#!/usr/bin/awk -f

# USAGE
#
# ./test_poly.awk -- $LAT $LON < PolyhoodCoords.poly

# https://wrf.ecse.rpi.edu/Research/Short_Notes/pnpoly.html
function test_intersection(x1,y1,x2,y2,xt,yt) {
	return ((y1>yt) != (y2>yt)) && (xt < (x2-x1) * (yt-y1) / (y2-y1) + x1)
}

BEGIN {
	lat = ARGV[1]
	lon = ARGV[2]
	ARGC -= 2

	in_poly = 0
}
NR==1{
	firstlat = $1
	firstlon = $2
	prevlat  = $1
	prevlon  = $2
}
NR>1{ 
	curlat = $1
	curlon = $2

	if (test_intersection(curlon,curlat,prevlon,prevlat,lon,lat)) {
		in_poly = !in_poly
	}

	prevlat = curlat
	prevlon = curlon
	#printf("%f %f\n", curlat, curlon)
}
END {
	if (test_intersection(firstlon,firstlat,prevlon,prevlat,lon,lat)) {
		in_poly = !in_poly
	}
	if (in_poly) {
		exit 0
	} else {
		exit 1
	}
}