package au.gov.amsa.geo;
   
   import com.github.davidmoten.grumpy.core.Position;
   import com.vividsolutions.jts.geom.Coordinate;
   import com.vividsolutions.jts.geom.Geometry;
   import com.vividsolutions.jts.geom.GeometryFactory;
   import com.vividsolutions.jts.geom.LineString;
   import com.vividsolutions.jts.geom.prep.PreparedGeometry;
   
  import au.gov.amsa.gt.Shapefile;
  import au.gov.amsa.risky.format.Fix;
  
  public class ShapefileUtil {
      
      public static TimedPosition findRegionCrossingPoint(Shapefile region, Fix fix1, Fix fix2) {
  
          Coordinate[] coords = new Coordinate[] { new Coordinate(fix1.lon(), fix1.lat()),
                  new Coordinate(fix2.lon(), fix2.lat()) };
          LineString line = new GeometryFactory().createLineString(coords);
          for (PreparedGeometry g : region.geometries()) {
              if (g.crosses(line)) {
                  Geometry intersection = g.getGeometry().intersection(line);
                  // expecting just one point
                  Coordinate coord = intersection.getCoordinate();
                  double longitude = coord.x;
                  double latitude = coord.y;
                  Position a = Position.create(fix1.lat(), fix1.lon());
                  Position b = Position.create(fix2.lat(), fix2.lon());
                  Position c = Position.create(latitude, longitude);
                  double ac = a.getDistanceToKm(c);
                  double bc = b.getDistanceToKm(c);
                  if (ac == 0) {
                      return new TimedPosition(fix1.lat(), fix1.lon(), fix1.time());
                  } else if (bc == 0) {
                      return new TimedPosition(fix2.lat(), fix2.lon(), fix2.time());
                  } else {
                      // predict the timestamp based on distance from a and b
                      long diff = fix2.time() - fix1.time();
                      long t = Math.round(fix1.time() + ac * diff / (ac + bc));
                      return new TimedPosition(latitude, longitude, t);
                  }
              }
          }
          throw new RuntimeException("crossing not found");
      }
  
  }