth/10) - ((float)(int)(depth/10));
		a = traveltimes[i][j+1] - traveltimes[i][j];
		a = traveltimes[i][j] + (a*s);
		b = traveltimes[i+1][j+1] - traveltimes[i+1][j];
		b = traveltimes[i+1][j] + (b*s);

          	*distance = theta;
		d = theta - ((float)(int)theta);
		t = b - a;
		*time = a + (t*d);
		if (*time < traveltimes[i][j]) *time = -1; /* don't interp -1 */
	} else	{
		*time = traveltimes[i][j];
		*distance = (float)((int)theta);
		
	}

	return i;
}


/* ---------------------------------------------------------------------- */

int tt_lookup(out, depth, distance, otime, odist)
int out;	/* flag ascii output to stdout */
float depth;	/* depth in km */
float distance;	/* angular distance in degrees */
float *otime;	/* output travel time */
float *odist;	/* output interpolated distance */
{
	int i;

	if ((depth < 0 ) || (depth > 2880)) {
		if (out) 
		    printf("%s: depth error: %.2f allowed range is 0-2880\n",
		    "tt_lookup",depth);
		return -1;
	}

	if ((distance < 0) || (distance > 98)) {
		if (out)
		    printf("%s: distance error: %.2f allowed range is 0-98\n",
			"tt_lookup",distance);
		return -2;
	}

	i = interpolate(depth, distance, otime, odist);
	if (out) {
		if (*otime != -1) {
			printf("%.2f km\t%.2f deg\t%.2f sec\n",
				(float)i*10,*odist,*otime);
		} else {
			printf("%.2f km\t%.2f deg\tno_data\n",
				(float)i*10,*odist);
		}
	}

	return (i);
}

/* ---------------------------------------------------------------------- */
/* EOF ttime.c */