/*
    * 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.BivariateFunction;
  import org.hipparchus.analysis.CalculusFieldBivariateFunction;
  import org.hipparchus.exception.MathIllegalArgumentException;
  import org.hipparchus.exception.NullArgumentException;
  import org.hipparchus.random.RandomDataGenerator;
  import org.hipparchus.util.Binary64;
  import org.hipparchus.util.FastMath;
  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.assertFalse;
  import static org.junit.jupiter.api.Assertions.assertTrue;
  import static org.junit.jupiter.api.Assertions.fail;
  
  /**
   * Test case for the piecewise bicubic function.
   */
  final class PiecewiseBicubicSplineInterpolatingFunctionTest {
      /**
       * Test preconditions.
       */
      @Test
      void testPreconditions() {
          double[] xval = new double[] { 3, 4, 5, 6.5, 7.5 };
          double[] yval = new double[] { -4, -3, -1, 2.5, 3.5 };
          double[][] zval = new double[xval.length][yval.length];
  
          @SuppressWarnings("unused")
          PiecewiseBicubicSplineInterpolatingFunction bcf = new PiecewiseBicubicSplineInterpolatingFunction(xval, yval, zval);
  
          try {
              new PiecewiseBicubicSplineInterpolatingFunction(null, yval, zval);
              fail("Failed to detect x null pointer");
          } catch (NullArgumentException iae) {
              // Expected.
          }
  
          try {
              new PiecewiseBicubicSplineInterpolatingFunction(xval, null, zval);
              fail("Failed to detect y null pointer");
          } catch (NullArgumentException iae) {
              // Expected.
          }
  
          try {
              new PiecewiseBicubicSplineInterpolatingFunction(xval, yval, null);
              fail("Failed to detect z null pointer");
          } catch (NullArgumentException iae) {
              // Expected.
          }
  
          try {
              final double[][] fnull = new double[1][];
              new PiecewiseBicubicSplineInterpolatingFunction(xval, yval, fnull);
              fail("Failed to detect z[0] null pointer");
          } catch (NullArgumentException iae) {
              // Expected.
          }
  
          try {
              final double[][] f = new double[1][1];
              new PiecewiseBicubicSplineInterpolatingFunction(new double[0], yval, f);
              fail("Failed to detect empty x pointer");
          } catch (MathIllegalArgumentException iae) {
              // Expected.
          }
  
          try {
              final double[][] f = new double[1][1];
              new PiecewiseBicubicSplineInterpolatingFunction(xval, new double[0], f);
              fail("Failed to detect empty y pointer");
          } catch (MathIllegalArgumentException iae) {
              // Expected.
          }
  
 
         try {
             final double[][] f = new double[1][0];
             new PiecewiseBicubicSplineInterpolatingFunction(xval, yval, f);
             fail("Failed to detect empty z[0] pointer");
         } catch (MathIllegalArgumentException iae) {
             // Expected.
         }
 
         try {
             final double[] xval1 = { 0.0, 1.0, 2.0, 3.0 };
             new PiecewiseBicubicSplineInterpolatingFunction(xval1, yval, zval);
             fail("Failed to detect insufficient x data");
         } catch (MathIllegalArgumentException iae) {
             // Expected.
         }
 
         try {
             final double[] yval1 = { 0.0, 1.0, 2.0, 3.0 };
             new PiecewiseBicubicSplineInterpolatingFunction(xval, yval1, zval);
             fail("Failed to detect insufficient y data");
         } catch (MathIllegalArgumentException iae) {
             // Expected.
         }
 
         try {
             final double[][] zval1 = new double[4][4];
             new PiecewiseBicubicSplineInterpolatingFunction(xval, yval, zval1);
             fail("Failed to detect insufficient z data");
         } catch (MathIllegalArgumentException iae) {
             // Expected.
         }
 
         try {
             final double[][] zval1 = new double[5][4];
             new PiecewiseBicubicSplineInterpolatingFunction(xval, yval, zval1);
             fail("Failed to detect insufficient z data");
         } catch (MathIllegalArgumentException iae) {
             // Expected.
         }
 
         try {
             final double[] xval1 = { 0.0, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 };
             new PiecewiseBicubicSplineInterpolatingFunction(xval1, yval, zval);
             fail("Failed to detect data set array with different sizes.");
         } catch (MathIllegalArgumentException iae) {
             // Expected.
         }
 
         try {
             final double[] yval1 = { 0.0, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 };
             new PiecewiseBicubicSplineInterpolatingFunction(xval, yval1, zval);
             fail("Failed to detect data set array with different sizes.");
         } catch (MathIllegalArgumentException iae) {
             // Expected.
         }
 
         // X values not sorted.
         try {
             final double[] xval1 = { 0.0, 1.0, 0.5, 7.0, 3.5 };
             new PiecewiseBicubicSplineInterpolatingFunction(xval1, yval, zval);
             fail("Failed to detect unsorted x arguments.");
         } catch (MathIllegalArgumentException iae) {
             // Expected.
         }
 
         // Y values not sorted.
         try {
             final double[] yval1 = { 0.0, 1.0, 1.5, 0.0, 3.0 };
             new PiecewiseBicubicSplineInterpolatingFunction(xval, yval1, zval);
             fail("Failed to detect unsorted y arguments.");
         } catch (MathIllegalArgumentException iae) {
             // Expected.
         }
     }
 
     /**
      * Interpolating a plane.
      * <p>
      * z = 2 x - 3 y + 5
      */
     @Test
     void testPlane() {
         final int numberOfElements = 10;
         final double minimumX = -10;
         final double maximumX = 10;
         final double minimumY = -10;
         final double maximumY = 10;
         final int numberOfSamples = 100;
 
         final double interpolationTolerance = 7e-15;
         final double maxTolerance = 6e-14;
 
         // Function values
         BivariateFunction f = (x, y) -> 2 * x - 3 * y + 5;
         CalculusFieldBivariateFunction<Binary64> fT = (x, y) -> x.multiply(2).subtract(y.multiply(3)).add(5);
 
         testInterpolation(minimumX,
                           maximumX,
                           minimumY,
                           maximumY,
                           numberOfElements,
                           numberOfSamples,
                           f, fT,
                           interpolationTolerance,
                           maxTolerance);
     }
 
     /**
      * Interpolating a paraboloid.
      * <p>
      * z = 2 x<sup>2</sup> - 3 y<sup>2</sup> + 4 x y - 5
      */
     @Test
     void testParabaloid() {
         final int numberOfElements = 10;
         final double minimumX = -10;
         final double maximumX = 10;
         final double minimumY = -10;
         final double maximumY = 10;
         final int numberOfSamples = 100;
 
         final double interpolationTolerance = 2e-14;
         final double maxTolerance = 6e-14;
 
         // Function values
         BivariateFunction f = (x, y) -> 2 * x * x - 3 * y * y + 4 * x * y - 5;
         CalculusFieldBivariateFunction<Binary64> fT = (x, y) -> x.square().multiply(2).
                                                              subtract(y.square().multiply(3)).
                                                              add(x.multiply(y).multiply(4)).
                                                              subtract(5);
 
         testInterpolation(minimumX,
                           maximumX,
                           minimumY,
                           maximumY,
                           numberOfElements,
                           numberOfSamples,
                           f, fT,
                           interpolationTolerance,
                           maxTolerance);
     }
 
     /**
      * @param minimumX Lower bound of interpolation range along the x-coordinate.
      * @param maximumX Higher bound of interpolation range along the x-coordinate.
      * @param minimumY Lower bound of interpolation range along the y-coordinate.
      * @param maximumY Higher bound of interpolation range along the y-coordinate.
      * @param numberOfElements Number of data points (along each dimension).
      * @param numberOfSamples Number of test points.
      * @param f Function to test.
      * @param fT Binary64 version of the function to test
      * @param meanTolerance Allowed average error (mean error on all interpolated values).
      * @param maxTolerance Allowed error on each interpolated value.
      */
     private void testInterpolation(double minimumX,
                                    double maximumX,
                                    double minimumY,
                                    double maximumY,
                                    int numberOfElements,
                                    int numberOfSamples,
                                    BivariateFunction f,
                                    final CalculusFieldBivariateFunction<Binary64> fT,
                                    double meanTolerance,
                                    double maxTolerance) {
         double expected;
         double actual;
         Binary64 expected64;
         Binary64 actual64;
         double currentX;
         double currentY;
         Binary64 currentX64;
         Binary64 currentY64;
         final double deltaX = (maximumX - minimumX) / ((double) numberOfElements);
         final double deltaY = (maximumY - minimumY) / ((double) numberOfElements);
         final double[] xValues = new double[numberOfElements];
         final double[] yValues = new double[numberOfElements];
         final double[][] zValues = new double[numberOfElements][numberOfElements];
 
         for (int i = 0; i < numberOfElements; i++) {
             xValues[i] = minimumX + deltaX * (double) i;
             for (int j = 0; j < numberOfElements; j++) {
                 yValues[j] = minimumY + deltaY * (double) j;
                 zValues[i][j] = f.value(xValues[i], yValues[j]);
             }
         }
 
         final PiecewiseBicubicSplineInterpolatingFunction interpolation
             = new PiecewiseBicubicSplineInterpolatingFunction(xValues,
                                                               yValues,
                                                               zValues);
 
         for (int i = 0; i < numberOfElements; i++) {
             currentX = xValues[i];
             currentX64 = new Binary64(currentX);
             for (int j = 0; j < numberOfElements; j++) {
                 currentY = yValues[j];
                 currentY64 = new Binary64(currentY);
                 assertTrue(Precision.equals(f.value(currentX, currentY),
                                                    interpolation.value(currentX, currentY)));
                 assertTrue(Precision.equals(fT.value(currentX64, currentY64).getReal(),
                                                    interpolation.value(currentX64, currentY64).getReal()));
             }
         }
 
         final RandomDataGenerator gen = new RandomDataGenerator(1234567L);
 
         double sumError   = 0;
         double sumError64 = 0;
         for (int i = 0; i < numberOfSamples; i++) {
             currentX = gen.nextUniform(xValues[0], xValues[xValues.length - 1]);
             currentY = gen.nextUniform(yValues[0], yValues[yValues.length - 1]);
             currentX64 = new Binary64(currentX);
             currentY64 = new Binary64(currentY);
             expected = f.value(currentX, currentY);
             actual = interpolation.value(currentX, currentY);
             expected64 = fT.value(currentX64, currentY64);
             actual64 = interpolation.value(currentX64, currentY64);
             sumError   += FastMath.abs(actual - expected);
             sumError64 += FastMath.abs(actual64.subtract(expected64)).getReal();
             assertEquals(expected, actual, maxTolerance);
             assertEquals(expected64.getReal(), actual64.getReal(), maxTolerance);
         }
 
         final double meanError = sumError / numberOfSamples;
         assertEquals(0, meanError, meanTolerance);
         final double meanError64 = sumError64 / numberOfSamples;
         assertEquals(0, meanError64, meanTolerance);
 
     }
 
     @Test
     void testIsValidPoint() {
         // GIVEN
         final double[] x = new double[] { 0., 1., 2., 3., 4. };
         final double[] y = x.clone();
         final PiecewiseBicubicSplineInterpolatingFunction interpolatingFunction =
                 new PiecewiseBicubicSplineInterpolatingFunction(x, y, new double[x.length][y.length]);
         // WHEN & THEN
         assertFalse(interpolatingFunction.isValidPoint(x[0] - 1, y[0]));
         assertFalse(interpolatingFunction.isValidPoint(x[x.length - 1] + 1, y[0]));
         assertFalse(interpolatingFunction.isValidPoint(x[0], y[0] - 1));
         assertFalse(interpolatingFunction.isValidPoint(x[0], y[y.length - 1] + 1));
     }
 
 }