/*
    * 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.rng.sampling.distribution;
  
  import org.apache.commons.rng.UniformRandomProvider;
  import org.apache.commons.rng.sampling.RandomAssert;
  import org.apache.commons.rng.sampling.SharedStateSampler;
  import org.junit.jupiter.api.Assertions;
  import org.junit.jupiter.api.Test;
  
  /**
   * Test for the {@link GaussianSampler}. The tests hit edge cases for the sampler.
   */
  class GaussianSamplerTest {
      /**
       * Test the constructor with a zero standard deviation.
       */
      @Test
      void testConstructorThrowsWithZeroStandardDeviation() {
          final UniformRandomProvider rng = RandomAssert.seededRNG();
          final NormalizedGaussianSampler gauss = ZigguratSampler.NormalizedGaussian.of(rng);
          final double mean = 1;
          final double standardDeviation = 0;
          Assertions.assertThrows(IllegalArgumentException.class,
              () -> GaussianSampler.of(gauss, mean, standardDeviation));
      }
  
      /**
       * Test the constructor with an infinite standard deviation.
       */
      @Test
      void testConstructorThrowsWithInfiniteStandardDeviation() {
          final UniformRandomProvider rng = RandomAssert.seededRNG();
          final NormalizedGaussianSampler gauss = new ZigguratNormalizedGaussianSampler(rng);
          final double mean = 1;
          final double standardDeviation = Double.POSITIVE_INFINITY;
          Assertions.assertThrows(IllegalArgumentException.class,
              () -> GaussianSampler.of(gauss, mean, standardDeviation));
      }
  
      /**
       * Test the constructor with a NaN standard deviation.
       */
      @Test
      void testConstructorThrowsWithNaNStandardDeviation() {
          final UniformRandomProvider rng = RandomAssert.seededRNG();
          final NormalizedGaussianSampler gauss = new ZigguratNormalizedGaussianSampler(rng);
          final double mean = 1;
          final double standardDeviation = Double.NaN;
          Assertions.assertThrows(IllegalArgumentException.class,
              () -> GaussianSampler.of(gauss, mean, standardDeviation));
      }
  
      /**
       * Test the constructor with an infinite mean.
       */
      @Test
      void testConstructorThrowsWithInfiniteMean() {
          final UniformRandomProvider rng = RandomAssert.seededRNG();
          final NormalizedGaussianSampler gauss = new ZigguratNormalizedGaussianSampler(rng);
          final double mean = Double.POSITIVE_INFINITY;
          final double standardDeviation = 1;
          Assertions.assertThrows(IllegalArgumentException.class,
              () -> GaussianSampler.of(gauss, mean, standardDeviation));
      }
  
      /**
       * Test the constructor with a NaN mean.
       */
      @Test
      void testConstructorThrowsWithNaNMean() {
          final UniformRandomProvider rng = RandomAssert.seededRNG();
          final NormalizedGaussianSampler gauss = new ZigguratNormalizedGaussianSampler(rng);
          final double mean = Double.NaN;
          final double standardDeviation = 1;
          Assertions.assertThrows(IllegalArgumentException.class,
              () -> GaussianSampler.of(gauss, mean, standardDeviation));
      }
  
      /**
       * Test the SharedStateSampler implementation.
       */
      @Test
      void testSharedStateSampler() {
          final UniformRandomProvider rng1 = RandomAssert.seededRNG();
         final UniformRandomProvider rng2 = RandomAssert.seededRNG();
         final NormalizedGaussianSampler gauss = ZigguratSampler.NormalizedGaussian.of(rng1);
         final double mean = 1.23;
         final double standardDeviation = 4.56;
         final SharedStateContinuousSampler sampler1 =
             GaussianSampler.of(gauss, mean, standardDeviation);
         final SharedStateContinuousSampler sampler2 = sampler1.withUniformRandomProvider(rng2);
         RandomAssert.assertProduceSameSequence(sampler1, sampler2);
     }
 
     /**
      * Test the SharedStateSampler implementation throws if the underlying sampler is
      * not a SharedStateSampler.
      */
     @Test
     void testSharedStateSamplerThrowsIfUnderlyingSamplerDoesNotShareState() {
         final UniformRandomProvider rng2 = RandomAssert.seededRNG();
         final NormalizedGaussianSampler gauss = new NormalizedGaussianSampler() {
             @Override
             public double sample() {
                 return 0;
             }
         };
         final double mean = 1.23;
         final double standardDeviation = 4.56;
         final SharedStateContinuousSampler sampler1 =
             GaussianSampler.of(gauss, mean, standardDeviation);
         Assertions.assertThrows(UnsupportedOperationException.class,
             () -> sampler1.withUniformRandomProvider(rng2));
     }
 
     /**
      * Test the SharedStateSampler implementation throws if the underlying sampler is
      * a SharedStateSampler that returns an incorrect type.
      */
     @Test
     void testSharedStateSamplerThrowsIfUnderlyingSamplerReturnsWrongSharedState() {
         final UniformRandomProvider rng2 = RandomAssert.seededRNG();
         final NormalizedGaussianSampler gauss = new BadSharedStateNormalizedGaussianSampler();
         final double mean = 1.23;
         final double standardDeviation = 4.56;
         final SharedStateContinuousSampler sampler1 =
             GaussianSampler.of(gauss, mean, standardDeviation);
         Assertions.assertThrows(UnsupportedOperationException.class,
             () -> sampler1.withUniformRandomProvider(rng2));
     }
 
     /**
      * Test class to return an incorrect sampler from the SharedStateSampler method.
      *
      * <p>Note that due to type erasure the type returned by the SharedStateSampler is not
      * available at run-time and the GaussianSampler has to assume it is the correct type.</p>
      */
     private static class BadSharedStateNormalizedGaussianSampler
             implements NormalizedGaussianSampler, SharedStateSampler<Integer> {
         @Override
         public double sample() {
             return 0;
         }
 
         @Override
         public Integer withUniformRandomProvider(UniformRandomProvider rng) {
             // Something that is not a NormalizedGaussianSampler
             return Integer.valueOf(44);
         }
     }
 }