/*
    * 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.core.source64;
  
  import org.apache.commons.rng.core.RandomAssert;
  import org.apache.commons.rng.core.source64.TwoCmres.Cmres;
  import org.junit.jupiter.api.Assertions;
  import org.junit.jupiter.api.Test;
  
  import java.util.ArrayList;
  
  
  class TwoCmresTest {
      @Test
      void testAsymmetric() {
          final int index1 = 2;
          final int index2 = 5;
          final int seed = -123456789;
  
          final TwoCmres rng1 = new TwoCmres(seed, index1, index2);
          final TwoCmres rng2 = new TwoCmres(seed, index2, index1);
  
          // Try a few values.
          final int n = 1000;
          for (int[] i = {0}; i[0] < n; i[0]++) {
              Assertions.assertNotEquals(rng1.nextLong(), rng2.nextLong(), () -> "i=" + i[0]);
          }
      }
  
      /**
       * This test targets the seeding procedure to verify any bit of the input seed contributes
       * to the output. Note: The seeding routine creates 2 16-bit integers from the 32-bit seed,
       * thus a change of any single bit should make a different output.
       */
      @Test
      void testSeedingWithASingleBitProducesDifferentOutputFromZeroSeed() {
          final int n = 100;
  
          // Output with a zero seed
          final long[] values = new long[n];
          final TwoCmres rng = new TwoCmres(0);
          for (int i = 0; i < n; i++) {
              values[i] = rng.nextLong();
          }
  
          // Seed with a single bit
          for (int bit = 0; bit < 32; bit++) {
              final int seed = 1 << bit;
              RandomAssert.assertNotEquals(values, new TwoCmres(seed));
          }
      }
  
      @Test
      void testSubcycleGeneratorsMustBeDifferent() {
          final int max = TwoCmres.numberOfSubcycleGenerators();
          for (int i = 0; i < max; i++) {
              final int subCycle = i;
              Assertions.assertThrows(IllegalArgumentException.class,
                  () -> new TwoCmres(-97845, subCycle, subCycle));
          }
      }
  
      @Test
      void testSubcycleGeneratorsIndex() {
          final int seed = 246810;
  
          // Valid indices are between 0 (included) and max (excluded).
          final int max = TwoCmres.numberOfSubcycleGenerators();
  
          for (int i = 0; i < max; i++) {
              for (int j = 0; j < max; j++) {
                  if (i != j) { // Subcycle generators must be different.
                      // Can be instantiated.
                      new TwoCmres(seed, i, j);
                  }
              }
          }
  
          for (int wrongIndex : new int[] {-1, max}) {
              Assertions.assertThrows(IndexOutOfBoundsException.class,
                  () -> new TwoCmres(seed, wrongIndex, 1),
                  () -> "Exception expected for index i = " + wrongIndex);
              Assertions.assertThrows(IndexOutOfBoundsException.class,
                  () -> new TwoCmres(seed, 1, wrongIndex),
                  () -> "Exception expected for index j = " + wrongIndex);
         }
     }
 
     @Test
     void testCmresFactoryThrowsWithDuplicateMultiplier() {
         final ArrayList<Cmres> list = new ArrayList<>();
         final long multiply = 0;
         final int rotate = 3;
         final int start = 5;
 
         list.add(new Cmres(multiply, rotate, start));
 
         long nextMultiply = multiply + 1;
         Assertions.assertDoesNotThrow(
             () -> Cmres.Factory.checkUnique(list, nextMultiply),
             () -> "The next multiply should be unique: " + nextMultiply);
 
         list.add(new Cmres(nextMultiply, rotate, start));
         // This should throw as the list now contains the multiply value
         Assertions.assertThrows(IllegalStateException.class, () -> Cmres.Factory.checkUnique(list, nextMultiply));
     }
 }