/*
    * 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
    *
    *      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.
   */
  
  /*
   * This is not the original file distributed by the Apache Software Foundation
   * It has been modified by the Hipparchus project
   */
  package org.hipparchus.transform;
  
  import org.hipparchus.exception.MathIllegalArgumentException;
  import org.hipparchus.util.Precision;
  import org.junit.jupiter.api.Test;
  
  import static org.junit.jupiter.api.Assertions.assertEquals;
  import static org.junit.jupiter.api.Assertions.assertTrue;
  import static org.junit.jupiter.api.Assertions.fail;
  
  
  /**
   * JUnit Test for HadamardTransformerTest
   * @see org.hipparchus.transform.FastHadamardTransformer
   */
  final class FastHadamardTransformerTest {
  
      /**
       * Test of transformer for the a 8-point FHT (means n=8)
       */
      @Test
      void test8Points() {
          checkAllTransforms(new int[] { 1, 4, -2, 3, 0, 1, 4, -1 },
                         new int[] { 10, -4, 2, -4, 2, -12, 6, 8 });
      }
  
      /**
       * Test of transformer for the a 4-points FHT (means n=4)
       */
      @Test
      void test4Points() {
          checkAllTransforms(new int[] { 1, 2, 3, 4 },
                             new int[] { 10, -2, -4, 0 });
      }
  
      /**
       * Test the inverse transform of an integer vector is not always an integer vector
       */
      @Test
      void testNoIntInverse() {
          FastHadamardTransformer transformer = new FastHadamardTransformer();
          double[] x = transformer.transform(new double[] { 0, 1, 0, 1}, TransformType.INVERSE);
          assertEquals( 0.5, x[0], 0);
          assertEquals(-0.5, x[1], 0);
          assertEquals( 0.0, x[2], 0);
          assertEquals( 0.0, x[3], 0);
      }
  
      /**
       * Test of transformer for wrong number of points
       */
      @Test
      void test3Points() {
          try {
              new FastHadamardTransformer().transform(new double[3], TransformType.FORWARD);
              fail("an exception should have been thrown");
          } catch (MathIllegalArgumentException iae) {
              // expected
          }
      }
  
      private void checkAllTransforms(int[]x, int[] y) {
          checkDoubleTransform(x, y);
          checkInverseDoubleTransform(x, y);
          checkIntTransform(x, y);
      }
  
      private void checkDoubleTransform(int[]x, int[] y) {
          // Initiate the transformer
          FastHadamardTransformer transformer = new FastHadamardTransformer();
  
          // check double transform
          double[] dX = new double[x.length];
          for (int i = 0; i < dX.length; ++i) {
              dX[i] = x[i];
          }
          double[] dResult = transformer.transform(dX, TransformType.FORWARD);
          for (int i = 0; i < dResult.length; i++) {
             // compare computed results to precomputed results
             assertTrue(Precision.equals(y[i], dResult[i], 1));
         }
     }
 
     private void checkIntTransform(int[]x, int[] y) {
         // Initiate the transformer
         FastHadamardTransformer transformer = new FastHadamardTransformer();
 
         // check integer transform
         int[] iResult = transformer.transform(x);
         for (int i = 0; i < iResult.length; i++) {
             // compare computed results to precomputed results
             assertEquals(y[i], iResult[i]);
         }
 
     }
 
     private void checkInverseDoubleTransform(int[]x, int[] y) {
         // Initiate the transformer
         FastHadamardTransformer transformer = new FastHadamardTransformer();
 
         // check double transform
         double[] dY = new double[y.length];
         for (int i = 0; i < dY.length; ++i) {
             dY[i] = y[i];
         }
         double[] dResult = transformer.transform(dY, TransformType.INVERSE);
         for (int i = 0; i < dResult.length; i++) {
             // compare computed results to precomputed results
             assertTrue(Precision.equals(x[i], dResult[i], 1));
         }
 
     }
 
 }