/**
    *
    */
   package org.opentrafficsim.road.network.factory.shape;
   
   import com.vividsolutions.jts.geom.Coordinate;
   import com.vividsolutions.jts.geom.CoordinateList;
   import com.vividsolutions.jts.geom.LineSegment;
   import com.vividsolutions.jts.geom.LineString;
  import com.vividsolutions.jts.util.Assert;
  
  /**
   * @author P070518
   */
  public class SubstringLine
  {
      /**
       * Computes a substring of a {@link LineString} between given distances along the line.
       * <ul>
       * <li>The distances are clipped to the actual line length
       * <li>If the start distance is equal to the end distance, a zero-length line with two identical points is returned
       * <li>FUTURE: If the start distance is greater than the end distance, an inverted section of the line is returned
       * </ul>
       * <p>
       * FUTURE: should handle startLength > endLength, and flip the returned linestring. Also should handle negative lengths
       * (they are measured from end of line backwards).
       */
  
      /**
       * @param line LineString;
       * @param startLength double;
       * @param endLength double;
       * @return the substring
       */
      public static LineString getSubstring(LineString line, double startLength, double endLength)
      {
          SubstringLine ls = new SubstringLine(line);
          return ls.getSubstring(startLength, endLength);
      }
  
      private LineString line;
  
      public SubstringLine(LineString line)
      {
          this.line = line;
      }
  
      public LineString getSubstring(double startDistance, double endDistance)
      {
          // future: if start > end, flip values and return an inverted line
          Assert.isTrue(startDistance <= endDistance, "inverted distances not currently supported");
  
          Coordinate[] coordinates = line.getCoordinates();
          // check for a zero-length segment and handle appropriately
          if (endDistance <= 0.0)
          {
              return line.getFactory().createLineString(new Coordinate[] { coordinates[0], coordinates[0] });
          }
          if (startDistance >= line.getLength())
          {
              return line.getFactory().createLineString(
                      new Coordinate[] { coordinates[coordinates.length - 1], coordinates[coordinates.length - 1] });
          }
          if (startDistance < 0.0)
          {
              startDistance = 0.0;
          }
          return computeSubstring(startDistance, endDistance);
      }
  
      /**
       * Assumes input is strictly valid (e.g. startDist < endDistance)
       * @param startDistance double;
       * @param endDistance double;
       * @return the substring
       */
      private LineString computeSubstring(double startDistance, double endDistance)
      {
          Coordinate[] coordinates = line.getCoordinates();
          CoordinateList newCoordinates = new CoordinateList();
          double segmentStartDistance = 0.0;
          double segmentEndDistance = 0.0;
          boolean started = false;
          int i = 0;
          LineSegment segment = new LineSegment();
          while (i < coordinates.length - 1 && endDistance > segmentEndDistance)
          {
              segment.p0 = coordinates[i];
              segment.p1 = coordinates[i + 1];
              i++;
              segmentStartDistance = segmentEndDistance;
              segmentEndDistance = segmentStartDistance + segment.getLength();
  
              if (startDistance > segmentEndDistance)
              {
                  continue;
              }
              if (startDistance >= segmentStartDistance && startDistance < segmentEndDistance)
              {
                 newCoordinates.add(LocatePoint.pointAlongSegment(segment.p0, segment.p1, startDistance - segmentStartDistance),
                         false);
             }
             /*
              * if (startDistance >= segmentStartDistance && startDistance == segmentEndDistance) { newCoordinates.add(new
              * Coordinate(segment.p1), false); }
              */
             if (endDistance >= segmentEndDistance)
             {
                 newCoordinates.add(new Coordinate(segment.p1), false);
             }
             if (endDistance >= segmentStartDistance && endDistance < segmentEndDistance)
             {
                 newCoordinates.add(LocatePoint.pointAlongSegment(segment.p0, segment.p1, endDistance - segmentStartDistance),
                         false);
             }
         }
         Coordinate[] newCoordinateArray = newCoordinates.toCoordinateArray();
         /**
          * Ensure there is enough coordinates to build a valid line. Make a 2-point line with duplicate coordinates, if
          * necessary There will always be at least one coordinate in the coordList.
          */
         if (newCoordinateArray.length <= 1)
         {
             newCoordinateArray = new Coordinate[] { newCoordinateArray[0], newCoordinateArray[0] };
         }
         return line.getFactory().createLineString(newCoordinateArray);
     }
 }