package org.opentrafficsim.road.network.lane;
   
   import java.util.LinkedHashMap;
   import java.util.Map;
   
   import org.djutils.draw.line.PolyLine2d;
   import org.djutils.draw.line.Polygon2d;
   import org.djutils.exceptions.Throw;
   import org.opentrafficsim.base.geometry.OtsLine2d;
  import org.opentrafficsim.core.geometry.ContinuousLine;
  import org.opentrafficsim.core.geometry.ContinuousLine.ContinuousDoubleFunction;
  import org.opentrafficsim.core.geometry.Flattener;
  import org.opentrafficsim.core.geometry.FractionalLengthData;
  
  /**
   * Cross-section element geometry. A static method {@code of(...)} is available to generate geometry based on a design line and
   * information on offset and width.
   * <p>
   * Copyright (c) 2024-2024 Delft University of Technology, PO Box 5, 2600 AA, Delft, the Netherlands. All rights reserved. <br>
   * BSD-style license. See <a href="https://opentrafficsim.org/docs/license.html">OpenTrafficSim License</a>.
   * </p>
   * @author <a href="https://github.com/wjschakel">Wouter Schakel</a>
   * @param centerLine center line
   * @param contour contour
   * @param offset offset
   * @param width width
   */
  @SuppressWarnings("javadoc")
  public record CrossSectionGeometry(OtsLine2d centerLine, Polygon2d contour, ContinuousDoubleFunction offset,
          ContinuousDoubleFunction width)
  {
  
      /**
       * Constructor.
       * @throws NullPointerException when centerLine, contour or slices is {@code null}
       */
      public CrossSectionGeometry
  
      {
          Throw.whenNull(centerLine, "Center line may not be null.");
          Throw.whenNull(contour, "Contour may not be null.");
          Throw.whenNull(offset, "Offset may not be null.");
          Throw.whenNull(width, "Width may not be null.");
      }
  
      /**
       * Create geometry based on design line, flattener, offset and width information.
       * @param designLine design line relative to which offsets are defined
       * @param flattener flattener to flatten center line and contour
       * @param offset offset information
       * @param width offset information
       * @return geometry for cross-section element
       */
      public static CrossSectionGeometry of(final ContinuousLine designLine, final Flattener flattener,
              final ContinuousDoubleFunction offset, final ContinuousDoubleFunction width)
      {
          PolyLine2d line = designLine.flattenOffset(offset, flattener);
          Map<Double, Double> leftMap = new LinkedHashMap<>();
          Map<Double, Double> rightMap = new LinkedHashMap<>();
          for (double f : offset.getKnots())
          {
              leftMap.put(f, offset.apply(f) + .5 * width.apply(f));
              rightMap.put(f, offset.apply(f) - .5 * width.apply(f));
          }
          for (double f : width.getKnots())
          {
              leftMap.put(f, offset.apply(f) + .5 * width.apply(f));
              rightMap.put(f, offset.apply(f) - .5 * width.apply(f));
          }
          PolyLine2d left = designLine.flattenOffset(new FractionalLengthData(leftMap), flattener);
          PolyLine2d right = designLine.flattenOffset(new FractionalLengthData(rightMap), flattener);
          Polygon2d cont = LaneGeometryUtil.getContour(left, right);
          return new CrossSectionGeometry(new OtsLine2d(line), cont, offset, width);
      }
  
  }