/**
    *
    */
   package org.opentrafficsim.road.network.factory.vissim;
   
   import org.locationtech.jts.geom.Coordinate;
   import org.locationtech.jts.geom.LineString;
   
   /**
   * Computes the location of the point a given distance along a LineString
   */
  public class LocatePoint
  {
  
      public static Coordinate pointAlongSegment(Coordinate p0, Coordinate p1, double distance)
      {
          double segLen = p1.distance(p0);
          double frac = distance / segLen;
          if (frac <= 0.0)
          {
              return p0;
          }
          if (frac >= 1.0)
          {
              return p1;
          }
  
          double x = (p1.x - p0.x) * frac + p0.x;
          double y = (p1.y - p0.y) * frac + p0.y;
          return new Coordinate(x, y);
      }
  
      public static Coordinate pointAlongLine(LineString line, double distance)
      {
          LocatePoint loc = new LocatePoint(line, distance);
          return loc.getPoint();
      }
  
      private Coordinate pt;
  
      private int index;
  
      public LocatePoint(LineString line, double distance)
      {
          compute(line, distance);
      }
  
      private void compute(LineString line, double distance)
      {
          // <TODO> handle negative distances (measure from opposite end of line)
          double totalDist = 0.0;
          Coordinate[] coord = line.getCoordinates();
          for (int i = 0; i < coord.length - 1; i++)
          {
              Coordinate p0 = coord[i];
              Coordinate p1 = coord[i + 1];
              double segLen = p1.distance(p0);
              if (totalDist + segLen > distance)
              {
                  pt = pointAlongSegment(p0, p1, distance - totalDist);
                  index = i;
                  return;
              }
              totalDist += segLen;
          }
          // distance is greater than line length
          pt = new Coordinate(coord[coord.length - 1]);
          index = coord.length;
      }
  
      public Coordinate getPoint()
      {
          return pt;
      }
  
      /**
       * Returns the index of the segment containing the computed point
       * @return the index
       */
      public int getIndex()
      {
          return index;
      }
  
  }