package org.djutils.draw.line;
   
   import java.awt.geom.Path2D;
   import java.awt.geom.Path2D.Double;
   import java.util.ArrayList;
   import java.util.Arrays;
   import java.util.Iterator;
   import java.util.List;
   
  import org.djutils.draw.bounds.Bounds2d;
  import org.djutils.draw.point.Point2d;
  import org.djutils.exceptions.Throw;
  
  /**
   * Closed PolyLine2d. The actual closing point (which is the same as the starting point) is NOT included in the super
   * PolyLine2d. The constructors automatically remove the last point if it is a at the same location as the first point.
   * <p>
   * Copyright (c) 2020-2025 Delft University of Technology, PO Box 5, 2600 AA, Delft, the Netherlands. All rights reserved. <br>
   * BSD-style license. See <a href="https://djutils.org/docs/current/djutils/licenses.html">DJUTILS License</a>.
   * </p>
   * @author <a href="https://www.tudelft.nl/averbraeck">Alexander Verbraeck</a>
   * @author <a href="https://github.com/peter-knoppers">Peter Knoppers</a>
   * @author <a href="https://github.com/wjschakel">Wouter Schakel</a>
   */
  public class Polygon2d extends PolyLine2d
  {
      /**
       * Construct a new Polygon2d.
       * @param x the x coordinates of the points
       * @param y the y coordinates of the points
       * @throws NullPointerException when <code>x</code>, or <code>y</code> is <code>null</code>
       * @throws IllegalArgumentException when any two successive points are equal, or when there are too few points, or when the
       *             lengths of the coordinate arrays are not equal
       */
      public Polygon2d(final double[] x, final double[] y)
      {
          this(NO_FILTER, x, y);
      }
  
      /**
       * Construct a new Polygon2d.
       * @param epsilon minimum distance between points to be considered different (these will <b>not</b> be filtered out)
       * @param x the x coordinates of the points
       * @param y the y coordinates of the points
       * @throws NullPointerException when <code>x</code>, or <code>y</code> is <code>null</code>
       * @throws IllegalArgumentException when any two successive points are equal, or when there are too few points, or when the
       *             lengths of the coordinate arrays are not equal
       */
      public Polygon2d(final double epsilon, final double[] x, final double[] y)
      {
          super(epsilon, fixClosingPoint(Throw.whenNull(x, "x"), Throw.whenNull(y, "y")), fixClosingPoint(y, x));
      }
  
      /**
       * Ensure that the last pair of values in two arrays are not equal to the first pair. Remove the last pair if necessary.
       * @param a the a array
       * @param b the b array
       * @return the <code>a</code> array (possibly a copy with the last element removed)
       */
      private static double[] fixClosingPoint(final double[] a, final double[] b)
      {
          if (a.length > 1 && b.length == a.length && a[0] == a[a.length - 1] && b[0] == b[a.length - 1])
          {
              return Arrays.copyOf(a, a.length - 1);
          }
          return a;
      }
  
      /**
       * Construct a new Polygon2d.
       * @param points array of Point2d objects.
       * @throws NullPointerException when <code>points</code> is <code>null</code>
       * @throws IllegalArgumentException when <code>points</code> is too short, or contains successive duplicate points
       */
      public Polygon2d(final Point2d[] points)
      {
          this(NO_FILTER, points);
      }
  
      /**
       * Construct a new Polygon2d.
       * @param epsilon minimum distance between points to be considered different (these will <b>not</b> be filtered out)
       * @param points array of Point2d objects.
       * @throws NullPointerException when <code>points</code> is <code>null</code>
       * @throws IllegalArgumentException when <code>points</code> is too short, or contains successive duplicate points
       */
      public Polygon2d(final double epsilon, final Point2d[] points)
      {
          this(epsilon, PolyLine2d.makeArray(points, p -> p.x), PolyLine2d.makeArray(points, p -> p.y));
      }
  
      /**
       * Construct a new Polygon2d.
       * @param point1 the first point of the new Polygon2d
       * @param point2 the second point of the new Polygon2d
       * @param otherPoints all remaining points of the new Polygon2d (may be <code>null</code>)
       * @throws NullPointerException when <code>point1</code> or <code>point2</code> is <code>null</code>, or
       *             <code>otherPoints</code> contains a <code>null</code> value
       * @throws IllegalArgumentException when <code>point1</code> is equal to the last entry of <code>otherPoints</code>, or any
      *             two successive points are equal
      */
     public Polygon2d(final Point2d point1, final Point2d point2, final Point2d... otherPoints)
     {
         this(NO_FILTER, point1, point2, otherPoints);
     }
 
     /**
      * Construct a new Polygon2d.
      * @param epsilon minimum distance between points to be considered different (these will <b>not</b> be filtered out)
      * @param point1 the first point of the new Polygon2d
      * @param point2 the second point of the new Polygon2d
      * @param otherPoints all remaining points of the new Polygon2d (may be <code>null</code>)
      * @throws NullPointerException when <code>point1</code> or <code>point2</code> is <code>null</code>, or
      *             <code>otherPoints</code> contains a <code>null</code> value
      * @throws IllegalArgumentException when <code>point1</code> is equal to the last entry of <code>otherPoints</code>, or any
      *             two successive points are equal
      */
     public Polygon2d(final double epsilon, final Point2d point1, final Point2d point2, final Point2d... otherPoints)
     {
         super(epsilon, Throw.whenNull(point1, "point1"), Throw.whenNull(point2, "point2"),
                 fixClosingPoint(point1, otherPoints));
     }
 
     /**
      * Ensure that the last point of otherPoints is not equal to point1. Remove the last point if necessary.
      * @param point1 the first point of a new Polygon2d
      * @param otherPoints the remaining points of a new Polygon2d (may be <code>null</code>)
      * @return <code>otherPoints</code> (possibly a copy thereof with the last entry removed)
      */
     private static Point2d[] fixClosingPoint(final Point2d point1, final Point2d[] otherPoints)
     {
         if (otherPoints == null || otherPoints.length == 0)
         {
             return otherPoints;
         }
         Point2d[] result = otherPoints;
         Point2d lastPoint = result[result.length - 1];
         if (point1.x == lastPoint.x && point1.y == lastPoint.y)
         {
             result = Arrays.copyOf(otherPoints, result.length - 1);
             lastPoint = result[result.length - 1];
         }
         Throw.when(point1.x == lastPoint.x && point1.y == lastPoint.y, IllegalArgumentException.class,
                 "Before last point and last point are at same location");
         return result;
     }
 
     /**
      * Construct a new Polygon2d from a list of Point2d objects.
      * @param points the list of points
      * @throws NullPointerException when <code>points</code> is <code>null</code>, or contains a <code>null</code> value
      * @throws IllegalArgumentException when <code>points</code> is too short, or the last two points are at the same location
      */
     public Polygon2d(final List<Point2d> points)
     {
         this(NO_FILTER, points);
     }
 
     /**
      * Construct a new Polygon2d from a list of Point2d objects.
      * @param epsilon minimum distance between points to be considered different (these will <b>not</b> be filtered out)
      * @param points the list of points
      * @throws NullPointerException when <code>points</code> is <code>null</code>, or contains a <code>null</code> value
      * @throws IllegalArgumentException when <code>points</code> is too short, or the last two points are at the same location
      */
     public Polygon2d(final double epsilon, final List<Point2d> points)
     {
         super(epsilon, fixClosingPoint(true, Throw.whenNull(points, "points")));
     }
 
     /**
      * Ensure that the last point in the list is different from the first point by possibly removing the last point.
      * @param doNotModifyList if <code>true</code>; the list of points will not be modified (if the last point is to be
      *            removed; the entire list up to the last point is duplicated)
      * @param points the list of points
      * @return the fixed list
      * @throws NullPointerException when <code>points</code> is <code>null</code>
      * @throws IllegalArgumentException when the (resulting) list is too short, or the before last and last point of points have
      *             the same coordinates
      */
     private static List<Point2d> fixClosingPoint(final boolean doNotModifyList, final List<Point2d> points)
     {
         Throw.when(points.size() < 2, IllegalArgumentException.class, "Need at least two points");
         Point2d firstPoint = points.get(0);
         Point2d lastPoint = points.get(points.size() - 1);
         List<Point2d> result = points;
         if (firstPoint.x == lastPoint.x && firstPoint.y == lastPoint.y)
         {
             if (doNotModifyList)
             {
                 result = new ArrayList<>(points.size() - 1);
                 for (int i = 0; i < points.size() - 1; i++)
                 {
                     result.add(points.get(i));
                 }
             }
             else
             {
                 result.remove(points.size() - 1);
             }
             lastPoint = result.get(result.size() - 1);
         }
         Throw.when(firstPoint.x == lastPoint.x && firstPoint.y == lastPoint.y, IllegalArgumentException.class,
                 "Before last point and last point are at same location");
         return result;
     }
 
     /**
      * Construct a new Polygon2d from an iterator that yields Point2d.
      * @param iterator the iterator
      * @throws NullPointerException when <code>iterator</code> is <code>null</code>, or the iterator returns a <code>null</code>
      *             value
      * @throws IllegalArgumentException when the <code>iterator</code> yields too few points, or the before last and last point
      *             have the same coordinates
      */
     public Polygon2d(final Iterator<Point2d> iterator)
     {
         this(NO_FILTER, iterator);
     }
 
     /**
      * Construct a new Polygon2d from an iterator that yields Point2d.
      * @param epsilon minimum distance between points to be considered different (these will <b>not</b> be filtered out)
      * @param iterator the iterator
      * @throws NullPointerException when <code>iterator</code> is <code>null</code>, or the iterator returns a <code>null</code>
      *             value
      * @throws IllegalArgumentException when the <code>iterator</code> yields too few points, or the before last and last point
      *             have the same coordinates
      */
     public Polygon2d(final double epsilon, final Iterator<Point2d> iterator)
     {
         this(epsilon, fixClosingPoint(false, iteratorToList(Throw.whenNull(iterator, "iterator"))));
     }
 
     /**
      * Construct a new Polygon2d from an existing one. This constructor is primarily intended for use in extending classes.
      * @param polygon the existing Polygon2d
      * @throws NullPointerException when <code>polygon</code> is <code>null</code>
      */
     public Polygon2d(final Polygon2d polygon)
     {
         super(polygon);
     }
 
     /**
      * Determine if this Polygon is convex. Returns bogus result for self-intersecting polygons. Derived from
      * <a href="http://paulbourke.net/geometry/polygonmesh/source2.c">Convex by Paul Bourke</a>
      * @return <code>true</code> if this <code>Polygon2d</code> is convex; <code>false</code> if this
      *         <code>Polygon2d</code> is concave
      */
     public final boolean isConvex()
     {
         int flag = 0;
         for (int i = 0; i < size(); i++)
         {
             int j = (i + 1) % size();
             int k = (j + 1) % size();
             double z = (getX(j) - getX(i)) * (getY(k) - getY(j)) - (getY(j) - getY(i)) * (getX(k) - getX(j));
             if (z < 0)
             {
                 flag |= 1;
             }
             else if (z > 0)
             {
                 flag |= 2;
             }
             if (flag == 3)
             {
                 return false;
             }
         }
         return flag != 0;
     }
 
     /**
      * Determine if a point is inside this Polygon. Returns bogus results for self-intersecting polygons.
      * @param point the point
      * @return <code>true</code> if the point is inside this <code>Polygon2d</code>, <code>false</code> if the point is
      *         outside this <code>Polygon2d</code>. Results are ill-defined for points on the edges of this
      *         <code>Polygon2d</code>.
      */
     public boolean contains(final Point2d point)
     {
         return contains(point.x, point.y);
     }
 
     /**
      * Determine if a point is inside this Polygon. Returns bogus results for self-intersecting polygons. Derived from
      * <a href="http://paulbourke.net/geometry/polygonmesh/">Polygons and meshes by Paul Bourke</a>
      * @param x the x-coordinate of the point
      * @param y the y-coordinate of the point
      * @return <code>true</code> if the point is inside this <code>Polygon2d</code>, <code>false</code> if the point is
      *         outside this <code>Polygon2d</code>. Results are ill-defined for points on the edges of this
      *         <code>Polygon2d</code>.
      */
     public boolean contains(final double x, final double y)
     {
         if (!getAbsoluteBounds().contains(x, y))
         {
             return false;
         }
         int counter = 0;
         // Unlike Paul Bourke, we initialize prevPoint to the last point of the polygon (so we never have to wrap around)
         double prevPointX = getX(size() - 1);
         double prevPointY = getY(size() - 1);
         for (int i = 0; i < size(); i++)
         {
             double curPointX = getX(i);
             double curPointY = getY(i);
             // Combined 4 if statements into one; I trust that the java compiler will short-circuit this nicely
             if (y > Math.min(prevPointY, curPointY) && y <= Math.max(prevPointY, curPointY)
                     && x <= Math.max(prevPointX, curPointX) && prevPointY != curPointY)
             {
                 double xIntersection = (y - prevPointY) * (curPointX - prevPointX) / (curPointY - prevPointY) + prevPointX;
                 if (prevPointX == curPointX || x <= xIntersection)
                 {
                     counter++;
                 }
             }
             prevPointX = curPointX;
             prevPointY = curPointY;
         }
         return counter % 2 != 0;
     }
 
     /**
      * Determine if this Polygon completely contains a Bounds2d object. If this Polygon self-intersects, the results is bogus.
      * @param bounds the Bounds2d object
      * @return <code>true</code> if the <code>Bounds2d</code> object is completely contained in this
      *         <code>Polygon2d</code>; <code>false</code> if any part (or all) of the Bounds2d object is outside this
      *         <code>Polygon2d</code>. If the Bounds2d object touches this <code>Polygon2d</code> the results are ill-defined.
      */
     public boolean contains(final Bounds2d bounds)
     {
         // Step 1: quick check to see if the bounds intersect
         if (getAbsoluteBounds().disjoint(bounds))
         {
             return false;
         }
         // This is a quick hack
         return toPath2D().contains(bounds.getMinX(), bounds.getMinY(), bounds.getDeltaX(), bounds.getDeltaY());
     }
 
     /**
      * Determine if this Polygon2d intersects another Polygon2d.
      * @param other the other Polygon2d
      * @return <code>true</code> if the polygons intersect; <code>false</code> if the polygons are disjunct.
      *         Ill-defined if the polygons touch.
      */
     public boolean intersects(final Polygon2d other)
     {
         // step 1: quick check to see if the bounds intersect
         if (!getAbsoluteBounds().intersects(other.getAbsoluteBounds()))
         {
             return false;
         }
 
         // step 2: quick check to see if any of the points of this polygon lies inside the other polygon
         for (Iterator<Point2d> iterator = iterator(); iterator.hasNext();)
         {
             if (other.contains(iterator.next()))
             {
                 return true;
             }
         }
 
         // step 3: quick check to see if any of the points of the other polygon lies inside this polygon
         for (Iterator<Point2d> iterator = other.iterator(); iterator.hasNext();)
         {
             if (contains(iterator.next()))
             {
                 return true;
             }
         }
 
         // step 4: see if any of the lines of shape 1 and shape 2 intersect (expensive!)
         for (int i = 0; i < this.size(); i++)
         {
             LineSegment2d ourSegment = getSegment(i);
             for (int j = 0; j < other.size(); j++)
             {
                 LineSegment2d otherSegment = other.getSegment(j);
                 Point2d intersection = Point2d.intersectionOfLineSegments(ourSegment, otherSegment);
                 if (intersection != null)
                 {
                     double p1x = ourSegment.startX, p1y = ourSegment.startY;
                     double d1x = ourSegment.endX - p1x, d1y = ourSegment.endY - p1y;
                     double p2x = otherSegment.startX, p2y = otherSegment.startY;
                     double d2x = otherSegment.endX - p2x, d2y = otherSegment.endY - p2y;
 
                     double det = d2x * d1y - d2y * d1x;
                     if (det != 0)
                     {
                         double z = (d2x * (p2y - p1y) + d2y * (p1x - p2x)) / det;
                         if (Math.abs(z) < 10.0 * Math.ulp(1.0) || Math.abs(z - 1.0) > 10.0 * Math.ulp(1.0))
                         {
                             return true; // intersection at end point
                         }
                     }
                 }
             }
         }
         return false;
     }
 
     /**
      * Compute the surface of this Polygon2d. Sign of the result reflects the winding-ness of this this Polygon2d. If this
      * Polygon2d self-intersects, the result is bogus.
      * @return the surface of this <code>Polygon2d</code>
      */
     public double surface()
     {
         // Translate all coordinates to the median of the bounding box to minimize rounding errors
         Point2d midPoint = getAbsoluteBounds().midPoint();
         double result = 0;
         // We initialize previous point to the last point of this Polygon2d to avoid wrapping problems
         double prevX = getX(size() - 1) - midPoint.x;
         double prevY = getY(size() - 1) - midPoint.y;
         for (int i = 0; i < size(); i++)
         {
             double thisX = getX(i) - midPoint.x;
             double thisY = getY(i) - midPoint.y;
             result += prevX * thisY - thisX * prevY;
             prevX = thisX;
             prevY = thisY;
         }
         return result / 2;
     }
 
     @Override
     public double getLength()
     {
         // Length of a polygon is computed by taking the length of the PolyLine and adding the length of the closing segment
         return super.getLength() + Math.hypot(getX(size() - 1) - getX(0), getY(size() - 1) - getY(0));
     }
 
     @Override
     public LineSegment2d getSegment(final int index)
     {
         if (index < size() - 1)
         {
             return super.getSegment(index);
         }
         Throw.when(index != size() - 1, IndexOutOfBoundsException.class, "index must be in range [0..size() - 1] (got %d)",
                 index);
         return new LineSegment2d(getX(index), getY(index), getX(0), getY(0));
     }
 
     @Override
     public Polygon2d reverse()
     {
         return new Polygon2d(super.reverse().iterator());
     }
 
     /**
      * Construct a Path2D from this PolyLine2d. The result is NOT cached (in the current implementation).
      * @return newly construct Path2D consisting solely of straight segments.
      */
     @Override
     public Path2D toPath2D()
     {
         Path2D.Double result = (Double) super.toPath2D();
         result.closePath();
         return result;
     }
 
     @Override
     public final String toString()
     {
         return toString("%f", false);
     }
 
     @Override
     public String toString(final String doubleFormat, final boolean doNotIncludeClassName)
     {
         StringBuilder result = new StringBuilder();
         if (!doNotIncludeClassName)
         {
             result.append("Polygon2d ");
         }
         result.append("[super=");
         result.append(super.toString(doubleFormat, false));
         result.append("]");
         return result.toString();
     }
 
 }