package org.opentrafficsim.road.network;
   
   import org.djunits.value.vdouble.scalar.Length;
   import org.djutils.base.Identifiable;
   import org.djutils.draw.bounds.Bounds2d;
   import org.djutils.draw.function.ContinuousPiecewiseLinearFunction;
   import org.djutils.draw.line.Polygon2d;
   import org.djutils.draw.point.DirectedPoint2d;
   import org.djutils.event.LocalEventProducer;
  import org.djutils.exceptions.Throw;
  import org.opentrafficsim.base.geometry.OtsLine2d;
  import org.opentrafficsim.base.geometry.OtsShape;
  import org.opentrafficsim.core.network.LateralDirectionality;
  
  /**
   * Cross section elements are used to compose a CrossSectionLink.
   * <p>
   * Copyright (c) 2013-2026 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 Alexander Verbraeck
   * @author Peter Knoppers
   * @author Guus Tamminga
   */
  public abstract class CrossSectionElement extends LocalEventProducer implements OtsShape, Identifiable
  {
      /** The id. Should be unique within the parentLink. */
      private final String id;
  
      /** Cross Section Link to which the element belongs. */
      @SuppressWarnings("checkstyle:visibilitymodifier")
      protected final CrossSectionLink link;
  
      /** The center line of the element. Calculated once at the creation. */
      private final OtsLine2d centerLine;
  
      /** The contour of the element. Calculated once at the creation. */
      private final Polygon2d absoluteContour;
  
      /** Relative contour.. */
      private final Polygon2d relativeContour;
  
      /** Offset. */
      private final ContinuousPiecewiseLinearFunction offset;
  
      /** Width. */
      private final ContinuousPiecewiseLinearFunction width;
  
      /** Location, center of contour. */
      private final DirectedPoint2d location;
  
      /**
       * Constructor.
       * @param link link
       * @param id id
       * @param geometry geometry
       */
      public CrossSectionElement(final CrossSectionLink link, final String id, final CrossSectionGeometry geometry)
      {
          Throw.whenNull(link, "link");
          Throw.whenNull(id, "id");
          Throw.whenNull(geometry, "geometry");
          this.link = link;
          this.id = id;
          this.centerLine = geometry.centerLine();
          this.location = geometry.centerLine().getLocationFractionExtended(0.5);
          this.absoluteContour = geometry.absoluteContour();
          this.relativeContour =
                  new Polygon2d(0.0, OtsShape.toRelativeTransform(this.location).transform(this.absoluteContour.iterator()));
          this.offset = geometry.offset();
          this.width = geometry.width();
  
          link.addCrossSectionElement(this);
  
          // clear lane change info cache for each cross section element created
          link.getNetwork().clearLaneChangeInfoCache();
      }
  
      /**
       * Returns the link of this cross-section element.
       * @return link of this cross-section element.
       */
      public final CrossSectionLink getLink()
      {
          return this.link;
      }
  
      /**
       * Returns network.
       * @return the road network to which the lane belongs
       */
      public final RoadNetwork getNetwork()
      {
          return this.link.getNetwork();
      }
  
      /**
       * Retrieve the lateral offset from the Link design line at the specified longitudinal position.
       * @param fractionalPosition fractional longitudinal position on this Lane
      * @return the lateralCenterPosition at the specified longitudinal position
      */
     public final Length getLateralCenterPosition(final double fractionalPosition)
     {
         return Length.ofSI(this.offset.get(fractionalPosition));
     }
 
     /**
      * Retrieve the lateral offset from the Link design line at the specified longitudinal position.
      * @param longitudinalPosition the longitudinal position on this Lane
      * @return the lateralCenterPosition at the specified longitudinal position
      */
     public final Length getLateralCenterPosition(final Length longitudinalPosition)
     {
         return getLateralCenterPosition(longitudinalPosition.si / getLength().si);
     }
 
     /**
      * Return the width of this CrossSectionElement at a specified longitudinal position.
      * @param longitudinalPosition the longitudinal position
      * @return the width of this CrossSectionElement at the specified longitudinal position.
      */
     public final Length getWidth(final Length longitudinalPosition)
     {
         return getWidth(longitudinalPosition.si / getLength().si);
     }
 
     /**
      * Return the width of this CrossSectionElement at a specified fractional longitudinal position.
      * @param fractionalPosition the fractional longitudinal position
      * @return the width of this CrossSectionElement at the specified fractional longitudinal position.
      */
     public final Length getWidth(final double fractionalPosition)
     {
         return Length.ofSI(this.width.get(fractionalPosition));
     }
 
     /**
      * Return the length of this CrossSectionElement as measured along the design line (which equals the center line).
      * @return the length of this CrossSectionElement
      */
     public final Length getLength()
     {
         return this.centerLine.getTypedLength();
     }
 
     /**
      * Retrieve the offset from the design line at the begin of the parent link.
      * @return the offset of this CrossSectionElement at the begin of the parent link
      */
     public final Length getOffsetAtBegin()
     {
         return Length.ofSI(this.offset.get(0.0));
     }
 
     /**
      * Retrieve the offset from the design line at the end of the parent link.
      * @return the offset of this CrossSectionElement at the end of the parent link
      */
     public final Length getOffsetAtEnd()
     {
         return Length.ofSI(this.offset.get(1.0));
     }
 
     /**
      * Retrieve the width at the begin of the parent link.
      * @return the width of this CrossSectionElement at the begin of the parent link
      */
     public final Length getBeginWidth()
     {
         return Length.ofSI(this.width.get(0.0));
     }
 
     /**
      * Retrieve the width at the end of the parent link.
      * @return the width of this CrossSectionElement at the end of the parent link
      */
     public final Length getEndWidth()
     {
         return Length.ofSI(this.width.get(1.0));
     }
 
     /**
      * Retrieve the Z offset (used to determine what covers what when drawing).
      * @return the Z-offset for drawing (what's on top, what's underneath).
      */
     @Override
     public double getZ()
     {
         // default implementation returns 0.0 in case of a null location or a 2D location
         return OtsShape.super.getZ();
     }
 
     /**
      * Retrieve the center line of this CrossSectionElement.
      * @return the center line of this CrossSectionElement
      */
     public final OtsLine2d getCenterLine()
     {
         return this.centerLine;
     }
 
     @Override
     public final Polygon2d getAbsoluteContour()
     {
         return this.absoluteContour;
     }
 
     @Override
     public final Polygon2d getRelativeContour()
     {
         return this.relativeContour;
     }
 
     @Override
     public final String getId()
     {
         return this.id;
     }
 
     /**
      * Retrieve the id of this CrossSectionElement.
      * @return the id of this CrossSectionElement
      */
     public final String getFullId()
     {
         return getLink().getId() + "." + this.id;
     }
 
     /**
      * Return the lateral offset from the design line of the parent Link of the Left or Right boundary of this
      * CrossSectionElement at the specified fractional longitudinal position.
      * @param lateralDirection LEFT, or RIGHT
      * @param fractionalLongitudinalPosition ranges from 0.0 (begin of parentLink) to 1.0 (end of parentLink)
      * @return Length
      * @throws IllegalArgumentException when lateral direction is {@code null} or NONE.
      */
     public final Length getLateralBoundaryPosition(final LateralDirectionality lateralDirection,
             final double fractionalLongitudinalPosition)
     {
         Length offsetAt = getLateralCenterPosition(fractionalLongitudinalPosition);
         Length halfWidth = getWidth(fractionalLongitudinalPosition).times(0.5);
 
         switch (lateralDirection)
         {
             case LEFT:
                 return offsetAt.minus(halfWidth);
             case RIGHT:
                 return offsetAt.plus(halfWidth);
             default:
                 throw new IllegalArgumentException("Bad value for LateralDirectionality " + lateralDirection);
         }
     }
 
     /**
      * Return the lateral offset from the design line of the parent Link of the Left or Right boundary of this
      * CrossSectionElement at the specified longitudinal position.
      * @param lateralDirection LEFT, or RIGHT
      * @param longitudinalPosition the position along the length of this CrossSectionElement
      * @return Length
      */
     public final Length getLateralBoundaryPosition(final LateralDirectionality lateralDirection,
             final Length longitudinalPosition)
     {
         return getLateralBoundaryPosition(lateralDirection, longitudinalPosition.getSI() / getLength().getSI());
     }
 
     @Override
     @SuppressWarnings("checkstyle:designforextension")
     public DirectedPoint2d getLocation()
     {
         return this.location;
     }
 
     @Override
     @SuppressWarnings("checkstyle:designforextension")
     public Bounds2d getRelativeBounds()
     {
         return this.relativeContour.getAbsoluteBounds();
     }
 
     /**
      * Returns the elevation at the given position.
      * @param position position.
      * @return elevation at the given position.
      */
     public Length getElevation(final Length position)
     {
         return getElevation(position.si / getLength().si);
     }
 
     /**
      * Returns the elevation at the given fractional position.
      * @param fractionalPosition fractional position.
      * @return elevation at the given fractional position.
      */
     public Length getElevation(final double fractionalPosition)
     {
         return getLink().getElevation(fractionalPosition);
     }
 
     /**
      * Returns the grade at the given position, given as delta_h / delta_f, where f is fractional position.
      * @param position position.
      * @return grade at the given position.
      */
     public double getGrade(final Length position)
     {
         return getGrade(position.si / getLength().si);
     }
 
     /**
      * Returns the grade at the given fractional position, given as delta_h / delta_f, where f is fractional position.
      * @param fractionalPosition fractional position.
      * @return grade at the given fractional position.
      */
     public double getGrade(final double fractionalPosition)
     {
         return getLink().getGrade(fractionalPosition);
     }
 
     @Override
     @SuppressWarnings("checkstyle:designforextension")
     public String toString()
     {
         return String.format("CSE offset %.2fm..%.2fm, width %.2fm..%.2fm", getOffsetAtBegin().getSI(),
                 getOffsetAtEnd().getSI(), getBeginWidth().getSI(), getEndWidth().getSI());
     }
 
     @Override
     @SuppressWarnings("checkstyle:designforextension")
     public int hashCode()
     {
         final int prime = 31;
         int result = 1;
         result = prime * result + ((this.id == null) ? 0 : this.id.hashCode());
         result = prime * result + ((this.link == null) ? 0 : this.link.hashCode());
         return result;
     }
 
     @Override
     @SuppressWarnings({"checkstyle:designforextension", "checkstyle:needbraces"})
     public boolean equals(final Object obj)
     {
         if (this == obj)
             return true;
         if (obj == null)
             return false;
         if (getClass() != obj.getClass())
             return false;
         CrossSectionElement other = (CrossSectionElement) obj;
         if (this.id == null)
         {
             if (other.id != null)
                 return false;
         }
         else if (!this.id.equals(other.id))
             return false;
         if (this.link == null)
         {
             if (other.link != null)
                 return false;
         }
         else if (!this.link.equals(other.link))
             return false;
         return true;
     }
 }