/*
    * Licensed to the Apache Software Foundation (ASF) under one or more
    * contributor license agreements.  See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * The ASF licenses this file to You under the Apache License, Version 2.0
    * (the "License"); you may not use this file except in compliance with
    * the License.  You may obtain a copy of the License at
    *
    *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.commons.math3.geometry.euclidean.threed;
  
  import java.util.ArrayList;
  
  import org.apache.commons.math3.geometry.euclidean.twod.Euclidean2D;
  import org.apache.commons.math3.geometry.euclidean.twod.PolygonsSet;
  import org.apache.commons.math3.geometry.euclidean.twod.Vector2D;
  import org.apache.commons.math3.geometry.partitioning.AbstractSubHyperplane;
  import org.apache.commons.math3.geometry.partitioning.BSPTree;
  import org.apache.commons.math3.geometry.partitioning.BSPTreeVisitor;
  import org.apache.commons.math3.geometry.partitioning.BoundaryAttribute;
  import org.apache.commons.math3.geometry.partitioning.RegionFactory;
  import org.apache.commons.math3.geometry.partitioning.SubHyperplane;
  import org.apache.commons.math3.util.FastMath;
  
  /** Extractor for {@link PolygonsSet polyhedrons sets} outlines.
   * <p>This class extracts the 2D outlines from {{@link PolygonsSet
   * polyhedrons sets} in a specified projection plane.</p>
   * @version $Id: OutlineExtractor.java 1416643 2012-12-03 19:37:14Z tn $
   * @since 3.0
   */
  public class OutlineExtractor {
  
      /** Abscissa axis of the projection plane. */
      private Vector3D u;
  
      /** Ordinate axis of the projection plane. */
      private Vector3D v;
  
      /** Normal of the projection plane (viewing direction). */
      private Vector3D w;
  
      /** Build an extractor for a specific projection plane.
       * @param u abscissa axis of the projection point
       * @param v ordinate axis of the projection point
       */
      public OutlineExtractor(final Vector3D u, final Vector3D v) {
          this.u = u;
          this.v = v;
          w = Vector3D.crossProduct(u, v);
      }
  
      /** Extract the outline of a polyhedrons set.
       * @param polyhedronsSet polyhedrons set whose outline must be extracted
       * @return an outline, as an array of loops.
       */
      public Vector2D[][] getOutline(final PolyhedronsSet polyhedronsSet) {
  
          // project all boundary facets into one polygons set
          final BoundaryProjector projector = new BoundaryProjector();
          polyhedronsSet.getTree(true).visit(projector);
          final PolygonsSet projected = projector.getProjected();
  
          // Remove the spurious intermediate vertices from the outline
          final Vector2D[][] outline = projected.getVertices();
          for (int i = 0; i < outline.length; ++i) {
              final Vector2D[] rawLoop = outline[i];
              int end = rawLoop.length;
              int j = 0;
              while (j < end) {
                  if (pointIsBetween(rawLoop, end, j)) {
                      // the point should be removed
                      for (int k = j; k < (end - 1); ++k) {
                          rawLoop[k] = rawLoop[k + 1];
                      }
                      --end;
                  } else {
                      // the point remains in the loop
                      ++j;
                  }
              }
              if (end != rawLoop.length) {
                  // resize the array
                  outline[i] = new Vector2D[end];
                  System.arraycopy(rawLoop, 0, outline[i], 0, end);
              }
          }
  
          return outline;
  
      }
  
      /** Check if a point is geometrically between its neighbour in an array.
      * <p>The neighbours are computed considering the array is a loop
      * (i.e. point at index (n-1) is before point at index 0)</p>
      * @param loop points array
      * @param n number of points to consider in the array
      * @param i index of the point to check (must be between 0 and n-1)
      * @return true if the point is exactly between its neighbours
      */
     private boolean pointIsBetween(final Vector2D[] loop, final int n, final int i) {
         final Vector2D previous = loop[(i + n - 1) % n];
         final Vector2D current  = loop[i];
         final Vector2D next     = loop[(i + 1) % n];
         final double dx1       = current.getX() - previous.getX();
         final double dy1       = current.getY() - previous.getY();
         final double dx2       = next.getX()    - current.getX();
         final double dy2       = next.getY()    - current.getY();
         final double cross     = dx1 * dy2 - dx2 * dy1;
         final double dot       = dx1 * dx2 + dy1 * dy2;
         final double d1d2      = FastMath.sqrt((dx1 * dx1 + dy1 * dy1) * (dx2 * dx2 + dy2 * dy2));
         return (FastMath.abs(cross) <= (1.0e-6 * d1d2)) && (dot >= 0.0);
     }
 
     /** Visitor projecting the boundary facets on a plane. */
     private class BoundaryProjector implements BSPTreeVisitor<Euclidean3D> {
 
         /** Projection of the polyhedrons set on the plane. */
         private PolygonsSet projected;
 
         /** Simple constructor.
          */
         public BoundaryProjector() {
             projected = new PolygonsSet(new BSPTree<Euclidean2D>(Boolean.FALSE));
         }
 
         /** {@inheritDoc} */
         public Order visitOrder(final BSPTree<Euclidean3D> node) {
             return Order.MINUS_SUB_PLUS;
         }
 
         /** {@inheritDoc} */
         public void visitInternalNode(final BSPTree<Euclidean3D> node) {
             @SuppressWarnings("unchecked")
             final BoundaryAttribute<Euclidean3D> attribute =
                 (BoundaryAttribute<Euclidean3D>) node.getAttribute();
             if (attribute.getPlusOutside() != null) {
                 addContribution(attribute.getPlusOutside(), false);
             }
             if (attribute.getPlusInside() != null) {
                 addContribution(attribute.getPlusInside(), true);
             }
         }
 
         /** {@inheritDoc} */
         public void visitLeafNode(final BSPTree<Euclidean3D> node) {
         }
 
         /** Add he contribution of a boundary facet.
          * @param facet boundary facet
          * @param reversed if true, the facet has the inside on its plus side
          */
         private void addContribution(final SubHyperplane<Euclidean3D> facet, final boolean reversed) {
 
             // extract the vertices of the facet
             @SuppressWarnings("unchecked")
             final AbstractSubHyperplane<Euclidean3D, Euclidean2D> absFacet =
                 (AbstractSubHyperplane<Euclidean3D, Euclidean2D>) facet;
             final Plane plane    = (Plane) facet.getHyperplane();
 
             final double scal = plane.getNormal().dotProduct(w);
             if (FastMath.abs(scal) > 1.0e-3) {
                 Vector2D[][] vertices =
                     ((PolygonsSet) absFacet.getRemainingRegion()).getVertices();
 
                 if ((scal < 0) ^ reversed) {
                     // the facet is seen from the inside,
                     // we need to invert its boundary orientation
                     final Vector2D[][] newVertices = new Vector2D[vertices.length][];
                     for (int i = 0; i < vertices.length; ++i) {
                         final Vector2D[] loop = vertices[i];
                         final Vector2D[] newLoop = new Vector2D[loop.length];
                         if (loop[0] == null) {
                             newLoop[0] = null;
                             for (int j = 1; j < loop.length; ++j) {
                                 newLoop[j] = loop[loop.length - j];
                             }
                         } else {
                             for (int j = 0; j < loop.length; ++j) {
                                 newLoop[j] = loop[loop.length - (j + 1)];
                             }
                         }
                         newVertices[i] = newLoop;
                     }
 
                     // use the reverted vertices
                     vertices = newVertices;
 
                 }
 
                 // compute the projection of the facet in the outline plane
                 final ArrayList<SubHyperplane<Euclidean2D>> edges = new ArrayList<SubHyperplane<Euclidean2D>>();
                 for (Vector2D[] loop : vertices) {
                     final boolean closed = loop[0] != null;
                     int previous         = closed ? (loop.length - 1) : 1;
                     Vector3D previous3D  = plane.toSpace(loop[previous]);
                     int current          = (previous + 1) % loop.length;
                     Vector2D pPoint       = new Vector2D(previous3D.dotProduct(u),
                                                          previous3D.dotProduct(v));
                     while (current < loop.length) {
 
                         final Vector3D current3D = plane.toSpace(loop[current]);
                         final Vector2D  cPoint    = new Vector2D(current3D.dotProduct(u),
                                                                  current3D.dotProduct(v));
                         final org.apache.commons.math3.geometry.euclidean.twod.Line line =
                             new org.apache.commons.math3.geometry.euclidean.twod.Line(pPoint, cPoint);
                         SubHyperplane<Euclidean2D> edge = line.wholeHyperplane();
 
                         if (closed || (previous != 1)) {
                             // the previous point is a real vertex
                             // it defines one bounding point of the edge
                             final double angle = line.getAngle() + 0.5 * FastMath.PI;
                             final org.apache.commons.math3.geometry.euclidean.twod.Line l =
                                 new org.apache.commons.math3.geometry.euclidean.twod.Line(pPoint, angle);
                             edge = edge.split(l).getPlus();
                         }
 
                         if (closed || (current != (loop.length - 1))) {
                             // the current point is a real vertex
                             // it defines one bounding point of the edge
                             final double angle = line.getAngle() + 0.5 * FastMath.PI;
                             final org.apache.commons.math3.geometry.euclidean.twod.Line l =
                                 new org.apache.commons.math3.geometry.euclidean.twod.Line(cPoint, angle);
                             edge = edge.split(l).getMinus();
                         }
 
                         edges.add(edge);
 
                         previous   = current++;
                         previous3D = current3D;
                         pPoint     = cPoint;
 
                     }
                 }
                 final PolygonsSet projectedFacet = new PolygonsSet(edges);
 
                 // add the contribution of the facet to the global outline
                 projected = (PolygonsSet) new RegionFactory<Euclidean2D>().union(projected, projectedFacet);
 
             }
         }
 
         /** Get the projection of the polyhedrons set on the plane.
          * @return projection of the polyhedrons set on the plane
          */
         public PolygonsSet getProjected() {
             return projected;
         }
 
     }
 
 }