/* geom3181 - put the 1981 observer's log geometry into NPRA line 31-81 traces
 * (Claude Opus 5.5, 2026-10-17).  SU filter: stdin -> stdout.
 *
 * From the GSI observer's log (party 1186, 12 March 1981): shot point SP = field file - 11 for
 * files 111..156, file 157 misfired, SP = file - 12 for files 158..167.  Split spread, 96 groups
 * at 110 ft, 48 each side of the shot, nearest groups 55 ft from it; shots every 440 ft.
 * Units are feet.  Group g is at x = 440*SP + 110*(g - 48.5); reverse=1 flips the spread
 * (group g -> 97 - g) to test which end group 1 is at.
 *
 * Output headers: fldr kept, tracf = group, ep = SP, sx, gx, offset (gx - sx, signed),
 * cdp (55 ft bins, 1 = first midpoint of the line), cdpt, trid = 2 for traces the log calls dead.
 * Drops test files, the misfire, file 168 and the auxiliary channels 97+.
 */
#include "su.h"
#include "segy.h"

char *sdoc[] = {
"geom3181 <in.su >out.su [reverse=0]   geometry for NPRA line 31-81 (see source)",
NULL};

segy tr;

int main(int argc, char **argv)
{
	int reverse, sp, g, x2, nin = 0, nout = 0;

	initargs(argc, argv);
	requestdoc(1);
	if (!getparint("reverse", &reverse)) reverse = 0;

	while (gettr(&tr)) {
		nin++;
		if (tr.fldr >= 111 && tr.fldr <= 156) sp = tr.fldr - 11;
		else if (tr.fldr >= 158 && tr.fldr <= 167) sp = tr.fldr - 12;
		else continue;
		g = tr.tracf;
		if (g < 1 || g > 96) continue;
		if (reverse) g = 97 - g;

		tr.ep = sp;
		tr.sx = 440 * sp;
		/* gx = 440*sp + 110*g - 5335 (exact in feet) */
		tr.gx = 440 * sp + 110 * g - 5335;
		tr.offset = tr.gx - tr.sx;
		tr.scalco = 1;
		tr.counit = 1;
		/* midpoint*2 = 880*sp + 110*g - 5335; bins of 55 ft: index 8*sp + g - 49 (exact,
		   midpoints sit 27.5 ft past each 55 ft boundary); first midpoint (sp 100, g 1) -> 1 */
		x2 = 8 * sp + g - 48;
		tr.cdp = x2 - (8 * 100 + 1 - 48) + 1;
		tr.cdpt = g;
		tr.trid = 1;
		if ((sp == 130 && (tr.tracf == 1 || tr.tracf == 2)) || (sp == 132 && tr.tracf == 92))
			tr.trid = 2;
		puttr(&tr);
		nout++;
	}
	warn("%d traces in, %d out", nin, nout);
	return 0;
}