/*
    * 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.analysis.interpolation;
  
  import org.hipparchus.analysis.UnivariateFunction;
  import org.hipparchus.exception.MathIllegalArgumentException;
  import org.hipparchus.util.FastMath;
  import org.junit.jupiter.api.Test;
  
  import java.util.Random;
  
  import static org.junit.jupiter.api.Assertions.assertEquals;
  import static org.junit.jupiter.api.Assertions.assertThrows;
  
  
  /**
   * Test for {@link UnivariatePeriodicInterpolator}.
   */
  class UnivariatePeriodicInterpolatorTest {
      private final Random rng = new Random(1224465L);
  
      @Test
      void testSine() {
          final int n = 30;
          final double[] xval = new double[n];
          final double[] yval = new double[n];
          final double period = 12.3;
          final double offset = 45.67;
  
          double delta = 0;
          for (int i = 0; i < n; i++) {
              delta += rng.nextDouble() * period / n;
              xval[i] = offset + delta;
              yval[i] = FastMath.sin(xval[i]);
          }
  
          final UnivariateInterpolator inter = new LinearInterpolator();
          final UnivariateFunction f = inter.interpolate(xval, yval);
  
          final UnivariateInterpolator interP
              = new UnivariatePeriodicInterpolator(new LinearInterpolator(),
                                                       period, 1);
          final UnivariateFunction fP = interP.interpolate(xval, yval);
  
          // Comparing with original interpolation algorithm.
          final double xMin = xval[0];
          final double xMax = xval[n - 1];
          for (int i = 0; i < n; i++) {
              final double x = xMin + (xMax - xMin) * rng.nextDouble();
              final double y = f.value(x);
              final double yP = fP.value(x);
  
              assertEquals(y, yP, Math.ulp(1d), "x=" + x);
          }
  
          // Test interpolation outside the primary interval.
          for (int i = 0; i < n; i++) {
              final double xIn = offset + rng.nextDouble() * period;
              final double xOut = xIn + rng.nextInt(123456789) * period;
              final double yIn = fP.value(xIn);
              final double yOut = fP.value(xOut);
  
              assertEquals(yIn, yOut, 1e-7);
          }
      }
  
      @Test
      void testLessThanOnePeriodCoverage() {
          final int n = 30;
          final double[] xval = new double[n];
          final double[] yval = new double[n];
          final double period = 12.3;
          final double offset = 45.67;
  
          double delta = period / 2;
          for (int i = 0; i < n; i++) {
              delta += period / (2 * n) * rng.nextDouble();
              xval[i] = offset + delta;
              yval[i] = FastMath.sin(xval[i]);
          }
 
         final UnivariateInterpolator interP
             = new UnivariatePeriodicInterpolator(new LinearInterpolator(),
                                                      period, 1);
         final UnivariateFunction fP = interP.interpolate(xval, yval);
 
         // Test interpolation outside the sample data interval.
         for (int i = 0; i < n; i++) {
             final double xIn = offset + rng.nextDouble() * period;
             final double xOut = xIn + rng.nextInt(123456789) * period;
             final double yIn = fP.value(xIn);
             final double yOut = fP.value(xOut);
 
             assertEquals(yIn, yOut, 1e-7);
         }
     }
 
     @Test
     void testMoreThanOnePeriodCoverage() {
         final int n = 30;
         final double[] xval = new double[n];
         final double[] yval = new double[n];
         final double period = 12.3;
         final double offset = 45.67;
 
         double delta = period / 2;
         for (int i = 0; i < n; i++) {
             delta += 10 * period / n * rng.nextDouble();
             xval[i] = offset + delta;
             yval[i] = FastMath.sin(xval[i]);
         }
 
         final UnivariateInterpolator interP
             = new UnivariatePeriodicInterpolator(new LinearInterpolator(),
                                                      period, 1);
         final UnivariateFunction fP = interP.interpolate(xval, yval);
 
         // Test interpolation outside the sample data interval.
         for (int i = 0; i < n; i++) {
             final double xIn = offset + rng.nextDouble() * period;
             final double xOut = xIn + rng.nextInt(123456789) * period;
             final double yIn = fP.value(xIn);
             final double yOut = fP.value(xOut);
 
             assertEquals(yIn, yOut, 1e-6);
         }
     }
 
     @Test
     void testTooFewSamples() {
         assertThrows(MathIllegalArgumentException.class, () -> {
             final double[] xval = {2, 3, 7};
             final double[] yval = {1, 6, 5};
             final double period = 10;
 
             final UnivariateInterpolator interpolator
                 = new UnivariatePeriodicInterpolator(new LinearInterpolator(), period);
             interpolator.interpolate(xval, yval);
         });
     }
 
     @Test
     void testUnsortedSamples() {
         assertThrows(MathIllegalArgumentException.class, () -> {
             final double[] xval = {2, 3, 7, 4, 6};
             final double[] yval = {1, 6, 5, -1, -2};
             final double period = 10;
 
             final UnivariateInterpolator interpolator
                 = new UnivariatePeriodicInterpolator(new LinearInterpolator(), period);
             interpolator.interpolate(xval, yval);
         });
     }
 }