/*
    * 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.statistics.distribution;
  
  import java.util.stream.Stream;
  import org.apache.commons.numbers.gamma.LogGamma;
  import org.junit.jupiter.api.Assertions;
  import org.junit.jupiter.api.Test;
  import org.junit.jupiter.params.ParameterizedTest;
  import org.junit.jupiter.params.provider.Arguments;
  import org.junit.jupiter.params.provider.CsvSource;
  import org.junit.jupiter.params.provider.MethodSource;
  
  /**
   * Test cases for {@link WeibullDistribution}.
   * Extends {@link BaseContinuousDistributionTest}. See javadoc of that class for details.
   */
  class WeibullDistributionTest extends BaseContinuousDistributionTest {
      @Override
      ContinuousDistribution makeDistribution(Object... parameters) {
          final double shape = (Double) parameters[0];
          final double scale = (Double) parameters[1];
          return WeibullDistribution.of(shape, scale);
      }
  
  
      @Override
      Object[][] makeInvalidParameters() {
          return new Object[][] {
              {0.0, 2.0},
              {-0.1, 2.0},
              {1.0, 0.0},
              {1.0, -0.1},
          };
      }
  
      @Override
      String[] getParameterNames() {
          return new String[] {"Shape", "Scale"};
      }
  
      @Override
      protected double getRelativeTolerance() {
          return 1e-14;
      }
  
      //-------------------- Additional test cases -------------------------------
  
      @ParameterizedTest
      @MethodSource
      void testAdditionalMoments(double shape, double scale, double mean, double variance) {
          final WeibullDistribution dist = WeibullDistribution.of(shape, scale);
          testMoments(dist, mean, variance, createRelTolerance(1e-15));
      }
  
      static Stream<Arguments> testAdditionalMoments() {
          // In R: 3.5*gamma(1+(1/2.5)) (or empirically: mean(rweibull(10000, 2.5, 3.5)))
          double mu1 = 3.5 * Math.exp(LogGamma.value(1 + (1 / 2.5)));
          double mu2 = 2.222 * Math.exp(LogGamma.value(1 + (1 / 10.4)));
          return Stream.of(
              Arguments.of(2.5, 3.5, mu1,
                  (3.5 * 3.5) *
                  Math.exp(LogGamma.value(1 + (2 / 2.5))) -
                  (mu1 * mu1)),
              Arguments.of(10.4, 2.222, mu2,
                  (2.222 * 2.222) *
                  Math.exp(LogGamma.value(1 + (2 / 10.4))) -
                  (mu2 * mu2))
          );
      }
  
      @ParameterizedTest
      @CsvSource({
          "1, 2",
          "0.1, 2.34",
      })
      void testAdditionalParameterAccessors(double shape, double scale) {
          final WeibullDistribution dist = WeibullDistribution.of(shape, scale);
          Assertions.assertEquals(shape, dist.getShape());
          Assertions.assertEquals(scale, dist.getScale());
      }
  
      @Test
      void testInverseCumulativeProbabilitySmallPAccuracy() {
         final WeibullDistribution dist = WeibullDistribution.of(2, 3);
         final double t = dist.inverseCumulativeProbability(1e-17);
         // Analytically, answer is solution to 1e-17 = 1-exp(-(x/3)^2)
         // x = sqrt(-9*log(1-1e-17))
         // If we're not careful, answer will be 0. Answer below is computed with care in Octave:
         Assertions.assertEquals(9.48683298050514e-9, t, 1e-17);
     }
 }