package org.opentrafficsim.road.network.lane;
   
   import java.util.LinkedHashMap;
   import java.util.Map;
   
   import org.djutils.draw.curve.OffsetCurve2d;
   import org.djutils.draw.curve.OffsetFlattener2d;
   import org.djutils.draw.function.ContinuousPiecewiseLinearFunction;
   import org.djutils.draw.line.PolyLine2d;
  import org.djutils.draw.line.Polygon2d;
  import org.djutils.draw.point.DirectedPoint2d;
  import org.djutils.exceptions.Throw;
  import org.djutils.math.functions.MathFunction.TupleSt;
  import org.opentrafficsim.base.geometry.OtsLine2d;
  import org.opentrafficsim.base.geometry.OtsShape;
  
  /**
   * 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 absoluteContour contour
   * @param offset offset
   * @param width width
   */
  public record CrossSectionGeometry(OtsLine2d centerLine, Polygon2d absoluteContour, ContinuousPiecewiseLinearFunction offset,
          ContinuousPiecewiseLinearFunction width)
  {
  
      /**
       * Constructor.
       * @throws NullPointerException when centerLine, contour or slices is {@code null}
       */
      public CrossSectionGeometry
  
      {
          Throw.whenNull(centerLine, "centerLine");
          Throw.whenNull(absoluteContour, "absoluteContour");
          Throw.whenNull(offset, "offset");
          Throw.whenNull(width, "width");
      }
  
      /**
       * 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 OffsetCurve2d designLine, final OffsetFlattener2d flattener,
              final ContinuousPiecewiseLinearFunction offset, final ContinuousPiecewiseLinearFunction width)
      {
          PolyLine2d line = designLine.toPolyLine(flattener, offset);
          Map<Double, Double> leftMap = new LinkedHashMap<>();
          Map<Double, Double> rightMap = new LinkedHashMap<>();
          for (TupleSt st : offset)
          {
              leftMap.put(st.s(), st.t() + .5 * width.get(st.s()));
              rightMap.put(st.s(), st.t() - .5 * width.get(st.s()));
          }
          for (TupleSt st : width)
          {
              leftMap.put(st.s(), offset.get(st.s()) + .5 * width.get(st.s()));
              rightMap.put(st.s(), offset.get(st.s()) - .5 * width.get(st.s()));
          }
          PolyLine2d left = designLine.toPolyLine(flattener, new ContinuousPiecewiseLinearFunction(leftMap));
          PolyLine2d right = designLine.toPolyLine(flattener, new ContinuousPiecewiseLinearFunction(rightMap));
          Polygon2d cont = LaneGeometryUtil.getContour(left, right);
          return new CrossSectionGeometry(new OtsLine2d(line), cont, offset, width);
      }
  
      /**
       * Returns the location.
       * @return returns the location of this geometry
       */
      public DirectedPoint2d getLocation()
      {
          return centerLine().getLocationFractionExtended(0.5);
      }
  
      /**
       * Returns the relative contour.
       * @return relative contour
       */
      public Polygon2d getRelativeContour()
      {
          return new Polygon2d(OtsShape.toRelativeTransform(getLocation()).transform(absoluteContour().iterator()));
      }
  
  }