/*
    * Licensed to the Hipparchus project under one or more
    * contributor license agreements.  See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * The Hipparchus project 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
    *
    *      https://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.hipparchus.geometry;
  
  import org.hipparchus.exception.LocalizedCoreFormats;
  import org.hipparchus.exception.MathIllegalArgumentException;
  import org.hipparchus.geometry.euclidean.threed.Vector3D;
  import org.hipparchus.geometry.euclidean.twod.Vector2D;
  import org.hipparchus.geometry.spherical.twod.S2Point;
  import org.hipparchus.util.CombinatoricsUtils;
  import org.junit.jupiter.api.Assertions;
  import org.junit.jupiter.api.Test;
  
  import java.util.Arrays;
  import java.util.Collections;
  import java.util.List;
  
  public class GeometryTest {
  
      @Test
      public void testBarycenterException() {
          try {
              final List<S2Point> points = Collections.emptyList();
              Geometry.barycenter(points);
              Assertions.fail("Should have thrown an exception");
          } catch (MathIllegalArgumentException miae) {
              Assertions.assertEquals(LocalizedCoreFormats.NUMBER_OF_ELEMENTS_SHOULD_BE_POSITIVE, miae.getSpecifier());
              Assertions.assertEquals(0, miae.getParts()[0]);
          }
      }
  
      @Test
      public void testBarycenterIdentity() {
          final Vector3D p = new Vector3D(1.0, 2.0, 3.0);
          Assertions.assertSame(p, Geometry.barycenter(Collections.singletonList(p)));
      }
  
      @Test
      void testBarycenter2D() {
          final List<Vector2D> points = Arrays.asList(new Vector2D(740.0, 1070.0),
                                                      new Vector2D(1010.0, 1330.0),
                                                      new Vector2D(1240.0, 1160.0),
                                                      new Vector2D(1250.0,  800.0),
                                                      new Vector2D( 890.0,  720.0));
          final Vector2D naive = barycenterNaive2D(points);
          CombinatoricsUtils.
                  permutations(points).
                  map(Geometry::barycenter).
                  forEach(barycenter -> Assertions.assertEquals(0.0, naive.distance(barycenter), 2.0e-13));
  
      }
  
      @Test
      void testBarycenter3D() {
          final List<Vector3D> points = Arrays.asList(new Vector3D( 740.0, 1070.0, -12.0),
                                                      new Vector3D(1010.0, 1330.0,   0.0),
                                                      new Vector3D(1240.0, 1160.0,   6.0),
                                                      new Vector3D(1250.0,  800.0,   6.0));
          final Vector3D naive = barycenterNaive3D(points);
          CombinatoricsUtils.
                  permutations(points).
                  map(Geometry::barycenter).
                  forEach(barycenter -> Assertions.assertEquals(0.0, naive.distance(barycenter), 1.0e-15));
  
      }
  
      private Vector2D barycenterNaive2D(final List<Vector2D> points) {
          double sumX = 0;
          double sumY = 0;
          for (final Vector2D point : points) {
              sumX += point.getX();
              sumY += point.getY();
          }
          return new Vector2D(sumX / points.size(), sumY / points.size());
      }
  
      private Vector3D barycenterNaive3D(final List<Vector3D> points) {
          double sumX = 0;
          double sumY = 0;
          double sumZ = 0;
          for (final Vector3D point : points) {
              sumX += point.getX();
              sumY += point.getY();
              sumZ += point.getZ();
          }
         return new Vector3D(sumX / points.size(), sumY / points.size(), sumZ / points.size());
     }
 
 }