/*
    * 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.junit.jupiter.api.Assertions;
  import org.junit.jupiter.api.Test;
  
  /**
   * Test for the {@link ChengBetaSampler}. The tests hit edge cases for the sampler.
   */
  class ChengBetaSamplerTest {
      /**
       * Test the constructor with a bad alpha.
       */
      @Test
      void testConstructorThrowsWithZeroAlpha() {
          final UniformRandomProvider rng = RandomAssert.seededRNG();
          final double alpha = 0;
          final double beta = 1;
          Assertions.assertThrows(IllegalArgumentException.class,
              () -> ChengBetaSampler.of(rng, alpha, beta));
      }
  
      /**
       * Test the constructor with a bad beta.
       */
      @Test
      void testConstructorThrowsWithZeroBeta() {
          final UniformRandomProvider rng = RandomAssert.seededRNG();
          final double alpha = 1;
          final double beta = 0;
          Assertions.assertThrows(IllegalArgumentException.class,
              () -> ChengBetaSampler.of(rng, alpha, beta));
      }
  
      /**
       * Test the SharedStateSampler implementation.
       */
      @Test
      void testSharedStateSamplerWithAlphaAndBetaAbove1AndAlphaBelowBeta() {
          testSharedStateSampler(1.23, 4.56);
      }
  
      /**
       * Test the SharedStateSampler implementation.
       */
      @Test
      void testSharedStateSamplerWithAlphaAndBetaAbove1AndAlphaAboveBeta() {
          testSharedStateSampler(4.56, 1.23);
      }
  
      /**
       * Test the SharedStateSampler implementation.
       */
      @Test
      void testSharedStateSamplerWithAlphaOrBetaBelow1AndAlphaBelowBeta() {
          testSharedStateSampler(0.23, 4.56);
      }
  
      /**
       * Test the SharedStateSampler implementation.
       */
      @Test
      void testSharedStateSamplerWithAlphaOrBetaBelow1AndAlphaAboveBeta() {
          testSharedStateSampler(4.56, 0.23);
      }
  
      /**
       * Test the SharedStateSampler implementation.
       *
       * @param alpha Alpha.
       * @param beta Beta.
       */
      private static void testSharedStateSampler(double alpha, double beta) {
          final UniformRandomProvider rng1 = RandomAssert.seededRNG();
          final UniformRandomProvider rng2 = RandomAssert.seededRNG();
          // Use instance constructor not factory constructor to exercise 1.X public API
          final SharedStateContinuousSampler sampler1 =
              new ChengBetaSampler(rng1, alpha, beta);
          final SharedStateContinuousSampler sampler2 = sampler1.withUniformRandomProvider(rng2);
          RandomAssert.assertProduceSameSequence(sampler1, sampler2);
      }
  
     /**
      * Test the toString method. This is added to ensure coverage as the factory constructor
      * used in other tests does not create an instance of the wrapper class.
      */
     @Test
     void testToString() {
         final UniformRandomProvider rng = RandomAssert.seededRNG();
         Assertions.assertTrue(new ChengBetaSampler(rng, 1.0, 2.0).toString()
                 .toLowerCase().contains("beta"));
     }
 }